Analysis of photocatalytic performance of nanostructured pyrogenic titanium dioxide powders in view of their polydispersity and phase transition: Critical anatase particle size as a factor for suppression of charge recombination

Series of TiO2 nanopowders from flame aerosol synthesis with average particle size from 7.1 to 21 nm with increased rutile content were studied for particle size distribution (PSD) and anatase-to-rutile transition to be correlated with their photocatalytic performance. The certain particles' growth regime favours the formation of defect-rich anatase nanoparticles which were found to condition the overall reactivity of polydispersed nanostructured powders. Two crucial roles of oxygen vacancies as key characteristics of nanoparticles are discussed: (a) they are responsible for anatase-to-rutile transition and (b) are vital for the adsorption of oxygen as electron acceptor, i.e. for the photoelectrochemical efficiency. The linear dependence of the photocatalytic oxidation reaction rate constant on the content of the specific anatase particles fraction amenable to phase transition was revealed by the regression analysis.