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  • 1.
    El Ghazaly, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Acoustic Platform for MXene Synthesis and Electrochemical Behaviour of i-MXenes in Aqueous Electrolytes2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Climate Change is believed to be the greatest global challenge and on its forefront is the topic of energy. While being of extreme importance, debates over energy have become a normality. The related field of material synthesis for energy storage applications has also been growing, as well as the demand for industrial electrification from renewable sources of energy. Water-based supercapacitors are a type of energy storage devices that can deliver high power densities while maintaining long term cyclability in an environmen-tally friendly media. However, their challenges include maintaining high per-formance in term of energy density, safety, and low cost of electrode manu-facturing. 

    MXene is family of two-dimensional transition metal carbides/nitrides that are terminated with H, OH and F groups. The material demonstrates superior physical and chemical properties related to energy applications in compari-son to its 3D parent material, the MAX phase. Since its discovery in 2011, MXene, such as Ti3C2Tz, has been widely investigated in the field of energy storage due to its high conductivity (20,000 S.cm-1) and a volumetric capac-itance that can reach 900 Fcm-3. However, reported synthesis processes for MXene are fraught with hazardous procedures that are time consuming. The first section of this thesis presents a new innovative method for Ti3C2Tz MXene synthesis, in which MXene was synthesized in a few milliseconds with the assistance of 30 MHz frequency surface acoustic waves (SAW) and 0.05M of LiF. The aluminium element in the Ti3AlC2 MAX phase was etched by so called “localized HF”, and the powder was converted to 2D Ti3C2Tz. This method showed resulting MXene comparable to that of previ-ously reported synthesis techniques, as demonstrated by the material’s elec-trochemical performance.  

    The second section of the thesis focuses on investigating the electrochemical performance of a comparatively new family of MXene, coined i-MXene, in aqueous electrolyte. i-MXene, reported in 2017, has the chemical formula Mo1.33CTz and is a product of chemical etching of the in-plane chemically ordered (Mo2/3Sc1/3)2AlC i-MAX phase. The Mo1.33CTz was studied in a sul-phuric acid electrolyte. This electrolyte sets a limit for the electrode potential window and capacitance, and therefore, post-synthesis treatment protocols was used to enhance the electrochemical performance. The Mo1.33CTz recorded a volumetric capacitance of 1050 Fcm-3 and1600 Fcm-3 for hydrogel treatment and heat-treated electrodes, respectively. Moreover, mixing Mo1.33CTz with MoS2 and graphene improved both the specific capacitance and the electrode stability even further.  

    The electrochemical properties of Mo1.33CTz were thereafter explored in dif-ferent sulfate-based aqueous electrolytes with univalent (Li+, Na+, and K+) and divalent (Mg2+ Mn2+ or Zn2+) cations. Mo1.33CTz exhibited a wider po-tential window without degradation, expanding the previously reported limit in sulphuric acid for both symmetric and asymmetric devices. Lithium chlo-ride gave the best results, being an electrolyte based on a natural salt that has high solubility at room temperature. It presented a large potential window, -1.2 to +0.3V (vs. Ag/AgCl), and a volumetric capacitance of ~800 Fcm−3 at a scan rate of 2 mVs−1. In addition, the performance of a Mo1.33CTz //MnxOn asymmetric device was tested in 5M LiCl electrolyte. The results showed a potential window of 2 V, a volumetric energy density of 58 mWhcm-3, and a 100% columbic efficiency after 10,000 charge/discharge cycles. A cyclic sta-bility is crucial for practical applications, and altogether, the promising re-sults motivate further exploration of i-MXenes for energy storage and be-yond.

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  • 2.
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aqueous Exfoliation of Transition Metal Oxides for Energy Storage and Photocatalysis Applications: Vanadium Oxide and Molybdenum Oxide Nanosheets2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Two-dimensional (2D) transition metal oxides (TMOs) are a category of materials which have unique physical and chemical properties compared to their bulk counterparts. However, the synthesis of 2D TMOs commonly includes the use of environmental threats such as organic solvents. In this thesis, we developed environmentally friendly strategies to fabricate TMO nanosheets from the commercially available bulk oxides. In particular, hydrated vanadium pentoxide (V2O5∙nH2O) nanosheets and oxygen deficient molybdenum trioxide (MoO3-x) nanosheets were prepared.  The V2O5∙nH2O nanosheets were drop-cast onto multi-walled carbon nanotube (MWCNT) paper and applied as a free-standing electrode (FSE) for a lithium battery. The accessible capacity of the FSE was dependent on the electrode thickness; the thickest electrode delivered the lowest accessible capacity.  Alternatively, a composite material of V2O5∙nH2O nanosheets with 10% MWCNT (VOx-CNT composite) was prepared and two types of electrodes, FSE and conventionally cast electrode (CCE), were employed as cathode materials for lithium batteries. A detailed comparison between these electrodes was presented. In addition, the VOx-CNT composite was applied as a negative electrode for a sodium-ion battery and showed a reversible capacity of about 140 mAh g-1. On the other hand, the MoO3-x nanosheets were employed as binder-free electrodes for supercapacitor application in an acidified Na2SO4 electrolyte. Furthermore, the MoO3-x nanosheets were used as photocatalysts for organic dye degradation. The simple eco-friendly synthesis methods coupled with the potential application of the TMO nanosheets reflect the significance of this thesis in both the synthesis and the energy-related applications of 2D materials.

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  • 3.
    Etman, Ahmed S.
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Aqueous Exfoliation of Transition Metal Oxides for Energy Storage and Photocatalysis Applications: Vanadium Oxide and Molybdenum Oxide Nanosheets2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Two-dimensional (2D) transition metal oxides (TMOs) are a category of materials which have unique physical and chemical properties compared to their bulk counterparts. However, the synthesis of 2D TMOs commonly includes the use of environmental threats such as organic solvents. In this thesis, we developed environmentally friendly strategies to fabricate TMO nanosheets from the commercially available bulk oxides. In particular, hydrated vanadium pentoxide (V2O5∙nH2O) nanosheets and oxygen deficient molybdenum trioxide (MoO3-x) nanosheets were prepared.  The V2O5∙nH2O nanosheets were drop-cast onto multi-walled carbon nanotube (MWCNT) paper and applied as a free-standing electrode (FSE) for a lithium battery. The accessible capacity of the FSE was dependent on the electrode thickness; the thickest electrode delivered the lowest accessible capacity.  Alternatively, a composite material of V2O5∙nH2O nanosheets with 10% MWCNT (VOx-CNT composite) was prepared and two types of electrodes, FSE and conventionally cast electrode (CCE), were employed as cathode materials for lithium batteries. A detailed comparison between these electrodes was presented. In addition, the VOx-CNT composite was applied as a negative electrode for a sodium-ion battery and showed a reversible capacity of about 140 mAh g-1. On the other hand, the MoO3-x nanosheets were employed as binder-free electrodes for supercapacitor application in an acidified Na2SO4 electrolyte. Furthermore, the MoO3-x nanosheets were used as photocatalysts for organic dye degradation. The simple eco-friendly synthesis methods coupled with the potential application of the TMO nanosheets reflect the significance of this thesis in both the synthesis and the energy-related applications of 2D materials.

  • 4.
    Colbin, Lars Olow Simon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hall, Charles Aram
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Etman, Ahmed S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. RISE Res Inst Sweden, Drottning Kristinas väg 61, S-11428 Stockholm, Sweden.
    Buckel, Alexander
    Altris AB, Kungsgatan 70b, S-75318 Uppsala, Sweden.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Anodic dissolution of aluminum in non-aqueous electrolyte solutions for sodium-ion batteries2024In: Energy Advances, E-ISSN 2753-1457, Vol. 3, no 1, p. 143-148Article in journal (Refereed)
    Abstract [en]

    Anodic dissolution of aluminum (commonly called aluminum corrosion) is a potential issue in sodium-ion batteries. Herein, it is demonstrated how different sodium-ion battery electrolyte solutions affect this phenomenon. The type of electrolyte was critical for the presence of anodic dissolution, while the solvent appeared to alter the dissolution process.

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  • 5.
    Etman, Ahmed S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Materials Design Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Halim, Joseph
    Materials Design Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Lind, Hans
    Materials Design Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Dorri, Megan
    Materials Design Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Palisaitis, Justinas
    Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Lu, Jun
    Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Hultman, Lars
    Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Persson, Per O. Å.
    Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Rosen, Johanna
    Materials Design Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden.
    Computationally Driven Discovery of Quaternary Tantalum-Based MAB-Phases: Ta4M″SiB2 (M″ = V, Cr, or Mo): Synthesis, Characterization, and Elastic Properties2023In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 23, no 6, p. 4442-4447Article in journal (Refereed)
  • 6.
    Nyholm, Leif
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ericson, Tove
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Etman, Ahmed S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Univ Alexandria, Fac Sci, Dept Chem, Alexandria 21321, Egypt.
    Revisiting the stability of aluminum current collectors in carbonate electrolytes for High-Voltage Li-ion batteries2023In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 282, article id 119346Article in journal (Refereed)
    Abstract [en]

    Anodic dissolution (often referred to as corrosion) of the aluminum positive electrode current collector above 3 V vs. Li+/Li can become performance-limiting in high-voltage Li-ion batteries. Herein, the results of a systematic reevaluation of this phenomenon at potentials up to 5.0 V vs. Li+/Li, using different carbonate electrolytes containing LiPF6, LiFSI or LiTFSI, are presented. The anodic dissolution is most likely caused by etching of the Al2O3 passive layer by protons released during the oxidation of the solvent. This sparks off a second oxidation step, involving the oxidation of the aluminum. While a passive AlF3 layer is formed in 1.0 M LiPF6, extensive anodic dissolution of aluminum is seen in 1.0 M LiFSI or LiTFSI at potentials where the solvent undergoes oxidation. In 5.0 M LiFSI, a passive layer of AlF3 is, however, formed most likely due to the presence of fluoride as an impurity in the LiFSI. No significant improvement was seen when using carbon-coated aluminum electrodes.

