Crystal-Plane-Engineered TiO₂-Anchored Vanadium Single Atoms and Clusters for Boosting Ultradeep Aerobic Oxidative Desulfurization of Diesel

Abstract

The crystal plane effect has gained extensive attention in heterogeneous catalysis reactions; however, it is far from being systematically probed in titanium dioxide (TiO 2 )-supported vanadium catalysts. Herein, a series of vanadium (V) single atoms and clusters anchored on TiO 2 with different crystal planes was fabricated by an improved “top-down” protocol. The dispersion state, electronic structure, and redox properties of the V single-atom and VO x cluster-supported catalysts were systematically analyzed by a series of characterization methods, including X-ray absorption near edge structure (XANES) and density functional theory (DFT) calculations, and their catalytic performances were examined for aerobic oxidative desulfurization (AODS) of 4,6-dimethyl-dibenzothiophen (4,6-DMDBT) with O 2 as the oxidant. The results unveiled that the synergistic effect between the V single atom and the VO x cluster perceptibly promoted the catalytic performances of VO x /TiO 2 samples. Therein, VO x /TiO 2 -(001) shows the lowest apparent activation energy ( E a ) value of 46.3 kJ/mol and the optimal AODS performance with complete 4,6-DMDBT conversion to 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO 2 ) within 60 min at 120 °C as compared with VO x /TiO 2 -(101) (81.9 kJ/mol and 180 min) and VO x /TiO 2 -(100) (68.0 kJ/mol and 240 min), which should be attributed to its higher V 5+ /V 4+ ratio, the optimal redox behavior of the V species, the moderate adsorption energy between 4,6-DMDBT and VO x active centers, and the synthetic effect of V single atoms and VO x clusters. Moreover, VO x /TiO 2 -(001) exhibits robust durability in seven cycles of reuse, showcasing the potential for practical applications in the future.