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Materials 2019, 12(1), 170; https://doi.org/10.3390/ma12010170

Solid-Gas Phase Photo-Catalytic Behaviour of Rutile and TiOn (1 < n < 2) Sub-Oxide Phases for Self-Cleaning Applications

1
BRE Centre for Innovative Construction Materials (CICM), Department of Architecture and Civil Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK
2
Department of Mechanical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK
3
Department of Materials and Ceramic Engineering/CICECO—Aveiro Institute of Materials, Campus Universitário de Santiago, University of Aveiro, 3810-193 Aveiro, Portugal
4
Center for Mechanical Technology and Automation—TEMA, Department of Mechanical Engineering, Campus Universitário de Santiago, University of Aveiro, 3810-193 Aveiro, Portugal
*
Author to whom correspondence should be addressed.
Received: 18 November 2018 / Revised: 20 December 2018 / Accepted: 29 December 2018 / Published: 7 January 2019
(This article belongs to the Special Issue Self-Cleaning Surfaces)
Full-Text   |   PDF [4985 KB, uploaded 7 January 2019]   |  

Abstract

The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-Ti4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (λ) 376–387 nm and 381–392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350–400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings. View Full-Text
Keywords: photocatalysis; TiO2; sub-oxide photocatalysis; TiO2; sub-oxide
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Nuño, M.; Adamaki, V.; Tobaldi, D.M.; Hortigüela Gallo, M.J.; Otero-Irurueta, G.; Bowen, C.R.; Ball, R.J. Solid-Gas Phase Photo-Catalytic Behaviour of Rutile and TiOn (1 < n < 2) Sub-Oxide Phases for Self-Cleaning Applications. Materials 2019, 12, 170.

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