Precise Identification of Active Sites of a High Bifunctional Performance 3D Co/N-C Catalyst in Zinc-air Batteries

Developing highly active and robust non-noble metal bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of dominant significance for global applications in rechargeable Metal-air Batteries. Fine-tuning the exposed active sites is a competent way to improve their performance. Herein, the NaCl template-assisted strategy for rationally designing a three-dimensional cellular structured nitrogen-doped carbon matrix integrated with nano-scaled Co species has been developed. The resulting elec-trocatalyst (3D Co/N-C) exhibits a positive half-wave potential of 0.84 V (vs RHE) in ORR, and a low potential of 1.56 V (vs RHE) at 10 mA cm-2 during OER process. Moreover, 3D Co/N-C based Zn-air Batteries (ZABs) exhibit excellent battery performance, especially remarkable power density. The poisoning experiments and DFT cal-culations identify active sites as pyridinic N and Co during ORR and OER processes, respectively. This work provides a general and easy-to-perform tactic to design bifunctional catalysts, thus helps precisely modulate effective components for ZABs.