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  • 7.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Lind, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Dorri, Megan
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Computationally Driven Discovery of Quaternary Tantalum-Based MAB-Phases: Ta4M & DPRIME;SiB2 (M & DPRIME; = V, Cr, or Mo): Synthesis, Characterization, and Elastic Properties2023In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 23, no 6, p. 4442-4447Article in journal (Refereed)
    Abstract [en]

    Out-of-plane chemically ordered transitionmetal boride(o-MAB) phases, Ta4M & DPRIME;SiB2 (M & DPRIME; = V, Cr), and a structurally equivalent disordered solidsolution MAB phase, Ta4MoSiB2, are synthesized.DFT calculations are used to examine the dynamic stability, elasticproperties, and electronic density states of the MAB phases. We report on the synthesis of computationally predictedout-of-planechemically ordered transition metal borides labeled o-MAB phases, Ta4M & DPRIME;SiB2 (M & DPRIME; =V, Cr), and a structurally equivalent disordered solid solution MABphase Ta4MoSiB2. The boride phases were preparedusing solid-state reaction sintering of the constituting elements.High-resolution scanning transmission electron microscopy along withRietveld refinement of the powder-X-ray diffraction patterns revealedthat the synthesized o-MAB phases Ta4CrSiB2 (98 wt % purity) and Ta4VSiB2 (81 wt% purity) possess chemical ordering with Ta preferentially residingin the 16l position and Cr and V in the 4c position, whereas Ta4MoSiB2 (46wt % purity) was concluded to form a disordered solid solution. Densityfunctional theory (DFT) calculations were used to investigate thedynamic stability, elastic properties, and electronic density statesfor the MAB phases, confirming the stability and suggesting the boridesbased on Cr and Mo to be stiffer than those based on V and Nb.

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  • 8. Etman, Ahmed S.
    et al.
    Zhou, Jie
    Rosen, Johanna
    Ti1.1V0.7Cr Nb1.0Ta0.6C3T high-entropy MXene freestanding films for charge storage applications2022In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 137, p. 107264-107264, article id 107264Article in journal (Refereed)
  • 9. El-Ghazaly, Ahmed
    et al.
    Halim, Joseph
    Ahmed, Bilal
    Etman, Ahmed S.
    Rosen, Johanna
    Exploring the electrochemical behavior of Mo1.33CTz MXene in aqueous sulfates electrolytes: Effect of intercalating cations on the stored charge2022In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 531, p. 231302-231302, article id 231302Article in journal (Refereed)
  • 10.
    El-Ghazaly, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Ahmed, Bilal
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Etman, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Exploring the electrochemical behavior of Mo1.33CTz MXene in aqueous sulfates electrolytes: Effect of intercalating cations on the stored charge2022In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 531, article id 231302Article in journal (Refereed)
    Abstract [en]

    MXenes have been introduced as a high energy and power density electrochemical supercapacitor material owing to their high specific capacitance and electrochemical stability. The operating potential window and, in turn, energy density of MXene based symmetric and asymmetric supercapacitors can be effectively enhanced by the proper choice of aqueous electrolyte. Herein, we investigate the electrochemical behavior of vacancy-containing 𝑖-MXene (Mo1.33CTz) in sulfate based aqueous electrolytes with univalent (Li+, Na+, or K+) or divalent (Mg2+, Mn2+, or Zn2+) cations. The results show that the Mo1.33CTz MXene electrodes can be operated in a potential window higher than 1 V without degradation in these sulfate electrolytes. The Mo1.33CTz MXene electrodes deliver a high volumetric capacitance up to ~677 F cm-3 as measured in 1.0 M MnSO4 solution. Furthermore, symmetric (Mo1.33CTz//Mo1.33CTz) and asymmetric (Mo1.33CTz//nitrogen-doped activated carbon (NAC)) devices in 0.5 M K2SO4 solution can be operated with a cell voltage of about 1.1 V and 1.8 V, respectively. The asymmetric devices retain about 97% of their initial capacitance after 5000 charge/discharge cycles. Overall, the results reveal that the choice of the intercalating cations is a viable route to boost the performance of Mo1.33CTz MXene and to construct energy storage devices.

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  • 11.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering. Alexandria Univ, Egypt.
    Zhou, Jie
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Ti1.1V0.7CrxNb1.0Ta0.6C3Tz high-entropy MXene freestanding films for charge storage applications2022In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 137, article id 107264Article in journal (Refereed)
    Abstract [en]

    High-entropy (HE) MXenes are a new emerging class of materials with unique properties, diverse compositions, and potential uses in energy storage devices. Herein, high-entropy MXene, Ti1.1V0.7CrxNb1.0Ta0.6C3Tz (Tz = -F, -O, -OH), freestanding films are prepared and tested as electrodes for Zn-ion hybrid supercapacitors (ZHSC), delivering a capacity up to 77 mAh g-1 (245 mAh cm-3) at 0.5 A g-1 with a capacity retention of 87% after 10,000 cycles. This promising performance in ZHSC is achieved when using Zn(CF3SO3)2 or low-cost ZnCl2 solutions. Furthermore, HE MXene films can be used as a negative electrode for Li-ion batteries with a capacity up to 126 mAh g-1 (400 mAh cm-3) at 0.01 A g-1. This report sheds light on the use of a new class of MXene films for various charge storage applications.

  • 12.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering. Alexandria Univ, Egypt.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    MXene-based Zn-ion hybrid supercapacitors: Effects of anion carriers and MXene surface coatings on the capacities and life span2022In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 52, article id 104823Article in journal (Refereed)
    Abstract [en]

    Energy storage devices such as rechargeable batteries and supercapacitors are of great importance for establishing clean energy sources. Accordingly, the production of these devices needs to rely on sustainable and environmentally friendly materials. This report provides an insight on the use of two-dimensional transition metal carbides (MXene) based electrodes, here shown for Mo(1.33)CTz-Ti3C2Tz mixed MXene, in Zn-ion hybrid supercapacitors (ZHSC) using aqueous and nonaqueous (acetonitrile-based) electrolytes. The effect of anion carriers on the accessible capacity, rate capability, and life span of the MXene//Zn hybrid supercapacitor is explored in-depth. Halide carriers such as chloride (Cl-) and iodide (I-) feature a superior performance, however, a fast passivation is observed in Cl- based electrolytes and a narrow potential window is achieved in I based electrolytes. Importantly, a few micron layer of Ti3C2Tz MXene coated on the surface of the Zn anode is found to inhibit the side reactions and passivation observed in ZnCl2 solutions, which enables the use of such low-cost Zn salt in MXene//Ti3C2Tz -coated-Zn cells. The cells can be reversibly cycled over 10,000 cycles, delivering a capacity up to 200 mAh g(-1 )at low rate (0.5 mV s(-1)) and a capacity retention of about 36% at high rate (100 mV s(-1)). Furthermore, the Ti3C2Tz surface coating layer enhanced the coulombic efficiency in Zn (CF3SO3)(2) electrolyte without affecting the accessible capacity or the rate capability. This work sheds light on the use of MXenes in sustainable low-cost ZHSC with high energy density and power density as a positive electrode material as well as a surface coating material for the Zn negative electrode.

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  • 13. Etman, Ahmed
    et al.
    Halim, Joseph
    Rosen, Johanna
    MXene-based Zn-ion hybrid supercapacitors: Effects of anion carriers and MXene surface coatings on the capacities and life span2022In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 52, p. 104823-104823, article id 104823Article in journal (Refereed)
    Abstract [en]

    Energy storage devices such as rechargeable batteries and supercapacitors are of great importance for establishing clean energy sources. Accordingly, the production of these devices needs to rely on sustainable and environmentally friendly materials. This report provides an insight on the use of two-dimensional transition metal carbides (MXene) based electrodes, here shown for Mo1.33CTz-Ti3C2Tz mixed MXene, in Zn-ion hybrid supercapacitors (ZHSC) using aqueous and nonaqueous (acetonitrile-based) electrolytes. The effect of anion carriers on the accessible capacity, rate capability, and life span of the MXene//Zn hybrid supercapacitor is explored in-depth. Halide carriers such as chloride (Cl−) and iodide (I−) feature a superior performance, however, a fast passivation is observed in Cl− based electrolytes and a narrow potential window is achieved in I− based electrolytes. Importantly, a few micron layer of Ti3C2Tz MXene coated on the surface of the Zn anode is found to inhibit the side reactions and passivation observed in ZnCl2 solutions, which enables the use of such low-cost Zn salt in MXene//Ti3C2Tz-coated-Zn cells. The cells can be reversibly cycled over 10,000 cycles, delivering a capacity up to 200 mAh g−1 at low rate (0.5 mV s−1) and a capacity retention of about 36% at high rate (100 mV s−1). Furthermore, the Ti3C2Tz surface coating layer enhanced the coulombic efficiency in Zn(CF3SO3)2 electrolyte without affecting the accessible capacity or the rate capability. This work sheds light on the use of MXenes in sustainable low-cost ZHSC with high energy density and power density as a positive electrode material as well as a surface coating material for the Zn negative electrode.

