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  • 51. Gao, Weiming
    et al.
    Sun, Junliang
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li, Mingrun
    Eriksson, Lars
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Åkermark, Björn
    Attachment of a Hydrogen-Bonding Carboxylate Side Chain to an FeFe -Hydrogenase Model Complex: Influence on the Catalytic Mechanism2010Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 8, s. 2537-2546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4-6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the Fe Fe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of [Ru(bpy)(3)](2+), complex 1, 2, or 3, and ascorbic acid in CH3CN/D2O solution by on-line mass spectrometry.

  • 52. Gao, Yan
    et al.
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Liu, Jianhui
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Åkermark, Björn
    Nucleophilic Attack of Hydroxide on a Mn-V Oxo Complex: A Model of the O-O Bond Formation in the Oxygen Evolving Complex of Photosystem II2009Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, nr 25, s. 8726-+Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A manganese(III) corrole complex, 1, has been synthesized and used to study a potential mechanism for oxidation of water to molecular oxygen. Oxidation by t-BuOOH gave the Mn-V=O complex 2. Addition of hydroxide Led to release of oxygen via the Mn-IV complex 4 and regeneration of complex 1. It could be shown that the oxygen from O-18-labeted water was incorporated in both the formed molecular oxygen and the peroxy intermediate 4.

  • 53.
    Gatty, Hithesh K
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Antelius, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Stemme, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Niclas, Roxhed
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    A ppb-level miniaturized amperometric nitric oxide sensor2013Konferansepaper (Annet vitenskapelig)
  • 54.
    Gatty, Hithesh K.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Antelius, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Stemme, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Roxhed, Niclas
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    An amperometric nitric oxide sensor with fast response and ppb-level concentration detection relevant to asthma monitoring2015Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 209, s. 639-644Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A MEMS-based amperometric nitric oxide (NO) gas sensor is reported in this paper. The sensor is designed to detect NO gas for the purpose of asthma monitoring. The unique property of this sensor lies in the combination of a microporous high-surface area electrode that is coated with Nafion (TM), together with a liquid electrolyte. The sensor is able to detect gas concentrations of the order of parts-per-billion (ppb) and has a measured NO sensitivity of 0.045 nA/ppb and an operating range between 25 and 65% relative humidity. The settling time of the sensor is measured to 8s. The selectivity to interfering gases such as ammonia (NH3) and carbon monoxide (CO) was high when placing an activated carbon fiber filter above the sensor. The ppb-level detection capability of this sensor combined with its relatively fast response, high selectivity to CO and NH3 makes the sensor potentially applicable in gas monitoring for asthma detection.

  • 55.
    Gatty, Hithesh Kumar
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Antelius, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Stemme, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Roxhed, Niclas
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    A ppb level, miniaturized fast response amperometric nitric oxide sensor for asthma diagnostics2013Inngår i: Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International Conference on, New York: IEEE , 2013, s. 1001-1004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper reports on a novel miniaturized MEMS-based amperometric nitric oxide sensor that is suitable for a point of care testing device for asthma. The novelty lies in the combination of a high surface area microporous structured electrode, nano-structured Nafion that is coated on the side walls of the micropores, and liquid electrolyte. This combination allows detection of very low concentration (parts-per-billion) gas, has a high sensitivity of 4 mu A/ppm/cm(2) and has both a response and a recovery time of 6 s. The sensor is integrated with a PCB potentiostat to form a complete measuring module. The limit of detection of this sensor was estimated to be 0.3 ppb.

  • 56.
    Gode, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Investigations of proton conducting polymers and gas diffusion electrodes in the polymer electrolyte fuel cell2005Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Polymer electrolyte fuel cells (PEFC) convert the chemically bound energy in a fuel, e.g. hydrogen, directly into electricity by an electrochemical process. Examples of future applications are energy conversion such as combined heat and power generation (CHP), zero emission vehicles (ZEV) and consumer electronics. One of the key components in the PEFC is the membrane / electrode assembly (MEA). Both the membrane and the electrodes consist of proton conducting polymers (ionomers). In the membrane, properties such as gas permeability, high proton conductivity and sufficient mechanical and chemical stability are of crucial importance. In the electrodes, the morphology and electrochemical characteristics are strongly affected by the ionomer content. The primary purpose of the present thesis was to develop experimental techniques and to use them to characterise proton conducting polymers and membranes for PEFC applications electrochemically at, or close to, fuel cell operating conditions. The work presented ranges from polymer synthesis to electrochemical characterisation of the MEA performance.

    The use of a sulfonated dendritic polymer as the acidic component in proton conducting membranes was demonstrated. Proton conducting membranes were prepared by chemical cross-linking or in conjunction with a basic functionalised polymer, PSU-pyridine, to produce acid-base blend membranes. In order to study gas permeability a new in-situ method based on cylindrical microelectrodes was developed. An advantage of this method is that the measurements can be carried out at close to real fuel cell operating conditions, at elevated temperature and a wide range of relative humidities. The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and electrochemical impedance measurements (EIS). Long-term experiments have been compared to fast ex situ testing in 3 % H2O2 solution. For the direct assessment of membrane degradation, micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF-based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. The influence of ionomer content on the structure and electrochemical characteristics of Nafion-based PEFC cathodes was also demonstrated. The electrodes were thoroughly investigated using various materials and electrochemical characterisation techniques. Electrodes having medium Nafion contents (35<x<45 wt %) showed the best performance. The mass-transport limitation was essentially due to O2 diffusion in the agglomerates. The performance of cathodes with low Nafion content (<30 wt %) is limited by poor kinetics owing to incomplete wetting of platinum (Pt) by Nafion, by proton migration throughout the cathode as well as by O2 diffusion in the agglomerates. At large Nafion content (>45 wt %), the cathode becomes limited by diffusion of O2 both in the agglomerates and throughout the cathode. Furthermore, models for the membrane coupled with kinetics for the hydrogen electrode, including water concentration dependence, were developed. The models were experimentally validated using a new reference electrode approach. The membrane, as well as the hydrogen anode and cathode characteristics, was studied experimentally using steady-state measurements, current interrupt and EIS. Data obtained with the experiments were in good agreement with the modelled results.

