Graphene and N-doped graphene for electrocatalysis

Abstract

Unique structural and electronic properties of graphene have evoked huge interest in its potential applications in a wide range of fields, e.g. nanoelectronic devices, sensors and catalysis. However, realization of these applications will rely on the availability of high quality graphene on a large scale. We developed here a non-liquid phase method for production of free-standing graphene nanosheets via one step thermal splitting of commercial polycrystalline silicon carbide granules. These graphene sheets contain few defects and exhibit a good stability against oxidation. This novel synthetic approach is expected to enable mass production of high quality graphene, which could promote further development of graphene-based technologies, in particular fuel cell electrocatalysts and other industrial catalysts. On the other hand, theoretical studies predicted that doping graphene with nitrogen can tailor its electronic properties and chemical reactivity. However, experimental investigations are still limited due to the lack of synthesis techniques that can deliver a reasonable quantity. We report here a novel bottom up approach for N-doped graphene based on a simple reaction of tetrachloromethane and lithium nitride under mild conditions. A gram scale N-graphene can be easily obtained in laboratory with varying nitrogen contents. The electronic structure perturbation in the graphene network due to the incorporation of nitrogen has been observed experimentally using STM, which is corroborated by density functional theory simulations. This method could enable a larger scale production since the one-pass yield only depends on the capacity of the autoclave. The obtained N-doped grapheme showed an enhanced activity as a catalyst for fuel cell cathode oxygen reduction reaction with respect to pure graphene and commercial carbon black XC-72