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Graphite oxides for preparation of graphene related materials: structure, chemical modification and hydrogen storage properties
Umeå University, Faculty of Science and Technology, Department of Physics.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbon materials have been studied for hydrogen storage for decades, but they showed too low capacity at ambient temperature compared to target values for practical applications. This thesis includes two parts. First one is fundamental study of graphite oxides (GO) structure and properties. Second part is focused on hydrogen storage properties of graphene related materials prepared using GO as a precursor.

We studied the effects of synthesis methods and oxidation degree on solvation/intercalation properties of GOs. New effect of temperature induced reversible delamination was observed for Hummers GO (HGO) immersed in liquid acetonitrile. Experiments with swelling of Brodie GO (BGO) in 1-octanol revealed parallel orientation of the intercalated solvent molecules relative to graphene oxide (GnO) layers. Chemical functionalization of GO in swelled state allowed us to synthesize the materials with subnanometer slit pores supported by molecular pillars. Structure and properties of pillared GO were characterized by variety of methods. Swelling properties of multilayered GnO membranes were compared to properties of precursor GO. GnO membranes were found to swell similarly to GO powders in some solvents and rather differently in other. Our experiments revealed important limitations in application of GO membranes for nanofiltration. Several parameters were found to affect the size of permeation “channels” provided by interlayers of GnO membrane structure: e.g. nature of solvent, pH of solutions and concentration of solutes.

Hydrogen storage parameters were studied for a set of graphene related materials with broad range of surface areas (SSA) (200 - 3300 m2/g). Hydrogen sorption weight percent (wt%) is found to correlate with SSA for all studied graphene materials following the trend standard for other nanostructured carbon materials. The highest hydrogen uptakes of ~1.2 wt% at 296 K and ~7.5 wt% at 77 K were measured for graphene material with SSA of over 3000 m2/g. Addition of Pd and Pt nanoparticles to graphene materials did not resulted in improvement of hydrogen storage compared to nanoparticles-free samples. No deviation from the standard wt% vs. SSA trends was also observed for pillared GO materials. Therefore, hydrogen storage properties of graphene related materials at room temperatures are not confirmed to be exceptional. However, high surface area graphene materials are found to be among the best materials for physisorption of hydrogen at liquid nitrogen temperature. Moreover, hydrogen storage capacity of 4 wt%, comparable to target values, was observed at temperature of solid CO2 (193 K) which can be maintained using common refrigeration methods.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2018. , p. 117
Keywords [en]
Graphite oxide, graphene oxide, hydrogen storage, nanomaterials, adsorption, surface area, pore volume
National Category
Other Physics Topics
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:umu:diva-144270ISBN: 978-91-7601-841-5 (print)OAI: oai:DiVA.org:umu-144270DiVA, id: diva2:1178376
Public defence
2018-03-02, N430, Naturvetarhuset, Umeå, 13:15 (English)
Opponent
Supervisors
Available from: 2018-02-09 Created: 2018-01-29 Last updated: 2018-06-09Bibliographically approved
List of papers
1. Hydrogen storage in bulk graphene-related materials
Open this publication in new window or tab >>Hydrogen storage in bulk graphene-related materials
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2015 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 210, p. 46-51Article in journal (Refereed) Published
Abstract [en]

Hydrogen sorption properties of graphene-related materials were studied by gravimetric and volumetric methods at 2931< and 77K. Rapid thermal exfoliation of different types of graphite oxide (GO) precursors yielded samples with maximal surface areas up to 850 m(2)/g, whereas surface areas up to 2300 m(2)/g were achieved by post-exfoliation activation treatments. Therefore, hydrogen storage parameters of graphene materials could be evaluated in a broad range of surface areas. The H-2 uptake vs surface area trend revealed in this study shows that hydrogen storage by graphene materials do not exceed 1 Wt% at 120 Bar H-2 at ambient temperatures. Linear increase of hydrogen adsorption vs surface area was observed at 77 K with maximal observed value of similar to 5 Wt% for 2300 m(2)/g sample. It can be concluded that bulk graphene samples obtained using graphite oxide exfoliation and activation follow standard for other nanostructured carbons hydrogen uptake trends and do not demonstrate superior hydrogen storage parameters reported in several earlier studies. Nevertheless, graphene remains to be one of the best materials for physisorption of hydrogen, especially at low temperatures.

