Modified titanium dioxide photocatalysts for the enhanced photodegradation of organic substrates

Two approaches to generate TiO2 photocatalyst for the enhanced photodegradation of substrates are described. One approach includes the surface modification of TiO2, with a layer consisting of a N,N'-bipyridinium pi-acceptor layer. The resulting photocatalyst reveals superior photocatalytic activity as compared to the non-modified TiO2 for the decomposition of pi-donor substrates such as 1,4-dimethoxybenzene (1), 1,2-dimethoxybenzene (2) and indole(3). The enhanced photocatalytic activity of the modified TiO2, V2+-TiO2 is attributed to the concentration of the pollutant at the heterogeneous catalyst surface via the formation of supramolecular pi donor-acceptor complexes. A second approach to improve the photocatalytic activity of TiO2, involves its doping with Fe(III)-Phthalocyanine, Fe(III)-Pc. The Fe(III)-Pc doped TiO2, Fe(III)-Pc/TiO2 is formed by the sol-gel method. The series of organic substrates p-nitrobenzoic acid (5), p-aminobenzoic acid (6), p-chlorophenoxyacetic acid (7), salicylic acid (8) and aniline (9), is effectively degraded by the Fe(III)Pc/TiO2 catalyst compared to the non-modified catalyst. Photodegradation of the organic pollutants in the presence of Fe(III)-Pc/TiO2, is substantially enhanced as compared to non-modified TiO2, and leads to complete mineralization. The enhanced activity of the Fe(III)-Pc doped TiO2, is attributed to the synergistic generation of (OH)-O-. radical, the active species in the degradation of the organic substrates, at the semiconductor surface, via the photochemical cleavage of light-induced generated H2O2 at the semiconductor surface.