Mesoporous Surface-Sulfurized Fe–Co3O4 Nanosheets Integrated with N/S Co-Doped Graphene as a Robust Bifunctional Electrocatalyst for Oxygen Evolution and Reduction Reactions

Playing a significant role in electrochemical energy conversion and storage systems, heteroatom-doped transition metal oxides are key materials for oxygen-involving reactions. Herein, mesoporous surface-sulfurized Fe–Co3O4 nanosheets integrated with N/S co-doped graphene (Fe–Co3O4–S/NSG) were designed as composite bifunctional electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Compared with the Co3O4–S/NSG catalyst, it exhibited superior activity in the alkaline electrolytes by delivering an OER overpotential of 289 mV at 10 mA cm−2 and an ORR half-wave potential of 0.77 V vs. RHE. Additionally, Fe–Co3O4–S/NSG kept stable at 4.2 mA cm−2 for 12 h without significant attenuation to render robust durability. This work not only demonstrates the satisfactory effect of the transition-metal cationic modification represented by iron doping on the electrocatalytic performance of Co3O4, but it also provides a new insight on the design of OER/ORR bifunctional electrocatalysts for efficient energy conversion.