Dual-active-sites design of CoSx anchored on nitrogen-doped carbon with tunable mesopore enables efficient Bi-Functional oxygen catalysis for ultra-stable zinc-air batteries

Developing highly efficient oxygen electrode is particular important in the application of electrochemical energy conversion and storage technologies. In this work, we report the synthesis of highly dispersed CoSx nanocrystals anchored on N-doped mesoporous carbon (CoSx@NMC) network electrode. CoSx@NMC, derived from Fe/Co dual tuning nitrogen/sulfur-containing polymer as carbon precursor, manifests discrete dual-active-sites endowing excellent bifunctional catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The zinc-air battery system assembled from this CoSx@NMC electrode exhibits an open circuit voltage of 1.44V (vs. Zn/Zn⁺) and a peak power density of 269.7 mW cm⁻². Notably, it exhibits a super stability in the galvanostatic discharge of 5 mA and 50 mA, and the voltage could be maintained stable at 1.25V over 90h galvanostatic discharge. Rechargeable zinc-air battery delivers an excellent cycling stability beyond 1288 charge/discharge cycles. The superior electrochemical catalytic properties for ORR/OER are attributed to the strongly coupled pyridine-N, graphitic-N and nanoscale CoSx, which can promote the simultaneous exposure of both OER and ORR active centres. Further investigations reveal that the microstructure of the mesoporous carbon might experience a structural remodeling during the charge/discharge process.