Engineering cobalt nitride nanosheet arrays with rich nitrogen defects as a bifunctional robust oxygen...

Developing high-activity bifunctional oxygen electrocatalysts to overcome the sluggish 4e^- kinetics is an urgent challenge for rechargeable metal-air batteries. Here, we prepared a CoN nanosheet catalyst with rich nitrogen defects (CoN-N_d) through solvothermal and low-temperature nitridation. Notably, the study finds for the first time that only Co LDH materials can be mostly converted to CoN-N_d under the same nitriding conditions relative to different Co-based precursors. Experiments indicate that the constructed CoN-N_d catalyst exhibits preeminent electrocatalytic activities for both oxygen evolution reaction (η₁₀ = 243 mV) and oxygen reduction reaction (J_L = 5.2 mA cm^-2). Moreover, the CoN-N_d-based Zinc-air battery showed a large power density of 120 mW cm^-2 and robust stability over 260 cycles, superior to the state-of-art Pt/C + RuO₂. The superior performance is attributed to a large number of defects formed by the disordered arrangement of local atoms on the catalyst that facilitate the formation of more active sites, and alternate array-like structures thereof improving electrolyte diffusion and gas emission.