  • 57.
    Gode, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Jannasch, Patric
    Polymer Science and Engineering, Lund University.
    Johansson, M.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Karlsson, Lina E.
    Polymer Science and Engineering, Lund University.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Sandquist, D.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A novel sulfonated dendritic polymer as the acidic component in proton conducting membranes2006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 7-8, s. 787-794Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study involves the synthesis of sulfonated poly(3-ethyl-3-(hydroxymethyl)oxetane), sPTMPO, by end-capping the hydroxy-groups in the PTMPO with 1,4-butane sultone. A series of the polymer with different degrees of substitution was investigated. Furthermore, the subsequent use of the sulfonated PTMPO as the acidic component in proton conducting membranes was explored. The membranes were prepared by either a) mixing the partly sulfonated PTMPO with hexamethoxymethyl melamine (HMMM) to form cross-links by ether formation between the methylol groups on HMMM and the remaining hydroxyl groups on the hyperbranched polyether or b) using the sulfonated polyether in conjunction with a pyridine functionalised polysulfone, PSU-pyridine, to produce acid-base blend membranes. Membrane properties such as proton conductivity, water uptake and mechanical properties are discussed.

  • 58.
    Guan, Tingting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Investigation of the prospect of energy self-sufficiency and technical performance of an integrated PEMFC (proton exchange membrane fuel cell), dairy farm and biogas plant system2014Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 130, s. 685-691Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A PEMFC fuelled with hydrogen is known for its high efficiency and low local emissions. However, the generation of hydrogen is always a controversial issue for the application of the PEMFC due to the use of fossil fuel and the possible carbon dioxide emissions. Presently, the PEMFC-CHP fed with renewable fuels, such as biogas, appears to be the most attractive energy converter-fuel combination. In this paper, an integrated PEMFC-CHP, a dairy farm and a biogas plant are studied. A PEMFC-CHP fed with reformate gas from the biogas plant generates electricity and heat to a dairy farm and a biogas plant, while the dairy farm delivers wet manure to the biogas plant as the feedstock for biogas production. This integrated system has been modelled for steady-state conditions by using Aspen Plus (R). The results indicate that the wet manure production of a dairy farm with 300 milked cows can support a biogas plant to give 1280 MW h of biogas annually. Based on the biogas production, a PEMFC-CHP with a stack having an electrical efficiency of 40% generates 360 MW h electricity and 680 MW h heat per year, which is enough to cover the energy demand of the whole system while the total efficiency of the PEMFC-CHP system is 82%. The integrated PEMFC-CHP, dairy farm and biogas plant could make the dairy farm and the biogas plant self-sufficient in a sustainable way provided the PEMFC-CHP has the electrical efficiency stated above. The effect of the methane conversion rate and the biogas composition on the system performance is discussed. Moreover, compared with the coal-fired CUP plant, the potentially avoided fossil fuel consumption and CO2 emissions of this self-sufficient system are also calculated.

  • 59.
    Gustavsson, John
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ activated hydrogen evolution from pH-neutral electrolytes2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The goal of this work was to better understand how molybdate and trivalent cations can be used as additives to pH neutral electrolytes to activate the Hydrogen Evolution Reaction (HER). Special emphasis was laid on the chlorate process and therefore also to some of the other effects that the additives may have in that particular process.

    Cathode films formed from the molybdate and trivalent cations have been investigated with electrochemical and surface analytical methods such as polarization curves, potential sweep, Electrochemical Impedance Spectroscopy (EIS), current efficiency measurements, Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), X-Ray Fluorescence (XRF) and Inductively Coupled Plasma (ICP) analysis.

    Trivalent cations and molybdate both activate the HER, although in different ways. Ligand water bound to the trivalent cations replaces water as reactant in the HER. Since the ligand water has a lower pKa than free water, it is more easily electrochemically deprotonated than free water and thus catalyzes the HER. Sodium molybdate, on the other hand, is electrochemically reduced on the cathode and form films which catalyze the HER (on cathode materials with poor activity for HER). Molybdate forms films of molybdenum oxides on the electrode surface, while trivalent cation additions form hydroxide films. There is a risk for both types of films that their ohmic resistance increases and the activity of the HER decreases during their growth. Lab-scale experiments show that for films formed from molybdate, these negative effects become less pronounced when the molybdate concentration is reduced.

    Both types of films can also increase the selectivity of the HER by hindering unwanted side reactions, but none of them as efficiently as the toxic additive Cr(VI) used today in the chlorate process. Trivalent cations are not soluble in chlorate electrolyte and thus not suitable for the chlorate process, whereas molybdate, over a wide pH range, can activate the HER on catalytically poor cathode materials such as titanium.

  • 60.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Hummelgård, Christine
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Bäckström, Joakim
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Rahman, Seikh Mohammad Habibur
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Eriksson, Sten
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes2012Inngår i: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 2, nr 3, s. 105-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 61.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hummelgård, Christine
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Bäckström, Joakim
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rahman, Seikh Mohammed Habibur
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Sten
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ Activated Hydrogen Evolution by Molybdate Addition to Neutral and Alkaline ElectrolytesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X‑ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X‑ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron‑molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 62.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li, Gongzhuo
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hummelgård, Christine
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE‐851 70 Sundsvall, Sweden.
    Bäckström, Joakim
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE‐851 70 Sundsvall, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    On the Suppression of Cathodic Hypochlorite Reduction by ElectrolyteAdditions of Molybdate and Chromate IonsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The goal of this study was to gain a better understanding of the feasibility of replacing Cr(VI) in the chlorate process by Mo(VI), focusing on the cathode reaction selectivity for hydrogen evolution on steel and titanium in a hypochlorite containing electrolyte.

    To evaluate the ability of Cr(VI) and Mo(VI) additions to hinder hypochlorite reduction, potential sweep experiments on rotating disc electrodes and cathodic current efficiency (CE) measurements on stationary electrodes were performed. Formed electrode films were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cathodic hypochlorite reduction is hindered by the Mo-containing films formed on the cathode surface after Mo(VI) addition to the electrolyte, but much less efficient compared to Cr(VI) addition. Very low levels of Cr(VI), in the mM range, can efficiently suppress hypochlorite reduction on polished titanium and steel. Phosphate does not negatively influence the CE in the presence of Cr(VI) or Mo(VI) and the Mo-containing cathode films become thinner if the electrolyte during the film build-up also contains phosphate. For a RuO2-TiO2 anode polarized in electrolyte with 40 mM Mo(VI), the anode potential increased and on the electrode surface, increased molybdenum levels were detected. In an earlier study 40 mM Mo(VI) gave increased by-product oxygen.

