Theoretical Insight into the Role of Defects and Facets in the Selectivity of Products in Water Oxidation over Bismuth Vanadate (BiVO4)

Bismuth vanadate (BiVO₄) is an efficient photocatalyst or photoanode in water oxidation. However, the product selectivity in water oxidation over the most exposed clean and defective (001) and (101) facets is not clear. In this work, we investigated the water oxidation reaction on clean and oxygen deficient (001) and (101) facets and on Mo/W-doped facets using density functional theory. The pure (001) facet, we found, promotes OH radical formation. In the presence of oxygen vacancies, the O₂ evolution is preferred on the (101) facet with an overpotential of 0.52 V. On doping with Mo/W, the H₂O₂ evolution is preferred on the (101) facet with the overpotential of about 0.40 V; while on the (001) facet, the O₂ evolution is preferred with the overpotential of about 0.5 V. We also found that, on the (101) facet, there is a strong charge transfer from Bi atoms to the intermediates of water oxidation; but on the (001) facet, there is not. Our calculations could guide the design of the photocatalyst toward specific products of the water oxidation reaction, such as an OH radical, H₂O₂, or O₂. Moreover, the results show that the preferred sorption on the (101) facet may be a reason for the photoinduced charge separation between (101) and (001) facets of BiVO₄.