Fast Interfacial Hole Consumption Suppresses Space-Charge Layer Trap Filling in BiVO₄ Photoanodes

Photoelectrochemical (PEC) oxidation of biomass-derived organics (e.g., glycerol) can outperform water oxidation while coproducing value-added chemicals. However, the kinetic basis of this enhanced performance, such as hole consumption dynamics and space-charge-layer (SCL) trap filling under PEC operating conditions, remains poorly understood. Using BiVO₄ as a model photoanode, we combine operando optical and photocurrent spectroscopies, including trap-selective pump-push photocurrent (PPPC) mapping, to track bulk and interfacial charge-carrier dynamics over the femtosecond-to-second (fs-s) time scale. Overall, we show that glycerol oxidation accelerates interfacial hole consumption, lowering the surface-hole density required to sustain a given photocurrent, thereby suppressing SCL trap filling and trap-mediated recombination. Glycerol increases the per-hole turnover frequency 32-fold (∼3.5 to ∼113.2 s^-1) and the photocurrent density at 1.23 V_RHE from ∼0.5 to ∼1.3 mA cm^-2, while formic acid and dihydroxyacetone are the dominant quantified liquid products. Spatially resolved PPPC mapping (over ∼20 mm²) shows that glycerol also suppresses localized trap-filled hot spots. Glycerol leaves the dominant early time bulk carrier dynamics largely unchanged while suppressing the microsecond buildup of trapped electrons in the SCL. These results highlight microsecond time-scale kinetic competition between interfacial hole consumption and SCL trap filling as a key design principle for PEC oxidation of renewable organics.