Acid-assisted hydrothermal synthesis of nanocrystalline TiO2 from titanate nanotubes: Influence of acids on the photodegradation of gaseous toluene

In order to efficiently remove volatile organic compounds (VOCs) from indoor air, one-dimensional titanate nanotubes (TiNTs) were hydrothermally treated to prepare TiO 2 nanocrystals with different crystalline phases, shapes and sizes. The influences of various acids such as CH 3 COOH, HNO 3 , HCl , HF and H 2 SO 4 used in the treatment were separately compared to optimize the performance of the TiO 2 nanocrystals. Compared with the strong and corrosive inorganic acids , CH 3 COOH was not only safer and more environmentally friendly, but also more efficient in promoting the photocatalytic activity of the obtained TiO 2 . It was observed that the anatase TiO 2 synthesized in 15   mol/L CH 3 COOH solution exhibited the highest photodegradation rate of gaseous toluene (94%), exceeding that of P25 (44%) by a factor of more than two. The improved photocatalytic activity was attributed to the small crystallite size and surface modification by CH 3 COOH. The influence of relative humidity (20%–80%) on the performance of TiO 2 nanocrystals was also studied. The anatase TiO 2 synthesized in 15   mol/L CH 3 COOH solution was more tolerant to moisture than the other TiO 2 nanocrystals and P25.