Preparation of Unique TiO 2 Nano-particle Photocatalysts by a Multi-gelation Method for Control of the Physicochemical P
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Catalysis Letters Vol. 105, Nos. 1–2, November 2005 (Ó 2005) DOI: 10.1007/s10562-005-8013-1
Preparation of unique TiO2 nano-particle photocatalysts by a multi-gelation method for control of the physicochemical parameters and reactivity Bernaurdshaw Neppoliana, Hiromi Yamashitaa, Yoshimi Okadab, Hiroaki Nishijimab, and Masakazu Anpoa,* a
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-Cho, Sakai, Osaka, 599-8531, Japan b Chiyoda Corporation, R & D Centre, 3-13, Moriya-Cho, Kanagawa, Yokohama, 221-0022, Japan
Received 18 July 2005; accepted 2 August 2005
A novel multi-gelation method to prepare TiO2 nano-particle photocatalysts showed good performance in controlling the important parameters determining the photocatalytic reactivity, i.e., the particle size, surface area, crystallinity, pore-volume, porediameter as well as the anatase and rutile phase composition of the catalysts. In particular, this method at higher pH swing times could prevent the phase transition from anatase to rutile, leading to higher photocatalytic activity. By adopting variations in the pH swing, the TiO2 nano-particle photocatalysts showed significantly higher photocatalytic reactivity for the complete oxidation of 2-propanol diluted with water into CO2 and H2O. It can be considered a viable alternative method for the preparation of high performance TiO2 nano-particle photocatalysts for widespread commercial applications KEY WORDS: TiO2 photocatalysts; multi-gelation method; photocatalytic degradation of 2-propanol.
1. Introduction Over the last two decades, a variety of semiconductor photocatalysts have been developed to improve the efficiency and selectivity for the photocatalytic degradation of toxic organic pollutants [1–11]. Among the various photocatalysts, TiO2 has attracted a great deal of attention due to its high photocatalytic activity, thermal stability and non-corrosive properties, in addition to its non-toxic and environmentally harmonious nature. It is well known that TiO2 has three modification phases: anatase, rutile and brookite. Of these, the anatase TiO2 is more active than the other two forms for the degradation of organic compounds [12] since anatase crystalline catalysts are constructed of very small-sized particles (250 nm) from a 100 W high-pressure Hg lamp with continuous stirring under oxygen atmosphere in the system. At periodic intervals, 2 mL aliquots were taken from the system, centrifuged, and then filtered through a Millipore filter to remove the TiO2 particles. The products were then analyzed by a gas chromatography.
3. Results and discussion 3.1. Characterization studies of the photocatalysts The XRD patterns of the catalysts prepared by different numbers of pH swings and calcined at 550 and 600°C are shown in figures 2 and 3. Table 1 summarizes the physicochemical characterizations of the photocatalysts prepared by variations in the pH swing and calcined at 400, 550 and 600°C. All of the catalysts exhibited XRD patterns assigned to the well-crystalline ana
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