Amorphous Ti(iv)-modified Bi₂WO₆ with enhanced photocatalytic performance

Crystalline TiO₂ is a well-known oxide which can be used to improve the photocatalytic performance of other photocatalytic materials by a semiconductor-coupling strategy. However, compared with crystalline TiO₂, amorphous TiO₂-modified semiconductors have seldom been reported. In this study, amorphous TiO₂ (referred to as Ti(iv)) as a hole cocatalyst was used to modify the photocatalytic performance of a Bi₂WO₆ photocatalyst by a facile wet-chemical method, where metallic Pt as the electron cocatalyst was also coated on the Bi₂WO₆ surface to promote the interfacial electron transfer. It was found that the dual-cocatalyst modified Ti(iv)–Pt/Bi₂WO₆ photocatalyst exhibited an obviously higher photocatalytic performance than the blank Bi₂WO₆ and single-cocatalyst modified Pt/Bi₂WO₆ and Ti(iv)/Bi₂WO₆. Based on the present experimental results, we propose a synergistic effect of amorphous Ti(iv) and Pt to illustrate the enhanced photocatalytic activity of the Ti(iv)–Pt/Bi₂WO₆ photocatalyst, namely amorphous Ti(iv) works as a hole cocatalyst to rapidly transfer the photogenerated holes in the valence band of Bi₂WO₆, while Pt acts as an electron cocatalyst to rapidly transfer the photogenerated electrons on its conduction band. As a consequence, the transfer rate and the interfacial catalytic reaction of photogenerated electrons and holes were simultaneously accelerated, which resulted in improved photocatalytic performance of the Ti(iv)–Pt/Bi₂WO₆ photocatalyst. The above synergistic effect mechanism in Ti(iv)-modified Bi₂WO₆ photocatalysts can further be demonstrated by using a low-cost Fe(iii) or Cu(ii) electron cocatalyst. The present study suggests that amorphous Ti(iv) can act as a new and effective hole cocatalyst for the enhanced photocatalytic performance of photocatalysts, which provides an approach for the design and development of high-performance visible-light photocatalysts with amorphous oxides.