Photocatalysis by Composite Particles Containing Inert Domains

Titanium dioxide is a well‐known photocatalyst for the treatment of air and water. The use of structures comprised of photocatalytic sites and high capacity adsorption sites may improve the TiO 2 photoefficiency, in cases where the contaminnants do not adsorb well onto the photocatalyst. In this work, composite particles composed of activated carbon, partially coated with sol‐gel‐made titanium dioxide, were prepared and characterized. It was found that chelating the titanium tetraiso‐propoxide, used as a precursor, with acetylacetone is crucial for obtaining reasonable loading (up to 12–15% in weight). High content of water or humidity tends to form thick films that might bridge over the pores of the activated carbon, thus reducing the available surface area. The photocatalytic activity of the composite particles was tested by following the rate of production of carbon dioxide during the photodegradation of Rhodamine 6G in an aqueous solution. Enhanced mineralization rates relative to sol‐gel‐made titanium dioxide particles (by ˜30%) were observed. This enhancement is attributed to the adsorption of the contaminants in the vicinity of the photoactive sites. It was further found that the composite particles produced relatively less of the toxic by‐product carbon monoxide, than sol‐gel‐made titanium dioxide or the commercially available Degussa P25. The reason for this effect is yet to be determined.