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  • 14.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mixed MXenes: Mo1.33CTz and Ti3C2Tz freestanding composite films for energy storage2021In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 88, article id 106271Article in journal (Refereed)
    Abstract [en]

    MXenes are a class of 2D materials with outstanding properties, including high electronic conductivity, hydrophilicity, and high specific capacitance. In particular, Mo1.33CTz MXene has a high specific capacitance, whereas films of Ti3C2Tz MXene possess high flexibility and high electronic conductivity. The fabrication of composite materials based on these two MXenes is therefore motivated, taking advantage of combining their good properties. In this article, we introduce a one-step approach to prepare composite MXene films using pristine Mo1.33CTz and Ti3C2Tz MXenes. The composite films display superior flexibility and electronic conductivity, as well as high capacitance, up to 1380 F cm(-3) (460 F g(-1)), in 1 M H2SO4. A capacitance retention of 96% is obtained after 17,000 cycles. In addition, the capacitance retentions are about 56% and 25% at scan rates of 200 mV s(-1) and 1000 mV s(-1), respectively. A significant rise in the capacitance at high rates, 875 F cm(-3) (282 F g(-1)) at a current density of 20 A g(-1), is achieved by using a 3 M H2SO4 solution. The use of composite MXene as negative electrodes for asymmetric supercapacitor devices, as well as lithium-ion batteries, is also discussed. This work suggests new pathways for the use of MXene composites with double transition metals (Mo and Ti) in energy storage devices.

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  • 15.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mo1.33CTz-Ti3C2Tz mixed MXene freestanding films for zinc-ion hybrid supercapacitors2021In: Materials Today Energy, ISSN 2468-6069, Vol. 22, article id 100878Article in journal (Refereed)
    Abstract [en]

    The high demand on fast rechargeable batteries and supercapacitors combined with the limited resources of their active materials (e.g. Li and Co) motivate the exploration of sustainable energy storage systems such as Zn-ion hybrid supercapacitors. MXenes are two-dimensional materials with outstanding properties such as high conductivity and capacitance which enhance their performance in energy storage devices. Herein, we report on the use of freestanding Mo(1.33)CTz-Ti3C2Tz mixed MXene films in Zn-ion hybrid supercapacitors. The mixed MXene films are prepared from pristine MXene suspensions using a one-step vacuum filtration approach. The mixed MXene delivers capacities of about 159 and 59 mAh/g at scan rates of 0.5 and 100 mV/s, respectively. These capacity values are higher than the pristine MXene films and previously reported values for MXene electrodes in Zn-ion supercapacitors. Furthermore, the electrodes offer a promising capacity retention of about 90% after 8,000 cycles. In addition, the mixed MXene features energy densities of about 103 and 38 Wh/kg at power densities of 0.143 and 10.6 kW/kg, respectively. Insights into the effect of electrode thickness on rate performance and the mechanism of charge storage are also discussed. This study opens a venue for the use of Mo(1.33)CTz-Ti3C2Tz mixed MXene electrodes in sustainable energy storage systems with high energy density and power density. (C) 2021 The Author(s). Published by Elsevier Ltd.

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  • 16.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Fabrication of Mo1.33CTz (MXene)-cellulose freestanding electrodes for supercapacitor applications2021In: Materials Advances, E-ISSN 2633-5409, Vol. 2, no 2, p. 743-753Article in journal (Refereed)
    Abstract [en]

    MXenes are two-dimensional (2D) transition metal carbides/nitrides with high potential for energy storage devices owing to their high flexibility, conductivity and specific capacitance. However, MXene films tend to suffer from diffusion limitation of ions within the film, and thus their thickness is commonly reduced to a few micrometers (mass loadings <1 mg cm(-2)). Herein, a straightforward one-step protocol for synthesizing freestanding Mo1.33CTz-cellulose composite electrodes with high MXene loading is reported. By varying the amount of the cellulose content, a high gravimetric capacitance (up to 440 F g(-1) for 45 wt% cellulose content, <similar to>5.9 mu m thick film) and volumetric capacitance (up to 1178 F cm(-3) for 5 wt% cellulose content, similar to 4.8 mu m thick film) is achieved. These capacitance values are superior to those for the pristine MXene film, of a similar MXene loading (1.56 mg cm(-2), similar to 4.2 mu m thick film), delivering values of about 272 F g(-1) and 1032 F cm(-3). Interestingly, the Mo1.33CTz-cellulose composite electrodes display an outstanding capacitance retention (similar to 95%) after 30000 cycles, which is better than those reported for other Mo1.33CTz-based electrodes. Furthermore, the presence of cellulose inside a thick composite electrode (similar to 26 mu m, MXene loading 5.2 mg cm(-2)) offers a novel approach for opening the structure during electrochemical cycling, with resulting high areal capacitance of about 1.4 F cm(-2). A symmetric device of Mo1.33CTz-cellulose electrodes featured a long lifespan of about 35000 cycles and delivered a device capacitance up to 95 F g(-1). The superior performance of the Mo1.33CTz-cellulose electrodes in terms of high gravimetric, volumetric, and areal capacitances, long lifespan, and promising rate capability, paves the way for their use in energy storage devices.

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  • 17.
    Zheng, Wei
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Halim, Joseph
    Linköpings universitet, Tunnfilmsfysik.
    Etman, Ahmed
    Linköpings universitet, Tunnfilmsfysik.
    El Ghazaly, Ahmed
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Barsoum, Michel
    Linköpings universitet, Tunnfilmsfysik; Drexel University.
    Boosting the volumetric capacitance of MoO3-x free-standing films with Ti3C2 MXene2021In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 370, article id 137665Article in journal (Refereed)
    Abstract [en]

    The high theoretical capacitance of molybdenum trioxide (MoO3) renders it an attractive supercapacitor electrode material. However, its low electronic conductivity restricts charge transfer and slows its reaction kinetics. Herein, we vacuum filtered porous, free-standing, flexible and highly conductive films comprised of oxygen vacancy-rich MoO3-x nanobelts and delaminated Ti3C2 MXene in a mass ratio of 80:20, respectively. When tested as supercapacitor electrodes, in a 5 M LiCl electrolyte, volumetric capacitances of 631 F cm−3 at 1 A g−1, and 474 F cm−3 at 10 A g−1 were obtained. To increase the energy density, asymmetric supercapacitors, wherein the anodes were MoO3-based and the cathodes were nitrogen-doped activated carbon were assembled and tested. The resulting volumetric energy density was 48.6 Wh L−1. After 20,000 continuous charge/discharge cycles at 20 A g−1, 96.3 % of the initial charge remained. These values are outstanding for free-standing supercapacitor electrodes, especially in aqueous electrolytes.

  • 18.
    Etman, Ahmed
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Halim, Joseph
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Mixed MXenes: Mo1.33CTz and Ti3C2Tz freestanding composite films for energy storage2021In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 88, article id 106271Article in journal (Refereed)
    Abstract [en]

    MXenes are a class of 2D materials with outstanding properties, including high electronic conductivity, hydrophilicity, and high specific capacitance. In particular, Mo1.33CTz MXene has a high specific capacitance, whereas films of Ti3C2Tz MXene possess high flexibility and high electronic conductivity. The fabrication of composite materials based on these two MXenes is therefore motivated, taking advantage of combining their good properties. In this article, we introduce a one-step approach to prepare composite MXene films using pristine Mo1.33CTz and Ti3C2Tz MXenes. The composite films display superior flexibility and electronic conductivity, as well as high capacitance, up to 1380 F cm−3 (460 F g−1), in 1 M H2SO4. A capacitance retention of 96% is obtained after 17,000 cycles. In addition, the capacitance retentions are about 56% and 25% at scan rates of 200 mV s−1 and 1000 mV s−1, respectively. A significant rise in the capacitance at high rates, 875 F cm−3 (282 F g−1) at a current density of 20 A g−1, is achieved by using a 3 M H2SO4 solution. The use of composite MXene as negative electrodes for asymmetric supercapacitor devices, as well as lithium-ion batteries, is also discussed. This work suggests new pathways for the use of MXene composites with double transition metals (Mo and Ti) in energy storage devices.

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  • 19.
    Etman, Ahmed
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Halim, Joseph
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Fabrication of Mo1.33CTz (MXene)-cellulose freestanding electrodes for supercapacitor applications2021In: Materials Advances, E-ISSN 2633-5409, Vol. 2, no 2, p. 743-753Article in journal (Refereed)
    Abstract [en]

    MXenes are two-dimensional (2D) transition metal carbides/nitrides with high potential for energy storage devices owing to their high flexibility, conductivity and specific capacitance. However, MXene films tend to suffer from diffusion limitation of ions within the film, and thus their thickness is commonly reduced to a few micrometers (mass loadings <1 mg cm−2). Herein, a straightforward one-step protocol for synthesizing freestanding Mo1.33CTz–cellulose composite electrodes with high MXene loading is reported. By varying the amount of the cellulose content, a high gravimetric capacitance (up to 440 F g−1 for 45 wt% cellulose content, ∼5.9 μm thick film) and volumetric capacitance (up to 1178 F cm−3 for 5 wt% cellulose content, ∼4.8 μm thick film) is achieved. These capacitance values are superior to those for the pristine MXene film, of a similar MXene loading (1.56 mg cm−2, ∼4.2 μm thick film), delivering values of about 272 F g−1 and 1032 F cm−3. Interestingly, the Mo1.33CTz–cellulose composite electrodes display an outstanding capacitance retention (∼95%) after 30 000 cycles, which is better than those reported for other Mo1.33CTz-based electrodes. Furthermore, the presence of cellulose inside a thick composite electrode (∼26 μm, MXene loading 5.2 mg cm−2) offers a novel approach for opening the structure during electrochemical cycling, with resulting high areal capacitance of about 1.4 F cm−2. A symmetric device of Mo1.33CTz–cellulose electrodes featured a long lifespan of about 35 000 cycles and delivered a device capacitance up to 95 F g−1. The superior performance of the Mo1.33CTz–cellulose electrodes in terms of high gravimetric, volumetric, and areal capacitances, long lifespan, and promising rate capability, paves the way for their use in energy storage devices.

