Defect structure and evolution mechanism of O2− radical in F-doped V2O5/TiO2 catalysts
Defect structure and evolution mechanism of O2− radical in F-doped V2O5/TiO2 catalysts
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DOI：
10.1016/j.colsurfa.2013.08.047
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发表时间：
2013-09
期刊：
影响因子：
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通讯作者：
Wei Zhao;Q. Zhong;Yanxiao Pan;Rui Zhang
中科院分区：
文献类型：
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作者：
Wei Zhao;Q. Zhong;Yanxiao Pan;Rui Zhang
采用溶胶-凝胶法合成了掺氟二氧化钛(TiO2)纳米粒子，该纳米粒子能在载体上形成更多的氧空位。X-射线衍射仪和高透射率电子显微镜的测试结果表明，F掺杂抑制了锐钛矿向金红石相的转变，活性组份V2O5在载体上分散性较好。本文阐述了F掺杂V2O5/TiO2催化剂的制备过程和F掺杂V2O5/TiO2催化剂表面稳定超氧阴离子(O2-−)的生成。用电子顺磁共振技术研究了O2−在V2O5/TiO2催化剂上的表征和稳定性。F掺杂可以在催化剂表面产生更多的氧空位，提高Ti3+的浓度。利用紫外可见光谱仪研究了F掺杂对样品禁带宽度的影响。光致发光(PL)谱有力地证实了F掺杂对氧空位的增强作用。X射线光电子能谱(XPS)证实了样品中Ti3+和V4+的存在。根据EPR谱和自由基物种的反应化学计量学研究结果，提出了以下机理：金属氧化物催化剂可以看作是电子供体，而被吸附的氧分子则是表面电子受体。在孤立的四面体钛物种上，F掺杂形成了[Ti3+-OV−]自由基对。选择性催化还原催化活性提高的一个可能原因是，Ti3+和V4+的存在是通过电荷补偿形成的，随后OV−部分与O2反应生成O2−，O2 DNA可与NO反应生成NO2。
Fluorine (F)-doped titania (TiO2) nanoparticles were synthesized by the sol–gel method, which could create more oxygen vacancies on the TiO2support. The experiments of X-ray diffraction (XRD) and high transmission electron microscopy (TEM) indicated that F-doping could inhibit anatase-to-rutile transition and active component V2O5had a good dispersion on the support. This paper illustrated the preparation process of the F-doped V2O5/TiO2catalyst and the generation of stabled superoxide radical anion (O2−) on the surface of the F-doped V2O5/TiO2catalyst. The characterization and stability of O2−over V2O5/TiO2was investigated by using electron paramagnetic resonance (EPR) spectroscopy. F-doping could produce more oxygen vacancies on the surface of the catalyst and increase the Ti3+concentration. UV–vis spectrophotometer was employed to characterize the effect of F-doping on the band gap of the samples. Photoluminescence (PL) spectra strongly confirmed the enhancement of oxygen vacancies by F-doping. The presence of Ti3+and V4+in the samples was confirmed by X-ray photoelectron spectroscopy (XPS) spectra. The following mechanism was proposed according to the results from EPR spectra and reaction stoichiometry studies of radical species. Metal oxide catalysts might be viewed as electron donors while the adsorbed oxygen molecules behaved as surface electron acceptors. Over the isolated tetrahedral Ti species, a [Ti3+-OV−] radical pair was formed by F-doping. One possible explanation for the enhancement of selective catalytic reduction (SCR) catalytic activity was that the presence of Ti3+and V4+formed by charge compensation, and the subsequently OV−moiety reacted with O2to form O2−, which could react with NO to yield NO2.