Recent progresses of value-added electrolysis that replace OER with value-added anodic reactions. Representation of the elements: hydrogen (white color), carbon (gray), oxygen (red), nitrogen (blue), and iodine (magenta).

Transition metal selenides (TMSes) have been identified as cost-efficient alternatives to platinum (Pt) for the alkaline hydrogen evolution reaction (HER) owing to their distinct electronic properties and excellent conductivity. However, they encounter challenges such as sluggish water dissociation and severe oxidative degradation, requiring further optimizations. In this study, we developed a dual-site heterogeneous catalyst, Ni₃Se₄-Ni₃N, by decorating Ni₃Se₄ nanoclusters on a Ni₃N substrate. This catalyst design promoted significant interfacial electronic interactions, modulated electronic structures, and enhanced the adsorption of the intermediates. Various spectroscopic analyses and theoretical calculations revealed that the nitride surfaces improved water adsorption and dissociation, enriching the surface with adsorbed hydrogen (H*) atoms, while the Se sites facilitated hydrogen coupling and subsequent release of H₂. Following a hydrogen spillover mechanism, the surface-adsorbed hydrogen atoms were transferred to nearby electron-dense selenide sites for H₂ formation and release. Consequently, the optimized catalyst demonstrated improved HER activity, requiring only an ∼60 mV overpotential at 10 mA cm^-2 current density and maintained stability under higher potential conditions.