  • 63.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ activation of hydrogen evolution in pH-neutral electrolytes by additions of multivalent cations2012Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, nr 12, s. 9496-9503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) in close to pH-neutral electrolytes can be achieved by addition of trivalent cations. This activation has been investigated using steady state polarization, electrochemical impedance spectroscopy (EIS) and chemical analysis of cathode films for yttrium. Several multivalent cations were included in this study, such as Al(III), Mg(II), Y(III), Sm(III), La(III) and Sc(III). In general the more acidic the metal ions the larger is the activation. Metal hydroxide films formed in the alkaline diffusion layer at the cathode surface can have a negative impact on the magnitude of this activation, and therefore complicate the interpretation of the results. The activation corresponds to a transport of metal ion complexes to the electrode surface and the reduction of bound ligand water to form hydrogen.

  • 64.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Nylen, Linda
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process2010Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 40, nr 8, s. 1529-1536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chromate is today added to industrial chlorate electrolyte, where it forms a thin cathode film of chromium hydroxide that hinders unwanted reduction of hypochlorite and chlorate. The aim of this study was to investigate rare earth metal (REM) ions as an environmentally friendly alternative to the toxic chromate addition. Potential sweeps and iR-corrected polarisation curves were recorded using rotating disc electrodes of iron and gold. Addition of Y(III), La(III) or Sm(III) to 5 M NaCl at 70 A degrees C suppressed hypochlorite reduction. Activation of hydrogen evolution by REM ion addition to 0.5 M NaCl was more significant at 25 A degrees C than at 50 and 70 A degrees C. Increasing the chloride concentration to 5 M had a detrimental effect on this activation. The major problem in replacing chromate with REM salts is the poor solubility of REM ions at normal chlorate process conditions, and therefore REM salts are not a realistic alternative to chromate addition.

  • 65.
    Gustavsson, Marie
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Kasemo, Bengt
    Chalmers tekniska högskola, Göteborg.
    Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell2007Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 163, nr 2, s. 671-678Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.

  • 66.
    Hagberg, Johan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Swerea KIMAB AB, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    High Precision Coulometry of Commercial PAN-Based Carbon Fibers as Electrodes in Structural Batteries2016Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, nr 8, s. A1790-A1797Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon fibers have the combined mechanical and electrochemical properties needed to make them particularly well suited for usage as electrodes in a structural lithium-ion battery, a material that simultaneously works as a battery and a structural composite. Presented in this paper is an evaluation of commercial polyacrylonitrile-based carbon fibers in terms of capacity and coulombic efficiency, as well as a microstructural and surface evaluation. Some polyacrylonitrile based carbon fibers intercalate lithium ions, resulting in a similar capacity as state-of-the-art graphite based electrodes, presently the most commonly used negative electrode material. Using high precision coulometry, we found a capacity of around 250-350 mAh/g and a very high coulombic efficiency of over 99.9% after ten cycles, which is even higher than a commercial state-of-the art graphitic electrode evaluated as reference. The high coulombic efficiency is attributed to the very low surface area of the carbon fibers, resulting in a small and stable solid-electrolyte interface layer. A highly graphitized ultra high modulus carbon fiber was evaluated as well and, compared to the other fibers, less lithium was inserted (corresponding to approximately 150 mAh/g). We show that the use of carbon fibers as an electrode material in a structural composite battery is indeed viable.

  • 67.
    Hallberg, Fredrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Vernersson, Thomas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thyboll Pettersson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Dvinskikh, Sergey V.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Electrokinetic transport of water and methanol in Nafion membranes as observed by NMR spectroscopy2010Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, nr 10, s. 3542-3549Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]
    Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nation 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant. (C) 2010 Elsevier Ltd. All rights reserved.
  • 68. Hassel, Beatriz I.
    et al.
    Trey, Stacy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. SP Tech Res Inst Sweden, Sweden.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    A Study on the Morphology, Mechanical, and Electrical Performance of Polyaniline-modified Wood - A Semiconducting Composite Material2014Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, nr 3, s. 5007-5023Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the morphology, electrochemical modification with respect to the wood fiber direction, and mechanical properties of wood modified by in situ polymerization with polyaniline (PANI). This polymerization formed a composite material with applications as an antistatic, electromagnetic, anti-corrosion, and heavy metal purifying materials. The polymer was found throughout the entire structure of the wood and was quantified within the wood cell wall and middle lamella by SEM-EDX. The presence of PANI affected the conductivity of the composite specimens, which was found to be higher in the fiber direction, indicating a more intact percolation pathway of connected PANI particles in this direction. The PANI modification resulted in a small reduction of the storage modulus, the maximum strength, and the ductility of the wood, with decreases in the properties of specimens conditioned in an environment above 66% relative humidity. The in situ-polymerized PANI strongly interacted with the lignin component of the veneers, according to the decrease in the lignin glass transition temperature (T-g) noted in DMA studies.

  • 69.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of Conventional and Structural Lithium-Ion Batteries2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion batteries have, in recent years, experienced a rapid development from small everyday devices towards hybrid electric vehicle (HEV) applications. Due to this shift in application area, the battery performance andits degradation with time are becoming increasingly important issues to besolved.In this thesis, lithium-ion batteries are investigated with focus on lifetime performance of an existing battery chemistry, and development of electrodes for so-called structural batteries. The systems are evaluated by electrochemical methods, such as cycling and electrochemical impedance spectroscopy (EIS),combined with material characterization and modeling.

    Lifetime performance of mesocarbon microbeads (MCMB)/LiFePO4 cells was investigated to develop an understanding of how this technology tolerates and is influenced by different conditions, such as cycling, storage and temperature.The lifetime of the LiFePO4-based cells was found to be significantly reduced by cycling at elevated temperature, almost five times shorter compared to cycle-aged cells at ambient temperature. The calendar-aged cells also showed major signs of degradation at elevated temperatures. The overall cause of aging was electrolyte decomposition which resulted in loss of cyclable lithium, i.e. capacity fade, and impedance increase.

    Commercially available polyacrylonitrile (PAN)-based carbon fibers were investigated, both electrochemically and mechanically, to determine their suitability as negative electrodes in structural batteries. The electrochemical performance of carbon fibers was found to be excellent compared to other negative electrode materials, especially for single or well-separated fibers. The mechanical properties, measured as changes in the tensile properties, showed that the tensile stiffness was unaffected by lithium-ion intercalation and cycling. The ultimate tensile strength, however, showed a distinct variation with state-of-charge (SOC). Overall, carbon fibers are suitable for structural battery applications.

