The role of Sn in enhancing the visible-light photocatalytic activity of hollow hierarchical microspheres of the Bi/BiOBr heterojunction

Hollow hierarchical microspheres of Bi/BiOBr (SBB) with oxygen vacancies were prepared using a one step solvothermal method. It was found that the stannous chloride dihydrate played key roles in the formation of Bi, defects and the stacking mode of hierarchical construction units. Positron annihilation lifetime spectroscopy (PALS) was used to demonstrate the oxygen vacancies in Bi/BiOBr samples. The density of states (DOS) of the valence band of BiOBr can be modulated by the introduction of oxygen vacancies according to the valence band XPS and Density Functional Theory (DFT) calculations. Analyses of photoluminescence and BET demonstrated that SBB hollow hierarchical microspheres with higher specific surface area have a lower recombination rate of photo-generated electrons and holes. The photocatalytic and adsorptive performances showed that the samples exhibited stronger adsorption capacity toward rhodamine B (RhB) and highly efficient photocatalytic activity in the degradation of RhB, which were attributed to the higher adsorption ability and synergistic effect of oxygen vacancies and construction of the heterojunction structure (Bi/BiOBr).