VOCs诱导TiO_2光生载流子的分离
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摘要
气体分子直接影响光生载流子的分离行为,进而影响光催化降解挥发性有机物(volatile organic compounds,VOCs)的效率.本研究以甲苯、环己烷和甲基环己烷为VOCs代表,采用气氛表面光电压谱仪研究VOCs和氧气-VOCs气氛条件下锐钛矿TiO_2光生载流子的传输行为.实验结果表明:VOCs可增强锐钛矿TiO_2可见光区域光生载流子的分离,其中甲苯的增强作用显著强于环己烷和甲基环己烷.3种VOCs对带带跃迁光生载流子分离效率的影响均不显著,但与氧气共存则均能显著提高光生载流子的分离效率,提高的趋势为:甲苯>甲基环己烷>环己烷.
Gas molecules exert a direct influence on the separation of photogenerated charge carriers,which affects the photocatalytic degradation efficiency of volatile organic compounds. In this study,toluene,cyclohexane,and methylcyclohexane were selected as representative VOCs. The charge separation of anatase TiO_2 in VOCs atmosphere or VOCs-oxygen atmosphere was measured via atmosphere-surface-photovoltage-spectroscopy. The results showed VOCs enhanced the separation of photogenerated charge carriers in the visible region. The enhancement of toluene was significantly greater than that of cyclohexane and methylcyclohexane. Further more,three VOCs had little effect on the photogenerated charge carriers from band-to-band transition. VOCs in the presence of oxygen obviously enhanced the separation of photogenerated charge carriers from band to band transition with the order of toluene> methylcyclohexane > cyclohexane.
Gas molecules exert a direct influence on the separation of photogenerated charge carriers,which affects the photocatalytic degradation efficiency of volatile organic compounds. In this study,toluene,cyclohexane,and methylcyclohexane were selected as representative VOCs. The charge separation of anatase TiO_2 in VOCs atmosphere or VOCs-oxygen atmosphere was measured via atmosphere-surface-photovoltage-spectroscopy. The results showed VOCs enhanced the separation of photogenerated charge carriers in the visible region. The enhancement of toluene was significantly greater than that of cyclohexane and methylcyclohexane. Further more,three VOCs had little effect on the photogenerated charge carriers from band-to-band transition. VOCs in the presence of oxygen obviously enhanced the separation of photogenerated charge carriers from band to band transition with the order of toluene> methylcyclohexane > cyclohexane.
引文
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[2] GENG F,TIE X X,XU J,et al. Characterizations of ozone,NOx and VOCs measured in Shanghai,China[J]. Atmospheric Environment,2008,42(29)∶6873-6883.
[3]曾斐,梅瑜,成卓韦,等.二氧化钛紫外光催化降解有机废气研究进展[J].环境科学与技术,2013,36(6)∶91-98.ZENG F,MEI Y,CHENG Z W,et al. Progress on Ti O2-based UV Photocatalysis for degradation of organic waste gas[J]. Environmental Science&Technology,2013,36(6):91-98(in Chinese).
[4] LI F F,JIANG Y S,XIA M S,et al. Effect of the P/Ti ratio on the visible-light photocatalytic activity of P-doped Ti O2[J]. Journal of Physical Chemistry C,2009,113(42):18134-18141.
[5] CHEN H H,NANAYAKKARA C E,GRASSIAN V H. Titanium dioxide photocatalysis in atmospheric chemistry[J]. Chemical Reviews,2012,112(11):5919-5948.
[6] MO J,ZHANG Y,XU Q. Photocatalytic purification of volatile organic compounds in indoor air:A literature review[J]. Atmospheric Environment,2009,43(14):2229-2246.
[7] NISCHK M,MAZIERSKI P,GAZDA M,et al. Ordered Ti O2nanotubes:The effect of preparation parameters on the photocatalytic activity in air purification process[J]. Applied Catalysis B-Environmental,2014,144:674-685.
[8] SULIGOJ A,STANGER U L,RISTIC A,et al. Ti O2-Si O2films from organic-free colloidal Ti O2anatase nanoparticles as photocatalyst for removal of volatile organic compounds from indoor air[J]. Applied Catalysis B-Environmental,2016,184:119-131.
[9] MAO M,LY H,LI Y,et al. Metal support interaction in pt nanoparticles partially confined in the mesopores of microsized mesoporous CeO2for highly efficient purification of volatile organic compounds[J]. ACS Catalysis,2016,6(1):418-427.
[10] HODGSON A I,DESTAILLATS H,SULLIVAN D P,et al. Performance of ultraviolet photocatalytic oxidation for indoor air cleaning applications[J]. Indoor Air,2007,17(4):305-316.
[11] YU K P,LEE G W M,HUANG W M,et al. The correlation between photocatalytic oxidation performance and chemical/physical properties of indoor volatile organic compounds[J]. Atmospheric Environment,2006,40(2):375-385.
[12] ZHAO Z Y,LI Z S,ZOU Z G. Understanding the interaction of water with anatase Ti O2(101)surface from density functional theory calculations[J]. Physics Letters A,2011,375(32):2939-2945.
[13] LEE J,SORESCU D C,DENG X Y. Electron-Induced Dissociation of CO2on Ti O2(110)[J]. Journal of the American Chemical Society,2011,133(26):10066-10069.
[14] KONG M,LI Y Z,CHEN X,et al. Tuning the relative concentration ratio of bulk defects to surface defects in Ti O2nanocrystals leads to high photocatalytic efficiency[J]. Journal of the American Chemical Society,2011,133(41):16414-16417.
[15] LECONTE J,MARKOVITS A,SKALLI M K,et al. Periodic ab initio study of the hydrogenated rutile Ti O2(1 1 0)surface[J]. Surface Science,2002,497(1-3):194-204.
[16] TIAN Z M,ZHANG Y J,YANG FY,et al. Comparative study on autoignition characteristics of methylcyclohexane and cyclohexane[J].Energy&Fuels,2015,29(4):2685-2695.
[17] KRONIK L,SHAPIRA Y. Surface photovoltage phenomena:Theory,experiment,and applications[J]. Surface Science Reports,1999,37(1-5):1-206.
[18] ZHAO J,NAIL B A,HOLMES M A,et al. Use of surface photovoltage spectroscopy to measure built-in voltage,space charge layer width,and effective band gap in CdSe quantum dot films[J]. Journal of Physical Chemistry Letters,2016,7(17):3335-3340.
[19] DONCHEV V,KIRILOV K,IVANOV T,et al. Surface photovoltage phase spectroscopy-a handy tool for characterisation of bulk semiconductors and nanostructures[J]. Materials Science and Engineering B,2006,129(1-3):186-192.
[20] STEVANOVIC A,BUETTNER M,ZHANG Z,et al. Photoluminescence of Ti O2:Effect of UV Light and Adsorbed Molecules on Surface Band Structure[J]. Journal of the American Chemical Society,2012,134(1):324-332.
[21]王晨森,陈立锋,曾皓,等.苯环电子云效应对苯胺聚合反应影响的初步探索[J].材料导报B:研究篇,2014,28(1)∶110-113.WANG C S,CHENG L F,ZENG H,et al. Exploration of the effect of the electron cloud density from aniline on its polmerization[J].Materials Review,2014,28(1):110-113(in Chinese).
[22]王存德.有机化学中的邻基参与和超共轭效应之辨析[J].广东化工,2014,41(14)∶236-244.WANG C D. Discrimination of the neighboring group participation and hyperconjugation in organic chemistry[J]. Guangdong Chemical Industry,2014,41(14):236-244(in Chinese).