Novel graphene-based electrodes for energy storage devices

Graphene sheets have exceptional electrical, mechanical and optical properties. Graphene-based nanocomposites can be utilized as an electrode for the fabrication of energy storage devices for practical applications. Graphene nanosheets were produced by an enhanced technique including graphite oxidation, ultrasonic treatment, expansion, and chemical reduction

Graphene manufacture and utilization

An improved, safer and mild method was proposed for the exfoliation of graphene like sheets from graphite to be used in fuel cells. The major aim in the proposed method is to reduce the number of layers in the graphite material and to produce large quantities of graphene bundles to be used as catalyst support in polymer electrolyte membrane fuel cells. Graphite oxide was prepared using potassium dichromate/sulfuric acid as oxidant and acetic anhydride as intercalating agent. The oxidation process seemed to create expanded and leafy structures of graphite oxide layers. Heat treatment of samples led to the thermal decomposition of acetic anhydride into carbondioxide and water vapor which further swelled the layered graphitic structure. Sonication of graphite oxide samples created more separated structures. Morphology of the sonicated graphite oxide samples exhibited expanded the layer structures and formed some tullelike translucent and crumpled graphite oxide sheets. The mild procedure applied was capable of reducing the average number of graphene sheets from 86 in the raw graphite to nine in graphene-based nanosheets. Raman spectroscopy analysis showed the significant reduction in size of the in-plane sp2 domains of graphene nanosheets obtained after the reduction of graphite oxide

Polypyrrole coated thermally exfoliated graphite nanoplatelets and the effect of oxygen surface groups on the interaction of platinum catalysts with graphene-based nanocomposites

Expanded graphite oxide (GO) synthesized by graphite oxidation and thermal expansion was exposed to ultrasonic vibration to obtain graphite nanoplatelets (GNFs). Then, expanded GO as conductive filler was dispersed in polypyrrole matrix in order to be utilized as catalyst support. Electrical conductivities and polymer thickness of GNF-based composites were tailored at different feeding mass ratios. Thermal expansion led to the removal of oxygen functional groups on the surface, and the C/O ratio increased to 6. The highest C/O ratio had less hydrophilic carbon surface, and this decreased the interaction of Pt particles with support. When comparing Pt deposition behavior of GO, expanded GO, graphene nanosheets, and their composites, the results showed that Pt dispersion increased with increasing amount of oxygen functional groups on the surface of the samples. This workwas the first comprehensive and quantitative investigation on the relationship between Pt dispersion and surface oxygen functional groups of graphene-based nanocomposites

An improved technique for the exfoliation of graphene nanosheets and utilization of their nanocomposites as fuel cell electrodes

Graphene nanosheets (GNS) were separated from graphite by an improved, safer and mild method including the steps of oxidation, thermal expansion, ultrasonic treatment and chemical reduction. Graphene nanosheets (GNS) were exfoliated by following two ways. 1st way, the longest exfoliation technique, contained these steps: graphite oxidation, ultrasonic treatment, thermal exfoliation, ultrasonic treatment and chemical reduction. 2nd way, the shortest exfoliation technique, included graphite oxidation, ultrasonic treatment and chemical reduction. Both the reaction procedures with thermal expansion and without thermal expansion led to the formation of GNS