What are the preferred CeO2 exposed planes for the synthesis of dimethyl carbonate? Answers from theory and experiments

Abstract

The synthesis of dimethyl carbonate (DMC) from CO2 and methanol was studied on CeO2 nanocatalysts with different exposed planes. The nanocatalysts were prepared by the hydrothermal method from different cerium nitrate precursor salts. XRD and HRTEM were used to characterize the different exposed planes, whereas EPR identified the presence of oxygen vacancies. The CeO2 nanocatalysts were more selective to DMC than the conventional CeO2 material and the results were correlated with the concentration of oxygen vacancies and strength of the basic sites of the materials. The nanocatalyst presenting the (110) plane was the most active and presented the highest concentration of oxygen vacancies. Periodic theoretical calculations, at DFT level, corroborated the experimental results, indicating the preference of CO2 adsorption on the oxygen vacancies of the (110) exposed CeO2 surface, which also led to formation of bidentate carbonate species, a key intermediate on the reaction pathway. The overall results indicated the importance of the (110) exposed plane on the CeO2 surface to increase the catalytic activity to DMC.