Visible-light sensitive hydrogen evolution photocatalyst ZnRh_2O_4

摘要

We investigated the ability of the oxide ZnRH_2O_4 to serve as a solar H_2-evolution photo-catalyst due to the predicted potential of its conduction band bottom, which may allow thermodynamically favorable H_2 evolution in spite of its small band-gap of 1.2 eV. ZnRH_2O_4 produced H_2 in the presence of HCHO, but only scarcely in the presence of CH_3OH, indicating that the potential of the valence band top of ZnRH_2O_4 lies at～0.1 V (vs. SHE). Thus, the conduction band bottom potential (～-1.1 V) lies much more negative than the potential of H/H_2, allowing thermodynamically favorable H_2 evolution. In addition, the irradiated-light-wavelength dependence of the quantum efficiency (QE) for H_2 evolution was consistent with the solar spectrum, and the QE was quite high (～27%), even at a wavelength of 770 ± 25 nm. Taken together, our findings indicate that ZnRH_2O_4 can utilize solar light effectively, not only the entire range of UV and visible light, but is also sensitive to infrared light.