CuCo₂S₄@B,N-Doped Reduced Graphene Oxide Hybrid as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions

Abstract

In this report, a facile synthetic route is adopted for typically designing a hybrid electrocatalyst containing boron, nitrogen dual-doped reduced graphene oxide (B,N-rGO) and thiospinel CuCo₂S₄ (CuCo₂S₄@B,N-rGO). The electrocatalytic activity of the hybrid catalyst is tested with respect to oxygen evolution (OER) and oxygen reduction (ORR) reactions in alkali. Physicochemical characterizations confirm the unique formation of a reduced graphene oxide-non-noble-metal sulfide hybrid. Electrochemical evaluation by cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) reveals that the CuCo₂S₄@B,N-rGO hybrid possesses enhanced ORR and OER activity compared to the B,N-rGO-free CuCo₂S₄ catalyst. The synthesized CuCo₂S₄@B,N-rGO hybrid demonstrates remarkable enhancement in catalytic performance with an improved onset potential (1.50 and 0.88 V) and low Tafel slope (112 and 73 mV dec^-1) for both OER and ORR processes, respectively. In addition, the catalyst exhibits a diminutive potential difference (0.81 V) between the potential corresponding to the 10 mA cm^-2 current density for OER and the half-wave potential for ORR. The superior catalytic activity and high durability of the hybrid material may be attributed to the synergistic effect arising from the metal sulfide and dual-doped reduced graphene oxide. The present study illuminates the possibility of using the dual-doped graphene oxide and metal sulfide hybrid as a competent bifunctional cathode catalyst for renewable energy application.