Engineering the multiscale structure of bifunctional oxygen electrocatalyst for highly efficient and ultrastable zinc-air battery

Rechargeable zinc-air batteries (ZABs) are attracting enormous attention owing to their low cost and high theoretical energy density. However, their practical applications are impeded by the low lifetimes and inferior energy conversion efficiency as a result of poor catalyst stability and sluggish oxygen reaction kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at their air cathode. Herein, a multiscale structural engineering of the novel catalyst of Fe/Co single atoms co-doped graphite nanoarrays mounted on carbon microspheres (FeCo(a)-ACM) is reported towards ORR and OER for ZABs. In micro-scale, 3D hierarchically porous carbon microspheres facilitate the mass and electron transport; in nano-scale, ordered graphite nanoarrays increase the accessible chances of the active sites; in atomic-scale, chemical doping of Fe/Co single atoms boost the intrinsic ORR and OER activity and finally enhance the performance of ZABs. The FeCo(a)-ACM exhibits excellent ORR (onset potential: 1.03 V, half-wave potential: 0.90 V) and OER (1.60 V at 10 mA cm−2) activity. In a practical demonstration, a low charge-discharge gap and a record rechargeable lifetime lasting 900 h at 10 mA cm−2 are achieved by zinc-air battery with FeCo(a)-ACM within the air electrode.