Preparation of Transition Metal Doped Titania-Silica photocatalyst through Two-Liquids Phase Separation

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In the system which has a stable two-liquid immiscibility region above its liquidus temperature, the variations of the holding temperature and the time of its melt can control the size and the composition of the phase separated texture of the quenched material. In this study, a visible light active photocatalyst, which comprises oxide semiconductor fine particles and glass matrix, was prepared through the quenching of the phase separated melt in TiO_2-SiO_2 system containing transition metal and the subsequent heat treatment and selective leaching.The Fe, Cr, V, Nb ions of 0.1-1 mass% to Ti were added to the granular TiO_2 photocatalysts comprising anatase phase which were synthesized by rapid quenching of phase-separated 40TiO_2-60SiO_2 (mass%) melts and subsequent selective reaching. The phase of TiO_2 was examined by XRD. The photocatalytic activities of the samples were also evaluated from the hydrogen generation from 20 vol% ethanol aqueous solution under the illumination of the 500W high pressure mercury lamp.The anatase ratios to rutile in the transition metal doped samples were smaller than that in non-doped one, though the relation between the ratio and the amount of transition metal was not clear. The hydrogen generation did occur by illumination of not the visible light but UV one. The generation rates of the doped samples were one tenth to five hundredth less than that of the non-doped sample (ca. 1.5 mmol・g^<-1>・h^<-1>) , and the rate decreased with increase of the amount of transition metals. As the degre6 of phase transition from anatase to rutile was not so much in the doped samples, the degradation of photocatalytic activity is considered to occur due to the recombination of photo-excited electrons and holes at the sites of the transition metal ions in the sample.