Titania-crystal-phase-engineered strong metal-support interactions and catalysis in CO2 hydrogenation

Abstract

Tailoring strong metal-support interactions (SMSIs) have been verified to become an efficient strategy for developing novel heterogeneous catalysts. Here, both TiO2 supports (anatase (A) and rutile (R)) were employed to prepare the Pd/TiO2 catalysts and strongly titania-crystal-phase-dependent Pd-TiO2 SMSIs and catalysis in CO2 hydrogenation were observed. A-TiO2 is more facile to undergo Pd-TiO2 SMSIs than R-TiO2, which could be relevant to better reducibility over calcined Pd/A-TiO2C catalyst. Catalytic performance of the Pd/TiO2-R (reduced) catalysts in CO2 hydrogenation are sensitive to the Pd-TiO2 structures, among which the Pd nanoparticles mostly encapsulated by TiO2-x overlayers over Pd/A-TiO2-R catalyst with more prominent SMSIs is more intrinsically active. This could be ascribed to both stronger H-spillover and hydrogenation property and better CO2 activation capacity over Pd/A-TiO2-R catalyst. However, its catalytic activity is seriously restricted by the number of intrinsically active sites due to less exposed Pd atoms to block H2 activation sites. These results clearly demonstrate the crystal-phase engineering as an efficient strategy to tailor the SMSIs for developing improved heterogeneous catalysts.