Tuning the Electronic Structure and ROS Generation of BiOCl via Salt-Mediated Precipitation

Herein, we investigated how the introduction of different metal salts during the synthesis of bismuth oxychloride affects its electronic structure, revealing that the nature of the metal salt plays a key role in determining the resulting  properties. Several species (Mo, Se, W, V, Ti, Mn, Hg, and Pb) were added to affect the precipitation of the BiOCl photocatalysts. Prepared samples were investigated concerning their crystal structure, elemental composition, morphology, surface area, and optical properties, which were discussed considering possible effects of Bi substitution from the density functional theory calculations. Ti and Hg influence only the crystal growth and morphology. Mo, W, and V, as metallates, shift the absorption to the visible region, but the resulting photocatalytic activity was hindered. Pb²⁺ and Mn²⁺ ions substitute for Bi, acting as acceptor defects. Moreover, MnCl₂ lead to significant crystal growth and formation of well-defined {100}, {110}, {101}, and {111} facets. The BiOCl:Mn sample shows increased activity, connected with conduction band (CB) shift and enhanced O₂ reduction to ∙O₂ ^-. Introduction of SeO₃ ^2- deposits Se⁴⁺/S⁰ species on the surface, leading to the formation of smaller, well-defined rectangular BiOCl crystals. Surface selenium acts as electron traps, increasing the charge carriers lifetime and promoting 2-electron reduction of O₂ to H₂O₂.