chapter  13
32 Pages

Photocatalytic Engineering

ByJean-Marie Herrmann, Eric Puzenat

Although old references mention photo-assisted phenomena, mainly in homogeneous phases, heterogeneous photocatalysis actually originated in the sixties in various catalysis laboratories in Europe. In England, F.S. Stone fi rst studied the photoadsorption/desorption of oxygen on ZnO (Barry and Stone 1960) before studying the photocatalytic oxidation of CO on the same solid (Romero-Rossi and Stone 1960). He subsequently switched to titania under rutile phase for oxygen photo-adsorption (Bickley and Stone 1973) and selective isopropanol oxidation in acetone (Bickley et al. 1973). This last reference was the fi rst one to mention OH° radicals as oxidizing agents formed by the neutralization of surface OH-surface anions by photo-holes h+. In addition, this simple and selective reaction was and still is a direct and simple test to demonstrate some photo-activity of solids. Simultaneously, in Germany, K. Hauffe was also studying the photocatalytic oxidation of CO on ZnO (Doerfl er and Hauffe 1964a,1964b) and, actually, this reference was the fi rst one to include the term “photocatalysis” in its title, according to the Chemical Abstracts database. In the same decade, while studying the sintering and the electrical properties of ultrapure oxide powders for nuclear applications, Juillet and Teichner in Lyon (France) obtained erratic results on titania anatase which puzzled them until they realized that titania was photosensitive to daylight, especially on sunny days (Juillet and Teichner 2003). They demonstrated photo-adsorption and photodesorption of oxygen and subsequently decided to use the photo-activated oxygen species to perform mild and selective oxidations of light alkanes in the gas phase (Formenti et al. 1970; Djeghri et al. 1974). In fact, whereas photocatalysis was developing behind closed doors in Europe, there was a great stimulus and impact from Japan, with the re-publication, in English, of a previous work by Fujishima and Honda (1972) on the photo-electrolysis of water using a UV-irradiated titania-based anode in the review “Nature”. This paper acted as a “catalyst” for the globalization of photocatalysis. Unfortunately,

newcomers in the fi eld of photocatalysis have never read this article and improperly cite it as the starting point for photocatalysis, which is clearly incorrect.