This study investigates the impact of facet-engineering on the charge carrier dynamics in bismuth vanadate (BiVO4) photocatalysts for water oxidation. Using photoinduced absorption spectroscopy (PIA), the researchers compared the accumulation and kinetics of photogenerated holes in facet-engineered BiVO4 (F-BiVO4) and non-faceted BiVO4 (NF-BiVO4) under operando conditions. Key findings include: 1. **Charge Accumulation and Kinetics**: F-BiVO4 exhibits a 10-fold increase in charge accumulation compared to NF-BiVO4, indicating improved charge separation and stabilization. With the addition of Fe(NO3)3, a reversible electron acceptor, F-BiVO4 shows a 30-fold increase in the accumulation of long-lived holes, accompanied by an increased half-life from 2 to 10 seconds. 2. **Pre-Illumination Effect**: Pre-illumination significantly influences hole accumulation, leading to the filling and passivation of deep and inactive hole traps on the BiVO4 surface. This results in a substantial increase in the accumulation of long-lived holes. 3. **Energetic Stabilization**: The addition of Fe(NO3)3 suppresses recombination losses, leading to a 30-fold increase in the density of accumulated holes and a 5-fold increase in their lifetime. This energetic stabilization is estimated to be in the order of hundreds of meV, contributing to the enhanced photocatalytic performance. 4. **Surface Faceting Impact**: Facet-engineering causes at least a 50–100 meV increase in band bending, stabilizing surface holes and retarding the OER relative to NF-BiVO4. However, this slower catalysis is offset by the increased density and lifetime of photoaccumulated holes. 5. **Stability and Performance**: F-BiVO4 demonstrates superior stability compared to typical BiVO4 photoanodes, retaining its OER activity even in highly acidic Fe(NO3)3 solutions for extended periods. Overall, the study quantifies how surface faceting can impact the kinetics of long-lived charge accumulation on metal oxide photocatalysts, highlighting the trade-off between lifetime gain and energetic loss critical for optimizing photocatalytic efficiency.This study investigates the impact of facet-engineering on the charge carrier dynamics in bismuth vanadate (BiVO4) photocatalysts for water oxidation. Using photoinduced absorption spectroscopy (PIA), the researchers compared the accumulation and kinetics of photogenerated holes in facet-engineered BiVO4 (F-BiVO4) and non-faceted BiVO4 (NF-BiVO4) under operando conditions. Key findings include: 1. **Charge Accumulation and Kinetics**: F-BiVO4 exhibits a 10-fold increase in charge accumulation compared to NF-BiVO4, indicating improved charge separation and stabilization. With the addition of Fe(NO3)3, a reversible electron acceptor, F-BiVO4 shows a 30-fold increase in the accumulation of long-lived holes, accompanied by an increased half-life from 2 to 10 seconds. 2. **Pre-Illumination Effect**: Pre-illumination significantly influences hole accumulation, leading to the filling and passivation of deep and inactive hole traps on the BiVO4 surface. This results in a substantial increase in the accumulation of long-lived holes. 3. **Energetic Stabilization**: The addition of Fe(NO3)3 suppresses recombination losses, leading to a 30-fold increase in the density of accumulated holes and a 5-fold increase in their lifetime. This energetic stabilization is estimated to be in the order of hundreds of meV, contributing to the enhanced photocatalytic performance. 4. **Surface Faceting Impact**: Facet-engineering causes at least a 50–100 meV increase in band bending, stabilizing surface holes and retarding the OER relative to NF-BiVO4. However, this slower catalysis is offset by the increased density and lifetime of photoaccumulated holes. 5. **Stability and Performance**: F-BiVO4 demonstrates superior stability compared to typical BiVO4 photoanodes, retaining its OER activity even in highly acidic Fe(NO3)3 solutions for extended periods. Overall, the study quantifies how surface faceting can impact the kinetics of long-lived charge accumulation on metal oxide photocatalysts, highlighting the trade-off between lifetime gain and energetic loss critical for optimizing photocatalytic efficiency.