CuCo₂S₄@B,N-Doped Reduced Graphene\nOxide Hybrid as a Bifunctional Electrocatalyst for Oxygen Reduction\nand Evolution Reactions

Abstract

In this report, a\nfacile synthetic route is adopted for typically\ndesigning a hybrid electrocatalyst containing boron, nitrogen dual-doped\nreduced graphene oxide (B,N-rGO) and thiospinel CuCo₂S₄ (CuCo₂S₄@B,N-rGO). The electrocatalytic\nactivity of the hybrid catalyst is tested with respect to oxygen evolution\n(OER) and oxygen reduction (ORR) reactions in alkali. Physicochemical\ncharacterizations confirm the unique formation of a reduced graphene\noxide–non-noble-metal sulfide hybrid. Electrochemical evaluation\nby cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) reveals\nthat the CuCo₂S₄@B,N-rGO hybrid possesses enhanced\nORR and OER activity compared to the B,N-rGO-free CuCo₂S₄ catalyst. The synthesized CuCo₂S₄@B,N-rGO hybrid demonstrates remarkable enhancement in catalytic\nperformance with an improved onset potential (1.50 and 0.88 V) and\nlow Tafel slope (112 and 73 mV dec^–1) for both OER\nand ORR processes, respectively. In addition, the catalyst exhibits\na diminutive potential difference (0.81 V) between the potential corresponding\nto the 10 mA cm^–2 current density for OER and the\nhalf-wave potential for ORR. The superior catalytic activity and high\ndurability of the hybrid material may be attributed to the synergistic\neffect arising from the metal sulfide and dual-doped reduced graphene\noxide. The present study illuminates the possibility of using the\ndual-doped graphene oxide and metal sulfide hybrid as a competent\nbifunctional cathode catalyst for renewable energy application.