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.