Encapsulated CoxSy nanoparticles decorated S, N-doped mesoporous carbon as effective bifunctional oxygen electrocatalyst in rechargeable Zn-air battery

Highlights: • The catalyst possesses desirable microstructure and abundant active sites. • The synergistic effect enhances the electrocatalytic activities. • The catalyst shows outstang ORR/OER activities in Zn-air battery. -- Abstract: Exploiting effective non-noble metal electrocatalysts is imperative and challenging for advanced Zn-air batteries (ZABs). This paper reports a type of S,N co-doped mesoporous carbon hybrids decorated with encapsulated cobalt sulfide nanoparticles (Co_xS_y/SNC) by a facile method. The hybrid pyrolyzed at 800 °C (Co_xS_y/SNC-800) shows optimal microstructure, and possesses abundant active sites. Additionally, the synergistic effect between the Co_xS_y nanoparticles and graphitic-carbon matrices can effectively improve the electrocatalytic activities. Therefore, Co_xS_y/SNC-800 exhibits a high half-wave potential of 0.80 V towards oxygen reduction, low overpotential of 350 mV at 10 mA cm⁻² towards oxygen evolution, and excellent electrocatalytic stability. The bifunctional oxygen activity is super to the commercial catalysts and comparable with the recent reported electrocatalysts. Moreover, a ZAB with the Co_xS_y/SNC-800 as air-electrode catalyst displays a peak power density of 136 mW cm⁻², low charge/discharge voltage gap and outstanding cycling stability. Undoubtedly, this finding provides a simple strategy for preparing low-cost bifunctional catalyst in advanced energy conversion and storage devices.