The photodegradation tendencies of mixed and isolated VOCs, e.g., benzene, toluene, and p-xylene were studied using TiO₂ P25 as a model photocatalyst. The degradation of VOCs in the mixture is significantly affected by the existence of different organic pollutants. For example, benzene only showed 10% degradation efficiency in the mixture whilst 67% in the isolated mode. The conversion efficiency of benzene was 20% and 27% when mixed with p-xylene and toluene, respectively. It shows that the degradability of benzene is influenced more by the presence of p-xylene than toluene. The dynamic adsorption-desorption experiments and DFT calculations on stoichiometric and defective TiO₂ surface revealed that benzene only weakly interacts with the stoichiometric TiO₂ surface than toluene and p-xylene. This behavior could be the fundamental factor for the lower degradation efficiency of benzene. Furthermore, the presence of oxygen vacancy (O_v) in TiO₂ surface tremendously improved the overall adsorption of VOCs. Several Langmuir-Hinshelwood kinetic models, which are based on different reaction dynamic assumptions, were used to determine rates of reactions, water adsorption equilibrium constant, and VOCs adsorption equilibrium constant. The results indicated that the oxidation of VOCs occurred on the catalyst surface, and the adsorption equilibrium constant of VOCs was higher than water adsorption equilibrium constant. The intermediate formation and hydroxyl groups consumption were further rationalized via in-situ FTIR study. This work provides a comprehensive analysis of VOCs degradation in the mixed and isolated mode, which will increase the possibility of implementing the photocatalytic oxidation technology for the VOCs abatement.

以TiO ₂ P25为模型光催化剂，研究了混合和分离的VOC（例如苯，甲苯和对二甲苯）的光降解趋势。混合物中VOC的降解受到不同有机污染物的存在的显着影响。例如，苯在混合物中的降解效率仅为10％，而在分离模式下为67％。与对二甲苯和甲苯混合时，苯的转化效率分别为20％和27％。它表明苯的可降解性受对二甲苯的影响比甲苯的影响更大。化学计量和有缺陷的TiO ₂的动态吸附-解吸实验和DFT计算表面显示苯仅比甲苯和对二甲苯与化学计量的TiO ₂表面弱相互作用。该行为可能是苯降解效率降低的根本因素。此外，TiO _2中存在氧空位（O _v）表面极大地改善了VOC的整体吸附。基于不同反应动力学假设的几种Langmuir-Hinshelwood动力学模型用于确定反应速率，水吸附平衡常数和VOCs吸附平衡常数。结果表明，VOCs在催化剂表面发生氧化，其吸附平衡常数高于水吸附平衡常数。通过原位FTIR研究进一步合理化了中间体的形成和羟基的消耗。这项工作提供了混合和隔离模式下VOCs降解的综合分析，这将增加为减少VOCs实施光催化氧化技术的可能性。