The adsorptive behavior and photoreduction processes of CrO₄²⁻ were investigated in 110-BiOBr and 001-BiOBr suspensions without/with visible-light irradiation. On the basis of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) measurements, CrO₄^2- ions were adsorbed on the surface of 001-BiOBr in the form of = Bi-O-Cr-O₃- complexes, and their photoreduction depended on the pH of the solution. By contrast, CrO₄^2- were predominantly intercalated into the bulk of 110-BiOBr, forming [OBi]⁺-(O-CrO₂-O)^2--[BiO]⁺ complexes. It was found that 110-BiOBr showed higher efficiency for photoreduction of CrO₄^2- at pH 2 and 7. Density functional theory (DFT) calculation further revealed that both the acceptor Cr 3d and donor O 2p of CrO₄^2- impurity levels were introduced into 110-BiOBr bulk, enlarging the visible absorption range of BiOBr. Therefore, the photoreduction of Cr(VI) occurred by direct photo-generated electron transfer from the improved valence band of 110-BiOBr to the Cr 3d orbitals for reduction of Cr(VI) to Cr(III) without the involvement of H⁺.

在没有/有可见光照射的情况下，在110-BiOBr和001-BiOBr悬浮液中研究了CrO ₄ ^2-的吸附行为和光还原过程。在X射线衍射（XRD），高分辨率透射电子显微镜（HRTEM）和X射线光电子能谱（XPS）测量的基础上，CrO ₄ ^2-离子以=的形式吸附在001-BiOBr的表面上。 Bi-O-Cr-O _3-配合物及其光还原取决于溶液的pH值。相比之下，CrO ₄ ^2-主要插入到110-BiOBr的主体中，形成[OBi] ⁺ -（O-CrO ₂ -O）² --[BiO] ⁺复合体。发现110-BiOBr在pH 2和7下对CrO ₄ ^2-的光还原效率更高。密度泛函理论（DFT）计算进一步表明，CrO ₄ ^2-杂质水平的受体Cr 3d和施主O 2p均为引入到110-BiOBr主体中，扩大了BiOBr的可见吸收范围。因此，Cr（VI）的光还原是通过直接的光生电子从改进的110-BiOBr价带到Cr 3d轨道发生的，从而将Cr（VI）还原为Cr（III）而发生的，而没有H ⁺参与。