Abstract:
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Bismuth vanadate (BiVO4) has emerged as one of the most promising
photoanode materials for solar fuel production. Oxygen vacancies play a pivotal role in the
photoelectrochemical efficiency, yet their electronic nature and contribution to n-type
conductivity are still under debate. Using first-principles calculations, we show that oxygen
vacancies in BiVO4 have two distinguishable geometric configurations characterized by
either undercoordinated, reduced VIVO3 and BiIIO7 subunits or a VIV−O−VIV/V bridge
(split vacancy), quenching the oxygen vacancy site. While both configurations have similar
energies in the bulk, the (001) subsurface acts like an energetic sink that stabilizes the split
oxygen vacancy by ∼1 eV. The barrierless creation of a bridging V2O7 unit allows for
partial electron delocalization throughout the near-surface region, consistent with recent
experimental observations indicating that BiVO4(001) is an electron-rich surface. |