In-situ synthesis of metal Bi to improve the stability of oxygen vacancies and enhance the photocatalytic activity of Bi4O5Br2 in H2 evolution

Bi4O5Br2 has received considerable interests for energy conversion and environment remediation in recent years. Fabrication of oxygen vacancies (OVs) is effective to improve the photocatalytic activity of Bi4O5Br2. However, OVs are instable and easy to deactivate during continuous photocatalytic process. In this paper, Bi4O5Br2 modified by metal Bi and OVs (Bi-OVs-Bi4O5Br2) have been prepared to improve the stability of OVs and the photocatalytic activity in H2 evolution. Bi-OVs-Bi4O5Br2 exhibited excellent photocatalytic activity with a H2 evolution rate of 67.9 μmol·g−1·h−1, which was 2.1 times higher than that of pure Bi4O5Br2. The enhancement may be attributed to the narrowed band gap, facilitated separation of photogenerated charge carriers, increased adsorption sites for H2O and reduced H2 adsorption energy on the surface of Bi4O5Br2. Notably, the metal Bi could act as reactive sites to activate H2O, so as to avoid OVs to be filled with H2O. As a result, Bi-OVs-Bi4O5Br2 exhibited high photocatalytic stability in continuous test. Results from this study clarified the intrinsic functionality of metal Bi and OVs in Bi4O5Br2 and provided new insights into rational design of highly-efficient Bi-based photocatalyst.