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Streszczenie:
This article presents the results of the cross-linking of oxidized flake graphene (GO) using hydrazine at room temperature. Conducting the process at temperatures up to 30 °C allowed to eliminate the phenomenon of thermal GO reduction to its non-oxidized form. In addition, based on the Infrared and Raman spectroscopy as well as X-ray photoelectron spectroscopy (XPS) analysis, the cross-linking ability of GO was observed depending on its size and degree of oxidation. These parameters were associated with selected physicochemical and electrical properties of obtained 3D structures. Three GO flakes sizes were tested in three different oxidation degrees. It was shown that, regardless of the size of GO, it is crucial to achieve a specific oxidation degree threshold which for the conducted tests was a >20% share of oxygen atoms in the whole structure. This value determines the ability to cross-link with hydrazine thanks to which it is possible to synthesize the spatial structure in which the π–π interactions among individual flakes are significantly reduced. This directly translates into the fact that the 3D structure shows an electrical resistance value in the range of 4–103 Ω, depending on the size and oxidation degree of the used material. The explanation of this phenomenon related to the electrical conductivity of 3D structures was confirmed based on the molecular modeling of the chemical structures.

Słowa kluczowe:
graphene, graphene oxide, cross-linking, 3D structures

Streszczenie:
This article discusses the effect of hydrogenation of graphene (one-sided and two-side hydrogenation) in relation to the change in the physicochemical properties of graphane as a material capable of reversible H2 storage. Therefore, the change of the system's energy was determined, differences in HOMO-LUMO molecular levels and the distribution of electrostatic potential as a function of its hydrogenation were simulated. At the same time, the mechanism of graphane reduction to graphene was discussed as a result of interaction with steam from the air. It has been shown that along with the increase in the degree of hydrogenation, the graphane changes its electrostatic potential from negative to positive, simultaneously pushing the negative charge to the edge of the graphene flake. This fact may have an impact on its further chemical reactions, which may significantly limit the sorption properties of graphene. Areas rich in negative charge will prefer chemical reactions with molecules of electrophilic properties, while positive areas with molecules of nucleophilic properties. This determines the elimination of the storage environment of graphene structures used as reversible sources of chemical bonding of hydrogen in order to increase their lifetime as well as sorption capacity.

Słowa kluczowe:
Graphene, Hydrogen, Hydrogen storage, Graphane, Molecular simulation