Promoted Electron Transfer along the Newly Formed Bi–O–S Bond in Bi₂O(OH)₂SO₄

Today, research is increasingly focused on surface control of semiconductors; however, very little is known about the effect of bulk chemical bonds on photoelectrochemistry properties. In this report, Bi₂O­(OH)₂SO₄ with and without specific Bi–O–S bonds (WB and WOB) is synthesized via hydrothermal and water bath methods, respectively, and we reveal the Bi–O–S bond-dependent photoelectrochemistry properties. Both WB and WOB belong to a monoclinic space group (P21/c), but the newly synthesized WB has different unit cell parameters of a = 8.062 Å, b = 8.384 Å, and c = 5.881 Å, compared with WOB (a = 7.692(3) Å, b = 13.87(1) Å, c = 5.688(2) Å). Compared with WOB (4.18 eV), WB has a narrower band gap (3.6 eV), higher electrical conductivity, and an increased charge separation efficiency. It is found that the electrons are easy to transfer along the newly formed Bi–O–S bond in bulk; thus, the Bi–O–S bonds in WB have efficiently improved the photoelectrochemistry properties. As a result, WB exhibits a 1.1 times higher photocatalytic activity than WOB for the degradation of RhB under ultraviolet light irradiation (<420 nm). This helps us to understand the photoelectrochemistry properties from crystal bulk, but not merely from the crystal surface; thus, this study provides a new idea for improved photoelectrochemistry properties of semiconductors.