  • 70.
    Hellqvist Kjell, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jacques, Eric
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    PAN-based carbon fiber negative electrodes for structural lithium-ion batteries2011Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, nr 12, s. A1455-A1460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several grades of commercially-available polyacrylonitrile (PAN)-based carbon fibers have been studied for structural lithium-ion batteries to understand how the sizing, different lithiation rates and number of fibers per tow affect the available reversible capacity, when used as both current collector and electrode, for use in structural batteries. The study shows that at moderate lithiation rates, 100 mA g-1, most of the carbon fibers display a reversible capacity close to or above 100 mAh g-1 after ten full cycles. For most of the fibers, removing the sizing increased the capacity to some extent. However, the main factor affecting the measured capacity was the lithiation rate. Decreasing the current by a tenth yielded an increase of capacity of around 100 for all the tested grades. From the measurements performed in this study it is evident that carbon fibers can be used as the active negative material and current collector in structural batteries. © 2011 The Electrochemical Society.

  • 71.
    Hellqvist Kjell, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jacques, Eric
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    PAN-based carbon fibers for structural lithium-ion batteries2012Inngår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials, European Conference on Composite Materials, ECCM , 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Structural batteries have the potential to become an integrated part of the device, functioning as both a structural element and as energy storage by combining electrochemical properties and mechanical properties in the same material. In addition, an increase of power and energy density on a system level could be achieved. The electrochemical properties of seven different commercially available PAN-based carbon fibers have been investigated as negative electrodes for structural lithium-ion batteries. All of the tested fibers showed some ability to intercalate lithium ions. The performance varied significantly between the different grades of fiber. Fibers with intermediate modulus showed the most promising results.

  • 72.
    Hellqvist Kjell, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Malmgren, Sara
    Ciosek, Katarzyna
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Edström, Kristina
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Comparing aging of graphite/LiFePO4 cells at 22 degrees C and 55 degrees C - Electrochemical and photoelectron spectroscopy studies2013Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 243, s. 290-298Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 degrees C and 55 degrees C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process-specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.

  • 73.
    Hellqvist Kjell, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zavalis, Tommy
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical characterization of lithium intercalation processes of PAN-based carbon fibers in a microelectrode system2013Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, nr 9, s. A1473-A1481Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A full electrochemical investigation of the lithium intercalation processes in a commercially available PAN-based carbon fiber, Toho Tenax IMS65 (unsized and sized) primarily intended to be used in structural lithium-ion batteries, has been performed. In order to extract the electrochemical properties, a specially designed microelectrode system consisting of a single fiber working electrode, lithium-foil counter electrode and well-characterized battery materials were utilized. The properties, for 5 to 100% state-of-charge (SOC), were mainly determined from electrochemical impedance spectroscopy (EIS) measurements by fitting of a physics-based model, and electronic conductivity examination. The study shows excellent mass transport and kinetic properties, especially at high SOCs for this specific carbon fiber compared to other negative electrode materials. Some electrochemical parameters vary depending on sizing, but are too small to affect the actual electrochemical performance. A strong SOC dependence is shown for most electrochemical properties, including the electronic conductivity.

  • 74.
    Hellqvist Kjell, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zavalis, Tommy Georgios
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Characterization of Lithium Intercalation Processes of PAN-based Carbon Fibers in a Microelectrode SystemArtikkel i tidsskrift (Annet vitenskapelig)
  • 75.
    Hildebrandt, Lars
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dinnebier, R.
    Jansen, M.
    Crystal structure and ionic conductivity of cesium trifluoromethyl sulfonate, CSSO3CF32005Inngår i: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 631, nr 9, s. 1660-1666Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crystal structures of the room and the high temperature modifications of cesium trifluoromethyl sulfonate were solved from high resolution X-ray powder diffraction data. At room temperature, alpha-CsSO3CF3 crystallizes in the monoclinic space group P2(1) with lattice parameters a = 9.7406(2) angstrom, b = 6.1640(1) angstrom, c = 5.4798(1) angstrom, and beta = 104.998(1)degrees; Z = 2. At temperatures above T = 380 K, a second order phase transformation towards a disordered C-centered orthorhombic phase in space group Cmcm occurs with lattice parameters at T = 492 K of a = 5.5074(3) angstrom, b = 19.4346(14) angstrom, and c = 6.2978(4) angstrom; Z = 4. Within the crystal structures, the triflate anions are arranged in double layers with the apolar CF3-groups pointing towards each other. The cesium ions are located between the SO3-groups. CsSO3CF3 shows a specific ion conductivity ranging from sigma = 1.06 center dot 10(-8) Scm(-1) at T = 393 K to sigma = 5.18 center dot 10(-4) Scm(-1) at T = 519 K.

  • 76.
    Hildebrandt, Lars
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dinnebier, R.
    Jansen, M.
    Crystal structure and ionic conductivity of three polymorphic phases of rubidium trifluoromethyl sulfonate, RbSO3CF32006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 8, s. 3217-3223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crystal structures of three polymorphic phases of rubidium trifluoromethyl sulfonate (RbSO3CF3, rubidium 'triflate') were solved from X-ray powder diffraction data. At room temperature, rubidium triflate crystallizes in the monoclinic space group Cm with lattice parameters of a = 19.9611(5) angstrom, b = 23.49113(7) angstrom, c = 5.1514(2) angstrom, beta = 102.758(2)degrees; Z = 16. At T = 321 K, a first-order phase transition occurs toward a monoclinic phase in space group P2(1) with lattice parameters at T = 344 K of a = 10,3434(5) angstrom, b = 5.8283(3) angstrom, c = 5.1982(3) angstrom, beta = 104.278(6)degrees; Z = 2). At T = 461 K, another phase transition, this time of second order, occurs toward an orthorhombic phase in space group Cmcm with lattice parameters at T = 510 K of a = 5.3069(2) angstrom, b = 20.2423(10) angstrom, c = 5.9479(2) angstrom; Z = 4. As a common feature within all three crystal structures of rubidium triflate, the triflate anions are arranged in double layers with the lipophilic CF3 groups facing each other. The rubidium ions are located between the SO3 groups. The general packing is similar to the packing in cesium triflate. Rubidium triflate can be classified as a solid electrolyte with a specific ionic conductivity of sigma = 9.89 x 10(-9) S/cm at T = 384 K and sigma = 3.84 x 10(-6) S/cm at T = 481 K.

