Formation of dimethyl carbonate via direct esterification of CO₂ with methanol on reduced or stoichiometric CeO₂(111) and (110) surfaces

CeO₂-Catalyzed esterification of CO₂, a well-known greenhouse gas, with methanol has been widely recognized as a promising alternative method to produce dimethyl carbonate (DMC). Herein, we performed a comprehensive study of catalytic mechanisms underlying the formation of DMC from CO₂ and methanol on both stoichiometric and reduced CeO₂(111) and (110) surfaces. To this end, the saddle-point searching algorithm is employed. Specifically, using the monomethyl carbonate (MMC) as the key intermediate, a three-step Langmuir-Hinshelwood (LH) mechanism, including the formation and esterification of monomethyl carbonate and removal of water molecule, is identified for the catalytic DMC formation on either the reduced or the stoichiometric CeO₂(111) and (110) surfaces. For both CeO₂(111) and (110) surfaces, our study indicates that the presence of oxygen vacancies can markedly lower the activation energy barrier. Different rate-limiting steps are identified, however, for the reduced CeO₂(111) and (110) surfaces. Successful identification of the rate-limiting step and the associated active CO₂ species will provide atomic-level guidance on selection of metal-oxide-based catalysts toward direct synthesis of DMC from the green-house gas CO₂ and methanol.