School of Chemistry and Chemical Engineering, Queens University Belfast, Stranmillis Road, Belfast, BT9 5AG, UK.
Photochem Photobiol Sci. 2022 Dec;21(12):2061-2069. doi: 10.1007/s43630-022-00278-0. Epub 2022 Aug 9.
The photocatalytic oxidation of stearic acid, SA, by O is a common test method used to assess the activity of new materials and underpins a standard test for self-cleaning activity. The kinetics of this process have been well-studied and are often interpreted using one of two simple models, which are revisited here in this overview. The first model is based on the common scenario of a SA layer on top of an all-photocatalyst layer which yields zero order kinetics, for which it is suggested that all the reaction sites are occupied by SA during the bulk of the photocatalytic process. An important, but rarely noted feature of this system is that the rate of SA removal depends directly upon the fraction of absorbed ultra-bandgap radiation, which suggests that the photocatalyst particles are extensively networked, thereby allowing the photogenerated electrons and holes to move rapidly and efficiently to the surface to effect the destruction of SA. The second kinetic model has been used to describe the first order kinetics of SA removal observed for mesoporous photocatalytic films comprised of isolated photocatalyst particles, in which the SA is inside (rather than on top) of the photocatalytic film, and is developed further here. It is shown that, contrary to previous reports, this model is not appropriate for porous photocatalytic films in which the particles are extensively networked, such as ones based on powders or sol-gel films, even though they too may exhibit decay kinetics where the order is > 0. The reason for the latter kinetics appears to be a distribution of reactivities through such films, i.e. high and low activity sites.
通过 O 对硬脂酸（SA）的光催化氧化是评估新材料活性的常用测试方法，也是自清洁活性的标准测试的基础。该过程的动力学已得到充分研究，通常使用两种简单模型之一进行解释，本文在此对这两种模型进行了回顾。第一种模型基于在全光催化剂层上的 SA 层的常见情况，其产生零级动力学，对于该模型，建议在光催化过程的大部分时间内，所有反应位点都被 SA 占据。该系统的一个重要但很少注意到的特征是，SA 去除速率直接取决于吸收的超带隙辐射的分数，这表明光催化剂颗粒广泛地形成网络，从而允许光生电子和空穴快速有效地移动到表面以有效地破坏 SA。第二种动力学模型已用于描述由孤立光催化剂颗粒组成的介孔光催化膜中观察到的 SA 去除的一级动力学，其中 SA 在光催化剂膜的内部（而不是顶部），并在此基础上进一步发展。结果表明，与先前的报告相反，该模型不适用于颗粒广泛形成网络的多孔光催化膜，例如基于粉末或溶胶-凝胶膜的光催化膜，即使它们也可能表现出高于 0 的阶数的衰减动力学。这种后一种动力学的原因似乎是通过这种膜的反应性分布，即高活性和低活性位点。