  • 77.
    Holmström, Nicklas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wiezell, Katarina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Studying Low-Humidity Effects in PEFCs Using EIS I: Experimental2012Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, nr 8, s. F369-F378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A suitable electrochemical characterization technique for studying water effects at low-humidity conditions is electrochemical impedance spectroscopy (EIS). In general, an EIS spectrum for a PEFC shows one or several capacitive loops and in some situations an inductive loop at the lowest frequencies depending on operating conditions. In this study, low-humidity effects in an operating polymer electrolyte fuel cell have been investigated by using electrochemical impedance spectroscopy (EIS), with the focus on the low-frequency impedance. Measurements have been carried out using several membranes with different thicknesses at various current densities and operating conditions. At frequencies, around 1 Hz down to 5 mHz a pseudo-inductive loop was seen. The magnitude of this loop increased with thicker membranes and at lower humidities. Based on the results the pseudo-inductive loop was attributed to water transport characteristics in the membrane, where the capacitive part is attributed to drying out of the anode and parts of the membrane closest to the anode while the inductive part is attributed to rehydration of the membrane and the anode by product water from the oxygen reduction reaction on the cathode. In addition, both the magnitude and the top-frequencies of the pseudo-inductive loop were affected by the flow rate.

  • 78.
    Holmström, Niklas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ihonen, J.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The influence of the gas diffusion layer on water management in polymer electrolyte fuel cells2007Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 7, nr 4, s. 306-313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Performance losses due to flooding of gas diffusion layers (GDLs) and flow fields as well as membrane dehydration are two of the major problems in PEFC. In this investigation, the effect of GDL on the cell water management in PEFC is studied using segmented and single cell experiments. The behaviour of four different commercial GDLs was investigated at both high and low inlet humidity conditions by galvanostatic fuel cell experiments. The influence of varying reactant humidity and gas composition was studied. The results at high inlet humidity show that none of the studied GDLs are significantly flooded on the anode side. On the other hand, when some of the GDLs are used on the cathode side they are flooded, leading to increased mass transfer losses. The results at low inlet humidity conditions show that the characteristics of the GDL influence the membrane hydration. It is also shown that inlet humidity on the anode side has a major effect on flooding at the cathode.

  • 79.
    Hu, Lan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Molten carbonate fuel cells for electrolysis2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The molten carbonate fuel cell has evolved to current megawatt-scale commercial power plants. When using the fuel cell for electrolysis, it provides a promising option for producing fuel gases such as hydrogen and syngas. The cell can thereby operate reversibly as a dual energy converter for electricity generation and fuel gas production. The so-called reversible molten carbonate fuel cell will probably increase the usefulness of the system and improve the economic benefits.

    This work has investigated the performance and durability of the cell in electrolysis and reversible operations. A lower polarization loss is found for the electrolysis cell than for the fuel cell, mainly due to the NiO electrode performing better in the MCEC. The stability of the cell in long-term tests evidences the feasibility of the MCEC and the RMCFC using a conventional fuel cell set-up, at least in lab-scale.

    This study elucidates the electrode kinetics of hydrogen production and oxygen production. The experimentally obtained partial pressure dependencies for hydrogen production are high, and they do not reasonably satisfy the reverse pathways of the hydrogen oxidation mechanisms. The reverse process of an oxygen reduction mechanism in fuel cell operation is found to suitably describe oxygen production in the MCEC.

    To evaluate the effect of the reverse water-gas shift reaction and the influence of the gas phase mass transport on the porous Ni electrode in the electrolysis cell, a mathematical model is applied in this study. When the humidified inlet gas compositions enter the current collector the decrease of the shift reaction rate increases the electrode performance. The model well describes the polarization behavior of the Ni electrode when the inlet gases have low contents of reactants. The experimental data and modeling results are consistent in that carbon dioxide has a stronger effect on the gas phase mass transport than other components, i.e. water and hydrogen.

  • 80.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. COMSOL AB, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A Model for Analysis of the Porous Nickel Electrode Polarization in the Molten Carbonate Electrolysis Cell2017Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 8, s. H5197-H5201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is important to know the electrode kinetics of hydrogen production as well as to understand the effect of the mass transport in the gas phase for the analysis of the molten carbonate electrolysis cell (MCEC). A one-dimensional model based on the Maxwell-Stefan diffusion equations was applied to predict the mass transfer behavior in gas phase of the porous nickel electrode in the MCEC, combined with equations describing the current distribution in the electrolyte phase. The model gave a fair match to the experimental polarization data of the Ni electrode for varied inlet gas compositions of H2O, CO2 and H-2 between 10 and 40%. The model was also deployed to evaluate the effect of the water-gas shift reaction (WGSR). The fitted kinetic coefficients and electrode porosity differed in the case when including the WGSR compared to when not including the WGSR. In both cases the model was able to well describe the porous nickel electrode behavior in the molten carbonate electrolysis cell.

  • 81.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A model for gas phase mass transport on the porous nickel electrode in the molten carbonate electrolysis cellManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A one-dimensional model based on the Maxwell-Stefan diffusion equations was applied to evaluate the effect of the reverse water-gas shift reaction and the influence of the gas phase mass transport on the performance of the porous nickel electrode in the molten carbonate electrolysis cell. The concentration gradients in the current collector are larger than in the electrode for the inlet gases not in equilibrium, due to the shift reaction taking place in the electrode. When the humidified gas compositions enter the current collector, the decrease of the shift reaction rate increases the electrode performance. The model well describes the polarization behavior of the Ni electrode in the electrolysis cell when the inlet gases have low contents of hydrogen. The mass-transfer limitations at low contents of water and carbon dioxide are captured in the model, but the effect on the electrode polarization, especially of carbon dioxide, is overestimated. Despite an overestimation in the calculations, the experimental data and the modeling results are still consistent in that carbon dioxide has a stronger effect on the gas phase mass transport than other components, i.e. water and hydrogen.

