Effect of calcination temperature on morphology and photocatalytic activity of anatase TiO2 nanosheets with exposed {0 0 1} facets

Abstract

Exploring anatase TiO2 with superior thermal stability and photocatalytic activity is of great importance and challenging. In the present work, surface-fluorinated anatase TiO2 nanosheets with dominant high reactive {001} facets were fabricated by hydrothermal treatment of tetrabutyl titanate in hydrofluoric acid solution at 200°C for 24h. The as-prepared anatase TiO2 nanosheets show a remarkable thermal stability against phase transition up to 1100°C, which is associated with the surface fluorination. Calcination treatment accelerates the desorption of surface-bounded fluorine from the {001} facets, which results in the formation of oxygen vacancy first, and then the fusion of neighbor TiO2 nanosheets along the [001] direction (c-axis) to minimize the surface energy. High crystallization (low impurity) and oxygen vacancy are responsible for the high thermal stability of the as-prepared TiO2 nanosheets. On the other hand, heat treatment influences the photocatalytic activity as a result of the change of the textural characteristics, crystallinity degree and surface chemical states. Surprisingly, high photocatalytic activity is still remained up to 1100°C for photocatalytic oxidation decomposition of acetone in air under UV light illumination.