Synergistically Enhanced Electrocatalytic Performance of Mn-Co-Ni Oxides/rGO Composite for Efficient Oxygen and Hydrogen Evolution Reactions

This study presents the development of a highly efficient NiCoMn@N,Co-rGO electrocatalyst designed to facilitate electrochemical water electrolysis, specifically addressing both the Oxygen Evolution and Hydrogen Evolution Reactions. This catalyst features a novel hybrid nanostructure comprising Co-Ni-Mn oxides integrated onto nitrogen- and cobalt-co-doped reduced graphene oxide (N,Co-rGO). The synthesis involved the improved Hummers’ method for graphene oxide preparation, followed by nitrogen and cobalt doping via calcination, and deposition of Co-Ni-Mn oxides through a solvothermal process. Physicochemical and electrochemical characterizations confirmed the successful formation of a mesoporous structure and efficient synergy between the metal oxides and graphene substrate. The NiCoMn@N,Co-rGO composite exhibits superior catalytic efficiency in facilitating the Oxygen Evolution Reaction in alkaline media, achieving a potential of 1.58 V at 10 mA/cm² (overpotential: 0.27 V), compared to 1.62 V (overpotential: 0.50 V) for NiCoMn oxide. For the Hydrogen Evolution Reaction, it achieves a potential of -0.50 V at -10 mA/cm² (overpotential: 0.49 V), similar to NiCoMn oxide. The improved efficiency is ascribed to the synergistic effects of nitrogen and cobalt doping in the reduced graphene oxide framework, improving conductivity, active site accessibility, and structural stability. These findings establish NiCoMn@N,Co-rGO as a more efficient electrocatalyst for OER.