  • 82.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)2015Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, nr 9, s. F1020-F1028Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to elucidate the kinetics of a porous nickel electrode for hydrogen production in a molten carbonate electrolysis cell. Stationary polarization data for the Ni electrode were recorded under varying gas compositions and temperatures. The slopes of these iR-corrected polarization curves were analyzed at low overpotential, under the assumption that the porous electrode was under kinetic control with mass-transfer limitations thus neglected. The exchange current densities were calculated numerically by using a simplified porous electrode model. Within the temperature range of 600-650 degrees C, the reaction order of hydrogen is not constant; the value was found to be 0.49-0.44 at lower H-2 concentration, while increasing to 0.79-0.94 when containing 25-50% H-2. The dependence on CO2 partial pressure increased from 0.62 to 0.86 with temperature. The reaction order of water showed two cases as did hydrogen. For lower H2O content (10-30%), the value was in the range of 0.47-0.67 at 600-650 degrees C, while increasing to 0.83-1.07 with 30-50% H2O. The experimentally obtained partial pressure dependencies were high, and therefore not in agreement with any of the mechanisms suggested for hydrogen production in molten carbonate salts in this study.

  • 83.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrode kinetics of the NiO porous electrode for oxygen production in the molten carbonate electrolysis cell (MCEC)2015Inngår i: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 182, s. 493-509Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance of a molten carbonate electrolysis cell (MCEC) is to a great extent determined by the anode, i.e. the oxygen production reaction at the porous NiO electrode. In this study, stationary polarization curves for the NiO electrode were measured under varying gas compositions and temperatures. The exchange current densities were calculated numerically from the slopes at low overpotential. Positive dependency on the exchange current density was found for the partial pressure of oxygen. When the temperature was increased in the range 600-650 degrees C, the reaction order of oxygen decreased from 0.97 to 0.80. However, there are two different cases for the partial pressure dependency of carbon dioxide within this temperature range: positive values, 0.09-0.30, for the reaction order at lower CO2 concentration, and negative values, -0.26-0.01, with increasing CO2 content. A comparison of theoretically obtained data indicates that the oxygen-producing reaction in MCEC could be reasonably satisfied by the reverse of oxygen reduction by the oxygen mechanism I, an n = 4 electron reaction, assuming a low coverage of oxide ions at high CO2 content and an intermediate coverage for a low CO2 concentration.

  • 84.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Operating the nickel electrode with hydrogen-lean gases in the molten carbonate electrolysis cell (MCEC)2016Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, nr 41, s. 18692-18698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    If a molten carbonate electrolysis cell (MCEC) is applied for fuel gas production it is important to know the polarization of the nickel electrode when operated at low concentration of hydrogen. Thus, the electrochemical performance of the Ni electrode was investigated under hydrogen-lean gases containing 1/24.5/24.5/50%, 1/49.5/24.5/25%, 1/24.5/49.5/25% and 1/49.5/49.5/0% H-2/CO2/H2O/N-2 in the temperature range of 600-650 degrees C and was then compared to the reference case with 25/25/25/25% H-2/CO2/H2O/N-2. The electrochemical measurements included polarization curve coupled with current interrupt, and electrochemical impedance spectroscopy. Polarization resistances of the Ni electrode obtained by the two different techniques agreed well. For the inlet gases containing low amounts of hydrogen the Ni electrode exhibited higher polarization losses than when using the reference case in the electrolysis cell. The electrochemical impedance measurements showed that both charge-transfer and mass-transfer polarizations were higher for hydrogen-lean gases at all measured temperatures. Except under the condition with 1/49.5/49.5% H-2/CO2/H2O at 650 degrees C, the Ni electrode exhibited lower mass-transfer polarization when compared to the reference case. Furthermore, the mass-transfer polarization was strongly dependent on temperature under H-2-lean gases, differing from the reference case when the temperature has almost no effect on mass-transfer polarization. The activation energy for hydrogen production was calculated to be in the range of 69 -138 kJ mol(-1) under all measured gases, indicating that the Ni electrode is under kinetic and/or mixed control in the MCEC.

  • 85.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Operating the nickel electrode with hydrogen-lean gases in the molten carbonate electrolysis cell (MCEC)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    If a molten carbonate electrolysis cell (MCEC) is applied for fuel gas production it is important to know the polarization of the nickel electrode when operated at low concentration of hydrogen. Thus, the electrochemical performance of the Ni electrode was investigated under hydrogen-lean gases containing 1/24.5/24.5/50%, 1/49.5/24.5/25%, 1/24.5/49.5/25% and 1/49.5/49.5/0% H2/CO2/H2O/N2 in the temperature range of 600–650 °C and was then compared to the reference case with 25/25/25/25% H2/CO2/H2O/N2. The electrochemical measurements included polarization curve coupled with current interrupt, and electrochemical impedance spectroscopy. Polarization resistances of the Ni electrode obtained by the two different techniques agreed well. For the inlet gases containing low amounts of hydrogen the Ni electrode exhibited higher polarization losses than when using the reference case in the electrolysis cell. The electrochemical impedance measurements showed that both charge-transfer and mass-transfer polarizations were higher for hydrogen-lean gases at all measured temperatures. Except under the condition with 1/49.5/49.5% H2/CO2/H2O at 650 °C, the Ni electrode exhibited lower mass-transfer polarization when compared to the reference case. Furthermore, the mass-transfer polarization was strongly dependent on temperature under H2-lean gases, differing from the reference case when the temperature has almost no effect on mass-transfer polarization. The activation energy for hydrogen production was calculated to be in the range of 69–138 kJ·mol-1 under all measured gases, indicating that the Ni electrode is under kinetic and/or mixed control in the MCEC.

  • 86.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance and Durability of the Molten Carbonate Electrolysis Cell and the Reversible Molten Carbonate Fuel Cell2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 25, s. 13427-13433Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The molten carbonate electrolysis cell (MCEC) provides the opportunity for producing fuel gases, e.g., hydrogen or syngas, in an environmentally friendly way, especially when in combination with renewable electricity resources such as solar, wind, and/or hydropower. The evaluation of the performance and durability of the molten carbonate cell is a key for developing the electrolysis technology. In this study, we report that the electrochemical performance of the cell and electrodes somewhat decreases during the long-term test of the MCEC. The degradation is not permanent, though, and the cell performance could be partially recovered. Since conventional fuel cell materials consisting of nickel-based porous catalysts and carbonate electrolyte are used in the MCEC durability test, it is also shown that the cell can alternatingly operate as an electrolysis cell for fuel gas production and as a fuel cell for electricity generation, i.e., as a so-called reversible molten carbonate fuel cell (RMCFC). This study reveals that the cell performance improves after a long period of RMCFC operation. The stability and durability of the cell in long-term tests evidence the feasibility of the electrolysis and reversible operations in carbonate melts using a conventional fuel cell setup, at least in lab scale.

