Exceptional Photocatalytic Activity of 001-Facet-Exposed TiO2 Mainly Depending on Enhanced Adsorbed Oxygen by Residual Hydrogen Fluoride

Abstract

Is it true that the exceptional photocatalytic activity of 001-facet-exposed TiO2 is attributed to its high-energy surfaces? In this work, nanocrystalline anatase TiO2 with different percentages of the exposed (001) facet has been controllably synthesized with a hydrothermal process using hydrofluoric acid as a morphology-directing agent. It is shown that the percentage of (001)-facet exposure is tuned from 6 to 73% by increasing the amount of used hydrofluoric acid, and meanwhile the amount of residual fluoride in the as-prepared TiO2 is gradually increased. As the percentage of (001) facet is increased, the corresponding TiO2 gradually exhibits much high photocatalytic activity for degrading gas-phase acetaldehyde and liquid-phase phenol. It was unexpected that the photocatalytic activity would obviously decrease when the residual fluoride was washed off with NaOH solution. By comparing F-free 001-facet-exposed TiO2 with the F-residual one, it is concluded that the exceptional photocatalytic activity of...