Highly Active Cobalt–Copper–Selenide Electrocatalysts for Solar-Driven Oxygen Evolution Reaction: An Electrochemical Activation Energy Aspect

Effective electrocatalysts with high activity for oxygen evolution reactions (OER) play a crucial role in generating environmentally and sustainable hydrogen fuel via electrolysis. Currently, most highly active electrocatalysts are synthesized through complex multisteps and high-temperature heat treatments, which limit their industrial applications. Herein, we developed a cobalt–copper–selenide (CoCuSe) electrocatalyst for the OER via simple electrodeposition and a hydrothermal method. CoCuSe showed exceptional OER activity by forming highly active oxyhydroxide species through surface reconstruction. In particular, CoCuSe demonstrated a significant reduction in the activation barrier for OER despite exhibiting the same OER mechanism as CoCu(OH)2 and thus improved OER activity. Furthermore, when utilizing CoCuSe in conjunction with an industrial crystalline silicon solar cell, the alkaline water electrolyzer effectively produced hydrogen energy in the presence of natural light, demonstrating a solar-to-hydrogen efficiency of around 13.0%. This research suggests that the remarkable activity of transition metal selenides results from a reduced activation barrier for OER.