Ni single atoms anchored on N-doped carbon nanosheets as bifunctional electrocatalysts for Urea-assisted rechargeable Zn-air batteries

The sluggish kinetics of oxygen electrode reactions is a bottleneck for the development of rechargeable Zn-air batteries (ZABs). Herein, we report a bifunctional electrocatalyst synthesized by anchoring individually dispersed Ni single atoms on N-doped carbon nanosheets (Ni SAs-NC), which exhibits an outstanding overall performance for oxygen reduction reaction (ORR) and urea oxidation reaction (UOR). Based on that, a conceptual urea-assisted rechargeable ZAB by coupling ORR with UOR of a low thermodynamic potential is demonstrated to have significantly decreased charging voltage and high urea elimination rate. The high bifunctional electrocatalytic activities of Ni SAs-NC endow the urea-assisted ZAB with a dramatically increased energy conversion efficiency of 71.8%, which is improved by 17.1% as compares with the conventional ZABs. The successful implementation of Ni SACs based urea-assisted rechargeable ZABs with an improved energy conversion efficiency may prompt ZAB technology towards practical applications.