Oxygen Vacancy Promoting Dimethyl Carbonate Synthesis from CO₂ and Methanol over Zr-Doped CeO₂ Nanorods

Abstract

The synthesis of dimethyl carbonate (DMC) from CO2 and methanol by Zr-doped CeO2 nanorods with different ratios of Zr/Ce has been studied at 6.8 MPa and 140 °C. The catalysts were characterized extensively by TEM, XRD, N2 adsorption, Raman spectroscopy, UV–vis spectroscopy, XPS, CO2-TPD, and in situ FTIR techniques. Doping of Zr atoms into the ceria lattice produced a fluorite-like solid solution, promoting the formation of oxygen vacancy sites. Zr-doped CeO2 nanorods exhibited significantly more oxygen vacancy sites than pure CeO2 nanorods. Zr0.1Ce nanorods which exhibited DMC synthesis activity also possess the highest concentration of oxygen vacancy sites. In situ FTIR studies further revealed that CO2 can adsorb on the oxygen vacancy to form bidentate carbonate and as intermediate to participate in the reaction. This study presents a strategy to design a high-efficiency CeO2-based catalysts by controlling the concentration of the surface oxygen vacancies.