Fumiaki Amano, B. Ohtani, H. Yoshida
Apr 1, 2016
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Influential Citations
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Journal
Journal of Electroanalytical Chemistry
Abstract
Abstract The photoelectrochemical properties of titanium-doped iron(III) oxide (α-Fe 2 O 3 , hematite) nanoparticulate thin films are investigated using two photoelectrode reactions, the oxidation of water and iodide ions (I − ) to elucidate the role of doped Ti 4+ species in the enhanced photocurrent. Increase in the calcination temperature of titanium-doped Fe 2 O 3 thin films from 450 °C to 550 °C provides significant enhancement in their efficiency for water oxidation to evolve O 2 , which is four-electron transfer slow reaction. In contrast, such a calcination effect is not remarkable for oxidation of I − to I 3 − , which is two-electron transfer fast reaction. The electrochemical impedance spectroscopy (EIS) study indicates that the surface reaction rates feature heterogeneity only for water oxidation. This heterogeneity in EIS responses decreased with increasing calcination temperature. This shows that calcination creates photoactive surface sites with doped Ti 4+ species especially for kinetically limited water oxidation. Long-lived photoholes might be effectively captured in the vicinity of these sites to suppress surface recombination and induce multi-electron transfer water oxidation.