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Andraz Suligoj, Speaker at Chemical Engineering Conferences
University of Ljubljana, Slovakia (Slovak Republic)
Title : Effects of surface Ni and Zn oxo nanoclusters on Tio2 for solar light photocatalysis


Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2)on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me:  Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides.
The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5wt%. We have shown in situ that metal-oxo-nanoclusters with a redox potential close to that of O2/O2•– were able to function as co-catalysts on the TiO2 surface which were excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2•– (reduction, Rz ink test) while the other detecting •OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications.
Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.


Andra┼ż Šuligoj is working in the field of applied photocatalysis. He started with the development of highly UV-active films on metal substrates (Fe, Al) for which he developed a silica protective layer, which was later patented. He then switched to designing novel systems combining TiO2 anatase and mesoporous silica for air cleaning applications. Lately, he is focused on designing solar light-active TiO2 by employing green and facile incipient wet impregnation, resulting in the surface modification of TiO2, giving rise to novel hetero-junctions. Thus he is studying the structure-activity relationship, with the focus on nano-clusters deposited on the anatase surface.