First-principles studies on facet-dependent photocatalytic properties of bismuth oxyhalides (BiOXs)

Abstract

The photocatalytic properties were compared for the {001}, {110} and {010} facets of bismuth oxyhalides (BiOXs) through density functional theory (DFT) computations. X-terminated bulk-like {001} facets with clear boundary of [Bi₂O₂] and halogen slabs result in high thermodynamic stability and efficient separation of photo-induced e⁻-h⁺ pairs. Moreover, surface O vacancies, which act as e⁻-h⁺ recombination centers, are energetically unfavorable within {001} facets. BiX-terminated {110} and other facets with surface O vacancies introduce deep defect levels to the band gap, which are detrimental to the separation of e⁻-h⁺ pairs. These findings can better understand the origin of facet-dependent photocatalytic activities in BiOXs, and provide guidance for the design of high-efficiency photocatalysts.