Amorphous titanium dioxide with abundant defects induced by incorporation of silicon dioxide: A potential non-radical activator of hydrogen peroxide

Catalysts based on titanium dioxide (TiO₂) have demonstrated a significant potential for oxidizing intractable organic pollutants in heterogenous Fenton-like reactions, even in the absence of light irradiation. In this study, defective amorphous TiO₂ enriched Ti³⁺ and oxygen vacancies (Ov) was synthesized by incorporation of silicon dioxide (SiO₂) via a simple sol-gel method. Based on a systematic exploration, an optimal amount of SiO₂ was found to be crucial in promoting the formation of Ov and Ti³⁺, which was achieved by maximizing the non-hexacoordinate structure (Ti_4/5/7c) in amorphous TiO₂. Furthermore, an unusual singlet oxygen (¹O₂) based non-radical mechanism was confirmed. It was proposed that the hydroxyl radicals (•OH) produced by Ti³⁺ active sites during hydrogen peroxide (H₂O₂) activation may adsorb on the TiO₂ surface for extended periods, owing to their favorable interactions with the surface Ov and hydroxyl groups (-OH), thus facilitating their transformation to ¹O₂. Moreover, the optimized catalyst exhibited favorably catalytic performance across a broad pH range (3-11), making it a promising candidate for applications in rigorous environmental conditions.