Unveiling the Synergistic Mechanism of Atomic Rh on Couple Phase CoSe₂/CoSeO₃ for Enhanced Alkaline Water Electrolysis Devices

Abstract Electrochemical water splitting stands out as a highly effective and environment‐friendly strategy for generating pure hydrogen. However, the expensive catalyst required, and the low efficiency of water electrolysis, are still of concern. Herein, a novel Rh–CoSe₂/CoSeO₃ nanocubes heterostructure is designed with a successful robust coupling between CoSe₂ and CoSeO₃, and employed as a bifunctional electrocatalyst for the water splitting system. The interaction enhances metal–substrate bonding and generates the anchor sites for intermediate species, which increases the electrocatalytic efficiency and mass transport kinetics, and offers exceptional stability. The water‐splitting device demonstrates remarkable performance, with a low voltage of 1.62 V at a current density of 20 mA cm⁻² and long‐lasting durability for ‐100 h. This study opens a new avenue toward the creation of extremely effective and long‐lasting catalysts to be used at an industrial scale to allow alkaline water splitting and for other energy conversion devices. The Rh–CoSe₂/CoSeO₃ heterostructure offers promising prospects for advancing sustainable energy technologies and positively impacting the clean energy of the future.