Anatase TiO2 nanocrystals with a large (001) surface have been synthesized by hydrothermal method with HF used as a shape-controlling agent. Chemical modification of the as-synthesized aTiO2 with reducing gases such as H2 and NH3 was performed at elevated temperatures up to 970 K. Such chemical treatments were found to change the crystal shape from the squared nanosheets into a shape of truncated tetragonal bipyramid with enlarged {101} facets. In addition, the defect density and distribution in the bulk/surface also changed significantly as measured from EPR. Resulting photocatalytic activity of the chemically modified aTiO2 nanocrystals, as measured by the photodegradation of methylene blue under UV irradiation, were found to be strongly dependent on the type and distribution of defects in the bulk as well as on the surface. Based on systematic measurements, we conclude that Ti3+ defects, formed in the early stage of reduction processes, eventually diffuse toward the surface to form surface oxygen vacancies which are converted into the surface O- species at ambient conditions. In addition, our study shows that the chemical modification methods at elevated temperatures can be successfully used to control the photoactivity of TiO2 nanocrystals.

Effect of defects on photocatalytic activity of chemically modified anatase TiO2 nanocrystals with H2 and NH3

247th National Meeting (2014)

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