Dual Mo‐Doping in BiVO 4 /FeCoNiO x Photoanode Enables Near‐Theoretical Photocurrent Density via Synergistic Bulk‐Surface Engineering for Solar Water Splitting

Abstract Bismuth vanadate (BiVO₄) is an auspicious photoanode material for photoelectrochemical (PEC) water splitting, but its performance is fundamentally limited by severe charge recombination and sluggish kinetics of the oxygen evolution reaction (OER). Herein, a dual electronic modulation strategy is developed by incorporating molybdenum (Mo) dopants simultaneously into the FeCoNiO x cocatalyst surface and the bulk phase of BiVO₄. The resulting Mo:FeCoNiO x /Mo:BiVO₄ photoanode delivers a near‐theoretical photocurrent density of 7.15 mA cm⁻ 2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5 G illumination. This exceptional performance arises from the Mo‐triggered cross‐scale electronic reconstruction: (1) In the bulk, Mo substitution at vanadium (V) sites in BiVO₄ enhances charge transport via n‐type doping; (2) At the surface, Mo incorporation into FeCoNiO x triggers electron redistribution, creating localized electron reservoirs at Fe/Co/Ni sites. Combined density functional theory (DFT) calculations and experimental validation reveal that the reconfigured Fe sites serve a dual function as efficient hole traps and highly active OER centers, reducing the reaction energy barrier (ΔG *OH ) by 1.26 eV. Moreover, the optimized interfacial charge transport boosts carrier separation efficiency from 84.9% to 96.5% and accelerates hole migration by 2.7‐fold compared to pristine BiVO₄. This work provides insights into multi‐scale electronic engineering for solar energy conversion.