多相光催化过程中的酸性作用机理研究
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摘要
采用溶胶—凝胶技术制备了TiO_2 TiO_2-ZrO_2固体酸和SO_4~(2-)/TiO_2固体超强酸光
催化剂，以乙烯和溴代甲烷的光催化降解反应为指标反应，运用X-射线衍射、比表
面测定、傅立叶红外光谱、X-射线光电子能谱、表面光电压普和Hammett指示剂法
等表征手段，系统地比较了三个系列催化剂的结构形态、表面酸性、光谱特性和光催
化性能。同时，还利用双功能探针分子吡啶作为光催化反应的探针和表面酸性的碱性
探针，在原位下，探讨了光催化剂表面酸性的性质及其与光催化性能的联系。研究结
果表明，表面酸化尤其是超强酸化可以显著提高催化剂的活性、选择性和抗湿性，提
高这些光催化性能的可能原因有三：1.改善了催化剂的物化性能，超强酸化使催化
剂的比表面增大，晶粒细化，同时也抑制了催化剂的相变；2 提高了光生电子—空穴
对的有效分离率，超强酸化使催化剂表面酸性大大增强，作为Brφnsted酸的表面键合
羟基是光生空穴的捕获中心，而超强化后形成的桥式双配位结构的表面硫络合物种则
是光生电子的捕获陷阱；3．活化光催化反应产物水，水分子通过催化剂表面的
Brφnsted酸中心和Lewis酸中心的协同作用转化为活性羟基。根据这些结果，论文提
出了超强酸中心在多相光催化过程中的作用模型，最后设计了一个原位实验证实了该
模型的合理性。
TiO2, TiO2-ZrO2 solid acid and SO42-/TiO2 solid superacid were prepared using modified sol-gel method. Structure, surface acidity, optical properties and photocatalytic performance of the above three series of catalysts were investigated by decomposition of ethylene and methyl bromide and by X-ray diffraction, surface area measurement, X-ray photoelectron spectroscopy, FTIR spectroscopy, surface photo-voltage spectroscopy, and Hammett indicator method. In addition, the nature of surface acidity and the relationship between surface acidity and photocatalytic performance were studied by in-situ FTIR technology using pyridine as bi-functional probe of reactant and basic probe for acidic site. The result revealed that increasing surface acidity of TiO2, especially, when it reached superacidity, could dramatically enhance photocatalytic performance including activity, selectivity and water-resistant ability, which may be resulted from the following three factors: 1. Bettering physical and chemical properties of catalyst, such as increasing surface area, decreasing crystal size, and inhibiting phase transformation from anatase to rutile which are favorable for increasing photoactivity; 2. Accelerating the separation rate of photogenerated electron-hole pairs. Sulfation greatly increased catalyst's Bronsted acidic sites that may serve as trapping sites for photogenerated holes, while the bridged bitentate sulfur complex bounded on catalyst could serve as capturing sites for light-induced electrons; 3. Activating H2O molecules produced from photocatalytic reaction by adsorbing them on Lewis acidic site of catalyst then transfer to Bronsted acidic sites to generate highly active OH radicals. In the end, a model of the mechanism of superacidity in the process of heterogeneous photocatalysis was put forward. The model was confirmed as reasonable by a designed in- situ experiment.
