It is noted that no signal of unreactive multi-carbonyl species at 2130 and 2075 cm -1 is detectable in the spectra of either catalyst, as these species are more prevalent on lowcoordinated Ru sites of subnanometer-sized metal atoms/clusters , which is not the case in the present study. With stepwise increasing temperatures above 200 C, the Ruif-CO band in the Ru/12%Ti-SiO2 spectra starts diminishing. Simultaneously, the band corresponding to gaseous CH4 at 3017 cm -1 appears. Additionally, this CH4 band is more intense for Ru/12%Ti-SiO2 than for the undoped catalyst. Taken together, these results suggest that higher concentration of interfacial adsorbed CO could be primarily responsible for higher catalytic activity of the Ti-doped catalyst.