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Brodie vs Hummers graphite oxides for preparation of multi-layered materials
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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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. Vol. 115, p. 430-440
Keywords [en]
graphite, oxide
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:umu:diva-130949DOI: 10.1016/j.carbon.2016.12.097ISI: 000395601300045OAI: oai:DiVA.org:umu-130949DiVA, id: diva2:1070416
Available from: 2017-02-01 Created: 2017-02-01 Last updated: 2018-06-09Bibliographically approved
In thesis
1. Graphite oxides for preparation of graphene related materials: structure, chemical modification and hydrogen storage properties
Open this publication in new window or tab >>Graphite oxides for preparation of graphene related materials: structure, chemical modification and hydrogen storage properties
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
Graphite oxide, graphene oxide, hydrogen storage, nanomaterials, adsorption, surface area, pore volume
National Category
Other Physics Topics
Research subject
Materials Science
Identifiers
urn:nbn:se:umu:diva-144270 (URN)978-91-7601-841-5 (ISBN)
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

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Talyzin, AlexandrMercier, GuillaumeKlechikov, AlexeyHedenström, MattiasJohnels, Dan

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