催化剂，以乙烯和溴代甲烷的光催化降解反应为指标反应，运用X-射线衍射、比表
面测定、傅立叶红外光谱、X-射线光电子能谱、表面光电压普和Hammett指示剂法
等表征手段，系统地比较了三个系列催化剂的结构形态、表面酸性、光谱特性和光催
化性能。同时，还利用双功能探针分子吡啶作为光催化反应的探针和表面酸性的碱性
探针，在原位下，探讨了光催化剂表面酸性的性质及其与光催化性能的联系。研究结
果表明，表面酸化尤其是超强酸化可以显著提高催化剂的活性、选择性和抗湿性，提
高这些光催化性能的可能原因有三：1.改善了催化剂的物化性能，超强酸化使催化
剂的比表面增大，晶粒细化，同时也抑制了催化剂的相变；2 提高了光生电子—空穴
对的有效分离率，超强酸化使催化剂表面酸性大大增强，作为Brφnsted酸的表面键合
羟基是光生空穴的捕获中心，而超强化后形成的桥式双配位结构的表面硫络合物种则
是光生电子的捕获陷阱；3．活化光催化反应产物水，水分子通过催化剂表面的
Brφnsted酸中心和Lewis酸中心的协同作用转化为活性羟基。根据这些结果，论文提
出了超强酸中心在多相光催化过程中的作用模型，最后设计了一个原位实验证实了该
模型的合理性。
TiO2, TiO2-ZrO2 solid acid and SO42-/TiO2 solid superacid were prepared using modified sol-gel method. Structure, surface acidity, optical properties and photocatalytic performance of the above three series of catalysts were investigated by decomposition of ethylene and methyl bromide and by X-ray diffraction, surface area measurement, X-ray photoelectron spectroscopy, FTIR spectroscopy, surface photo-voltage spectroscopy, and Hammett indicator method. In addition, the nature of surface acidity and the relationship between surface acidity and photocatalytic performance were studied by in-situ FTIR technology using pyridine as bi-functional probe of reactant and basic probe for acidic site. The result revealed that increasing surface acidity of TiO2, especially, when it reached superacidity, could dramatically enhance photocatalytic performance including activity, selectivity and water-resistant ability, which may be resulted from the following three factors: 1. Bettering physical and chemical properties of catalyst, such as increasing surface area, decreasing crystal size, and inhibiting phase transformation from anatase to rutile which are favorable for increasing photoactivity; 2. Accelerating the separation rate of photogenerated electron-hole pairs. Sulfation greatly increased catalyst's Bronsted acidic sites that may serve as trapping sites for photogenerated holes, while the bridged bitentate sulfur complex bounded on catalyst could serve as capturing sites for light-induced electrons; 3. Activating H2O molecules produced from photocatalytic reaction by adsorbing them on Lewis acidic site of catalyst then transfer to Bronsted acidic sites to generate highly active OH radicals. In the end, a model of the mechanism of superacidity in the process of heterogeneous photocatalysis was put forward. The model was confirmed as reasonable by a designed in- situ experiment.
引文
[1] A. Fujishima, K. Honda, Nature, 37, 238(1972)
[2] V. N. Parmon, K. I. Iamarave, IN Photo Catalysis Foundamentals and Applications, N. Serpone, E. Pelizzeyyi, Eds, Wiley Interscienee, New York, 1989,P. 565
[3] E. Pelizzetti, M. Schiavello,Eds, Photochemieal Conversion and Storage of Solar Engery, Kluwer Academic Publishers, Dordrecht, 1991
[4] 金振声，98’全国光催化学术会议论文摘要集，1998年10月，pl
[5] 李琳，相光催化在水污染治理中的应用，环境科学进展，1994，2167：23
[6] A. Fujishima, K. Honda, Nature, 1997, 388:431
[7] 黄汉生，现代化工，1998，18(12)：39
[8] 付贤智，2000’全国光催化学术会议论文摘要集，2000年10月,p21
[9] A. Fujishima, TiO_2 Photocatalysis Fundamentals and Applications, May,1999,P129.
[10] Michael R.Hoffmann, Scot T. Martin, Wonyong Choi, and Delef W. Bahnemann, Chem. Rev., 1995,95:69
