Spectroscopic study of polycrystalline TiO2 doped with vanadium

The structure of coordination sites (V⁴⁺ ions) and their spatial distribution in the polycrystalline titanium dioxide (rutile) lattice were studied by ESR. It was found that at low degrees of doping, at [V⁴⁺] < 0.5 at.%, the vanadium ions are isotropically distributed in the rutile lattice. At [V⁴⁺] > 0.5 at.% a new microphase with the mixed composition {TiO₂—VO²} is formed. The mixed microphase has a noticeably narrower band gap than the initial TiO₂. Comparison of the photocurrent spectra and the plots of the integral photocurrent vs. vanadium content with the structural data obtained using ESR spectroscopy showed that the formation of the {TiO₂—VO²} microphases deteriorates the photoelectrochemical properties of the modified photoelectrodes. Synthetic procedures interfering the formation of such microphases in the doped rutile are discussed.