Crystal facet growth behavior and thermal stability of {001} faceted anatase TiO2: mechanistic role of gaseous HF and visible-light photocatalytic activity

Thermal stability and crystal facet growth behavior of anatase TiO2 nanosheets with exposed high-reactive {001} facets were systematically investigated by heating a mixture of TiO2 and NH4F. Results indicate that anatase TiO2 nanosheets can grow into {001} facets dominated anatase TiO2 microsheets through surface fusion along the [001] crystallographic direction by employing gaseous HF as the capping agent. By controlling the initial concentration of NH4F, visible-light responsive TiO2 sheets with different sizes, percentages of {001} facets, and inner structures were obtained, hence, the crystal facet growth mechanism and thermal stability of the {001} facets were proposed. Owing to the exposed high-reactive facets, incorporated N species, and little surface adsorbed F atoms, the as-prepared samples exhibited enhanced visible-light photocatalytic activity.