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    FULLTEXT01
  • 20.
    Halim, Joseph
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Etman, Ahmed S.
    Linköpings universitet, Tunnfilmsfysik.
    Elsukova, Anna
    Linköpings universitet, Tunnfilmsfysik.
    Polcik, Peter
    Plansee Composite Mat GmbH, Germany.
    Palisaitis, Justinas
    Linköpings universitet, Tunnfilmsfysik.
    Barsoum, Michel W.
    Linköpings universitet, Tunnfilmsfysik.
    Persson, Per O. Å.
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Tailored synthesis approach of (Mo2/3Y1/3)2AlC i-MAX and its two-dimensional derivative Mo1.33CTz MXene: enhancing the yield, quality, and performance in supercapacitor applications2021In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 13, no 1, p. 311-319Article in journal (Refereed)
    Abstract [en]

    A vacancy-ordered MXene, Mo1.33CTz, obtained from the selective etching of Al and Sc from the parent i-MAX phase (Mo2/3Sc1/3)2AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (Mo2/3Y1/3)2AlC, have not been able to match its forerunner. Herein, we show that the use of an AlY2.3 alloy instead of elemental Al and Y for the synthesis of (Mo2/3Y1/3)2AlC i-MAX, results in a close to 70% increase in sample purity due to the suppression of the main secondary phase, Mo3Al2C. Furthermore, through a modified etching procedure, we obtain a Mo1.33CTz MXene of high structural quality and improve the yield by a factor of 6 compared to our previous efforts. Free-standing films show high volumetric (1308 F cm−3) and gravimetric (436 F g−1) capacitances and a high stability (98% retention) at the level of, or even beyond, those reported for the Mo1.33CTz MXene produced from the Sc-based i-MAX. These results are of importance for the realization of high quality MXenes through use of more abundant elements (Y vs. Sc), while also reducing waste (impurity) material and facilitating the synthesis of a high-performance material for applications.

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    FULLTEXT01
  • 21.
    Etman, Ahmed S.
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Halim, Joseph
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Mo1.33CTz-Ti3C2Tz mixed MXene freestanding films for zinc-ion hybrid supercapacitors2021In: Materials Today Energy, ISSN 2468-6069, Vol. 22, article id 100878Article in journal (Refereed)
    Abstract [en]

    The high demand on fast rechargeable batteries and supercapacitors combined with the limited resources of their active materials (e.g. Li and Co) motivate the exploration of sustainable energy storage systems such as Zn-ion hybrid supercapacitors. MXenes are two-dimensional materials with outstanding properties such as high conductivity and capacitance which enhance their performance in energy storage devices. Herein, we report on the use of freestanding Mo1.33CTz–Ti3C2Tz mixed MXene films in Zn-ion hybrid supercapacitors. The mixed MXene films are prepared from pristine MXene suspensions using a one-step vacuum filtration approach. The mixed MXene delivers capacities of about 159 and 59 mAh/g at scan rates of 0.5 and 100 mV/s, respectively. These capacity values are higher than the pristine MXene films and previously reported values for MXene electrodes in Zn-ion supercapacitors. Furthermore, the electrodes offer a promising capacity retention of about 90% after 8,000 cycles. In addition, the mixed MXene features energy densities of about 103 and 38 Wh/kg at power densities of 0.143 and 10.6 kW/kg, respectively. Insights into the effect of electrode thickness on rate performance and the mechanism of charge storage are also discussed. This study opens a venue for the use of Mo1.33CTz–Ti3C2Tz mixed MXene electrodes in sustainable energy storage systems with high energy density and power density.

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    fulltext
  • 22.
    Zheng, Wei
    et al.
    Linköpings universitet, Tunnfilmsfysik.
    Halim, Joseph
    Linköpings universitet, Tunnfilmsfysik.
    El Ghazaly, Ahmed
    Linköpings universitet, Tunnfilmsfysik.
    Etman, Ahmed S.
    Linköpings universitet, Tunnfilmsfysik.
    Tseng, Eric Nestor
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Persson, Per O. Å.
    Linköpings universitet, Tunnfilmsfysik.
    Rosén, Johanna
    Linköpings universitet, Tunnfilmsfysik.
    Barsoum, Michel
    Linköpings universitet, Tunnfilmsfysik; Drexel University.
    Flexible Free-Standing MoO3/Ti3C2Tz MXene Composite Films with High Gravimetric and Volumetric Capacities2021In: Advanced Science, E-ISSN 2198-3844, Vol. 8, no 3, article id 2003656Article in journal (Refereed)
    Abstract [en]

    Enhancing both the energy storage and power capabilities of electrochemical capacitors remains a challenge. Herein, Ti3C2Tz MXene is mixed with MoO3 nanobelts in various mass ratios and the mixture is used to vacuum filter binder free, open, flexible, and free-standing films. The conductive Ti3C2Tz flakes bridge the nanobelts, facilitating electron transfer; the randomly oriented, and interconnected, MoO3 nanobelts, in turn, prevent the restacking of the Ti3C2Tz nanosheets. Benefitting from these advantages, a MoO3/Ti3C2Tz film with a 8:2 mass ratio exhibits high gravimetric/volumetric capacities with good cyclability, namely, 837 C g−1 and 1836 C cm−3 at 1 A g−1 for an ≈ 10 µm thick film; and 767 C g−1 and 1664 C cm−3 at 1 A g−1 for ≈ 50 µm thick film. To further increase the energy density, hybrid capacitors are fabricated with MoO3/Ti3C2Tz films as the negative electrodes and nitrogen-doped activated carbon as the positive electrodes. This device delivers maximum gravimetric/volumetric energy densities of 31.2 Wh kg−1 and 39.2 Wh L−1, respectively. The cycling stability of 94.2% retention ratio after 10 000 continuous charge/discharge cycles is also noteworthy. The high energy density achieved in this work can pave the way for practical applications of MXene-containing materials in energy storage devices.

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    FULLTEXT01
  • 23.
    Zheng, Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    El Ghazaly, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Etman, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tseng, Eric Nestor
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel Univ, PA 19104 USA.
    Flexible Free-Standing MoO3/Ti3C2Tz MXene Composite Films with High Gravimetric and Volumetric Capacities2021In: Advanced Science, E-ISSN 2198-3844, Vol. 8, article id 2003656Article in journal (Refereed)
    Abstract [en]

    Enhancing both the energy storage and power capabilities of electrochemical capacitors remains a challenge. Herein, Ti3C2Tz MXene is mixed with MoO3 nanobelts in various mass ratios and the mixture is used to vacuum filter binder free, open, flexible, and free-standing films. The conductive Ti3C2Tz flakes bridge the nanobelts, facilitating electron transfer; the randomly oriented, and interconnected, MoO3 nanobelts, in turn, prevent the restacking of the Ti3C2Tz nanosheets. Benefitting from these advantages, a MoO3/Ti3C2Tz film with a 8:2 mass ratio exhibits high gravimetric/volumetric capacities with good cyclability, namely, 837 C g(-1) and 1836 C cm(-3) at 1 A g(-1) for an approximate to 10 mu m thick film; and 767 C g(-1) and 1664 C cm(-3) at 1 A g(-1) for approximate to 50 mu m thick film. To further increase the energy density, hybrid capacitors are fabricated with MoO3/Ti3C2Tz films as the negative electrodes and nitrogen-doped activated carbon as the positive electrodes. This device delivers maximum gravimetric/volumetric energy densities of 31.2 Wh kg(-1) and 39.2 Wh L-1, respectively. The cycling stability of 94.2% retention ratio after 10 000 continuous charge/discharge cycles is also noteworthy. The high energy density achieved in this work can pave the way for practical applications of MXene-containing materials in energy storage devices.

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    fulltext
  • 24.
    Halim, Joseph
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Etman, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Polcik, Peter
    Plansee Composite Mat GmbH, Germany.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel Univ, PA 19104 USA.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tailored synthesis approach of (Mo2/3Y1/3)(2)AlC i-MAX and its two-dimensional derivative Mo1.33CTz MXene: enhancing the yield, quality, and performance in supercapacitor applications2021In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 13, no 1, p. 311-319Article in journal (Refereed)
    Abstract [en]

    A vacancy-ordered MXene, Mo1.33CTz, obtained from the selective etching of Al and Sc from the parent i-MAX phase (Mo2/3Sc1/3)(2)AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (Mo2/3Y1/3)(2)AlC, have not been able to match its forerunner. Herein, we show that the use of an AlY2.3 alloy instead of elemental Al and Y for the synthesis of (Mo2/3Y1/3)(2)AlC i-MAX, results in a close to 70% increase in sample purity due to the suppression of the main secondary phase, Mo3Al2C. Furthermore, through a modified etching procedure, we obtain a Mo1.33CTz MXene of high structural quality and improve the yield by a factor of 6 compared to our previous efforts. Free-standing films show high volumetric (1308 F cm(-3)) and gravimetric (436 F g(-1)) capacitances and a high stability (98% retention) at the level of, or even beyond, those reported for the Mo1.33CTz MXene produced from the Sc-based i-MAX. These results are of importance for the realization of high quality MXenes through use of more abundant elements (Y vs. Sc), while also reducing waste (impurity) material and facilitating the synthesis of a high-performance material for applications.

