Acta Chim. Sinica ›› 2019, Vol. 77 ›› Issue (4): 351-357.DOI: 10.6023/A19010009 Previous Articles     Next Articles

Article

锐钛矿光催化降解苯酚:氟离子吸附的影响大于磷酸根

刘胜伟, 赵建军, 许宜铭   

  1. 浙江大学化学系 硅材料国家重点实验室 杭州 310027
  • 收稿日期:2019-01-04 出版日期:2019-04-15 发布日期:2019-03-05
  • 通讯作者: 许宜铭 E-mail:xuym@zju.edu.cn
  • 基金资助:

    项目受NSFC创新群体基金(No.21621005)资助.

Larger Adsorption Effect of Fluoride than Phosphate on Phenol Degradation over the Irradiated Anatase TiO2 and Pt/TiO2

Liu Shengwei, Zhao Jianjun, Xu Yiming   

  1. Department of Chemistry and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027
  • Received:2019-01-04 Online:2019-04-15 Published:2019-03-05
  • Contact: 10.6023/A19010009 E-mail:xuym@zju.edu.cn
  • Supported by:

    Project supported by the Funds for Creative Research Group of NSFC (No. 21621005).

It is known that fluoride and phosphate in aqueous solution can accelerate the photocatalytic degradation of phenol over anatase or P25 TiO2. But the mechanism still remains under debate. In this work, an anion-free anatase TiO2 is prepared, followed by deposition with 0.52 wt% Pt (Pt/TiO2). Reaction was performed in aqueous solution at initial pH 5.2, where 99% of anions were in the form of F- or H2PO4-. On the addition of 0.1~30 mmol/L anions, the rate constants of phenol degradation (kobs) were all increased, confirming the positive effect of fluoride and phosphate, respectively. Interestingly, there was a linear relationship between the increase of kobs and the amounts of anion adsorption, the slope of which became larger in the order of fluoride>phosphate, and Pt/TiO2>TiO2. These observations indicate that the positive effect of anions originates from the adsorbed anions on solid, and that fluoride was more active than phosphate. A (photo)electrochemical measurement showed that fluoride and phosphate were negative and positive, respectively, to O2 reduction, but they were all beneficial to phenol oxidation. Furthermore, in the presence of fluoride and phosphate, the flat band potentials of TiO2 were shifted by -159 and 89 mV, respectively. The former favors orbital overlapping of phenol with TiO2 valence band, and the latter favors orbital overlapping of O2 with TiO2 conduction band, all of which promotes the interfacial charge transfers. Since inorganic anions are widely present, this result would benefit the mechanism study of a semiconductor photocatalyis and its application. As a reference, pure anatase was prepared from the hydrolysis of tetrabutyl titanate, followed by calcination in air at 400℃ for 2 h. The solid was then deposited with Pt, produced in situ from the photocatalytic reduction of H2PtCl6 in the presence of methanol. Solid was characterized with X-ray diffraction, N2 adsorption, Raman, and X-ray photoelectron spectroscopy. After Pt deposition, anatase phase remained unchanged, but the solid pores were blocked by a mixture of Pt and PtO2. Photoreactions were performed at room temperature under UV light at wavelengths equal to and longer than 320 nm. Organic compounds and inorganic anions were quantitatively analyzed with a high performance liquid and ionic chromatography, respectively. (Photo)electrochemical measurement was performed in a three-electrode compartment, where a Pt gauze was used as counter electrode, and a AgCl/Ag as reference electrode.

Key words: anatase TiO2, fluoride, phosphate, adsorption, photoelectrocatalysis, charge transfer