Keywords
Graphene, Graphene oxide, Hydrogen storage
National Category
Physical Sciences Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-103716 (URN)10.1016/j.micromeso.2015.02.017 (DOI)000353733300007 ()
Available from: 2015-06-11 Created: 2015-05-28 Last updated: 2018-06-07Bibliographically approved
2. Hydrogen adsorption by perforated graphene
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2015 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 20, p. 6594-6599Article in journal (Refereed) Published
Abstract [en]

We performed a combined theoretical and experimental study of hydrogen adsorption in graphene systems with defect-induced additional porosity. It is demonstrated that perforation of graphene sheets results in increase of theoretically possible surface areas beyond the limits of ideal defect-free graphene (∼2700 m2/g) with the values approaching ∼5000 m2/g. This in turn implies promising hydrogen storage capacities up to 6.5 wt% at 77 K, estimated from classical Grand canonical Monte Carlo simulations. Hydrogen sorption was studied for the samples of defected graphene with surface area of ∼2900 m2/g prepared using exfoliation of graphite oxide followed by KOH activation. The BET surface area of studied samples thus exceeded the value of single-layered graphene. Hydrogen uptake measured at 77 K and 296 K amounts to 5.5 wt% (30 bar) and to 0.89 wt% (120 bar), respectively. 

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Graphene-based nanostructures, Hydrogen storage, High surface area, Porous materials
National Category
Physical Sciences Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-104374 (URN)10.1016/j.ijhydene.2015.03.139 (DOI)000354581100013 ()
Available from: 2015-07-06 Created: 2015-06-10 Last updated: 2018-06-07Bibliographically approved
3. Hydrogen storage in high surface area graphene scaffolds
Open this publication in new window or tab >>Hydrogen storage in high surface area graphene scaffolds
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2015 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 83, p. 15280-15283Article in journal (Refereed) Published
Abstract [en]

Using an optimized KOH activation procedure we prepared highly porous graphene scaffold materials with SSA values up to 3400 m2 g−1 and a pore volume up to 2.2 cm3 g−1, which are among the highest for carbon materials. Hydrogen uptake of activated graphene samples was evaluated in a broad temperature interval (77–296 K). After additional activation by hydrogen annealing the maximal excess H2 uptake of 7.5 wt% was obtained at 77 K. A hydrogen storage value as high as 4 wt% was observed already at 193 K (120 bar H2), a temperature of solid CO2, which can be easily maintained using common industrial refrigeration methods.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2015
Keywords
graphene hydrogen storage adsorption
National Category
Condensed Matter Physics
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-109475 (URN)10.1039/c5cc05474e (DOI)000363167000013 ()26335949 (PubMedID)
Funder
Swedish Research Council, 621-2012-3654
Available from: 2015-09-28 Created: 2015-09-28 Last updated: 2018-06-07Bibliographically approved
4. Graphene decorated with metal nanoparticles: Hydrogen sorption and related artefacts
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2017 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 250, p. 27-34Article in journal (Refereed) Published
Abstract [en]

Hydrogen sorption by reduced graphene oxides (r-GO) is not found to increase after decoration with Pd and Pt nanoparticles. Treatments of metal decorated samples using annealing under hydrogen or air were tested as a method to create additional pores by effects of r-GO etching around nanoparticles. Increase of Specific Surface Area (SSA) was observed for some air annealed r-GO samples. However, the same treatments applied to activated r-GO samples with microporous nature and higher surface area result in breakup of structure and dramatic decrease of SSA. Our experiments have not revealed effects which could be attributed to spillover in hydrogen sorption on Pd or Pt decorated graphene. However, we report irreversible chemisorption of hydrogen for some samples which can be mistakenly assigned to spillover if the experiments are incomplete.

Keywords
Graphene, Hydrogen storage, Graphene oxide, Nanoparticles, Decoration
National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-135589 (URN)10.1016/j.micromeso.2017.05.014 (DOI)000405045800004 ()
Funder
EU, Horizon 2020
Available from: 2017-05-31 Created: 2017-05-31 Last updated: 2018-06-09Bibliographically approved
5. Brodie vs Hummers graphite oxides for preparation of multi-layered materials
Open this publication in new window or tab >>Brodie vs Hummers graphite oxides for preparation of multi-layered materials
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2017 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 115, p. 430-440Article in journal (Refereed) Published
Abstract [en]