    Download full text (pdf)
    fulltext
  • 25.
    Zheng, Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Etman, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    El Ghazaly, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel Univ, PA 19104 USA.
    Boosting the volumetric capacitance of MoO3-x free-standing films with Ti3C2 MXene2021In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 370, article id 137665Article in journal (Refereed)
    Abstract [en]

    The high theoretical capacitance of molybdenum trioxide (MoO3) renders it an attractive supercapacitor electrode material. However, its low electronic conductivity restricts charge transfer and slows its reaction kinetics. Herein, we vacuum filtered porous, free-standing, flexible and highly conductive films comprised of oxygen vacancy-rich MoO3-x nanobelts and delaminated Ti3C2 MXene in a mass ratio of 80:20, respectively. When tested as supercapacitor electrodes, in a 5 M LiCl electrolyte, volumetric capacitances of 631 F cm(-3) at 1 A g(-1), and 474 F cm(-3) at 10 A g(-1) were obtained. To increase the energy density, asymmetric supercapacitors, wherein the anodes were MoO3-based and the cathodes were nitrogen-doped activated carbon were assembled and tested. The resulting volumetric energy density was 48.6 Wh L-1. After 20,000 continuous charge/discharge cycles at 20 A g(-1), 96.3 % of the initial charge remained. These values are outstanding for free-standing supercapacitor electrodes, especially in aqueous electrolytes. (C) 2020 ElsevierLtd. Allrights reserved.

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  • 26.
    Etman, Ahmed S.
    et al.
    Linköping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden.;Alexandria Univ, Dept Chem, Fac Sci, Alexandria 21321, Egypt..
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Peoples R China..
    Yuan, Youyou
    Peking Univ, Coll Chem & Mol Engn, Yiheyuan Rd 5, Beijing 100871, Peoples R China..
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rosen, Johanna
    Linköping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden..
    On the Capacities of Freestanding Vanadium Pentoxide-Carbon Nanotube-Nanocellulose Paper Electrodes for Charge Storage Applications2020In: ENERGY TECHNOLOGY, ISSN 2194-4288, Vol. 8, no 12, article id 2000731Article in journal (Refereed)
    Abstract [en]

    Herein, a one-step protocol for synthesizing freestanding 20 mu m thick cellulose paper electrodes composed of V2O5 . H2O nanosheets (VOx), carbon nanotubes (CNTs), and Cladophora cellulose (CC) is reported. In 1.0 m Na2SO4, the VOx-CNT-CC electrodes deliver capacities of about 200 and 50 C g(-1) at scan rates of 20 and 500 mV s(-1), respectively. The obtained capacities are compared with the theoretical capacities and are discussed based on the electrochemical reactions and the mass loadings of the electrodes. It is shown that the capacities are diffusion rate limited and, consequently, depend on the distribution and thickness of the V2O5 . H2O nanosheets, whereas the long-term cycling stabilities depend on vanadium species dissolving in the electrolyte. The electrodes feature high mass loadings (2 mg cm(-2)), good rate performances (25% capacity retention at 500 mV s(-1)), and capacity retentions of 85% after 8000 cycles. A symmetric VOx-CNT-CC energy storage device with a potential window of about 1 V exhibits a capacity of 40 C g(-1) at a scan rate of 2 mV s(-1).

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  • 27. Bischak, Connor G.
    et al.
    Lai, Minliang
    Fan, Zhaochuan
    Lu, Dylan
    David, Philippe
    Dong, Dengpan
    Chen, Hong
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Lei, Teng
    Sun, Junliang
    Grünwald, Michael
    Limmer, David T.
    Yang, Peidong
    Ginsberg, Naomi S.
    Liquid-like Interfaces Mediate Structural Phase Transitions in Lead Halide Perovskites2020In: Matter, ISSN 2590-2393, E-ISSN 2590-2385, Vol. 3, no 2, p. 534-545Article in journal (Refereed)
    Abstract [en]

    Microscopic pathways of structural phase transitions inmetal halide perovskites are difficult to probe because they occur over disparate time and length scales and because electron-based microscopies typically used to directly probe nanoscale dynamics of phase transitions often damage metal halide perovskite materials. Using in situ nanoscale cathodoluminescence microscopy with low electron beam exposure, we visualize nucleation and growth in the thermally driven transition to the perovskite phase in hundreds of non-perovskite phase nanowires. In combination with molecular dynamics simulations, we reveal that the transformation does not follow a simple martensitic mechanism, but proceeds despite a substantial energy barrier via ion diffusion through a liquid-like interface between the two structures. While cations are disordered in this liquid-like region, the halide ions retain substantial spatial correlations. This detailed picture not only reveals how phase transitions between disparate structures can proceed, but also opens the possibility to control such processes.

  • 28. Bischak, Connor G.
    et al.
    Lai, Minliang
    Fan, Zhaochuan
    Lu, Dylan
    David, Philippe
    Dong, Dengpan
    Chen, Hong
    Etman, Ahmed S.
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Lei, Teng
    Sun, Junliang
    Grünwald, Michael
    Limmer, David T.
    Yang, Peidong
    Ginsberg, Naomi S.
    Liquid-like Interfaces Mediate Structural Phase Transitions in Lead Halide Perovskites2020In: Matter, ISSN 2590-2393, E-ISSN 2590-2385, Vol. 3, no 2, p. 534-545Article in journal (Refereed)
    Abstract [en]

    Microscopic pathways of structural phase transitions inmetal halide perovskites are difficult to probe because they occur over disparate time and length scales and because electron-based microscopies typically used to directly probe nanoscale dynamics of phase transitions often damage metal halide perovskite materials. Using in situ nanoscale cathodoluminescence microscopy with low electron beam exposure, we visualize nucleation and growth in the thermally driven transition to the perovskite phase in hundreds of non-perovskite phase nanowires. In combination with molecular dynamics simulations, we reveal that the transformation does not follow a simple martensitic mechanism, but proceeds despite a substantial energy barrier via ion diffusion through a liquid-like interface between the two structures. While cations are disordered in this liquid-like region, the halide ions retain substantial spatial correlations. This detailed picture not only reveals how phase transitions between disparate structures can proceed, but also opens the possibility to control such processes.

  • 29.
    Etman, Ahmed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Alexandria Univ, Egypt.
    Wang, Zhaohui
    Uppsala Univ, Sweden; Hunan Univ, Peoples R China.
    Yuan, Youyou
    Peking Univ, Peoples R China.
    Nyholm, Leif
    Uppsala Univ, Sweden.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    On the Capacities of Freestanding Vanadium Pentoxide-Carbon Nanotube-Nanocellulose Paper Electrodes for Charge Storage Applications2020In: ENERGY TECHNOLOGY, ISSN 2194-4288, Vol. 8, no 12, article id 2000731Article in journal (Refereed)
    Abstract [en]

    Herein, a one-step protocol for synthesizing freestanding 20 mu m thick cellulose paper electrodes composed of V2O5 . H2O nanosheets (VOx), carbon nanotubes (CNTs), and Cladophora cellulose (CC) is reported. In 1.0 m Na2SO4, the VOx-CNT-CC electrodes deliver capacities of about 200 and 50 C g(-1) at scan rates of 20 and 500 mV s(-1), respectively. The obtained capacities are compared with the theoretical capacities and are discussed based on the electrochemical reactions and the mass loadings of the electrodes. It is shown that the capacities are diffusion rate limited and, consequently, depend on the distribution and thickness of the V2O5 . H2O nanosheets, whereas the long-term cycling stabilities depend on vanadium species dissolving in the electrolyte. The electrodes feature high mass loadings (2 mg cm(-2)), good rate performances (25% capacity retention at 500 mV s(-1)), and capacity retentions of 85% after 8000 cycles. A symmetric VOx-CNT-CC energy storage device with a potential window of about 1 V exhibits a capacity of 40 C g(-1) at a scan rate of 2 mV s(-1).

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  • 30.
    Etman, Ahmed
    et al.
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden.;Alexandria Univ, Fac Sci, Dept Chem, POB 426, Alexandria 21321, Egypt..
    Carboni, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden.;Peking Univ, Coll Chem & Mol Engn, Yiheyuan Rd 5, Beijing 100871, Peoples R China..
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Acetonitrile-Based Electrolytes for Rechargeable Zinc Batteries2020In: ENERGY TECHNOLOGY, ISSN 2194-4288, Vol. 8, no 9, article id 2000358Article in journal (Refereed)
    Abstract [en]

    Herein, Zn plating-stripping onto metallic Zn using a couple of acetonitrile (AN)-based electrolytes (0.5 mZn(TFSI)(2)/AN and 0.5 mZn(CF3SO3)(2)/AN) is studied. Both electrolytes show a reversible Zn plating/stripping over 1000 cycles at different applied current densities varying from 1.25 to 10 mA cm(-2). The overpotentials of Zn plating-stripping over 500 cycles at constant current of 1.25 and 10 mA cm(-2)are +/- 0.05 and +/- 0.2 V, respectively. X-ray photoelectron spectroscopy analysis reveals that no decomposition product is formed on the Zn surface. The anodic stability of four different current collectors of aluminum foil (Al), carbon-coated aluminum foil (C/Al), TiN-coated titanium foil (TiN/Ti), and multiwalled carbon nanotube paper (MWCNT-paper) is tested in both electrolytes. As a general trend, the current collectors have a higher anodic stability in Zn(TFSI)(2)/AN compared with Zn(CF3SO3)(2)/AN. The Al foil displays the highest anodic stability of approximate to 2.25 V versus Zn2+/Zn in Zn(TFSI)(2)/AN electrolyte. The TiN/Ti shows a comparable anodic stability with that of Al foil, but its anodic current density is higher than Al. The promising reversibility of the Zn plating/stripping combined with the anodic stability of Al and TiN/Ti current collectors paves the way for establishing highly reversible Zn-ion batteries.

