Adsorption, Dissociation, and Spillover of Hydrogen over Au/TiO2 Catalysts: The Effects of Cluster Size and Metal–Support Interaction from DFT

• Published in: Journal of physical chemistry. C Vol. 122; no. 31; pp. 17895 - 17916
• Main Authors: Wan, Wenjia, Nie, Xiaowa, Janik, Michael J, Song, Chunshan, Guo, Xinwen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.08.2018
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.8b05482

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.