Distinguishing the roles of TiO2 {101}, {001}, and {010} facets in benzene semi-hydrogenation over Ru/TiO2 catalysts

Highlights: • TiO₂ crystals dominated by {1 0 1}, {0 0 1}, and {0 1 0} facets were prepared. • Ru NPs on ATCs-101 and ATCs-010 are more electron-deficient than on ATCs-001. • ATCs-001 and ATCs-010 possess a higher density of cus Ti_5c atoms than ATCs-101. • The activity and selectivity increase in Ru/ATCs-101 < Ru/ATCs-001 < Ru/ATCs-010. • A cooperative effect between electron-deficient Ru and cus Ti_5c is identified. Ru nanoparticles (NPs, approximately 10.2 wt%) were deposited on anatase TiO₂ crystals (ATCs) with dominant {1 0 1}, {0 0 1}, and {0 1 0} facets, aiming at discriminating the roles of support facets of the Ru/ATCs catalysts in benzene semi-hydrogenation (BSH), so as to boost their catalytic efficiency. With the assistance of comprehensive characterizations, it is confirmed that ATCs-101 dominated by {1 0 1} facets and ATCs-010 dominated by {0 1 0} facets have a stronger electrophilicity in contrast to ATCs-001 with dominant {0 0 1} facets, resulting in electron-deficient Ru on the formers, while ATCs-101 possesses a lower density of coordinatively unsaturated (cus) fivefold-coordinated Ti (Ti_5c) atoms than ATCs-001 and ATCs-010. A cooperative effect between electron-deficient Ru and cus Ti_5c atoms was uncovered on Ru/ATCs in BSH, which is beneficial to boosting both the activity and cyclohexene selectivity, rendering them to increase in the order of Ru/ATCs-101 < Ru/ATCs-001 < Ru/ATCs-010. Temperature-programmed desorption (TPD) and kinetic investigations identified that such enhancements were derived from promoting benzene adsorption, regulating hydrogenation rates of benzene and cyclohexene, and reducing adsorption sites and capacity of cyclohexene by this cooperative effect.