Ceria morphology-dependent Pd-CeO2 interaction and catalysis in CO2 hydrogenation into formate

Abstract

Several Pd catalysts supported on CeO2 with different morphologies (i.e. CeO2 rods (r-CeO2), cubes (c-CeO2) and polyhedra (p-CeO2)) were tested for the CO2 hydrogenation into formate. Remarkable morphology - dependent Pd-CeO2 interaction was observed, which was related to the oxygen vacancies in the CeO2. The r-CeO2 with the highest concentration of oxygen vacancy resulted in smaller Pd particles and more positively-charged Pd species in the Pd/r-CeO2 catalyst. The best performance was obtained over the Pd/p-CeO2 catalyst, giving a turnover frequency of 746 h−1 at 40 °C. The enhanced activity was due to the highest content of metallic Pd species in the catalyst, which was responsible for the facile activation of H2. Moreover, in situ spectroscopic results revealed that the hydrogenation of the carbonaceous intermediates was the rate - determining step. This work demonstrates oxide morphology engineering as a powerful strategy in developing efficient Pd - based catalysts for CO2 hydrogenation.