Kinetics of photocatalyzed film removal on self-cleaning surfaces: Simple configurations and useful models

We develop simple reaction kinetic models for photocatalyzed removal of carbonaceous and sulfur films, and demonstrate their applicability to a common range of deposited film-catalyst configurations studied in the photocatalyst literature: 1. Non-porous photocatalyst, non-porous transparent organic overlayer (stearic, palmitic acids). 2. Porous photocatalyst: transparent organic (stearic acid) in catalyst void volume. 3. Non-porous photocatalyst, non-transparent porous overlayer (sulfur). 4. Non-porous photocatalyst, adjacent organic layer (soot). In each case, we consider a simple film-catalyst configuration, propose a corresponding one-dimensional physical model for reaction, and compare model results with literature data to evaluate the correspondence between model and experiment. These examples cover both direct and lateral oxidation by photocatalysis. The respective physical and chemical phenomena which determine these rates of film removal include intrinsic catalyst kinetics (1), simultaneous reaction and light attenuation (2), reaction with light absorption by non-transparent organic film (3), and oxidant lateral transport (surface diffusion) (4). In each case, a simple model suffices to represent the key kinetic phenomena. In all cases, the true kinetic order is zero, but the apparent order may be influenced by light absorption (case 2). The apparent rate constant may be influenced by catalyst light absorption (case 2) or overlayer (case 3), or by catalyst-reactant separation (case 4). (C) 2010 Elsevier B.V. All rights reserved.