Tuning the CO2 hydrogenation activity and selectivity of TiO2 nanorods supported Rh catalyst via secondary-metals addition

Secondary-metals promotion is key to tune the CO 2 hydrogenation performance of Rh-based catalyst. We describe the addition of Cu or Co in TiO 2 nanorods supported Rh catalyst (viz., RhM x /TiO 2 ), showing significant impact on the CO 2 hydrogenation activity and productivity. Cu addition can promote the partial hydrogenation to alcohols (methanol and ethanol), whereas Co led to the deep hydrogenation to alkanes (CH 4 , C 2 H 6 ). Comparative time-resolved in situ DRIFTS studies with H 2 /D 2 isotopic exchange further reveal that both surface adsorbed CO* and formates could be the key reaction intermediates during the CO 2 hydrogenation over RhM x /TiO 2 (especially the RhCu 2.5 /TiO 2 ), in which the interaction strength of CO* regulated by secondary-metals addition was key to tune the reaction pathways and productivity. The findings suggested that rational design of active metal sites, for example the synergy between Rh and secondary-metals, is highly needed to promote the CO insertion and C  C coupling to produce ethanol.