Enriched Surface Oxygen Vacancies of Photoanodes by Photoetching with Enhanced Charge Separation

A facile photoetching approach is described that alleviates the negative effects from bulk defects by confining the oxygen vacancy (O_vac ) at the surface of BiVO₄ photoanode, by 10-minute photoetching. This strategy could induce enriched O_vac at the surface of BiVO₄ , which avoids the formation of excessive bulk defects. A mechanism is proposed to explain the enhanced charge separation at the BiVO₄  /electrolyte interface, which is supported by density functional theory (DFT) calculations. The optimized BiVO₄ with enriched surface O_vac presents the highest photocurrent among undoped BiVO₄ photoanodes. Upon loading FeOOH/NiOOH cocatalysts, photoetched BiVO₄ photoanode reaches a considerable water oxidation photocurrent of 3.0 mA cm^-2 at 0.6 V vs. reversible hydrogen electrode. An unbiased solar-to-hydrogen conversion efficiency of 3.5 % is realized by this BiVO₄ photoanode and a Si photocathode under 1 sun illumination.