Interface Catalysts of Ni/Co₂N for Hydrogen Electrochemistry

The development of active, durable, and nonprecious electrocatalysts for hydrogen electrochemistry is highly desirable but challenging. In this work, we design and fabricate a novel interface catalyst of Ni and Co₂N (Ni/Co₂N) for hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). The Ni/Co₂N interfacial catalysts not only achieve a current density of -10.0 mA cm^-2 with an overpotential of 16.2 mV for HER but also provide a HOR current density of 2.35 mA cm^-2 at 0.1 V vs reversible hydrogen electrode (RHE). Furthermore, the electrode couple made of the Ni/Co₂N interfacial catalysts requires only a cell voltage of 1.57 V to gain a current density of 10 mA cm^-2 for overall water splitting. Hybridizations in the three elements of Ni-3d, N-2p, and Co-3d result in charge transfer in the interfacial junction of the Ni and Co₂N materials. Our density functional theory calculations show that both the interfacial N and Co sites of Ni/Co₂N prefer to hydrogen adsorption in the hydrogen catalytic activities. This study provides a new approach for the construction of multifunctional catalysts for hydrogen electrochemistry.