Highly selective catalytic hydrogenation conversion of CO2 to CO over lanthanum-doped supported ruthenium catalysts.

The selective catalytic hydrogenation of CO2 to CO via the RWGS reaction is an effective avenue for resource utilization of CO2. In this study, we prepared serial La2O3-doped Ru catalysts (i.e., RuLa/SBA-15) using a facile sequential impregnation method, and applied it for the selective hydrogenation conversion of CO2 into CO. The La2O3 doping remarkably promotes the dispersion of Ru nanoparticles and induces the formation of electron-deficient Ru species (Run+). In-situ DRIFTS study reveals that the hydrogenation of CO2 over Ru catalysts with and without La2O3 doping proceeds through different pathways. Both CO and CH4 are formed on non-doped Ru/SBA-15 with formate as the key intermediate, but only CO is generated on RuLa/SBA-15 via carbonate as the intermediate because of the weakened CO adsorption on Run+. Thus, RuLa/SBA-15 exhibits outstanding CO selectivity for the hydrogenation of CO2 without significant decline of activity. It achieves a CO2 conversion of 51 % at 600 °C and nearly 100 % of CO selectivity across the examined reaction temperature of 300-600 °C, surpassing the performances of the non-doped counterpart (CO2 conversion of 58 % at 600 °C and CO selectivity ranging from 2 %-63 %). This study provides a facile and cost-effective strategy to tune the structure of Ru catalysts for the hydrogenation conversion of CO2 to obtain value-added products.