Stabilization of photoelectrochemically highly reactive anatase structures with defect-rich surfaces

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The anatase-to-rutile transformation is accompanied with defect-rich oxygen-deficient TiO2-x surfaces, which nevertheless exhibit high reactivity. Thus, preliminary studies showed that using controlled synthesis and identifying homologous sequences of titania nano-particles, the photoelectrochemical efficiency of polydis-perse pyrogenic TiO2 materials is directly controlled by a specific anatase particle fraction, which have the characteristics of being closest to the anatase-to-rutile transformation. Due to their poor thermal stability the fraction of these highly reactive anatase stuctures is very small. Therefore, the research project is focused on the study of the fundamental mechanisms contributing to the formation and stabilization of the highly reactive anatase fraction in the gas-aerosol flow. This includes a knowledge-based synthesis of the nano-materials, in which particle structures will be varied systematically by quenching, i.e. freezing-in their structure. With respect to process engineering this project aims in clarifying the relationships between the conditions of particle growth in the flame and the evolution of the highly-active anatase fraction of polycrystalline pyrogenic photocatalysts. In view of material science it is plant to use the fractional analysis of polydisperse TiO2-powders as well as a variation of photocatalytic process parameters in order to study the kinetics of the oxidation reaction as an equivalent to the photochemical processes at the surface with respect to adsorption and consumption of oxygen, i.e. tracking the concentration of oxygen vacancies as function of the particle size and its location on the anatase-rutile diagram. The interrelation of defect structures and phpotocatalytic performance will be achieved by bringing together the expertise of the applicants in the fields of process technology and materials science as well as by combining complementary experimental and analytic metoods. In particular, cross-disciplinary knowledge transfer and feedback of interim results will be used to adopt the modular structured working program.