Interfacial modification of BiVO4 photocatalyst: Construction of heterojunction with AgI

Abstract

To resolve BiVO₄'s overly negative valence band potential inhibiting hydroxyl radical generation, AgI/BiVO₄ photocatalyst composites were synthesized via a precipitation method. The photocatalytic performance and photogenerated charge transfer mechanism were studied. When the molar ratio of Ag to Bi was 0.5, the photocatalytic performance peaked, achieving an 83.0 % degradation degree of methylene blue solution after 60 min of light irradiation. The first-order reaction rate constant (k) was 0.0256 min⁻¹, which was 15.0 times and 2.3 times higher than that of pure AgI and pure BiVO₄, respectively. BiVO₄ and AgI coupling formed a Z-scheme heterojunction, transferring photogenerated electrons from the conduction band of AgI to valence band of BiVO₄ while retaining highly oxidative holes on AgI and highly reductive electrons on BiVO₄, which is beneficial to the photocatalytic performance. Reactive species trapping experiments identified hydroxyl radicals as the dominant active species. This charge transfer mechanism facilitated charge separation, promoted the formation of hydroxyl radicals, and enhanced photocatalytic activity.