Morphology-Dependent Evolutions of Sizes, Structures, and Catalytic Activity of Au Nanoparticles on Anatase TiO2 Nanocrystals

Au nanoparticles with different loadings were prepared on anatase TiO2 nanocrystals with various morphologies predominantly exposing {001} facets (denoted as TiO2{001}), {100} facets (denoted as TiO2{100}) and {101} facets (denoted as TiO2{001}) by the deposition–precipitation method. Sizes, structures, and catalytic activity in low-temperature CO oxidation of the resulting Au/TiO2 catalysts were comprehensively characterized. Nucleation, growth, and agglomeration of Au particles on TiO2 supports were observed to depend on TiO2 morphologies due to the morphology-dependent defect structures of TiO2 nanocrystals and subsequent Au–TiO2 interactions. Au particles mainly homogeneously nucleate and grow on these three TiO2 nanocrystals with Au loadings of 0.2–1%. With the increase in Au loadings to 2 and 5%, Au particles mainly agglomerate on TiO2{001}, mainly homogeneously nucleate and grow on TiO2{100}, and both nucleate and grow and slightly agglomerate on TiO2{101}. The electronic effect of supported Au particles on CO adsorption was observed, in which fine Au nanoparticles with electronic structures deviating from that of bulk Au exhibit a decreased adsorption capacity of CO. Meanwhile, fine Au nanoparticles are less able to activate surface lattice oxygen at the Au–TiO2 perimeters than large Au nanoparticles and exhibit a lowered intrinsic catalytic activity in low-temperature CO oxidation. These results nicely exemplify morphology-dependent metal–oxide interactions and catalysis.