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

Pd supported on different anatase TiO2 nanocrystals predominantly exposing either {1 0 0}, {1 0 1}, or {0 0 1} facets were tested for CO2 hydrogenation into formate. Remarkable morphology-dependent catalysis was observed. Compared to 2%Pd/TiO2{1 0 1} and 2%Pd/TiO2{0 0 1} catalysts, 2%Pd/TiO2{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/TiO2{1 0 0} contribute to the activations of CO2 and H2, respectively, favorable for the activity; On the other hand, higher oxygen vacancy concentrations in the TiO2{1 0 0} promote the Pd-TiO2 interactions and result in the formation and stability of flat Pd particles over 2%Pd/TiO2{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 CO2 hydrogenation.