Supported Molybdenum Carbide Nanoparticles as an Excellent Catalyst for CO2 Hydrogenation

Experiments under controlled conditions show that MoC x nanoclusters supported on an inert Au(111) support are efficient catalysts for CO2 conversion, although with a prominent role of stoichiometry. In particular, C-deficient nanoparticles directly dissociate CO2 and rapidly become deactivated. On the contrary, nearly stoichiometric nanoparticles reversibly adsorb/desorb CO2 and, after exposure to hydrogen, CO2 converts predominantly to CO with a significant amount of methanol and no methane or other alkanes as reaction products. The apparent activation energy for this process (14 kcal/mol) is smaller than that corresponding to bulk δ-MoC (17 kcal/mol) or a Cu(111) benchmark system (25 kcal/mol). This trend reflects the superior ability of MoC1.1/Au­(111) to bind and dissociate CO2. Model calculations carried out in the framework of density functional theory provide insights into the underlying mechanism suggesting that CO2 hydrogenation on the hydrogen-covered stoichiometric MoC x nanoparticles supported on Au(111) proceeds mostly under an Eley–Rideal mechanism. The influence of the Au(111) is also analyzed and proven to have a role on the final reaction energy but almost no effect on the activation energy and transition state structure of the analyzed reaction pathways.