Photocatalytic oxidation of nitrogen oxides over {001}TiO₂: the influence of F⁻ ions.

Huang, Qianqian; He, Guangying; Lin, Chunjing; Hu, Yun; Wei, Chaohai

A series of anatase TiO2 nanosheets with different percentage of {001} facets ({001}TiO2) were synthesized through a hydrothermal route using tetrabutyltitanate as a titanium precursor and HF as a shape controlling agent. The amount of HF exhibits an obvious influence on the structures and activities of TiO2 samples. The adsorbed surface F− ions on the {001} facets of the anatase TiO2 were removed by washing them with NaOH solution. The as-prepared catalysts were characterized by X-ray diffraction, Brunner−Emmet−Teller measurements, ultraviolet-visible diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy techniques, and X-ray photoelectron spectroscopy analysis. The results indicated that all the as-prepared catalysts showed an anatase crystalline and nanosheet structure, as well as a strong ultraviolet light absorbance. With the increase of HF content, the crystallite size and the percentage of {001} facets increased first and later decreased, state the opposite change observed in BET. When the content of HF was 4.4 mL, the percentage of {001} facets reached the maximum up to 61.62%. After all samples were treated with 0.1 M NaOH solution, the percentage of {001} facets increased to a maximum of 64.46%. All the samples washed by NaOH solution exhibited much higher photocatalytic activity for NOx oxidation under UV light irradiation than P25, {101}TiO2, and {001}TiO2 without NaOH washing, suggesting that the surface F− ions inhibited the photocatalytic NOx oxidation. Moreover, the results showed that the NaOH-washed {001}TiO2 has a high humidity tolerance.

PHOTOCATALYSIS; NITROGEN oxides; OXIDATION; TITANIUM dioxide; METAL ions

Environmental Science & Pollution Research, 2018, Vol 25, Issue 35, p35342

0944-1344

Academic Journal

10.1007/s11356-018-3435-7