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

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 cocatalyst surface and the bulk phase of BiVO₄. The resulting Mo:FeCoNiO/Mo:BiVO₄ photoanode delivers a near-theoretical photocurrent density of 7.15 mA cm⁻ 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 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) 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.