Preparation And Investigation Of Graphene Based Electrocatalysts For Oxygen Reduction Reaction

Platinum-based catalysts for oxygen reduction reaction (ORR) are used in current fuel cell prototypes, but their large-scale commercial applications have been precluded by high costs. Therefore, searching for efficient, less expensive and more abundant non-precious metal catalysts (NPMCs) for ORR is thus of great importance. In this regard, carbon-supported transition metal-nitrogen (M-Nx-C) materials are generally considered the most promising ORR catalysts. Here, graphene is used as carbon material for fabricating electrocatalyst supports. The structure and the electroactivity of these graphene-based catalysts were thoroughly characterized, and the main research contents and conclusions are as follows:(1) Graphene based non precious metal catalysts for ORR have been fabricated through pyrolysis of a mixture of Fe, Co salts, polyaniline, and rGO. The TEM, EDX, Raman spectrum and XPS analysis’s indicated the transition metal nitrogen containing moieties (M-Nx) could be embedded into the graphene sheets. The effects of Fe and Co on electrochemical properties toward ORR were also investigated, and the results showed the binary metal FeCo-N-rGO was the most active ORR catalyst.(2) Graphene-xerogel-based cathode catalyst for ORR was prepared via supramolecular interaction promoted gelation method followed by a pyrolysis process. The Co-N-GX showed a more positive onset potential, higher cathodic density for the ORR in alkaline media than graphene-sheet-based Co-N catalyst (Co-N-GS), highlighting the importance of high specific surface area for improving the ORR performance.(3) We report a facile and economical procedure to large-scale production of nitrogen-doped graphene nanosheets by a combined process of ball milling of pristine graphite in the presence of melamine and subsequent pyrolysis treatment. The resulted graphene nanosheets are demonstrated as an electrocatalyst with high electrocatalytic activity for ORR, coupling with long-term stability and excellent methanol tolerance. The present approach opens up a possibility for simple mass production of high-quality nitrogen-doped graphene as efficient cathodic electrocatalyst for fuel cells in practice.