  • 87.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance and durability of the molten carbonate electrolysis cell (MCEC) and the reversible molten carbonate fuel cell (RMCFC)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The molten carbonate electrolysis cell (MCEC) provides the opportunity for producing fuel gases, e.g. hydrogen or syngas, in an environmentally friendly way, especially when in combination with renewable electricity resources such as solar, wind and/or hydropower. The evaluation of the performance and durability of the molten carbonate cell is a key for developing the electrolysis technology. In this study, we report that the electrochemical performance of the cell and electrodes somewhat decreases during the long-term test of the MCEC. The degradation is not permanent, though, and the cell performance could be partially recovered. Since conventional fuel cell materials consisting of Ni-based porous catalysts and carbonate electrolyte are used in the MCEC durability test, it is also shown that the cell can alternatingly operate as an electrolysis cell for fuel gas production and as a fuel cell for electricity generation, i.e. as a so-called reversible molten carbonate fuel cell (RMCFC). This study reveals that the cell performance improves after a long period of RMCFC operation. The stability and durability of the cell in long-term tests evidence the feasibility of the electrolysis and reversible operations in carbonate melts using a conventional fuel cell set-up, at least in lab-scale.

  • 88.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rexed, Ivan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical performance of reversible molten carbonate fuel cells2014Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, nr 23, s. 12323-12329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrochemical performance of a state-of-the-art molten carbonate cell was investigated in both fuel cell (MCFC) and electrolysis cell (MCEC) modes by using polarization curves and electrochemical impedance spectroscopy (EIS). The results show that it is feasible to run a reversible molten carbonate fuel cell and that the cell actually exhibits lower polarization in the MCEC mode, at least for the short-term tests undertaken in this study. The Ni hydrogen electrode and the NiO oxygen electrode were also studied in fuel cell and electrolysis cell modes under different operating conditions, including temperatures and gas compositions. The polarization of the Ni hydrogen electrode turned out to be slightly higher in the electrolysis cell mode than in the fuel cell mode at all operating temperatures and water contents. This was probably due to the slightly larger mass-transfer polarization rather than to charge-transfer polarization according to the impedance results. The CO2 content has an important effect on the Ni electrode in electrolysis cell mode. Increasing the CO2 content the Ni electrode exhibits slightly lower polarization in the electrolysis cell mode. The NiO oxygen electrode shows lower polarization loss in the electrolysis cell mode than in the fuel cell mode in the temperature range of 600-675 degrees C. The impedance showed that both charge-transfer and mass-transfer polarization of the NiO electrode are lower in the electrolysis cell than in the fuel cell mode.

  • 89. Huang, Yong
    et al.
    Gao, Weiming
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li, Mingrun
    Akermark, Bjorn
    An Air-Stable Fe3S4 Complex with Properties Similar to Those of the HOXair State of the Diiron Hydrogenases2012Inngår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, nr 27, s. 4259-4263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Fe3S4 complex bridged by azapropanedithiolate (adt), complex 6, was prepared as a potential model of the HOXair state of [FeFe]-hydrogenases. Complex 6 was characterized by IR and 1H NMR spectroscopy, and its structure was determined by X-ray crystallography. The electrochemical studies show that complex 6 is redox-active under acidic conditions, which provides insight into the catalytic mechanism. Hydrogen evolution, driven by visible light, was observed in CH3CN/D2O solution by online mass spectroscopy.

  • 90.
    Huiran, Lu
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wood-based Materials for Lithium-ion Batteries2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion batteries (LIB) have become very important recently as power sources for portable electronics and electric vehicles. Today non-renewable petroleum-based polymers are used as binders in state-of-the-art LIB. Therefore, it is essential to investigate alternative binders, which are environmentally friendly and inexpensive. Using wood-based materials, such as cellulose and lignin, could make the batteries more environmentally benign, cheaper and easier to produce.

    Lignin, a byproduct from the pulping industry and the second most abundant bio-polymer in wood, has been investigated for the first time as binder material for eco-friendly LIB. Both LiFePO4 (LFP) positive and graphite negative electrodes using pretreated lignin as binder exhibited good electrochemical performance. The drawback of lignin as binder is that its poor mechanical properties limit the preparation of a thick electrode, constraining the energy density for LIB.

    In order to meet the demands of flexible and bendable electronic devices, cellulose nanofibrils (CNF) as binder materials have been successfully fabricated for flexible batteries by a water-based paper making process. It showed excellent binding properties for different kinds of electrode materials, which were homogenously dispersed in its visible network. The flexible electrodes obtained good mechanical and electrochemical properties. A study of different CNF shows that the manufacturing process affects the performance of the electrodes.

    Another innovative LIB concept in this thesis was to build both lightweight and bendable LIB. Chopped carbon fibers (CF), bound by CNF, were demonstrated as both current collector and as a current collector-free negative electrode, produced by an easy filtration process. The gravimetric energy density was increased compared to cells with metallic current collectors. The CF-based lightweight and flexible electrode achieved a good cycling stability, rate capability, even after 4000 times of bending.

  • 91. Hummelgard, Christine
    et al.
    Gustavsson, John
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Olin, Hakan
    Backstrom, Joakim
    Spin coated titanium-ruthenium oxide thin films2013Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 536, s. 74-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Substrates of different roughness spin coated with Ti0.7Ru0.3O2 films have been evaluated as model system for fundamental studies of the industrially and scientifically interesting (Ti, Ru)O-2 based electrodes. The approach allowed for much more accurate control over the material synthesis than the traditionally used brush-, dip-, or spray-coating, on titanium-metal substrates. It moreover yielded well-defined samples suitable for basic studies of the surface properties that are of fundamental importance for understanding the electrochemical functionality of the electrode. We have compared the films on silicon substrates to films prepared by spin coating the same material on titanium-metal substrates. Samples have been characterized using atomic force microscopy (AFM), X-ray diffraction, scanning electronmicroscopy (SEM), and cyclic voltammetry. The samples displayed a uniformity of the films appropriate for AFM characterization. The smoother the substrate the less cracks in the coating. Using easily broken silicon wafers as substrate, a straightforward sample preparation technique was demonstrated for cross-section SEM. In addition, using high spinning velocities we have deposited the oxide films directly on silicon-nitride grids, thin enough to allow for studies with transmission electron microscopy without further sample preparation.

