Composite Titanium Dioxide Photocatalysts and the "Adsorb & Shuttle" Approach: A Review
Composite photocatalysts, made of titanium dioxide and high surface area adsorbents become more and more common. To large extent, this is due to the phenomenon of "Adsorb & Shuttle", i.e. the adsorption of molecules on the inert, adsorptive, domains, followed by diffusion to the photocatalytic domains. This manuscript reviews the published literature on composite photocatalysts, and analyzes the various aspects affecting their performance. One of these aspects is the enhancement of the degradation rate of pollutants, which is governed by a variety of factors including surface area, adsorpticity, strength of interaction, the loading of photocatalyst in the composite, and operation parameters (such as temperature, humidity and pH). Other aspects include a reduction in the emission of intermediate products and a different distribution of end-products. Care was taken to describe the possibility of using the inert adsorptive domains to enhance the degradation of specific species, as well as to discuss the effect of composite photocatalysts on deactivation phenomena, and the interrelation between "Adsorb & Shuttle" phenomena and out- diffusion of oxidizing species from the TiO2 domains, known as the "remote degradation" phenomenon.
Maria K. Nowotny and Janusz Nowotny
Y. Paz, "Composite Titanium Dioxide Photocatalysts and the "Adsorb & Shuttle" Approach: A Review ", Solid State Phenomena, Vol. 162, pp. 135-162, 2010