Decoupling Volmer and Tafel Steps via Dual‐Site Interface Engineering in Ni/MoBT _x for Efficient Hydrogen Electrocatalysis

Abstract Metallic nickel is a promising Pt‐free catalyst for alkaline hydrogen evolution reaction (HER), but suffers from sluggish water dissociation in the Volmer step and excessively strong hydrogen adsorption in the Tafel step. These two steps impose conflicting demands on surface binding strength, making it difficult to optimize both on a single active site. To address this issue, a dual‐site synergistic catalyst is constructed by coupling Ni with a MoBT _x support possessing strong water dissociation ability. This design enables water dissociation on MoBT _x and subsequent transfer of generated hydrogen species to adjacent Ni sites via reverse hydrogen spillover, thus decoupling Volmer and Tafel steps for hydrogen evolution. Experimental and computational results consistently verify this mechanism. Meanwhile, the metal–support interaction modulates the electronic structure of Ni, tuning the intermediate binding energies to favorable levels for both HER and hydrogen oxidation reaction (HOR). Benefiting from this design, the Ni/MoBT _x heterogeneous electrocatalyst exhibits superior HER performance to Pt/C (32 mV@10 mA cm ⁻² ; Tafel slope: 26.8 mV dec ⁻¹ ), and achieves Pt‐comparable HOR activity with a mass activity of 60.29 mA mg _Ni ⁻¹ at 50 mV. This work highlights 2D metal borides as efficient platforms for alkaline hydrogen electrocatalysis and proposes a dual‐site design to boost catalytic performance.