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Kejian DengCorresponding author Key Laboratory of Catalysis and Materials Sciences of the State Ethnic Affairs Commission & Ministry of Education, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
In order to distinguish the roles of four types of nitrogen species in oxygen reduction reaction, the ketoamine condensation reactions between the ketone group of graphene oxide and amidogen of aniline and o-phenylenediamine were employed to generate –C=N- bond at the edge of graphene nanoplatelets, and then nitrogen-doped graphene nanoplatelets with pyrrolic N, pyridinic N and pyridinic N+-O- rather than graphitic nitrogen were obtained by post thermal treatments. The resulting catalysts were characterized by X-ray diffraction analysis, X-ray photoelectron spectroscopy and electrochemical measurements. It is found that edge-selectively nitrogen-doped graphene nanopaltelets with nitrogen content of up to 4.28 atom% have been prepared. Nitrogen doping helps to improve activity of oxygen reduction reaction slightly, suggesting nitrogen doping at the edge of graphene does not contribute a lot to the enhancement of activity.
Kendall KevinCorresponding author University of Birmingham, B15 2TT, UK
Graphene-Ceramic Composites (GCCs) have been little studied compared to graphene-polymer composites 1. Recent reviews 23 indicate that both mechanical and electrical property ceramic improvements can be obtained by mixing small quantities, typically 1 to 15% of graphene material with a ceramic precursor, then compacting and sintering. The greatest effect is on the electrical properties. The electrical conductivity of a material was first shown to rise by several orders of magnitude for only a 1% volume addition of graphene as in polymer composites 4 but the stiffness, strength and toughness only increased by 20-160% or so at 5% addition, a rather minor improvement compared to significant increases caused by slight ceramic process changes. Some crack bridging and pull-out mechanism was observed by electron microscopy in graphene-alumina composites, though the effects were modest. Surface friction and wear improvements of around 100% were also notable. This paper seeks to show that much higher toughness increases might be produced using the method pioneered by Clegg et al 5, where the graphite interlayers are replaced with graphene to produce improved ordered interfaces with reliable coverage and consistent interface fracture energy, enabling an increase in the fracture resistance of the ceramic by two orders of magnitude.