Enhanced photocatalytic desulfurization: unlocking the power of Anderson-type polyoxometalate-boosted (001) TiO2 nanodisks using deep eutectic solvents

Abstract

Achieving optimal preparation and application of TiO₂ as a high-performance photocatalyst for desulfurization remains a significant challenge, driving ongoing research and innovation. This study introduces environmentally friendly deep eutectic solvents (DESs) employed as solvents, templates and inhibitors, alongside an Anderson-type polyoxometalate (POM) during TiO₂ synthesis. The resulting catalyst demonstrated exceptional activity, selectivity, and stability in the desulfurization of diesel model oil under visible light, achieving a 99% removal rate of dibenzothiophene (DBT) within three hours. The nanodisk-like 5% ZnMo₆/DTO ((NH₄)₄H₆ZnMo₆O₂₄-modified TiO₂ with DESs as solvents) catalysts feature a unique microstructure with a highly active (001) facet and enhanced active sites due to the incorporation of Anderson-type POMs. This catalyst maintained its superior performance across five cycles, highlighting its stability under repeated use. Comparative tests with model oils containing monocyclic and bicyclic aromatic hydrocarbons revealed higher desulfurization rates, underscoring its potential for commercial diesel applications. The photocatalytic reaction was primarily driven by superoxide free radicals, with holes playing a supportive role. Additionally, density functional theory (DFT) calculations confirmed that the high-activity (001) facet of ZnMo₆/DTO has significant adsorption capacity for DBT, further explaining the enhanced photocatalytic desulfurization performance. This research provides valuable insights into the design of cooperative electron transfer mechanisms for efficient photocatalytic desulfurization.