Vapor Phase Dealloying Derived Nanoporous Co@CoO/RuO₂ Composites for Efficient and Durable Oxygen Evolution Reaction

Abstract The development of low‐cost and effective oxygen evolution reaction (OER) electrocatalysts to expedite the slow kinetics of water splitting is crucial for increasing the efficiency of energy conversion from electricity to hydrogen fuel. Herein, 3D bicontinuous nanoporous Co@CoO/RuO₂ composites with tunable sizes and chemical compositions are fabricated by introducing vapor phase dealloying of cobalt‐based alloys. The influence of physical parameters on the formation of nanoporous Co substrates with various feature ligament sizes is systematically investigated. The CoO/RuO₂ shell is constructed by integrating a thin layer of RuO₂ on the inner surface of nanoporous Co, where the CoO interlayer is formed by annealing oxidization. The composite catalyst delivers an ultralow overpotential of 198 mV at 10 mA cm⁻², Tafel slope of 57.1 mV dec⁻¹, and long‐term stability of 50 h. The superior OER activity and fast reaction kinetics are attributed to charge transfer through the coupling of CoORu bonds at the interface and the excellent nanopore connectivity, while the durability originates from the highly stable CoO/RuO₂ interface.