Oxygen vacancies in Ru/TiO - drivers of low-temperature CO methanation assessed by multimodal operando spectroscopy.

Hydrogenation of CO is very attractive for transforming this greenhouse gas into valuable high energy density compounds. In this work, we developed a highly active and stable Ru/TiO catalyst for CO methanation prepared by a solgel method that revealed much higher activity in methanation of CO (ca. 4-14 times higher turnover frequencies at 140-210°C) than state-of-the-art Ru/TiO catalysts and a control sample prepared by wetness impregnation. This is attributed to a high concentration of O-vacancies, inherent to the solgel methodology, which play a dual role for 1) activation of CO and 2) transfer of electrons to interfacial Ru sites as evident from operando DRIFTS and EPR investigations. These results suggest that charge transfer from O-vacancies to interfacial Ru sites and subsequent electron donation from filled metal d-orbitals to antibonding orbitals of adsorbed CO are decisive factors in boosting the CO methanation activity.