Abstract

Performance of nanocrystal photocatalysts depends on not only their size, shape, composition, crystal phase, but also crystal facets. For anatase TiO₂ crystals, the {001} faceted crystal surface possesses superior photocatalytic activity, highly attractive for degradation of organic pollutants, solar fuel production and solar energy conversion applications. A considerable research interest has arisen over recent years primarily driven by the demand for synthetic methods capable of producing anatase TiO₂ crystals with high percentage of exposed {001} facets. However, the growth of anatase TiO₂ crystals with exposed {001} facets dominated surface has been regarded as thermodynamically unfavourable due to its high surface energy (0.90 J/m²) relative to other anatase crystal facets such as {100} and {101} facets. A recently reported breakthrough [1] demonstrated that surface fluorination can dramatically reduce the {001} faceted surface energy to a level lower than that of the {101} faceted surface, producing anatase TiO₂ single crystals with 47% exposed {001} facets. This concept has now been widely applied to obtain TiO₂ crystals with higher percentages of exposed {001} facets. Herein, we report a series of facile liquid [2-4] and vapour [5-7] phase hydrothermal methods to control growth anatase TiO₂ crystals with exposed {001} facets. The mechanisms of control growth {001} facets under liquid and vapour phases are investigated in details. The resultant {001} faceted anatase TiO₂ crystals have been used as the photoanode for water oxidation and dye sensitised solar cells.

© 2013 Optical Society of America