Interface Engineering of Co/CoMoN/NF Heterostructures for High‐Performance Electrochemical Overall Water Splitting

Abstract The development of low‐cost and high‐efficiency catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte is still challenging. Herein, interfacial Co/CoMoN heterostructures supported on Ni foam (Co/CoMoN/NF) are constructed by thermal ammonolysis of CoMoOx. In 1.0 m KOH solution, Co/CoMoN/NF heterostructures exhibit excellent HER activity with an overpotential of 173 mV at 100 mA cm−2 and a Tafel slope of 68.9 mV dec−1. Density functional theory calculations indicate that the low valence state Co site acts as efficient water‐dissociation promoter, while CoMoN substrate has favorable hydrogen adsorption energy, leading to an enhanced HER activity. The Co/CoMoN/NF heterostructures also achieve high OER activity with an overpotential of 303 mV at 100 mA cm−2 and a Tafel slope of 56 mV dec−1. Using Co/CoMoN/NF heterostructures as the cathode and anode, the alkaline electrolyzer requires a low voltage of 1.56 V to reach the current density of 100 mA cm−2 along with superior long‐term durability. This study provides a new design strategy toward low‐cost and excellent catalysts for water splitting.