Coordination Engineering of Dual Co, Ni Active Sites in N-Doped Carbon Fostering Reversible Oxygen Electrocatalysis.

The development of affordable and non-noble-metal-based reversible oxygen electrocatalysts is required for renewable energy conversion and storage systems like metal-air batteries (MABs). However, the nonbifunctionality of most of the catalysts impedes their use in rechargeable MAB applications. Moreover, the loss of active sites also affects the long-term performance of the electrocatalyst toward oxygen electrocatalysis. In this work, we report a simplistic yet controllable chemical approach for the synthesis of dual transitional metals such as cobalt, nickel, and nitrogen-doped carbon (CoNi-NC) as bifunctional electrode materials for rechargeable zinc-air batteries (ZABs). The spatially isolated Ni-N and Co-N active units were rendered for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. The individual efficacy of both reversible reactions enables an Δ value of ∼0.72 V, which outperforms several bifunctional electrocatalysts reported in the literature. The half-wave potential () and overpotential were achieved at 0.83 V and 330 mV (vs RHE) for ORR and OER, respectively. The peak power density of ZAB equipped with the CoNi-NC catalyst was calculated to be 194 mW cm. The present strategy for the synthesis of bifunctional electrocatalysts with dual active sites offers prospects for developing electrochemical energy storage and conversion systems.