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  • 31.
    Huang, Jing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. KTH Royal Inst Technol, Sch Engn Sci, Dept Appl Phys, Stockholm, Sweden.
    Xu, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pati, Palas Baran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Etman, Ahmed S.
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden.
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 55, p. 7918-7921Article in journal (Refereed)
    Abstract [en]

    Heavy metal-free CuInS2 quantum dots (QDs) were employed as a photosensitizer on a NiO photocathode to drive an immobilized molecular Re catalyst for photoelectrochemical CO2 reduction for the first time. A photocurrent of 25 mu A cm(-2) at -0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

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  • 32.
    Etman, Ahmed S.
    et al.
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden;Alexandria Univ, Fac Sci, Dept Chem, Alexandria 21321, Egypt;Linkoping Univ, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Pell, Andrew J.
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hedin, Niklas
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Zou, Xiaodong
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden;Peking Univ, Coll Chem & Mol Engn, Beijing 100871, Peoples R China.
    Bernin, Diana
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden;Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.
    Insights into the Exfoliation Process of V2O5 center dot nH(2)O Nanosheet Formation Using Real-Time V-51 NMR2019In: ACS Omega, E-ISSN 2470-1343, Vol. 4, no 6, p. 10899-10905Article in journal (Refereed)
    Abstract [en]

    Nanostructured hydrated vanadium oxides (V2O5 center dot nH(2)O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V2O5 center dot nH(2)O nano-sheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V2O5 center dot nH(2)O nanosheets from the V2O5 and VO2 precursors in real using solution- and solid-state V-51 NMR. Solution-state V-51 NMR showed that the aqueous solution contained mostly the decavanadate anion [H2V10O28](4-) and the hydrated dioxova-nadate cation [VO2 center dot 4H(2)O](+), and during the exfoliation process, decavanadate was formed, while the amount of [VO2 center dot 4H(2)O](+) remained constant. The conversion of the solid precursor V2O5, which was monitored with solid-state V-51 NMR, was initiated when VO2 was in its monoclinic forms. The dried V2O5 center dot nH(2)O nanosheets were weakly paramagnetic because of a minor content of isolated V4+. Its solid-state V-51 signal was less than 20% of V2O5 and arose from diamagnetic V4+ or V5+.This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials.

  • 33.
    Etman, Ahmed S.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Alexandria Univ, Egypt.
    Wang, Zhaohui
    Uppsala Univ, Sweden.
    El Ghazaly, Ahmed
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sun, Junliang
    Peking Univ, Peoples R China.
    Nyholm, Leif
    Uppsala Univ, Sweden.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Flexible Freestanding MoO3-x-Carbon Nanotubes-Nanocellulose Paper Electrodes for Charge-Storage Applications2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 23, p. 5157-5163Article in journal (Refereed)
    Abstract [en]

    Herein, a one-step synthesis protocol was developed for synthesizing freestanding/flexible paper electrodes composed of nanostructured molybdenum oxide (MoO3-x) embedded in a carbon nanotube (CNT) and Cladophora cellulose (CC) matrix. The preparation method involved sonication of the precursors, nanostructured MoO3-x, CNTs, and CC with weight ratios of 7:2:1, in a water/ethanol mixture, followed by vacuum filtration. The electrodes were straightforward to handle and possessed a thickness of approximately 12 mu m and a mass loading of MoO3-x-CNTs of approximately 0.9 mg cm(-2). The elemental mapping showed that the nanostructured MoO3-x was uniformly embedded inside the CNTs-CC matrix. The MoO3-x-CNTs-CC paper electrodes featured a capacity of 30 C g(-1), normalized to the mass of MoO3-x-CNTs, at a current density of 78 A g(-1) (corresponding to a rate of approximately 210 C based on the MoO3 content, assuming a theoretical capacity of 1339 C g(-1)), and exhibited a capacity retention of 91 % over 30 000 cycles. This study paves the way for the manufacturing of flexible/freestanding nanostructured MoO3-x-based electrodes for use in charge-storage devices at high charge/discharge rates.

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  • 34.
    Etman, Ahmed S.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Stockholm Univ, Sweden; Alexandria Univ, Egypt.
    Pell, Andrew J.
    Stockholm Univ, Sweden.
    Svedlindh, Peter
    Uppsala Univ, Sweden.
    Hedin, Niklas
    Stockholm Univ, Sweden.
    Zou, Xiaodong
    Stockholm Univ, Sweden.
    Sun, Junliang
    Stockholm Univ, Sweden; Peking Univ, Peoples R China.
    Bernin, Diana
    Stockholm Univ, Sweden; Chalmers Univ Technol, Sweden.
    Insights into the Exfoliation Process of V2O5 center dot nH(2)O Nanosheet Formation Using Real-Time V-51 NMR2019In: ACS Omega, E-ISSN 2470-1343, Vol. 4, no 6, p. 10899-10905Article in journal (Refereed)
    Abstract [en]

    Nanostructured hydrated vanadium oxides (V2O5 center dot nH(2)O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V2O5 center dot nH(2)O nano-sheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V2O5 center dot nH(2)O nanosheets from the V2O5 and VO2 precursors in real using solution- and solid-state V-51 NMR. Solution-state V-51 NMR showed that the aqueous solution contained mostly the decavanadate anion [H2V10O28](4-) and the hydrated dioxova-nadate cation [VO2 center dot 4H(2)O](+), and during the exfoliation process, decavanadate was formed, while the amount of [VO2 center dot 4H(2)O](+) remained constant. The conversion of the solid precursor V2O5, which was monitored with solid-state V-51 NMR, was initiated when VO2 was in its monoclinic forms. The dried V2O5 center dot nH(2)O nanosheets were weakly paramagnetic because of a minor content of isolated V4+. Its solid-state V-51 signal was less than 20% of V2O5 and arose from diamagnetic V4+ or V5+.This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials.

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  • 35.
    Etman, Ahmed S.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Wang, Ligang
    Edström, Kristina
    Nyholm, Leif
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Molybdenum Oxide Nanosheets with Tunable Plasmonic Resonance: Aqueous Exfoliation Synthesis and Charge Storage Applications2019In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 4, article id 1806699Article in journal (Refereed)
    Abstract [en]

    Herein, a simple aqueous‐exfoliation strategy is introduced for the fabrication of a series of MoO3−x nanosheets (where x stands for oxygen vacancies) using two commercial molybdenum oxide precursors, MoO2 and MoO3. The nanosheets offer a localized surface plasmon resonance (LSPR) effect which is dependent on the structure and local environment of the nanosheets. The LSPR can be efficiently tuned by changing the weight ratio between the molybdenum oxide precursor(s) and/or by solar light irradiation using a low‐energy UV lamp (36 W). For the pristine MoO3−x nanosheets, the highest LSPR signal is obtained for nanosheets prepared using 80% MoO2. On the contrary, after solar light irradiation, the nanosheets prepared using pure MoO3 offer the highest LSPR response. The nanosheets also show an outstanding rate capability when used as binder‐free supercapacitor electrodes in an acidified Na2SO4 electrolyte. The electrodes exhibit discharge capacities of 110 and 75 C g−1 at a scan rate of 20 and 1000 mV s−1, respectively. The MoO3−x nanosheets can likewise be used as a negative electrode material for lithium‐ion batteries. The efficient eco‐friendly synthesis and the ability to tune the photochemical and electrochemical properties of the nanosheets make this approach interesting to many energy‐related research fields.

  • 36. Xu, Bo
    et al.
    Tian, Lei
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Tian, Haining
    Solution-processed nanoporous NiO-dye-ZnO photocathodes: Toward efficient and stable solid-state p-type dye-sensitized solar cells and dye-sensitized photoelectrosynthesis cells2019In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 55, p. 59-64Article in journal (Refereed)
    Abstract [en]

    A solution-processed NiO-dye-ZnO photocathode was developed for applications in both solid-state p-type dye-sensitized solar cells (p-ssDSCs) and p-type dye-sensitized photoelectrosynthesis cells (p-DSPECs). In p-ssDSCs, the solar cell using ZnO as electron transport material showed a short circuit current, up to 680 mu A cm(-2), which is 60-fold larger than that previously reported device using TiO2 as electron transport material with similar architecture. In the p-DSPECs, a remarkable photocurrent of 100 mu A cm(-2) was achieved in a pH = 5.0 acetate buffer solution under a bias potential at 0.05 V vs RHE with platinum as the proton reduction catalyst. A Faradaic efficiency approaching 100% for the H-2 evolution reaction was obtained after photoelectrolysis for 9 h. Importantly, the solution-processed NiO-dye-ZnO photocathode exhibited excellent long-term stability in both p-ssDSCs and p-DSPECs. To the best of our knowledge, this is the first study where a solution-processable, nanoporous NiO-dye-ZnO photocathode is used for both p-ssDSCs and p-DSPECs having both excellent device performance and stability.