  • 92. Hummelgård, Christine
    et al.
    Karlsson, Rasmus K. S.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bäckström, Joakim
    Rahman, Seikh M. H.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Sten
    Olin, Håkan
    Physical and electrochemical properties of cobalt doped (Ti,Ru)O-2 electrode coatings2013Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 178, nr 20, s. 1515-1522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The physical and electrochemical properties of ternary oxides Ti0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O-2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types.

  • 93. Ipek, N.
    et al.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Vynnycky, M.
    A mathematical model for the electrochemical pickling of steel2007Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, nr 10, s. P108-P119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen. To obtain a better understanding of this process, we derive in this paper a mathematical model for predicting the potential, current density and ionic species distributions in a vertical pickling cell, as well as the oxide dissolution rate at the steel strip. The model is two dimensional, steady state and isothermal, and is based on the conservation equations for ionic species in dilute solution, involving convection, diffusion, migration and reaction. Kinetic Tafel expressions for the electrochemical gas evolving reactions at the lead anode, stainless steel cathode and at the bipolar steel strip surface are introduced. The derived model comprises six ionic species; numerical solutions for a full version and two reduced versions of this model are then obtained. Finally, the implications of the results for the actual pickling process are discussed.

  • 94. Ipek, N.
    et al.
    Vynnycky, M.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A coupled electrochemical and hydrodynamical two-phase model for the electrolytic pickling of steel2008Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, nr 4, s. P33-P43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen bubbles. In this paper, we extend an earlier mathematical model for the electrochemical aspects of the process, which took account only of the liquid phase, to include the effect of the gas phase. The model is two-dimensional, steady-state and isothermal, and comprises five ionic species, the mixture velocity, pressure, and the gas fraction; numerical solutions of this model are then obtained. The results of the single and two-phase models are compared, and their implications for the actual pickling process are discussed.

  • 95.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lithium-intercalated Carbon Fibers as Piezo-electrochemical Transducer for Energy HarvestingManuskript (preprint) (Annet vitenskapelig)
  • 96.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Piezo-electrochemical effect in lithium-intercalated carbon fibres2013Inngår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 35, s. 65-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we have conducted experiments to investigate the coupling between electrochemical and mechanical properties of lithium (Li)-intercalating carbon fibres (CFs). The results show promising potential for new functionalities of CFs for electrochemical actuation, sensing and energy harvesting. Li-intercalation at 1 C-rate in CFs subjected to a constant tensile extension induced a free reversible longitudinal expansion strain of approximately 0.30% which can be used as mechanical actuation. Varying the tensile extension of lithiated CFs resulted in a piezoelectric response of the open-circuit potential, in the range of several mV, enabling strain sensing. If the electrical potential is kept constant during a tensile extension a piezo-electrochemical current response is found with about 50% mechanical to electrical energy conversion efficiency, enabling energy harvesting.

  • 97.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The effect of lithium-intercalation on the mechanical properties of carbon fibres2014Inngår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 68, s. 725-733Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon fibres (CFs) can be used as lightweight structural electrodes since they have high specific tensile stiffness and ultimate tensile strength (UTS), and high lithium (Li)-intercalation capability. This paper investigates the relationship between the amount of intercalated Li and the changes induced in the tensile stiffness and UTS of polyacrylonitrile-based CF tows. After a few electrochemical cycles the stiffness was not degraded and independent of the measured capacity. A drop in the UTS of lithiated CFs was only partly recovered during delithiation and clearly larger at the highest measured capacities, but remained less than 40% at full charge. The reversibility of this drop with the C-rate and measured capacity supports that the fibres are not damaged, that some Li is irreversibly trapped in the delithiated CFs and that reversible strains develop in the fibre. However, the drop in the strength does not vary linearly with the measured capacity and the drop in the ultimate tensile strain remains lower than the CF longitudinal expansion at full charge. These results suggest that the loss of strength might relate to the degree of lithiation of defectives areas which govern the tensile failure mode of the CFs.

  • 98.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Hellqvist, Kjell Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    PERFORMANCE OF LITHIUM-INTERCALATED CARBONFIBRES FOR STRUCTURAL ELECTRODE APPLICATIONS2013Inngår i: ICCM19, 2013, s. 1-8Konferansepaper (Annet vitenskapelig)
  • 99.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Kjell, M. HKTH, Skolan för kemivetenskap (CHE), Kemiteknik.Zenkert, DanKTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.Lindbergh, GöranKTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.Behm, MårtenKTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    IMPACT OF MECHANICAL LOADING ON THEELECTROCHEMICAL BEHAVIOUR OF CARBON FIBERS FORUSE IN ENERGY STORAGE COMPOSITE2011Konferanseproceedings (Annet vitenskapelig)
  • 100.
    Jacques, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Kjell, Maria H.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Willgert, Markus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Impact of electrochemical cycling on the tensile properties of carbon fibres for structural lithium-ion composite batteries2012Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 72, nr 7, s. 792-798Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon fibres are particularly well suited for use in a multifunctional lightweight design of a structural composite material able to store energy as a lithium-ion battery. The fibres will in this case act as both a high performance structural reinforcement and one of the battery electrodes. However, the electrochemical cycling consists of insertions and extractions of lithium ions in the microstructure of carbon fibres and its impact on the mechanical performance is unknown. This study investigates the changes in the tensile properties of carbon fibres after they have been subjected to a number of electrochemical cycles. Consistent carbon fibre specimens were manufactured with polyacrylonitrile-based carbon fibres. Sized T800H and desized IMS65 were selected for their mechanical properties and electrochemical capacities. At the first lithiation the ultimate tensile strength of the fibres was reduced of about 20% but after the first delithiation some strength was recovered. The losses and recoveries of strength remained unchanged with the number of cycles as long as the cell capacity remained reversible. Losses in the cell capacity after 1000 cycles were measured together with smaller losses in the tensile strength of the lithiated fibres. These results show that electrochemical cycling does not degrade the tensile properties which seem to depend on the amount of lithium ions inserted and extracted. Both fibre grades exhibited the same trends of results. The tensile stiffness was not affected by the cycling. Field emission scanning electron microscope images taken after electrochemical cycling did not show any obvious damage of the outer surface of the fibres.

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