Graphite oxides synthesized by one and two step Brodie oxidation (BGO) and Hummers (HGO) methods were analyzed by a variety of characterization methods in order to evaluate the reasons behind the difference in their properties. It is found that the Brodie method results in a higher relative amount of hydroxyl groups and a more homogeneous overall distribution of functional groups over the planar surface of the graphene oxide flakes. The higher number of carbonyl and carboxyl groups in HGO, detected by several methods, including XPS, NMR and FTIR, unavoidably results in defects of the graphene "skeleton", holes and overall disruption of the carbon-carbon bond network, stronger deviation from planar flake shape and poor ordering of the graphene oxide layers. It is also suggested that functional groups in HGO are less homogeneously distributed over the flake surface, forming some nanometer-sized graphene areas. The presence of differently oxidized areas on the GO surface results in inhomogeneous solvation and hydration of HGO and effects of inter- and intra-stratification. The proposed interpretation of the data explains the higher mechanical strength of multi-layered BGO membranes/papers, which are also less affected by humidity changes, thus providing an example of a membrane property superior to that of HGO.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
graphite, oxide
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-130949 (URN)10.1016/j.carbon.2016.12.097 (DOI)000395601300045 ()
Available from: 2017-02-01 Created: 2017-02-01 Last updated: 2018-06-09Bibliographically approved
6. Delamination of graphite oxide in a liquid upon cooling
Open this publication in new window or tab >>Delamination of graphite oxide in a liquid upon cooling
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2015 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 29, p. 12625-12630Article in journal (Refereed) Published
Abstract [en]

Graphite oxide (GO) in liquid acetonitrile undergoes a transition from an ordered phase around ambient temperature to a gel-like disordered phase at temperatures below 260 K, as demonstrated by in situ X-ray diffraction. The stacking order of GO layers is restored below the freezing point of acetonitrile (199 K). The reversible swelling transition between a stacked crystalline phase and an amorphous delaminated state observed upon cooling provides an unusual example of increased structural disorder at lower temperatures. The formation of the gel-like phase is attributed to the thermo-responsive conformational change of individual GO flakes induced by stronger solvation. Scanning force microscopy demonstrates that GO flakes deposited onto a solid substrate from acetonitrile dispersions at a temperature below 260 K exhibit corrugations and wrinkling which are not observed for the flakes deposited at ambient temperature. The thermo-responsive transition between the delaminated and stacked phases reported here can be used for sonication-free dispersion of graphene oxide, micro-container applications, or the preparation of new composite materials.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-107187 (URN)10.1039/c5nr02564h (DOI)000358207700046 ()26147576 (PubMedID)
Funder
Swedish Research Council, 621-2012-3654
Available from: 2015-08-19 Created: 2015-08-19 Last updated: 2018-06-07Bibliographically approved
7. Multilayered intercalation of 1-octanol into Brodie graphite oxide
Open this publication in new window or tab >>Multilayered intercalation of 1-octanol into Brodie graphite oxide
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2017 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 20, p. 6929-6936Article in journal (Refereed) Published
Abstract [en]

Multilayered intercalation of 1-octanol into the structure of Brodie graphite oxide (B-GO) was studied as a function of temperature and pressure. Reversible phase transition with the addition/removal of one layer of 1-octanol was found at 265 K by means of X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The same transition was observed at ambient temperature upon a pressure increase above 0.6 GPa. This transition was interpreted as an incongruent melting of the low temperature/high pressure B-GO intercalated structure with five layers of 1-octanol parallel to GO sheets (L-solvate), resulting in the formation of a four-layered structure that is stable under ambient conditions (A-solvate). Vacuum heating allows the removal of 1-octanol from the A-solvate layer by layer, while distinct sets of (00 l) reflections are observed for three-, two-, and one-layered solvate phases. Step by step removal of the 1-octanol layers results in changes of distance between graphene oxide planes by similar to 4.5 angstrom. This experiment proved that both L- and A-solvates are structures with layers of 1-octanol parallel to GO planes. Unusual intercalation with up to five distinct layers of 1-octanol is remarkably different from the behaviour of small alcohol molecules (methanol and ethanol), which intercalate B-GO structure with only one layer under ambient conditions and a maximum of two layers at lower temperatures or higher pressures. The data presented in this study make it possible to rule out a change in the orientation of alcohol molecules from parallel to perpendicular to the GO planes, as suggested in the 1960s to explain larger expansion of the GO lattice due to swelling with larger alcohols.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-136327 (URN)10.1039/c7nr01792h (DOI)000402034400038 ()28509924 (PubMedID)
Funder
EU, Horizon 2020, 696656
Available from: 2017-06-30 Created: 2017-06-30 Last updated: 2018-06-09Bibliographically approved
8. Structure of graphene oxide membranes in solvents and solutions
Open this publication in new window or tab >>Structure of graphene oxide membranes in solvents and solutions
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2015 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 37, p. 15374-15384Article in journal (Refereed) Published
Abstract [en]

