光催化降解VOCs过程中载流子的表界面双向诱导机制研究

Interaction of photogenerated charge carriers and gaseous composites is the key process of VOCs photocatalytic degradation. This process directly effects the behavior of VOCs adsorption, mineralization, and harmful byproducts release. However, the behavior and interaction mechanism of charge carriers in the process of VOCs photo-oxidation is still unknown, therefore the separation behavior of charge carriers in the near surface region cannot be efficiently optimized to enhance VOCs mineralization and diminish byproducts. To improve this, surface photovoltage spectroscopy, in-suit Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry are applied to study the effects of functional group, carbon number, amount of surface defects on the separation efficiency and migration tendency of charge carriers in adsorption experiments. Moreover, the dynamic process and interaction mechanism of charge carriers and VOCs in reaction system are discussed after the interaction between O2 (H2O) and charge carriers is studied. On the other hand, the effect of charge carrier separation on the adsorption and photocatalytic process is studied. Finally, the optimized behavior of charge carriers is going to be established to enhance the mineralization efficiency of VOCs and diminish the release of harmful byproducts. This proposal will help in developing highly efficient VOCs photocatalytic purification materials and technology.

光生载流子和气体组分的界面作用是光催化降解VOCs的核心环节，直接影响VOCs的吸附行为、矿化效率和副产物释放。然而，光生载流子的分离行为与VOCs吸附-反应过程的作用机制尚不清楚，因此难以有效制定载流子分离行为的调控策略，以实现VOCs的高效矿化和有害副产物的消减。为此，本课题采用气氛表面光电压谱、原位红外光谱和气相质谱技术，建立吸附态VOCs官能团种类、C数、TiO2表面缺陷含量等参数与载流子分离效率和迁移趋势间的定性定量关系，结合大气主要活性组分（O2和H2O）影响载流子分离行为的规律，研究反应体系中VOCs诱导表面态和带隙跃迁载流子分离行为的机制和动力学过程，进而探索载流子分离行为反向作用VOCs吸附及光催化氧化过程的机制，形成基于载流子分离行为调控的VOCs降解策略，提升VOCs矿化效率，消减有害副产物，力图为针对性研发经济高效的光催化降解VOCs新材料和技术提供科学依据。

光生载流子和气体组分的界面作用是光催化降解VOCs的核心环节，直接影响VOCs的吸附行为、矿化效率和副产物释放。然而，光生载流子的分离行为与VOCs吸附-反应过程的作用机制尚不明确，因此难以有效调控载流子分离行为，以实现VOCs的高效矿化和有害副产物的消减。为此，本课题采用气氛表面光电压谱、原位红外光谱和气相质谱技术，探究了O2、H2O、VOCs及复合气氛条件下锐钛矿TiO2光生载流子的传输行为，分析了反应体系中VOCs诱导表面态和带隙跃迁载流子分离行为的作用机制，为理解VOCs实际降解过程与优化光催化剂性能提供了理论支撑，为研发不同环境条件下针对不同种类VOCs的光催化降解新材料和技术提供科学依据。主要结果如下：.（1）探明了O2对光生电子的定域及稳定作用。O2捕获并定域光生电子从而提高带带跃迁光生载流子的分离效率并促进表面电荷积累，同时吸附O2抑制了表面态光生载流子的产生。.（2）研究了水对光生载流子的捕获行为和水-氧气共存对光生载流子分离的协同促进作用。湿度小于20%，水分子对带带跃迁光生载流子的分离有一定促进作用；湿度大于20%，水分子可显著促进带带跃迁光生载流子分离；湿度高于85%时带带跃迁载流子分离效率略有下降。表面态跃迁产生的光生载流子随湿度升高先增加后减少。锐钛矿TiO2表面水和氧气共存可协同促进带带跃迁和表面态跃迁载流子分离。.（3）探索了VOCs及其与水和氧气共存对光生载流子传输行为的影响。VOCs（甲苯、环己烷、甲基环己烷）单独存在时对带带跃迁光生载流子的传输行为无显著影响，而带尾态跃迁产生的光生载流子随VOCs浓度升高先增加后减少。明确了锐钛矿TiO2表面VOCs和O2共存对带隙跃迁载流子分离的抑制作用。VOCs和水共存可协同促进带带跃迁载流子分离。