[11] P. V. Kamat, Chem. Rev., 1993, 93:341
[12] 刘恩科，朱秉升，罗晋生等，《半导体物理》，西安交通大学出版社，1998，P120
[13] Martin, S. T. et al.. Trans. Faraday Soc., 1994, 90, 3315-3330
[14] 吴越，《催化化学》(第二版)，科学出版社，1998，p1341
[15] Anders Hagfedt, Michael Gratzel, Chem. Rev., 1995,95:494
[16] Su Wen-Yue (苏文悦), Fu Xian-Zhi i(付贤智),Wei Ke-Mei (魏可镁),Acta Phys.-Chim.,Sin 物理化学学报)., 2001, 17(1): 28-31
[17] 沈韧飞，赵文宽，贺飞，方佑龄，化学进展，1998，10(4)：349
[18] Xianzhi Fu, Walter A. Zeltner, Marc A. Anderson, Applied Catakysis B: Environmental 6(1995) 209-224
[19] 吴合进，吴鸣，刘鸿，谢茂松，2000’全国光催化学术会议论文摘要集，2000年10月，p29
[20] 郑宜，李旦振，付贤智，刘平，2000’全国光催化学术会议论文摘要集，2000年10月，p191
[21] Choi W. Termin A., Hoffmann M. R., J. Phys. Chem., 1994, 51: 13669
[22] Yamashita H., Anpo M., Kagaku, 1997, 52(9):74
[23] 吴越，《催化化学》(第二版)，科学出版社，1998，p1346
[24] Kamat P. V., Fox M. A., Chem. Phys. Lett., 1983, 102(4)93:384
[25] B. Patrick, P. V. Kamat,. J. Phys. Chem., 1997, 101(6):930
[26] Idriss. Bedja, Surat. Hotchandani and Prashant. V. Kamat, J. Phys. Chem., 1997, 101:1651
[27] Spanhel L et al., J. Am. Chem. Soc., 1987, 109 6632
[28] Vogel R et al., J. Phys. Chem 1994, 98,3183
[29] Vogel R et al., J. Phys. Chem 1990, 174, 241
[30] Kohtani S et al., Chem. Phys Lett., 1991, 174,241
[31] Gopidas K R et al., J. Phys. Chem 1990,94(16), 6435
[32] Fu X.Z, et al. ,Environmental science & Technolog3, 1996,30,647-653
[33] Rabani J, J. Phys. Chem 1989, 93:7707
[34] 刘恩科，朱秉升，罗晋生等，《半导体物理》，西安交通大学出版社，1998，
[35] Masakazu A et al., J. Phys. Chem 1988, 99(2),438-440
[36] Alemany L J et al., J. Catal., 1995, 155:117-130
[37] Do Y R et al., J. Solid State Chem., 1994, 108:198
[38] Papp J et al., Chem. Mater., 1994,6:496
[39] Oosawa Y et al., J. Chem. Soo. Faraday Trans., 1988,84(1):197
[40] 吴越，《催化化学》(第二版)，科学出版社，1998，p1036
[41] Itoh M et al., J. Catal.,35,225(1974)
[42] Olah G. A., Lucus J., J. Am. Chem. Soc., 89,2227;4739,1969
[43] Kemp J..D.,U. S. Pat.,3,852,371,1974
[44] Bloch H.S.,U.S. Pat.,3,678,120,1972
[45] Olah G. A.,U.S.Pat.,3,708,553;3,766,286,1973
[46] Magnotta V.C., Gates B.C., J. Catal., 46,266,1977
[47] Hino M., Arata K., J.Chem. Soc., Chem. Commun., 1259,1988.
[48] Hino M., Arata K., J. Am. Chem. Soc.,101,6439,1979
[49] Hino M., Arata K., J. Chem. Soc., Chem. Commun., 1148,1979
[50] Hino M., Arata K., J.Chem. Soc., Chem. Commun., 851,1980
[51] Hino M., Arata K., Chem. Lett., 1671,1981
[52] Tanabe K., Yamaguchi T., Jpn. Patent., 55-115570, 1980
[53] Arata K.,Hino M., Appl. Catal., 59,197,1990
[54] Darrin S. Muggli, Lefei Ding, Applied Catalysis B: Environmental 839(2001)1-4
[55] 苏文悦，陈亦琳，付贤智等，催化学报，2001，22(2)：175-176
[2] V. N. Parmon, K. I. Iamarave, IN Photo Catalysis Foundamentals and Applications, N. Serpone, E. Pelizzeyyi, Eds, Wiley Interscienee, New York, 1989,P. 565
[3] E. Pelizzetti, M. Schiavello,Eds, Photochemieal Conversion and Storage of Solar Engery, Kluwer Academic Publishers, Dordrecht, 1991
[4] 金振声，98’全国光催化学术会议论文摘要集，1998年10月，pl
[5] 李琳，相光催化在水污染治理中的应用，环境科学进展，1994，2167：23
[6] A. Fujishima, K. Honda, Nature, 1997, 388:431
[7] 黄汉生，现代化工，1998，18(12)：39
[8] 付贤智，2000’全国光催化学术会议论文摘要集，2000年10月,p21
[9] A. Fujishima, TiO_2 Photocatalysis Fundamentals and Applications, May,1999,P129.
