Experimental catalytic activity measurements, Diffuse Reflectance Infrared Fourier Spectroscopy, and Density Functional Theory calculations are used to investigate the role and dynamics of surface oxygen vacancies in the CO oxidation with O2 catalyzed by Au nanoparticles supported on a Y-doped TiO2catalyst. We observe that, under reactive flow dry conditions, the surface gets dehydroxilated and, simultaneously, the gold nanoparticles are redispersed on the surface. This results in a highly active catalyst in the second cycle of reaction. It is also found that the presence of water in the reactive flow inhibits the reaction in some way.Theoretical calculations show that there is a competition between Au nanoparticles and the OH to occupy the surface oxygen vacancies and that the adsorption energy of gold on these sites increase as the surface gets dehydroxilated, explaining the observed redispersion of the gold catalyst. The oxygen vacancies act as electron density reservoirs that allow the activation of the O2 molecule when it is adsorbed on the Au/TiO2 perimeter interface during the CO oxidation reaction. The oxidation reaction is found to proceed through the formation of a peroxo-like complex where molecular oxygen is simultaneously bound to CO and to the Au/TiO2 perimeter atoms. The rate-determining step is the formation of this complex with an energetic barrier significantly lower than for the direct O2dissociation  .Figure.  Energy profiles for the CO oxidation reaction of Au10/Y-doped TiO2 (101) surface models.?

Role of the surface oxygen vacancies in CO oxidation catalyzed by gold supported on yttrium modified anatase

246th National Meeting (2013)

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