随着全球工业化进程的快速发展，大气中挥发性有机物(VOCs)的含量与日俱增。大多数VOCs不仅具有生物毒性及“三致作用”，而且是二次有机气溶胶的重要前体物，因此全球范围内都致力于对大气中VOCs的污染控制和空气净化等相关工作的研究。光催化氧化法是一种普遍认可并具有广阔应用前景的VOCs净化技术，特别是二氧化钛(TiO₂)因其卓越的光催化氧化性能、稳定性好、无毒价廉等优点而被广泛应用到大气中VOCs的降解研究中，但是由于降解过程存在活性自由基难以捕获、中间产物难于有效分离和鉴定等问题，导致其相关降解机理还不是非常明确，因此研究典型VOCs在TiO₂催化剂表面的吸附和催化降解过程，将为消除和控制VOCs对人类健康及其生态环境的影响具有重要的科学意义。 

　　广州地化所博士生王红红及导师安太成研究员团队采用密度泛函理论系统研究了典型工业排放VOCs苯乙烯在(TiO₂)_n分子簇表面的吸附机理及其^？OH引发的光催化降解过程与机制。研究结果发现：苯乙烯吸附到TiO₂表面的过程是强放热的化学吸附过程，主要以侧链乙烯基模式进行吸附。而吸附到TiO₂表面的苯乙烯极容易被光催化原位生成的表面^？OH进攻发生降解反应，该过程主要以^？OH加成路径为主，形成乙烯基加成产物。同时采用变分过渡态理论得到的218-297K温度范围内的动力学计算结果表明：反应体系的温度对TiO₂光催化降解苯乙烯的速率常数影响较小。通过与无催化剂存在情况下的^？OH均相反应的结果对比发现：TiO₂催化剂的存在并不会改变苯乙烯降解反应的机理，但是却可以大大提高了苯乙烯的降解速度，且在一定的催化剂颗粒尺寸范围内，TiO₂纳米颗粒的增大将有利于提高苯乙烯的光催化降解速度。

   本论文的实验结果从分子水平系统阐释了典型VOCs苯乙烯在TiO₂催化剂表面的吸附机理以及其^？OH引发的催化剂界面光催化降解过程，明晰了光催化降解反应机理及其TiO₂的催化作用与其尺寸效应的关系。该研究结果可为大气中挥发性有机物的污染控制提供一定的理论研究基础和科学技术支撑。 

　　本研究得到国家杰出青年基金(No.41425015), 国家自然科学基金(No.41205088 和41373102)和广东省团队项目(S2012030006604)的资助。 

　　该研究成果发表在Scientific Reports杂志上(Honghong Wang, YuemengJi, Jiangyao Chen, Guiying Li, Taicheng An*. Theoretical investigation on the adsorption configuration and ？OH-initiated photocatalytic degradation mechanism of typical atmospheric VOCs styrene onto (TiO₂)_n clusters, 2015, 5: 15059)。 

　　论文英文摘要见下文： 

　　In this study, the adsorption mechanism and ^？OH-initiated photocatalytic degradation mechanism of styrene onto different (TiO₂)_n clusters were investigated using density function theory.Styrene, atypical model atmospheric volatile organic compound (VOC),was found to be more readily adsorbed onto(TiO₂)_nclusters through its vinyl group with strong chemisorption. This suggests that (TiO₂)_nclusters are able to effectively adsorb and trap styrene. Adsorbed styrene is then easily attacked by the hydroxyl radical (^？OH) to form a series of vinyl-OH-adducts. Conversely, phenyl-OH-adducts and H-abstraction products are very difficult to form in this system. Kinetics calculations using canonical variational transition state theory show thattemperature has little effect on the rate constants during this photocatalytic degradation process. In the presence of TiO₂does not change the degradation mechanism of styrene, but can accelerate its degradation rate. Therate of the photocatalyic degradation of styrene will increase as TiO₂cluster size increases; as such, the TiO₂particle catalyst should have the photocatalytic ability to effectively degrade styrene.This theory-based study offers insights into the catalytic effect of the TiO₂catalyst, and the photocatalytic degradation mechanism ofbenzene series airpollutantsat the molecular level. 

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