The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite oxide powder samples. Intercalation of liquid dioxolane, acetonitrile, acetone, and chloroform into the GO membrane structure occurs with maximum one monolayer insertion (Type I), in contrast with insertion of 2-3 layers of these solvents into the graphite oxide structure. However, the structure of GO membranes expands in liquid DMSO and DMF solvents similarly to precursor graphite oxide (Type II). It can be expected that Type II solvents will permeate GO membranes significantly faster compared to Type I solvents. The membranes are found to be stable in aqueous solutions of acidic and neutral salts, but dissolve slowly in some basic solutions of certain concentrations, e.g. in NaOH, NaHCO3 and LiF. Some larger organic molecules, alkylamines and alkylammonium cations are found to intercalate and expand the lattice of GO membranes significantly, e.g. up to similar to 35 angstrom in octadecylamine/methanol solution. Intercalation of solutes into the GO structure is one of the limiting factors for nano-filtration of certain molecules but it also allows modification of the inter-layer distance of GO membranes and tuning of their permeation properties. For example, GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-110218 (URN)10.1039/c5nr04096e (DOI)000361675300045 ()26332400 (PubMedID)
Available from: 2015-10-16 Created: 2015-10-16 Last updated: 2018-06-07Bibliographically approved
9. Porous Graphene Oxide/Diboronic Acid Materials: Structure and Hydrogen Sorption
Open this publication in new window or tab >>Porous Graphene Oxide/Diboronic Acid Materials: Structure and Hydrogen Sorption
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2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 49, p. 27179-27191Article in journal (Refereed) Published
Abstract [en]

Solvothermal reaction of graphite oxide (GO) with benzene-1,4-diboronic acid (DBA) was reported previously to result in formation of graphene oxide framework (GOP) materials. The theoretical structure of GOFs consists of graphene layers separated by benzene-diboronic "pillars" with similar to 1 nm slit pores thus providing the opportunity to use it as a model material to verify the effect of a small pore size on hydrogen adsorption. A set of samples with specific surface area (SSA) in the range of similar to 50-1000 m(2)/g were prepared using variations of synthesis conditions and GO/DBA proportions. Hydrogen storage properties of GOF samples evaluated at 293 and 77 K were found to be similar to other nanocarbon trends in relation to SSA values. Structural characterization of GO/DBA samples showed all typical features reported as evidence for formation of a framework structure such as expanded interlayer distance, increased temperature of thermal exfoliation, typical features in FTIR spectra, etc. However, the samples also exhibited reversible swelling in polar solvents which is not compatible with the idealized GOF structure linked by benzenediboronic molecular pillars. Therefore, possible alternative nonframework models of structures with pillars parallel and perpendicular to GO planes are considered.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-113842 (URN)10.1021/acs.jpcc.5b06402 (DOI)000366339000001 ()
Funder
Swedish Research Council, 621-2012-3654
Available from: 2016-03-30 Created: 2016-01-04 Last updated: 2018-06-07Bibliographically approved
10. Porous graphite oxide pillared with tetrapod-shaped molecules
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2017 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 120, p. 145-156Article in journal (Refereed) Published
Abstract [en]

Porous pillared graphene oxide (GO) materials were prepared using solvothermal reaction of Hummers GO with solution of Tetrakis(4-aminophenyl)methane (TKAm) in methanol. The intercalation of TKAm molecules between individual GO sheets, performed under swelling condition, results in expansion of inter-layer distance of GO from ∼7.5 Å to 13-14 Å. Pillaring GO with bulky, rigid 3D shaped TKAm molecules could be an advantage for the preparation of stable pillared structures compared to e.g. aliphatic or aromatic diamines. Insertion of TKAm molecules into inter-layer space of GO results in formation of interconnected network of sub-nanometer slit pores. The expanded GO structure prepared with optimized GO/TKAm composition shows Specific Surface Area (SSA) up to 660 m2/g which is among the highest reported for GO materials pillared using organic spacers. Modelling of GO structures pillared with TKAm molecules shows that maximal SSA of about 2300 m2/g is theoretically possible for realistic concentration of pillaring molecules in GO interlayers. Hydrogen sorption by pillared GO/TKAm is found to follow standard correlation with SSA both at ambient and liquid nitrogen temperatures with highest uptakes of 1.66 wt% achieved at 77 K and 0.25 wt% at 295 K. Our theoretical simulations show that pillared GO structures do not provide improvement of hydrogen storage beyond well-established physisorption trends even for idealized materials with subnanometer pores and SSA of 2300–3700 m2/g.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-137608 (URN)10.1016/j.carbon.2017.05.007 (DOI)000403665000019 ()
Available from: 2017-07-10 Created: 2017-07-10 Last updated: 2018-06-09Bibliographically approved

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