中文摘要：

作为在能源和环境领域有着重要应用前景的绿色技术,光催化的发展受到了广泛的关注.然而,光催化反应机理和动力学方面的研究却远远落后于光催化剂的发展.一系列的研究结果表明,TiO2表面光催化反应起始于光的吸收.TiO2吸收大于其带隙的光子后,则会产生电子空穴对,而电子,空穴分离后,会在百飞秒量级时间范围内弛豫到导带或者是价带边上,多余的能量则会激发声子振动.而分离的电子或者是空穴会在皮秒或者是更长时间范围内与反应物相互作用,来驱动反应发生.因此,在这种前提下,反应速率和激发光的波长就没有直接联系了.相反,反应速率和TiO2对不同光波长的光吸收系数有很大关系.本文总结了本课题组最近在金红石TiO2（110）表面开展的甲醇和水的光解离基元过程的研究结果.首先,我们发现在金红石TiO2（110）表面,利用400nm去照射甲醇或者水覆盖的金红石TiO2（110）表面,甲醇能够高效的发生解离,而水却没有观察的解离.通过基于基态反应的理论计算,发现水两步解离的低能垒是反应不能有效发生的关键.另外,我们也研究了甲醇在355和266 nm光照射下在金红石TiO2（110）表面的解离,结果发现,甲醇在266 nm照射下的解离速率比355 nm快了100倍,而TiO2对266 nm光的吸收系数比355 nm也就高了2–4倍.这充分说明了光子能量对反应有非常显著的贡献,现有的光催化模型已经不能很好地解释我们观察的实验现象.在此基础上,我们提出了一个基于非绝热过程和基态反应的模型来解释这些新的实验现象.这个模型不仅能解释我们的实验结果,还能为增进光催化的理解打开一扇新的大门.为了能让这个模型应用到一般的光催化过程中,需要着重开展表面附近电子-空穴复合导致的基态光催化反应的研究,来验证和完善这个新的模型.

英文摘要：

1. Introduction Photocatalysis has been under intense investigation for decades because of its potential applications in water splitting for efficient hydrogen production, synthesis of molecules from simple precursors, or decomposition of toxic compounds, etc. During the last few decades, significant effort has been devoted to the study of heterogeneous photocatalysis, especially in de- veloping efficient photocatalysts for water splitting. A theoreti- cal picture of heterogeneous photocatalysis has also been gradually developed, based mostly on bulk heterogeneous photocatalysis experiments [1]. Many of the important concepts in this picture of heterogeneous photocatalysis have originated from solid state physics and photoelectrochemistry. The key concept in this commonly used photocatalysis model, which has tremendous influence in this field, is that photocatalytic chemistry is driven by separated electrons and holes upon photoexcitation of electron-hole pairs in the photocatalysis.