  • 37. Lin, Jia
    et al.
    Chen, Hong
    Gao, Yang
    Cai, Yao
    Jin, Jianbo
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kang, Joohoon
    Lei, Teng
    Lin, Zhenni
    Folgueras, Maria C.
    Quan, Li Na
    Kong, Qiao
    Sherburne, Matthew
    Asta, Mark
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Toney, Michael F.
    Wu, Junqiao
    Yang, Peidong
    Pressure-induced semiconductor-to-metal phase transition of a charge-ordered indium halide perovskite2019In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 47, p. 23404-23409Article in journal (Refereed)
    Abstract [en]

    Phase transitions in halide perovskites triggered by external stimuli generate significantly different material properties, providing a great opportunity for broad applications. Here, we demonstrate an In-based, charge-ordered (In+/In3+) inorganic halide perovskite with the composition of Cs2In(I)In(III)Cl-6 in which a pressure-driven semiconductor-to-metal phase transition exists. The single crystals, synthesized via a solid-state reaction method, crystallize in a distorted perovskite structure with space group I4/m with a = 17.2604(12) angstrom, c = 11.0113(16) angstrom if both the strong reflections and superstructures are considered. The supercell was further confirmed by rotation electron diffraction measurement. The pressure-induced semiconductor-to-metal phase transition was demonstrated by high-pressure Raman and absorbance spectroscopies and was consistent with theoretical modeling. This type of charge-ordered inorganic halide perovskite with a pressure-induced semiconductor-to-metal phase transition may inspire a range of potential applications.

  • 38.
    Xu, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Etman, Ahmed S.
    Stockholm Univ, Dept Mat & Environm Chem, Svante Arrhenius Vag 16C, SE-10691 Stockholm, Sweden.
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem, Svante Arrhenius Vag 16C, SE-10691 Stockholm, Sweden;Peking Univ, Beijing Natl Lab Mol Sci, Coll Chem & Mol Engn, Beijing 100871, Peoples R China.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Solution-processed nanoporous NiO-dye-ZnO photocathodes: Toward efficient and stable solid-state p-type dye-sensitized solar cells and dye-sensitized photoelectrosynthesis cells2019In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 55, p. 59-64Article in journal (Refereed)
    Abstract [en]

    A solution-processed NiO-dye-ZnO photocathode was developed for applications in both solid-state p-type dye-sensitized solar cells (p-ssDSCs) and p-type dye-sensitized photoelectrosynthesis cells (p-DSPECs). In p-ssDSCs, the solar cell using ZnO as electron transport material showed a short circuit current, up to 680 mu A cm(-2), which is 60-fold larger than that previously reported device using TiO2 as electron transport material with similar architecture. In the p-DSPECs, a remarkable photocurrent of 100 mu A cm(-2) was achieved in a pH = 5.0 acetate buffer solution under a bias potential at 0.05 V vs RHE with platinum as the proton reduction catalyst. A Faradaic efficiency approaching 100% for the H-2 evolution reaction was obtained after photoelectrolysis for 9 h. Importantly, the solution-processed NiO-dye-ZnO photocathode exhibited excellent long-term stability in both p-ssDSCs and p-DSPECs. To the best of our knowledge, this is the first study where a solution-processable, nanoporous NiO-dye-ZnO photocathode is used for both p-ssDSCs and p-DSPECs having both excellent device performance and stability.

  • 39. Lin, Jia
    et al.
    Chen, Hong
    Gao, Yang
    Cai, Yao
    Jin, Jianbo
    Etman, Ahmed S.
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Kang, Joohoon
    Lei, Teng
    Lin, Zhenni
    Folgueras, Maria C.
    Quan, Li Na
    Kong, Qiao
    Sherburne, Matthew
    Asta, Mark
    Sun, Junliang
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Toney, Michael F.
    Wu, Junqiao
    Yang, Peidong
    Pressure-induced semiconductor-to-metal phase transition of a charge-ordered indium halide perovskite2019In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 47, p. 23404-23409Article in journal (Refereed)
    Abstract [en]

    Phase transitions in halide perovskites triggered by external stimuli generate significantly different material properties, providing a great opportunity for broad applications. Here, we demonstrate an In-based, charge-ordered (In+/In3+) inorganic halide perovskite with the composition of Cs2In(I)In(III)Cl-6 in which a pressure-driven semiconductor-to-metal phase transition exists. The single crystals, synthesized via a solid-state reaction method, crystallize in a distorted perovskite structure with space group I4/m with a = 17.2604(12) angstrom, c = 11.0113(16) angstrom if both the strong reflections and superstructures are considered. The supercell was further confirmed by rotation electron diffraction measurement. The pressure-induced semiconductor-to-metal phase transition was demonstrated by high-pressure Raman and absorbance spectroscopies and was consistent with theoretical modeling. This type of charge-ordered inorganic halide perovskite with a pressure-induced semiconductor-to-metal phase transition may inspire a range of potential applications.

  • 40. Huang, Jing
    et al.
    Xu, Bo
    Tian, Lei
    Pati, Palas Baran
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hammarstrom, Leif
    Tian, Haining
    A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 55, p. 7918-7921Article in journal (Refereed)
    Abstract [en]

    Heavy metal-free CuInS2 quantum dots (QDs) were employed as a photosensitizer on a NiO photocathode to drive an immobilized molecular Re catalyst for photoelectrochemical CO2 reduction for the first time. A photocurrent of 25 mu A cm(-2) at -0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

  • 41.
    Etman, Ahmed S.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Pell, Andrew J.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svedlindh, Peter
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Bernin, Diana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Chalmers University of Technology, Sweden.
    Insights into the Exfoliation Process of V2O5 center dot nH(2)O Nanosheet Formation Using Real-Time V-51 NMR2019In: ACS Omega, E-ISSN 2470-1343, Vol. 4, no 6, p. 10899-10905Article in journal (Refereed)
    Abstract [en]

    Nanostructured hydrated vanadium oxides (V2O5 center dot nH(2)O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V2O5 center dot nH(2)O nano-sheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V2O5 center dot nH(2)O nanosheets from the V2O5 and VO2 precursors in real using solution- and solid-state V-51 NMR. Solution-state V-51 NMR showed that the aqueous solution contained mostly the decavanadate anion [H2V10O28](4-) and the hydrated dioxova-nadate cation [VO2 center dot 4H(2)O](+), and during the exfoliation process, decavanadate was formed, while the amount of [VO2 center dot 4H(2)O](+) remained constant. The conversion of the solid precursor V2O5, which was monitored with solid-state V-51 NMR, was initiated when VO2 was in its monoclinic forms. The dried V2O5 center dot nH(2)O nanosheets were weakly paramagnetic because of a minor content of isolated V4+. Its solid-state V-51 signal was less than 20% of V2O5 and arose from diamagnetic V4+ or V5+.This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials.

  • 42.
    Etman, Ahmed S.
    et al.
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden; Alexandria Univ, Fac Sci, Dept Chem, Alexandria 21321, Egypt.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    El Ghazaly, Ahmed
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden.
    Sun, Junliang
    Peking Univ, Coll Chem & Mol Engn, Yiheyuan Rd 5, Beijing 100871, Peoples R China.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rosen, Johanna
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden.
    Flexible Freestanding MoO3-x-Carbon Nanotubes-Nanocellulose Paper Electrodes for Charge-Storage Applications2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 23, p. 5157-5163Article in journal (Refereed)
    Abstract [en]

    Herein, a one‐step synthesis protocol was developed for synthesizing freestanding/flexible paper electrodes composed of nanostructured molybdenum oxide (MoO3−x) embedded in a carbon nanotube (CNT) and Cladophora cellulose (CC) matrix. The preparation method involved sonication of the precursors, nanostructured MoO3−x, CNTs, and CC with weight ratios of 7:2:1, in a water/ethanol mixture, followed by vacuum filtration. The electrodes were straightforward to handle and possessed a thickness of approximately 12 μm and a mass loading of MoO3−x–CNTs of approximately 0.9 mg cm−2. The elemental mapping showed that the nanostructured MoO3−x was uniformly embedded inside the CNTs–CC matrix. The MoO3−x–CNTs–CC paper electrodes featured a capacity of 30 C g−1, normalized to the mass of MoO3−x–CNTs, at a current density of 78 A g−1 (corresponding to a rate of approximately 210 C based on the MoO3 content, assuming a theoretical capacity of 1339 C g−1), and exhibited a capacity retention of 91 % over 30 000 cycles. This study paves the way for the manufacturing of flexible/freestanding nanostructured MoO3−x‐based electrodes for use in charge‐storage devices at high charge/discharge rates.

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  • 43.
    Etman, Ahmed S
    et al.
    Stockholm University.
    Wang, Ligang
    Peking University.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sun, Junliang
    Stockholm University.
    Molybdenum Oxide Nanosheets with Tunable Plasmonic Resonance: Aqueous Exfoliation Synthesis and Charge Storage Applications2019In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 4, article id 1806699Article in journal (Refereed)
    Abstract [en]

    Herein, a simple aqueous-exfoliation strategy is introduced for the fabrication of a series of MoO3−x nanosheets (where x stands for oxygen vacancies) using two commercial molybdenum oxide precursors, MoO2 and MoO3. The nanosheets offer a localized surface plasmon resonance (LSPR) effect which is dependent on the structure and local environment of the nanosheets. The LSPR can be efficiently tuned by changing the weight ratio between the molybdenum oxide precursor(s) and/or by solar light irradiation using a low-energy UV lamp (36 W). For the pristine MoO3−x nanosheets, the highest LSPR signal is obtained for nanosheets prepared using 80% MoO2. On the contrary, after solar light irradiation, the nanosheets prepared using pure MoO3 offer the highest LSPR response. The nanosheets also show an outstanding rate capability when used as binder-free supercapacitor electrodes in an acidified Na2SO4 electrolyte. The electrodes exhibit discharge capacities of 110 and 75 C g−1 at a scan rate of 20 and 1000 mV s−1, respectively. The MoO3−x nanosheets can likewise be used as a negative electrode material for lithium-ion batteries. The efficient eco-friendly synthesis and the ability to tune the photochemical and electrochemical properties of the nanosheets make this approach interesting to many energy-related research fields.

