Efficient Photocatalytic Two-Electron Halide Oxidation over p-Block Metal Bi- and Sb-Based Catalysts

Halide (X–, X = Cl, Br) oxidation provides a promising alternative to water oxidation reaction (WOR) due to the feasibility of the reaction, richness of the reactants, and extensive application of the products (X2, HOX, and OX–) for photocatalysis. Bismuth oxyhalide (BiOX) is still the most efficient photocatalyst applied for halide oxidation ever reported, but relative reaction mechanisms remain understudied, and the reactivity needs to be optimized. Herein, Sb(III) is introduced into BiOX (Sb-BiOX), and by involving itself in the cycle of reactive oxygen species, the reaction was significantly boosted, affording HClO up to 482.5 μM within 30 min. Endowed by the favorable 2e– redox couple due to their unique s2 electron configuration of Bi(III) and Sb(III), the oxidation of X– was performed in a 2e– manner over Sb-BiOX. Because of the introduction of Sb(III), high-valent metal (M(V), M = Sb, Bi) and metal peroxide (M-OOH) could be generated more expeditiously and more easily in situ under light irradiation, which are revealed to be the key oxidizing species for halide oxidation. This work provides an in-depth understanding of promoting the photocatalytic oxidation of halide and could offer more inspiring photocatalytic paradigms for energy-related small-molecule conversion reactions that rely on the WOR half-reaction.