Effect of Graphene Encapsulation of NiMo Alloys on Oxygen Evolution Reaction

Electrochemical water splitting is an ecofriendly technology for generating oxygen and hydrogen from water. The electrode is a key component that controls the efficiency of water splitting. Although noble metals such as Pt, Ru and Ir can achieve high energy efficiencies, their application in water splitting is limited by their high cost. Thus, developing efficient noble-metal-free electrodes is necessary to achieve sustainable hydrogen societies. Here, we report a technique of graphene encapsulation of NiMo alloys for realizing both high catalytic activity and high chemical stability in non-noble metal anodes in transition metal impurities-free aqueous KOH electrolyte. Electrochemical analysis showed that graphene encapsulation significantly enhanced the oxygen evolution reaction (OER) activities of the NiMo anodes and provided long electrode lifetimes and performances comparable to those of commercially available anodes. Density functional theory calculation revealed that graphene encapsulation significantly reduced the adsorption energy of intermediates onto the NiMo surface, thereby remarkably enhancing the OER activity. The graphene encapsulation method provides a promising electrode design to improve the performance in water splitting electrolyzers.