Significantly enhanced photocatalytic activity of TiO 2 /TiC coatings under visible light
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ORIGINAL PAPER
Significantly enhanced photocatalytic activity of TiO2/TiC coatings under visible light Sujun Guan 1
&
Liang Hao 2 & Yaqiang Yang 3 & Hiroyuki Yoshida 4 & Xinwei Zhao 1 & Yun Lu 5
Received: 28 June 2020 / Revised: 14 September 2020 / Accepted: 1 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Rutile TiO2 forms on TiC coatings (TiO2/TiC coatings) during carbon-embedding heat treatment (cHT) for TiC coatings. The photocatalytic activity of TiO2/TiC coatings has been significantly enhanced, especially under visible light. The influence of cHT temperature for TiC and Ti coatings on surface morphology, formed compounds, and photocatalytic activity has also been investigated. In general, rutile TiO2 forms on TiC coatings, whereas TiCxOy forms on Ti coatings. By raising the cHT temperature for TiC coatings, the surface morphology of TiO2/TiC coatings with a pore-like structure significantly changes from nano-size to micro-size, inevitably resulting in the reduction of the accessible surface area. However, the influence of cHT temperature on the Ti coatings is insignificant, demonstrating a smooth surface morphology. Notably, owing to the increased accessible surface area and formed heterojunction of TiO2/TiC, the photocatalytic activity of TiO2/TiC coatings has been significantly enhanced approximately 6 times especially under visible light, compared with that of TiCxOy/Ti coatings. Furthermore, when the cHT temperature has been raised, the photocatalytic activity of TiO2/TiC coatings initially increases and then decreases, achieving their most satisfaction at 1073 K, which is attributed to the narrowed band gap of TiO2 owing to the shifted O 1s spectra. Keywords TiO2 . TiC . Heterojunction . Visible light response . Photocatalytic activity . Carbon-embedding heat treatment
Introduction Owing to the suitable band edge positions, excellent chemical stability, low-cost, and satisfactory photosensitivity, titanium dioxide (TiO2) is one of the photocatalysts materials widely used to solve energy and environmental issues, especially in the areas of self-cleaning surfaces, purification filter for water and air, carbonaceous solar fuels [1–3]. With increasing application
* Sujun Guan [email protected] * Yun Lu [email protected] 1
Department of Physics, Tokyo University of Science, Tokyo, Japan
2
College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, China
3
School of Architecture and Civil Engineering, Jiangsu University of Science and Technology, Zhenjiang, China
4
Chiba Industrial Technology Research Institute, Chiba, Japan
5
Graduate School and Faculty of Engineering, Chiba University, Chiba, Japan
requirements, TiO2 has been limited by its UV responsiveness because of its wide band gap of 3.0 eV, and the fast recombination between its electrons and holes caused by the high density of trap states [4–6]. Currently, numerous studies have been dedicated to eliminating these setbacks to further meet the application re
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