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.