Substrate-Assisted Deposition of Metal Oxides on Three-Dimensional Porous Reduced Graphene Oxide Networks as Bifunctional Hybrid Electrocatalysts for the Oxygen Evolution and Oxygen Reduction Reactions

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are of great importance for energy conversion processes, such as water electrolysis, metal–air batteries, and fuel cells. Herein, we report a substrate-assisted in situ reduction method to prepare three-dimensional reduced graphene oxide (3DRGO) networks decorated with a range of mixed cobalt oxide and nickel oxide nanosheets as a new type of bifunctional catalyst for oxygen evolution and oxygen reduction. Among the different composite catalysts, Co₃O₄@3DRGO showed highest catalytic activities in OER and ORR with an excellent stability. This catalyst is used to catalyze the oxygen reactions in a Zn–air battery as a proof-of-concept. The current results render new insights into developing low-cost, next-generation bifunctional catalysts for photoelectrochemical cells for energy storage and conversion.