The photodegradation of gaseous perchloroethylene (PCE) was investigated on titanium dioxide under UV light at 365 nm at the gas/solid interface in a CSTR photo-reactor (Continuous Stirred Tank Reactor). The rate and products are strongly affected by oxygen presence. Gaseous products of PCE degradation agree with literature. The production of active chlorine (sum of Cl₂, HClO, ClO and ClO₂) was investigated both in the presence of oxygen and in anoxic conditions. At low O₂ concentration no gaseous active chlorine was determined, while a significant amount was measured in the presence of oxygen. By considering that in the absence of O₂ the only possible form of active chlorine is Cl₂, this highlights that Cl is not produced, and that chain reactions promoted by the chlorine radical do not occur on the TiO₂ surface.

The photocatalytic transformation of C₂Cl₄ was investigated at different concentrations. The rate follows a first order kinetic that is rationalized with a photocatalytic kinetic model in which the substrate is able to react simultaneously with both photogenerated holes and electrons. In anoxic conditions adsorbed halogenated organic compounds with molecular weights higher than that of PCE were produced and chloride ions accumulated at the surface. Reductive pathways have a key role in PCE degradation. The water vapor has a detrimental role on the PCE transformation rate due to the competition with PCE adsorption on reactive sites with 2:1 stoichiometry.

The addition of chloride ions on TiO₂ surface slows down the PCE degradation rate and the production of gaseous CCl₄ but increments that of C₂Cl₆ in anoxic conditions. This is rationalized by a mechanism in which direct hole transfer to substrate occurs followed by chloride anion addition to the carbocation.

在CSTR光反应器（连续搅拌釜反应器）的气/固界面上，在365 nm的紫外线下，在二氧化钛上研究了气态全氯乙烯（PCE）的光降解。速率和产物受氧气的存在强烈影响。PCE降解的气态产物与文献一致。在氧气存在和缺氧条件下都研究了活性氯（Cl ₂，HClO，ClO和ClO _2的总和）的产生。在低O ₂浓度下，未测定出气态活性氯，而在有氧条件下测得了大量的活性氯。考虑到在不存在O ₂的情况下，活性氯的唯一可能形式是Cl ₂，这说明了Cl不会产生，并且在TiO ₂表面上不会发生由氯自由基促进的链反应。

研究了不同浓度下C ₂ Cl ₄的光催化转化。该速率遵循用光催化动力学模型合理化的一级动力学，其中基质能够同时与光生空穴和电子反应。在缺氧条件下，会产生分子量高于PCE的吸附卤代有机化合物，并且氯离子会在表面积聚。还原途径在PCE降解中起关键作用。由于在化学计量比为2：1的反应位点上与PCE吸附的竞争，水蒸气对PCE的转化率具有有害作用。

在TiO ₂表面添加氯离子减慢了PCE的降解速度和气态CCl ₄的生成，但在缺氧条件下增加了C ₂ Cl _6的生成。这可以通过一种机制来合理化，在该机制中，将空穴直接转移到基质上，然后将氯离子添加到碳正离子中。