Enhanced electrocatalytic performance of sulfur vacancy-rich bimetallic cobalt iron sulfide on N, S co-doped rGO for rechargeable Zn-air battery

Herein, bimetallic sulfide with sulfur vacancies and N, S co-doped reduced graphene oxide (Vs-CoxFe1-xS2/N,S- rGO) are synthesized and employed as bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. Generation of sulfur vacancies into the bimetal sulfides not only modifies the electronic structure but enhances the surface charge and polarity, which is beneficial for the electrocatalytic performance in alkaline condition. Furthermore, homogeneously introduced heteroatom dopants in rGO provides numerous defect sites, leading to the effective adsorption of reactants for both ORR and OER. Based on the above features, the electrocatalyst exhibits exceptional performance with high half-wave potential and low overpotential for ORR and OER, respectively, outperforming precious metal-based catalysts. Also, the Vs- CoxFe1-xS2/N,S-rGO-based rechargeable Zn-air battery (ZAB) displayed outstanding battery performances with high specific capacity (754.8 mAh g Zn-1 ) and superior long-term cyclability over 420 cycles. These findings highlight the Vs-CoxFe1-xS2/N,S-rGO catalyst as a promising candidate for high performance electrochemical energy conversion and storage devices.