Role of gold nanoclusters supported on TiO2(110) model catalyst in CO oxidation reaction

It was reported previously that O adatoms adsorbed dissociatively on the five-fold Ti rows of rutile TiO2(110) made the surface O-rich and reacted with CO molecules to form CO2. An electronic charge transfer taking place from gold nanoclusters to the O-rich TiO2(110) support played a crucial role to enhance the catalytic activity [Mitsuhara et al., J. Chem. Phys. 136, 124303 (2012)]. In this study, the authors have further accumulated experimental data for the CO oxidation reaction enhanced by gold nanoclusters on the TiO2(110) surface. Based on the results obtained here and previously, the authors propose an "interface dipole model," which explains the strong activity of Au nanoclusters supported on O-rich TiO2(110) in CO oxidation reaction. Simultaneously, the authors also discuss the cationic cluster model proposed by Wang and Hammer [Phys. Rev. Lett. 97, 136107 (2006)] and the d-band model predicted by Hammer and Norskov [Adv. Catal. 45, 71 (2000)]. The latter is, in particular, widely accepted to explain the activities of heterogeneous catalysts. Contrary to the d-band model, our ab initio calculations demonstrate that the d-band center for Au nanoclusters moves apart from the Fermi level with decreasing the cluster size and this is due to contraction of the Au-Au bond length. (C) 2013 American Vacuum Society.