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      Suspension plasma sprayed coatings using dilute hydrothermally produced titania feedstocks for photocatalytic applications

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          Abstract

          SPS titania coatings, with applications in water purification, were formed using continuous hydrothermally produced feedstocks for the first time. Coating photoactivity was compared with CVD and P25 analogues.

          Abstract

          Titanium dioxide coatings have potential applications including photocatalysts for solar assisted hydrogen production, solar water disinfection and self-cleaning windows. Herein, we report the use of suspension plasma spraying (SPS) for the deposition of conformal titanium dioxide coatings. The process utilises a nanoparticle slurry of TiO 2 ( ca. 6 and 12 nm respectively) in water, which is fed into a high temperature plasma jet ( ca. 7000–20 000 K). This facilitated the deposition of adherent coatings of nanostructured titanium dioxide with predominantly anatase crystal structure. In this study, suspensions of nano-titanium dioxide, made via continuous hydrothermal flow synthesis (CHFS), were used directly as a feedstock for the SPS process. Coatings were produced by varying the feedstock crystallite size, spray distance and plasma conditions. The coatings produced exhibited ca. 90–100% anatase phase content with the remainder being rutile (demonstrated by XRD). Phase distribution was homogenous throughout the coatings as determined by micro-Raman spectroscopy. The coatings had a granular surface, with a high specific surface area and consisted of densely packed agglomerates interspersed with some melted material. All of the coatings were shown to be photoactive by means of a sacrificial hydrogen evolution test under UV radiation and compared favourably with reported values for CVD coatings and compressed discs of P25.

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          Most cited references38

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          Band alignment of rutile and anatase TiO₂.

          The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO₂. The discovery of the photolysis of water on the surface of TiO₂ in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO₂ (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.
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            Fabrication of screen-printing pastes from TiO2 powders for dye-sensitised solar cells

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              Metal oxide photoanodes for solar hydrogen production

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                Author and article information

                Journal
                JMCAET
                Journal of Materials Chemistry A
                J. Mater. Chem. A
                Royal Society of Chemistry (RSC)
                2050-7488
                2050-7496
                2015
                2015
                : 3
                : 24
                : 12680-12689
                Affiliations
                [1 ]Department of Chemistry
                [2 ]University College London
                [3 ]London
                [4 ]UK
                [5 ]School of Chemistry and Chemical Engineering
                [6 ]Queen's University Belfast
                [7 ]Belfast BT9 5AG
                [8 ]TWI Ltd.
                [9 ]Cambridge
                Article
                10.1039/C4TA05397D
                03e50131-e700-45e9-b991-a8d4726575e0
                © 2015
                History

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