Surface species formed over Rh/TiO2 (W6+) catalysts during CO and CO2 hydrogenation were investigated by in situ FTIR spectroscopy and transient techniques. It was found that at least four carbon-containing species, namely, linear CO, bridged CO, active carbon (C-alpha) and less-active carbon (C-beta), exist on Rh crystallites, while formate and/or carbonate and/or hydrocarbonate species are on the TiO2 support. A reduction of CO coverage by 25 similar to 40% and a shift of the linear CO band to higher wavenumber values by 10 similar to 14 cm(-1) were observed under CO and CO2 hydrogenation upon doping the TiO2 carrier with small amounts of W6+ cations (< 1 at.%). This implies that the Rh-CO bond is significantly weakened by doping, presumably due to an alteration of the electronic structure of the TiO2 carrier, which modifies the electronic state of surface Rh via electronic interactions at the metal-support interface. The concentrations of the C-alpha and C-beta species on Rh crystallites and carbon-containing species on the support were also found to be influenced by doping. While the concentration of the C-alpha species (including CHx species) was reduced and that of the C-beta species was enhanced with increasing W6+ dopant content, the concentration of the carbonate and/or hydrocarbonate species on the carrier exhibited a maximum at a W6+ content of 0.11 similar to 0.22 at.%. It is reasoned that hydrogen chemisorption is favored on the doped catalysts, as the CO coverage and the strength of the Rh-CO bond are significantly reduced. This has twofold consequences which result in a large increase of the CO and CO2 hydrogenation activity, as previously observed over the Rh/TiO2 (W6+) catalysts : there is an increase in the concentration of surface hydrogen participating in the rate-determining step and an enhancement of the formation of Rh carbonyl hydride species, through which the reaction proceeds via a route of lower activation energy (H-assisted CO dissociation).