Morphology-engineered highly active and stable Pd/TiO2 catalysts for CO2 hydrogenation into formate

Pd supported on different anatase TiO 2 nanocrystals predominantly exposing either {1   0   0}, {1   0   1}, or {0   0   1} facets were tested for CO 2 hydrogenation into formate. Remarkable morphology-dependent catalysis was observed. Compared to 2%Pd/TiO 2 {1   0   1} and 2%Pd/TiO 2 {0   0   1} catalysts, 2%Pd/TiO 2 {1   0   0} is highly active and stable, affording an unprecedented turnover frequency of ca. 1369 h −1 and keeping stable after 6 cycles at 313 K. This can be associated with, on the one hand, higher density of moderate basic site and relatively more Pd(0) species over 2%Pd/TiO 2 {1   0   0} contribute to the activations of CO 2 and H 2 , respectively, favorable for the activity; On the other hand, higher oxygen vacancy concentrations in the TiO 2 {1   0   0} promote the Pd-TiO 2 interactions and result in the formation and stability of flat Pd particles over 2%Pd/TiO 2 {1   0   0}, beneficial to the stability. These results highlight the importance of oxide morphology in formate formation and open up possibilities of oxide morphology engineering for developing efficient Pd-based catalysts for CO 2 hydrogenation.