One- and Two-Step Modification of Multiheterojunction Bismuth-Based Photocatalysts and Their Synergistic Mechanism of VO and Z-Type Heterojunction

The solid-phase method is a common method for the industrial preparation of bismuth-based materials, but it is difficult to achieve efficient photocatalytic performance due to the serious agglomeration of the material after calcination. In this study, bismuth silicate (BSO), bismuth tungstate (BWO), and BWO-BSO bismuth-based photocatalysts are successfully prepared by the solid-phase method, and BiOBr is introduced by one-step and two-step modification processes, which can create a "bridging" effect on BWO-BSO to solve the interfacial transport problem. These processes enhance the oxygen vacancies (V_O) and adsorbed oxygen content, which facilitates the formation of a multi-Z heterogeneous structure and increases the electron (e^-) transport rate, improving the photocatalytic performance. In particular, although Bi₁₂SiO₂₀ is completely converted to Bi₂SiO₅, more V_O and adsorbed oxygen are generated during the preparation, which can solve the problem of a heterojunction. In addition, the one-step modification process can also improve the yield of the photocatalyst and solve the problem of preparation efficiency. Compared with the unmodified photocatalyst, the degradation rate of rhodamine B (Rh B) by the photocatalyst TBBB (BWO-BSO-BiOBr modified by the two-step process) and OBBB (BWO-BSO-BiOBr modified by the one-step process) obtained by the two-step method and the one-step method increases by 83.8% and 88.67% within 50 min, respectively. The study provides a new idea for the efficient preparation and modification of bismuth-based photocatalysts by the solid-phase method and provides a new way for the control of defects and multiheterojunctions.