Synergizing Mon Clusters and Mo2C Nanoparticles on Oxidized Carbon Nanotubes Boosting the CO2 Reduction Activity

The design and synthesis of highly efficient and selective catalysts for the CO2 thermal reduction remains a challenging issue of modern catalysis. Molybdenum carbide has attracted great interest in CO2-to-CO conversion (Reverse Water Gas Shift process, RWGS) because of its unique ability to dissociate CO2 and H2. However, single dominant Mo- or C-terminated facets of molybdenum carbide unlikely activate CO2 and H2 molecules simultaneously. Herein we demonstrate how structural diversity of co-generated molybdenum species (i.e., Mon nanoclusters and Mo2C nanoparticles) at the surface of an oxygen-enriched C-carrier, boost synergistically the chemoselective RWGS process with rates up to 581 μmolCO2·gMo-1·s-1 with CO selectivity> 99% already at 400 °C under H2-rich environment. This catalytic outcome ranks among the highest reported so far for molybdenum carbide- or noble metal-based catalysts in the process and it is up to 1.8 times higher than that measured on structurally homogeneous Mo2C-based nanoparticles. The superior activity of the structurally mixed catalyst has been ascribed to a synergistic modulation of geometrical and electronic structure of different Mo sites that reduce the temperature at which CO production starts and facilitates the chemoselective CO desorption pathway. Experimental and in-silico studies have also unveiled the existence of a linear correlation between the percentage of high-valence molybdenum species in the metal active-phase composition (Moδ+ %) and the increase of RWGS rate.