Computational and Photoelectrochemical Study of Hydrogenated Bismuth Vanadate

We demonstrate hydrogenation as a facile method to significantly enhance the performance of BiVO4 films for photoelectrochemical water oxidation. Hydrogenation was performed for BiVO4 films by annealing them in hydrogen atmosphere at elevated temperatures between 200 and 400 °C. Hydrogen gas can reduce BiVO4 to form oxygen vacancies as well as hydrogen impurities. DFT calculation predicted that both oxygen vacancies and hydrogen impurities are shallow donors for BiVO4 with low formation energies. These defects could increase the donor densities of BiVO4 without introducing deep trap states. Electrochemical impedance measurements showed that the donor densities of BiVO4 films were significantly enhanced upon hydrogenation. Hydrogen-treated BiVO4 (H-BiVO4) photoanodes achieved a maximum photocurrent density of 3.5 mA/cm2 at 1.0 V vs Ag/AgCl, which is 1 order of magnitude higher than that of air-annealed BiVO4 obtained at the same potential. The enhanced photoactivities were attributed to increased donor densities of H-BiVO4, which facilitates the charge transport and collection.