物理化学学报 >> 2001, Vol. 17 >> Issue (09): 781-787.doi: 10.3866/PKU.WHXB20010904

研究论文 上一篇    下一篇

表面过剩S2-对CdS光催化的影响与带位匹配

陈德文;刘延秋;易筱筠;徐广智   

  1. 中国科学院化学研究所,分子动态与稳态结构国家重点实验室,北京 100080
  • 收稿日期:2001-01-22 修回日期:2001-03-22 发布日期:2001-09-15
  • 通讯作者: 陈德文 E-mail:Chendw@xxl.icas.ac.cn

Influence of Excess S2- Ion on the Interfacial Photocatalysis in Superfine CdS System and Band-Potential Matching

Chen De-Wen;Liu Yan-Qiu;Yi Xiao-Yun;Xu Guang-Zhi   

  1. State Key Laboratory for Structural Chemistry of Unstable and Stable Species,Institute of Chemistry,Chinese Academy of Sciences,Beijing 100080
  • Received:2001-01-22 Revised:2001-03-22 Published:2001-09-15
  • Contact: Chen De-Wen E-mail:Chendw@xxl.icas.ac.cn

摘要: 用ESR方法研究了硫化镉超微粒子表面被不同浓度的过剩硫离子S2-改性后对其光诱导电子转移及底物的氧化还原反应进程的影响.结果表明,在较高浓度下光还原反应易于进行.若所用底物的氧化还原电位E0为负值,在无过剩S2-存在及低浓度S2-环境中不发生光还原反应,但却可在高浓度S2-环境发生反应; 若底物的E0为正值,则在无硫离子及较低硫离子浓度下能够发生的光氧化反应,在高浓度时则被完全抑止.这是由于表面过剩S2-的作用,改变了底物的氧化还原电位与半导体超细微粒带隙间的匹配关系.根据Langmuir 等温吸附模型,进一步导出了修饰物的浓度c与平带电位负移值间的关系表达式ΔEfb=Δ Kc/(1+Kc).可以合理解释修饰物 S2-的浓度越高,Efb负移越大,越有利于光还原反应的实验事实.因此根据需要,适当地选择修饰物并控制浓度,使带隙位置与底物氧化还原电位间能有合适的匹配,有助于调节光化学反应的选择性与方向.

关键词: 硫化镉, 超微粒子, ESR, 平带电位, 电子转移, 带位匹配

Abstract: The influence of S2- ion and its concentration upon the photoinduced electron transfer and redox reaction of substrates on the surface of modified CdS colloid have been studied by means of ESR technique.The experimental results show that the existence of S2- ion with high concentration is advantageous to the interfacial photoreduction reaction and may restrain the photooxidation reaction.If the redox potential E0 of the substrate is negative,photoreduction reaction is impossible to occur in the system with low concentration of S2- ion,but it can take place as the concentration of S2- ion is sufficient high; when E0 of the substrate is positive,photooxidation reaction can be prohibited entirely under condition of high S2- ion concentration,even though it is able to occur while the concentration of S2- ion is low.Due to the strong interaction of S2- ion with the surface of CdS superfine particles,negative shift in flat potential Efb of CdS leads to a change of gap position,and then to a variation in match relation between the redox potential E0 of the substrate and the position of conducton band to valence band in semiconductor particles.According to Langmuir's adsorption isotherm model,a formula expressing the relation between the concentration c of modification compound and the negative shift ΔEfb in flat potential was derived:ΔEfb=Δ Kc/(1+Kc).By using this formula,experiment facts may be explained rationally,the higher the concentration,the greater the amount of negative shift ΔEfb,and thus the more favourable to photoreduction reaction.Therefore,by choosing suitable modification substance and adjusting its concentration,the selection,direction as well as the mechanism of interfacial photoreaction can be controlled effectively.

Key words: CdS, Superfine particles, ESR, Flat potential, Electron transfer, Bandpotential matching