Surface Propertiesof High-Performing Bi₂₄O₃₁Br₁₀ andits Acid-Driven Conversion to BiOXPhotocatalysts (X = Cl, Br)

Bismuth oxyhalides, including Bi₂₄O₃₁X₁₀ and BiOX (X = Cl and Br), are emerging materials for photocatalysis. In this study, we demonstrate the transformation of Bi₂₄O₃₁X₁₀ (X = Br and Cl) into pure-halide and mixed-halide solid solutions (ss) of BiOX by suspending the Bi₂₄O₃₁X₁₀ powder in HX_(aq) acid solutions. The photocatalytic activity of all BiOX and Bi₂₄O₃₁X₁₀ materials were screened for the photooxidation of benzylamine to <i>N</i>-benzylidenebenzylamine under UV irradiation, i.e., a reaction involving a hydrogen transfer reaction. The catalytic properties of the acid-derived BiOX were impacted by both the parent Bi₂₄O₃₁X₁₀ precursor the acid concentration used in the transformation and the halide content. BiOBr and BiOCl-ss materials derived from Bi₂₄O₃₁Br₁₀ exhibited better catalytic performance compared to those derived from Bi₂₄O₃₁Cl₁₀, and parent Bi₂₄O₃₁Br₁₀ exhibited the highest catalytic activity of all materials. The superior properties of parent Bi₂₄O₃₁Br₁₀ and all Bi₂₄O₃₁Br₁₀-derived materials were then scrutinized by investigating the mechanism of the light-assisted hydrogen transfer of Bi₂₄O₃₁X₁₀ by using inelastic neutron scattering (INS) and X-ray photoelectron spectroscopy (XPS). Bi₂₄O₃₁Br₁₀ exhibited a remarkably higher capability of abstracting and binding H-atoms in comparison with Bi₂₄O₃₁Cl₁₀, which is essential for reactions involving an H-transfer. We propose that this property explains the difference in the catalytic activity between the two Bi₂₄O₃₁X₁₀ materials.