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Multilayered intercalation of 1-octanol into Brodie graphite oxide
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
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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.

Place, publisher, year, edition, pages
2017. Vol. 9, no 20, p. 6929-6936
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-136327DOI: 10.1039/c7nr01792hISI: 000402034400038PubMedID: 28509924OAI: oai:DiVA.org:umu-136327DiVA, id: diva2:1118299
Funder
EU, Horizon 2020, 696656Available from: 2017-06-30 Created: 2017-06-30 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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Klechikov, AlexeySun, JinhuaTalyzin, Alexandr V.

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