Potential of metal-free graphene alloy as electrocatalysts for oxygen reduction reaction

Extensive research and development on theoretical calculation and synthetic methods over the past few years have made doped graphene one of the most promising candidates for metal-free oxygen reduction reaction (ORR) catalysts. However, from the performance point of view, there is still a long way to go for these doped graphene-based catalysts to meet the requirements needed for commercial applications. What is the key to further improve the catalytic activity of doped graphene toward ORR to make them commercially viable? In this review, we will try to answer this question by fundamentally giving a detailed analysis based on the theoretical calculations to reveal the origin of ORR activity of doped graphene and the structure-performance relationship of such materials. Thereafter, we will provide an overview on the recent advances in the catalytic activity improvement of doped graphene, including major works using approaches of increasing the number of active sites, controlling the doping types (particularly for nitrogen doped graphene), developing co-doped graphene, and extending the surface area of doped graphene. Finally, in this perspective, we discuss some development opportunities and pathways that can lead to more efficient doped-graphene based ORR electrocatalysts approaching the practical use for fuel cells and metal-air batteries.