CdS/Zr:Fe2 O3 Nanorod Arrays with Al2 O3 Passivation Layer for Photoelectrochemical Solar Hydrogen Generation.

CdS-sensitized 1 D Zr:Fe2 O3 nanorod arrays were synthesized on fluorine-doped tin oxide substrates by a two-step hydrothermal method. The photoelectrochemical results demonstrate that the current density (4.2 mA cm-2 at 0 V vs. Ag/AgCl) recorded under illumination for the CdS/1 D Zr:Fe2 O3 photoanodes is 2.8 time higher than the bare 1 D Zr:Fe2 O3 . The extended absorbance spectrum, the reduced recombination, and the effective transport of photogenerated holes in CdS to the electrolyte facilitate enhancement in the photoelectrochemical performance. From X-ray photoelectron spectroscopy and TEM observations of the bare and aluminum oxide-treated CdS/1 D Zr:Fe2 O3 photoanodes, we could confirm that the 1 D Zr:Fe2 O3 nanorods were covered by the CdS layer and Al2 O3 layer present on surface of CdS. Furthermore, the photocurrent and stability of the CdS/1 D Zr:Fe2 O3 nanorods was significantly enhanced by Al2 O3 compared to bare CdS/1 D Zr:Fe2 O3 heterojunction owing to its ability to act as an effective holetransport- as well as photocorrosion-protecting layer. These remarkable enhancements in light-energy harvesting, improvement in charge transport, and stability directly suggest the usefulness of photoanodes for solar hydrogen generation.