On the Reactions of Methyl Radicals with TiO2 Nanoparticles and Granular Powders Immersed in Aqueous Solutions

Methyl radicals react with TiO2 nanoparticles (NPs) immersed in aqueous solutions to form transients in which the methyls are covalently bound to the particles. The rate constant for this reaction approaches the diffusion-controlled limit and increases somewhat with the number of methyls bound to the particle. The transients decompose to yield ethane. Thus, formally the particles catalyse the dimerization of the radicals, a reaction that is diffusion-controlled. Rutile powders behave similarly to the TiO2 NPs whereas the mechanism for the decomposition of the transients formed in the analogous reaction of the radicals with anatase powders differs. These results are of importance as alkyl radicals are formed near the surface of TiO2 in a variety of important photocatalytic processes. The results imply that the reactions of alkyl radicals with TiO2 have to be considered in these processes.