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.