Active sites in CO2 hydrogenation over confined VOx-Rh catalysts

Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation, especially for the ethanol synthesis. However, this reaction usually suffers low CO2 conversion and alcohols selectivity due to the formation of byproducts methane and CO. This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41. The Rh-0.3VO(x)/MCM-41 catalyst shows superior conversion (12%) and ethanol selectivity (24%) for CO2 hydrogenation. The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VOx-Rh interface sites. Experimental and theoretical results indicate the formation of til-CO at VOx-Rh interface sites is easily dissociated into *CHx, and then *CHx can be inserted by CO to form CH3CO*, followed by CH3CO* hydrogenation to ethanol.