Effect of the addition of a small amount of vanadium on the photocatalytic activities of N- and Si- co-doped titanias un
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Catalysis Letters, Vol. 113, Nos. 3–4, February 2007 ( 2007) DOI: 10.1007/s10562-007-9029-5
Effect of the addition of a small amount of vanadium on the photocatalytic activities of N- and Si- co-doped titanias under visible-light irradiation Hirotaka Ozaki, Shinji Iwamoto,* and Masashi Inoue Department of Energy and Hydrocarbon Chemistry Graduate School of Engineering, Kyoto University, Katsura, Kyoto 615-8510, Japan
Received 1 November 2006; accepted 15 December 2006
Si-doped titanias with a Si/Ti charged ratio of 0.2 was prepared by thermal reactions of titanium tetraisopropoxide and tetraethyl orthosilicate in 1,4-butanediol at 300 C (glycothermal reaction) and N- and Si- co-doped titanias were prepared by heating the thus-obtained Si-doped titanias in an NH3 flow. N- and Si- co-doped titanias had a stronger absorption in a visible light region of 400–550 nm, and exhibited high photocatalytic activities for decomposition of acetaldehyde under visible-light irradiation. In this study, N- and Si- co-doped titanias were further modified with vanadium by an impregnation method using an ammonium vanadate solution, and the obtained catalysts were characterized by XRD, BET surface area measurement, UV-vis, and ESR. Photocatalytic decomposition of acetaldehyde using the V-loaded N- and Si- co-doped titanias was examined and it was demonstrated that a very small amount of V-loading (V/Ti = 0.0001–0.001) significantly enhanced the photocatalytic activity under visible-light irradiation. KEY WORDS: Si-doped titania; nitrogen-doping; visible-light photocatalyst; glycothermal method; V-loading.
1. Introduction Numerous studies have been reported in the last decade on the photodecomposition of organic pollutants using semiconductor materials as photocatalysts. Titanium dioxide (TiO2) is one of the most widely studied materials [1, 2] because of its favorable physical, chemical and optoelectronic properties. The utilization of TiO2 photocatalysts is, however, limited only under ultraviolet (UV) irradiation because of the relatively wide band gap energies, for instance, 3.0 eV for rutile and 3.2 eV for anatase. A number of researches on the development of visible-light sensitive photocatalysts has been made in order to utilize the solar energy efficiently. A nitrogen-doped TiO2 material with a visible light responsibility was reported by Sato for the first time in 1986 [3], and recently, several groups reported the visible-light responsibility of N-doped TiO2 materials prepared by different methods [4–9]. We recently reported that when nanocrystalline Si-doped titanias prepared by thermal reactions of titanium tetraisopropoxide and tetraethyl orthosilicate in 1,4-butanediol (glycothermal reaction) were heated in NH3 at high temperatures, N- and Si- codoped titanias with higher nitrogen contents were obtained, and that the obtained samples exhibited high photocatalytic activities for decomposition of acetalde*To whom correspondence should be addressed. E-mail: [email protected]
hyde under visible-light irradiation [10].
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