Hierarchical CdS Nanorod@SnO 2 Nanobowl Arrays for Efficient and Stable Photoelectrochemical Hydrogen Generation

An efficient photoanode based on CdS nanorod@SnO 2 nanobowl (CdS NR@SnO 2 NB) arrays is designed and fabricated by the preparation of SnO 2 nanobowl arrays via nanosphere lithography followed by hydrothermal growth of CdS nanorods on the inner surface of the SnO 2 nanobowls. A photoelectrochemical (PEC) device constructed by using this hierarchical CdS NR@SnO 2 NB photoanode presents significantly enhanced performance with a photocurrent density of 3.8 mA cm −2 at 1.23 V versus a reversible hydrogen electrode (RHE) under AM1.5G solar light irradiation, which is about 2.5 times higher than that of CdS nanorod arrays. After coating with a thin layer of SiO 2 , the photostability of the CdS NR@SnO 2 NB arrays is greatly enhanced, resulting in a stable photoanode with a photocurrent density of 3.0 mA cm −2 retained at 1.23 V versus the RHE. The much improved performance of the CdS NR@SnO 2 NB arrays toward PEC hydrogen generation can be ascribed to enlarged surface area arising from the hierarchical nanostructures, improved light harvesting owing to the NR@NB architecture containing multiple scattering centers, and enhanced charge separation/collection efficiency due to the favorable CdS–SnO 2 heterojunction.