Computational and Photoelectrochemical Study of Hydrogenated
Bismuth Vanadate
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Abstract
We
demonstrate hydrogenation as a facile method to significantly enhance
the performance of BiVO<sub>4</sub> films for photoelectrochemical
water oxidation. Hydrogenation was performed for BiVO<sub>4</sub> films
by annealing them in hydrogen atmosphere at elevated temperatures
between 200 and 400 °C. Hydrogen gas can reduce BiVO<sub>4</sub> to form oxygen vacancies as well as hydrogen impurities. DFT calculation
predicted that both oxygen vacancies and hydrogen impurities are shallow
donors for BiVO<sub>4</sub> with low formation energies. These defects
could increase the donor densities of BiVO<sub>4</sub> without introducing
deep trap states. Electrochemical impedance measurements showed that
the donor densities of BiVO<sub>4</sub> films were significantly enhanced
upon hydrogenation. Hydrogen-treated BiVO<sub>4</sub> (H-BiVO<sub>4</sub>) photoanodes achieved a maximum photocurrent density of 3.5
mA/cm<sup>2</sup> at 1.0 V vs Ag/AgCl, which is 1 order of magnitude
higher than that of air-annealed BiVO<sub>4</sub> obtained at the
same potential. The enhanced photoactivities were attributed to increased
donor densities of H-BiVO<sub>4</sub>, which facilitates the charge
transport and collection