Surface termination modulation for superior S-Scheme Bi₂WO₆/BiOI heterojunction photocatalyst: a hybrid density...

The prevailing theoretical frameworks indicate that depending on the growth conditions, the Bi₂WO₆(001) surface can manifest in three distinct terminations-DL-O-Bi (DL: double layers), O-Bi, and O-W. In this study, we conduct a comprehensive examination of the interplay between these terminations on Bi₂WO₆(001) and the 1I-terminated BiOI(001) facet, especially focusing on their impact on the photocatalytic activity of Bi₂WO₆/BiOI heterostructure, applying hybrid functional calculations. The models formulated for this research are designated as Bi₂WO₆(O-Bi)/BiOI(1I), Bi₂WO₆(DL-O-Bi)/BiOI(1I), and Bi₂WO₆(O-W)/BiOI(1I). Our findings reveal that Bi₂WO₆(O-Bi)/BiOI(1I) shows a type II band alignment, which facilitates the spatial separation of photo-generated electrons and holes. Notably, the Bi₂WO₆(DL-O-Bi)/BiOI(1I) configuration has the lowest binding energy and results in an S-scheme (or Step-scheme) heterostructure. In contrast to the type II heterostructure, this particular configuration demonstrates enhanced photocatalytic efficiency due to improved photo-generated carrier separation, augmented oxidation capability, and better visible-light absorption. Conversely, Bi₂WO₆(O-W)/BiOI(1I) presents a type I projected band structure, which is less conducive for the separation of photo-generated electron-hole pairs. In summation, this investigation points out that one could significantly refine the photocatalytic efficacy of not only Bi₂WO₆/BiOI but also other heterostructure photocatalysts by modulating the coupling of different terminations via precise crystal synthesis or growth conditions.