Monitoring the Structure Evolution of Titanium Oxide Photocatalysts: From the Molecular Form via the Amorphous State to the Crystalline Phase |
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Authors: | Dr Ezgi Onur ?ahin Dr Yitao Dai Prof Candace K Chan Priv?Doz?Dr Harun Tüysüz Dr Wolfgang Schmidt Prof Joohyun Lim Dr Siyuan Zhang Prof Christina Scheu Priv?Doz?Dr Claudia Weidenthaler |
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Institution: | 1. Heterogeneous Catalysis, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz?1, 45470 Mülheim an der Ruhr, Germany;2. Materials Science and Engineering, School for Engineering of Matter, Transport and Energy (SEMTE), Arizona State University, AZ 85287-8706 Tempe, USA;3. Nanoanalytics and Interfaces, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany |
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Abstract: | Amorphous TixOy with high surface area has attracted significant interest as photocatalyst with higher activity in ultraviolet (UV) light-induced water splitting applications compared to commercial nanocrystalline TiO2. Under photocatalytic operation conditions, the structure of the molecular titanium alkoxide precursor rearranges upon hydrolysis and leads to higher connectivity of the structure-building units. Structurally ordered domains with sizes smaller than 7 Å form larger aggregates. The experimental scattering data can be explained best with a structure model consisting of an anatase-like core and a distorted shell. Upon exposure to UV light, the white TixOy suspension turns dark corresponding to the reduction of Ti4+ to Ti3+ as confirmed by electron energy loss spectroscopy (EELS). Heat-induced crystallisation was followed by in situ temperature-dependent total scattering experiments. First, ordering in the Ti?O environment takes place upon to 350 °C. Above this temperature, the distorted anatase core starts to grow but the structure obtained at 400 °C is still not fully ordered. |
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Keywords: | crystallization nanoparticles PDF (pair distribution function) photocatalysis reduced titania |
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