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

Shuo Cao,Zun Guan,Ying Ma,Bing Xu,Jun Ma,Wei Chu,Riguang Zhang,Giuliano Giambastiani,Yuefeng Liu

The design and synthesis of highly efficient and selective catalysts for CO2 thermal reduction remain 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 ability to dissociate CO2 and H2. However, single dominant Mo- or C-terminated facets of molybdenum carbide are unlikely to activate CO2 and H2 molecules simultaneously. Herein, we demonstrate how structural diversity of cogenerated molybdenum species (i.e., Mon nanoclusters and Mo2C nanoparticles) on the surface of an oxygen-enriched C-carrier boosts synergistically the chemoselective RWGS process with rates up to 581 μmolCO2·gMo–1·s–1 with CO selectivity > 99% already at 400 °C under an 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 Mo2C-based nanoparticles. The enhanced reactivity of the structurally mixed catalyst has been ascribed to a synergistic modulation of the geometrical and electronic structure of different Mo sites that reduces 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 in the RWGS rate.