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Structure of graphene oxide membranes in solvents and solutions
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.
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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.

Place, publisher, year, edition, pages
2015. Vol. 7, no 37, p. 15374-15384
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-110218DOI: 10.1039/c5nr04096eISI: 000361675300045PubMedID: 26332400OAI: oai:DiVA.org:umu-110218DiVA, id: diva2:861349
Available from: 2015-10-16 Created: 2015-10-16 Last updated: 2018-06-07Bibliographically 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)
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Supervisors
Available from: 2018-02-09 Created: 2018-01-29 Last updated: 2018-06-09Bibliographically approved

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Klechikov, AlexeyYu, JunchunSharifi, TivaTalyzin, Alexandr V.

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