  • 44.
    Etman, Ahmed S.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Younesi, Reza
    V2O5·nH2O nanosheets and multi-walled carbon nanotube composite as a negative electrode for sodium-ion batteries2019In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 30, p. 145-151Article in journal (Refereed)
    Abstract [en]

    Two dimensional (2D) transition metal oxides and chalcogenides demonstrate a promising performance in sodium-ion batteries (SIBs) application. In this study, we investigated the use of a composite of freeze dried V2O5·nH2O nanosheets and multi-walled carbon nanotube (MWCNT) as a negative electrode material for SIBs. Cyclic voltammetry (CV) results indicated that a reversible sodium-ion insertion/deinsertion into the composite electrode can be obtained in the potential window of 0.1–2.5 V vs. Na+/Na. The composite electrodes delivered sodium storage capacities of 140 and 45 mAh g−1 under applied current densities of 20 and 100 mA g−1, respectively. The pause test during constant current measurement showed a raise in the open circuit potential (OCP) of about 0.46 V, and a charge capacity loss of ∼10%. These values are comparable with those reported for hard carbon electrodes. For comparison, electrodes of freeze dried V2O5·nH2O nanosheets were prepared and tested for SIBs application. The results showed that the MWCNT plays a significant role in the electrochemical performance of the composite material.

  • 45. Etman, Ahmed
    et al.
    Sun, Junliang
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    V2O5·nH2O nanosheets and multi-walled carbon nanotube composite as a negative electrode for sodium-ion batteries2019In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 30, p. 145-151Article in journal (Refereed)
    Abstract [en]

    Two dimensional (2D) transition metal oxides and chalcogenides demonstrate a promising performance in sodium-ion batteries (SIBs) application. In this study, we investigated the use of a composite of freeze dried V2O5 center dot nH(2)O nanosheets and multi-walled carbon nanotube (MWCNT) as a negative electrode material for SIBs. Cyclic voltammetry (CV) results indicated that a reversible sodium-ion insertion/deinsertion into the composite electrode can be obtained in the potential window of 0.1-2.5 V vs. Na+/Na. The composite electrodes delivered sodium storage capacities of 140 and 45 mAh g(-1) under applied current densities of 20 and 100 mA g(-1), respectively. The pause test during constant current measurement showed a raise in the open circuit potential (OCP) of about 0.46 V, and a charge capacity loss of similar to 10%. These values are comparable with those reported for hard carbon electrodes. For comparison, electrodes of freeze dried V2O5 center dot nH(2)O nanosheets were prepared and tested for SIBs application. The results showed that the MWCNT plays a significant role in the electrochemical performance of the composite material. 

  • 46.
    Huang, Jing
    et al.
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden.
    Xu, Bo
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Tian, Lei
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Pati, Palas Baran
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Etman, Ahmed S.
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden..
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem MMK, SE-10691 Stockholm, Sweden..
    Hammarstrom, Leif
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Tian, Haining
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 55, p. 7918-7921Article in journal (Refereed)
    Abstract [en]

    Heavy metal-free CuInS2 quantum dots (QDs) were employed as a photosensitizer on a NiO photocathode to drive an immobilized molecular Re catalyst for photoelectrochemical CO2 reduction for the first time. A photocurrent of 25 mu A cm(-2) at -0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

  • 47. Ma, Tianqiong
    et al.
    Li, Jian
    Niu, Jing
    Zhang, Lei
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lin, Cong
    Shi, Dier
    Chen, Pohua
    Li, Li-Hua
    Du, Xin
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Wang, Wei
    Observation of Interpenetration Isomerism in Covalent Organic Frameworks2018In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, no 22, p. 6763-6766Article in journal (Refereed)
    Abstract [en]

    We report herein the first example of interpenetration isomerism in covalent organic frameworks (COFs). As a well-known three-dimensional (3D) COF, COF-300 was synthesized and characterized by the Yaghi group in 2009 as a 5-fold interpenetrated diamond structure (dia-cS topology). We found that adding an aging process prior to the reported synthetic procedure afforded the formation of an interpenetration isomer, dia-c7 COF-300. The 7-fold interpenetrated diamond structure of this new isomer was identified by powder Xray diffraction and rotation electron diffraction analyses. Furthermore, we proposed a universal formula to accurately determine the number of interpenetration degrees of dia-based COFs from only the unit cell parameters and the length of the organic linker. This work not only provides a novel example to the category of interpenetration isomerism but also provides new insights for the further development of 3D COFs.

  • 48.
    Etman, Ahmed S.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yuan, Youyou
    Wang, Ligang
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Facile Water-Based Strategy for Synthesizing MoO3-x Nanosheets: Efficient Visible Light Photocatalysts for Dye Degradation2018In: ACS Omega, E-ISSN 2470-1343, Vol. 3, no 2, p. 2193-2201Article in journal (Refereed)
    Abstract [en]

    Nanostructured molybdenum oxides are promising materials for energy storage, catalysis, and electronic-based applications. Herein, we report the synthesis of MoO3-x nanosheets (x stands for oxygen vacancy) via an environmentally friendly liquid exfoliation approach. The process involves the reflux of the bulk alpha-MoO3 precursor in water at 80 degrees C for 7 days. Electron microscopy and atomic force microscopy show that the MoO3-x nanosheets are a few nanometer thick. MoO3-x nanosheets exhibit near infrared plasmonic property that can be enhanced by visible light irradiation for a short time (10 min). Photocatalytic activity of MoO3-x nanosheets for organic dye decolorization is examined using two different dyes (rhodamine B and methylene blue). Under visible light irradiation, MoO3-x nanosheets make a rapid decolorization for the dye molecules in less than 10 min. The simple synthesis procedure of MoO3-x nanosheets combined with their remarkable photochemical properties reflect the high potential for using the nanosheets in a variety of applications.

  • 49. Huang, Jing
    et al.
    Gatty, Melina Gilbert
    Xu, Bo
    Pati, Palas Baran
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tian, Lei
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hammarström, Leif
    Tian, Haining
    Covalently linking CuInS2 quantum dots with a Re catalyst by click reaction for photocatalytic CO2 reduction2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 31, p. 10775-10783Article in journal (Refereed)
    Abstract [en]

    Covalently linking photosensitizers and catalysts in an inorganic-organic hybrid photocatalytic system is beneficial for efficient electron transfer between these components. However, general and straightforward methods to covalently attach molecular catalysts on the surface of inorganic semiconductors are rare. In this work, a classic rhenium bipyridine complex (Re catalyst) has been successfully covalently linked to the low toxicity CuInS2 quantum dots (QDs) by click reaction for photocatalytic CO2 reduction. Covalent bonding between the CuInS2 QDs and the Re catalyst in the QD-Re hybrid system is confirmed by UV-visible absorption spectroscopy, Fourier-transform infrared spectroscopy and energy-dispersive X-ray measurements. Time-correlated single photon counting and ultrafast time-resolved infrared spectroscopy provide evidence for rapid photo-induced electron transfer from the QDs to the Re catalyst. Upon photo-excitation of the QDs, the singly reduced Re catalyst is formed within 300 fs. Notably, the amount of reduced Re in the linked hybrid system is more than that in a sample where the QDs and the Re catalyst are simply mixed, suggesting that the covalent linkage between the CuInS2 QDs and the Re catalyst indeed facilitates electron transfer from the QDs to the Re catalyst. Such an ultrafast electron transfer in the covalently linked CuInS2 QD-Re hybrid system leads to enhanced photocatalytic activity for CO2 reduction, as compared to the conventional mixture of the QDs and the Re catalyst.

  • 50.
    Etman, Ahmed S.
    et al.
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Abdelhamid, Hani Nasser
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Yuan, Youyou
    Wang, Ligang
    Zou, Xiaodong
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Sun, Junliang
    Stockholms universitet, Institutionen för material- och miljökemi (MMK).
    Facile Water-Based Strategy for Synthesizing MoO3-x Nanosheets: Efficient Visible Light Photocatalysts for Dye Degradation2018In: ACS Omega, E-ISSN 2470-1343, Vol. 3, no 2, p. 2193-2201Article in journal (Refereed)
    Abstract [en]

    Nanostructured molybdenum oxides are promising materials for energy storage, catalysis, and electronic-based applications. Herein, we report the synthesis of MoO3-x nanosheets (x stands for oxygen vacancy) via an environmentally friendly liquid exfoliation approach. The process involves the reflux of the bulk alpha-MoO3 precursor in water at 80 degrees C for 7 days. Electron microscopy and atomic force microscopy show that the MoO3-x nanosheets are a few nanometer thick. MoO3-x nanosheets exhibit near infrared plasmonic property that can be enhanced by visible light irradiation for a short time (10 min). Photocatalytic activity of MoO3-x nanosheets for organic dye decolorization is examined using two different dyes (rhodamine B and methylene blue). Under visible light irradiation, MoO3-x nanosheets make a rapid decolorization for the dye molecules in less than 10 min. The simple synthesis procedure of MoO3-x nanosheets combined with their remarkable photochemical properties reflect the high potential for using the nanosheets in a variety of applications.

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