Electrodeposition of Unary Oxide on a Bimetallic Hydroxide as a Highly Active and Stable Catalyst for Water Oxidation

For industrial-scale water electrolysis, development of a highly stable and active oxygen evolution reaction (OER) electrocatalyst is highly demanded. In this study, we report an efficient OER electrocatalyst of CeO_x (unary oxide) and NiFe-OH (bimetallic hydroxide) electrochemically deposited on a macroporous nickel foam substrate. The synthesized electrocatalyst exhibits remarkably improved OER performance by reaching a current density of 100 mA cm^-2 at a low overpotential of 280 mV, which is quite superior to that of most of the previously reported non-noble-metal-based OER electrocatalysts. Furthermore, the developed catalyst demonstrated a minor Tafel slope of 43.2 mV dec^-1 with good stability under a large current at a continuous operation of 80 000 s in a strong alkaline electrolyte. Experimental observations revealed that the combination of CeO_x and NiFe-OH accelerates the electroadsorption energies between the electrocatalyst surface and oxygen intermediates, considerably contributing to the OER enhancement. These results undoubtedly represent an important milestone toward the development of efficient OER electrocatalysts for applications as industrial water electrolyzers.