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Tetrahedral surface vanadium oxide species

It should be noted that all of the above studies were performed under ambient conditions where the surface vanadium oxide species are known to be hydrated due to adsorbed moisture. It has been shown that dehydration can alter the structures of the surface vanadium oxide species. For example, dehydration of surface vanadium oxide species on 7-AI2O3, which initially possesses vanadia octahedra and tetrahedra, tranforms most of the surface vanadia species to a tetrahedral coordination (4). Dehydration studies on the V2O5/6,0-A12O3 and V205/a-AI2O3 samples are currently underway. [Pg.326]

Vanadium-containing mesoporous silica with highly dispersed and tetrahedrally coordinated V-oxide species ( 04) has been prepared by a modified surfactant templating method [127]. This catalyst shows high photocatalytic activity (X > 300 nm) even in water, while other V-containing silica catalysts, prepared by impregnation or conventional templating methods, have no activity in the presence of water due to hydrolysis of the V 04 species. Retention of activity in water is due to the fact that V 04 species are confined within the silica layer and not exposed on the surface. Despite its confined structure, this photocatalyst is able to oxidize cyclohexane mainly to its alcohol and ketone with only traces of CO2. [Pg.202]

Figure 19 shows the typical photoluminescencc spectrum of the anchored vanadium oxide catalyst prepared by photo-CVD methods (a), its corresponding excitation spectrum (b), and the UV absorption spectrum of the catalyst (c) (56,115,116). These absorption and photoluminescence spectra (phosphorescence) are attributed to the following charge-transfer processes on the surface vanadyl group (V=0) of the tetrahedrally coordinated VO4 species involving an electron transfer from to V and a reverse radia-... [Pg.160]


See other pages where Tetrahedral surface vanadium oxide species is mentioned: [Pg.324]    [Pg.194]    [Pg.303]    [Pg.365]    [Pg.324]    [Pg.985]    [Pg.247]    [Pg.210]    [Pg.324]    [Pg.86]    [Pg.213]    [Pg.230]    [Pg.267]    [Pg.168]    [Pg.23]    [Pg.47]    [Pg.614]    [Pg.414]    [Pg.1692]    [Pg.194]    [Pg.105]    [Pg.339]    [Pg.352]    [Pg.353]    [Pg.131]    [Pg.19]    [Pg.55]    [Pg.281]    [Pg.257]    [Pg.279]    [Pg.285]    [Pg.287]    [Pg.648]   


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Oxidants vanadium

Oxidation species

Oxidation vanadium

Oxides vanadium oxide

Tetrahedral oxidations

Tetrahedral species

Vanadium oxides

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