Construction of p-Si/n-CdS core/shell nanowire heterojunction for photoelectrochemical water splitting

Si-based heterojunctions have been intensively employed to reduce the large overpotential of Si single-absorber photoelectrodes in the field of photoelectrochemical (PEC) water splitting, but achievement of high-quality heterojunctions with an appropriate bandgap on the Si nanostructure host remains a great challenge. Herein, the p-Si/n-CdS core/shell nanowire heterojunction photocathode has been achieved by a combination of nanosphere lithography, metal-assisted chemical etching, atomic layer deposition , and chemical bath deposition. Compared to the bare Si nanowire photocathode , the overpotential maintaining a photocurrent density of 10 mA cm −2 for the optimized p-Si/n-CdS core/shell nanowire heterojunction photocathode under AM 1.5G illumination is reduced by 0.93 V, and simultaneously the saturated photocurrent density is increased by 4.4 mA cm −2 . Analyses indicate that the introduced CdS shell can greatly facilitate the separation and transfer of the photogenerated carriers , as well as partly enhancing the optical absorption .