Unveiling Fast Charge Transfer Dynamics at Semiconductor/Electrocatalyst/Electrolyte Dual Interfaces via Boron Engineering for Efficient Water Splitting

Abstract Promoting the generation of highly active species at semiconductor/electrocatalyst/electrolyte interfaces can enhance photoelectrochemical (PEC) water splitting performance, yet achieving this goal remains challenging with current strategies. Herein, a feasible boron (B) engineering strategy is proposed to simultaneously modulate interface charge transfer and surface catalytic reaction dynamics by incorporating electron‐deficient B into a state‐of‐the‐art semiconductor/electrocatalyst system (BiVO ₄ /FeNiOOH). Scanning photoelectrochemical microscopy and X‐ray photoelectron spectroscopy reveal that the introduction of B into FeNiOOH facilitates internal charge transfer (electrons migrate along the direction of Ni→B→Fe) via a charge relay effect, and generates more active species (Fe ^3‐δ and Ni ^3+δ ) at the BiVO ₄ /FeNiOOH‐B/electrolyte interface, thereby accelerating both charge transfer and surface reaction dynamics. As anticipated, the BiVO ₄ /FeNiOOH‐B photoanode achieves a remarkable photocurrent density of 6.58 mA cm ⁻² at 1.23 V _RHE , along with excellent photostability. Furthermore, this B‐engineering effect can be applied to develop alternative TiO ₂ /FeNiOOH‐B configurations to further enhance PEC activity. This work opens new possibilities for B engineering in semiconductor/electrocatalyst systems, enabling highly efficient and stable water‐splitting applications.