[10] Michael R.Hoffmann, Scot T. Martin, Wonyong Choi, and Delef W. Bahnemann, Chem. Rev., 1995,95:69
[11] P. V. Kamat, Chem. Rev., 1993, 93:341
[12] 刘恩科，朱秉升，罗晋生等，《半导体物理》，西安交通大学出版社，1998，P120
[13] Martin, S. T. et al.. Trans. Faraday Soc., 1994, 90, 3315-3330
[14] 吴越，《催化化学》(第二版)，科学出版社，1998，p1341
[15] Anders Hagfedt, Michael Gratzel, Chem. Rev., 1995,95:494
[16] Su Wen-Yue (苏文悦), Fu Xian-Zhi i(付贤智),Wei Ke-Mei (魏可镁),Acta Phys.-Chim.,Sin 物理化学学报)., 2001, 17(1): 28-31
[17] 沈韧飞，赵文宽，贺飞，方佑龄，化学进展，1998，10(4)：349
[18] Xianzhi Fu, Walter A. Zeltner, Marc A. Anderson, Applied Catakysis B: Environmental 6(1995) 209-224
[19] 吴合进，吴鸣，刘鸿，谢茂松，2000’全国光催化学术会议论文摘要集，2000年10月，p29
[20] 郑宜，李旦振，付贤智，刘平，2000’全国光催化学术会议论文摘要集，2000年10月，p191
[21] Choi W. Termin A., Hoffmann M. R., J. Phys. Chem., 1994, 51: 13669
[22] Yamashita H., Anpo M., Kagaku, 1997, 52(9):74
[23] 吴越，《催化化学》(第二版)，科学出版社，1998，p1346
[24] Kamat P. V., Fox M. A., Chem. Phys. Lett., 1983, 102(4)93:384
[25] B. Patrick, P. V. Kamat,. J. Phys. Chem., 1997, 101(6):930
[26] Idriss. Bedja, Surat. Hotchandani and Prashant. V. Kamat, J. Phys. Chem., 1997, 101:1651
[27] Spanhel L et al., J. Am. Chem. Soc., 1987, 109 6632
[28] Vogel R et al., J. Phys. Chem 1994, 98,3183
[29] Vogel R et al., J. Phys. Chem 1990, 174, 241
[30] Kohtani S et al., Chem. Phys Lett., 1991, 174,241
[31] Gopidas K R et al., J. Phys. Chem 1990,94(16), 6435
[32] Fu X.Z, et al. ,Environmental science & Technolog3, 1996,30,647-653
[33] Rabani J, J. Phys. Chem 1989, 93:7707
[34] 刘恩科，朱秉升，罗晋生等，《半导体物理》，西安交通大学出版社，1998，
[35] Masakazu A et al., J. Phys. Chem 1988, 99(2),438-440
[36] Alemany L J et al., J. Catal., 1995, 155:117-130
[37] Do Y R et al., J. Solid State Chem., 1994, 108:198
[38] Papp J et al., Chem. Mater., 1994,6:496
[39] Oosawa Y et al., J. Chem. Soo. Faraday Trans., 1988,84(1):197
[40] 吴越，《催化化学》(第二版)，科学出版社，1998，p1036
[41] Itoh M et al., J. Catal.,35,225(1974)
[42] Olah G. A., Lucus J., J. Am. Chem. Soc., 89,2227;4739,1969
[43] Kemp J..D.,U. S. Pat.,3,852,371,1974
[44] Bloch H.S.,U.S. Pat.,3,678,120,1972
[45] Olah G. A.,U.S.Pat.,3,708,553;3,766,286,1973
[46] Magnotta V.C., Gates B.C., J. Catal., 46,266,1977
[47] Hino M., Arata K., J.Chem. Soc., Chem. Commun., 1259,1988.
[48] Hino M., Arata K., J. Am. Chem. Soc.,101,6439,1979
[49] Hino M., Arata K., J. Chem. Soc., Chem. Commun., 1148,1979
[50] Hino M., Arata K., J.Chem. Soc., Chem. Commun., 851,1980
[51] Hino M., Arata K., Chem. Lett., 1671,1981
[52] Tanabe K., Yamaguchi T., Jpn. Patent., 55-115570, 1980
[53] Arata K.,Hino M., Appl. Catal., 59,197,1990
[54] Darrin S. Muggli, Lefei Ding, Applied Catalysis B: Environmental 839(2001)1-4
[55] 苏文悦，陈亦琳，付贤智等，催化学报，2001，22(2)：175-176