Atomically Dispersed Cobalt- and Nitrogen-Codoped Graphene toward Bifunctional Catalysis of Oxygen Reduction and Hydrogen Evolution Reactions

Development of high-efficiency and stable single-site catalysts for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is an attractive strategy to substitute precious metal platinum for addressing energy and environmental issues. Here, we adopt a simple annealing strategy to embed atomic cobalt into nitrogen-doped graphene for efficient catalysis of HER and ORR. The as-prepared catalyst shows high activity and durability for HER with a low overpotential of 182 and 172 mV at 10 mA cm–2 in 0.5 M H2SO4 and 0.1 M KOH, respectively. In addition, it also exhibits excellent ORR performance in both alkaline and acid electrolytes, including a positive onset potential (0.97 V versus 0.79 V) and half-wave potential (0.87 V versus 0.69 V), and a low Tafel slope (46.1 mV·dec–1 versus 48.2 mV·dec–1). Meanwhile, it manifests remarkable electrochemical stability, and strong tolerance to methanol crossover. The atomic cobalt coordinated with several nitrogen atoms should be the active centers for HER and ORR. The good stability of electrochemical HER and ORR should be attributed to the stable Co-Nx moieties and the strong interaction between the Co-Nx and the graphene support. Our work provides a facile strategy for developing high-efficiency and durable HER and ORR electrocatalysts