The effects of cluster size and metal–support interaction on the catalytic activity of Au nanoparticles supported on anatase TiO2(101) and (001) surfaces for H2 adsorption, activation and dissociation were investigated by periodic density functional theory (DFT) calculations. On the stoichiometric TiO2 surfaces, it was found that the adsorptions of both Au clusters and H2 molecules are sensitive to the cluster size of gold, and the (001) facet with “soft” lattice and coordination unsaturated atoms on the surface is superior for Au adsorption stability, but H2 adsorption does not show apparent distinction on the two catalysts. The Au atoms active for H2 activation should be neutral in charge and located at the edge or corner of the Au nanoparticles in lower coordination. The metal–support interaction plays an important role for H2 activation and dissociation, and the O2––H+–H––Au structure was identified in the transition state through which H2 dissociation occurred via a heterolytic dissociation process at the Au–TiO2 interface for both facets. H* spillover from the Au site to the bridging −O2cH site can generate H2O molecules on the two facets, and O-vacancy formation is energetically more favorable on (101) than (001). The presence of O-vacancy defects significantly impacts the adsorption stability of Au clusters and H2 molecule but has small effect on the energy barrier for H2 dissociation, which proceeds fast on both the stoichiometric and reduced anatase TiO2(101) and (001) surfaces.

The mechanism and kinetic features of hydrodeoxygenation of hydroquinone over the oxygen-defective anatase (a-TiO 2 ) supported gold (Au) catalyst were studied by density functional theory calculations. The investigation of reaction pathways and energetics identified that the conversion of hydroquinone over Au 10 /a-TiO 2 (001) went through several key reaction intermediates including benzoquinone, 1,4-cyclohexanediol, and cyclohexanol. The dehydrogenation of hydroquinone to benzoquinone intermediate occurred via H-transfer on both the TiO 2 surface and Au cluster. Subsequent hydrogenation of the C C bonds of benzoquinone mainly occurs from H*−Au sites, which has relatively low barriers, indicating the facile formation of ringsaturated species. The "1,4-cyclohexanediol" pathway dominates the overall reaction in hydroquinone conversion with favorable kinetic feature due to low barriers, leading to a large amount of cyclohexane in the product. The presence of oxygen vacancies on the a-TiO 2 (001) surface is critically important as active sites to facilitate the cleavage of C−O bond of intermediate species. The interface of Au−TiO 2 also plays an important role in stabilizing reaction intermediates and promoting the H transfer between Au cluster and the adsorbed species on the TiO 2 surface.