Ag2S/CdS nanorod-array heterojunctions for efficient photoelectrochemical water splitting

Oriented CdS nanorod arrays (NRAs) and their heteorojunctions formed with Ag2S nanoparticles have been successfully prepared via a one–step hydrothermal method and a successive ionic layer adsorption and reaction (SILAR) process. Their morphology, structural, and optical properties were characterised by scanning electron microscope, transmission electron microscopy, X–ray diffraction, and UV–vis spectra. Photoelectrochemical properties were also studied via current–voltage (I–V) and action spectrum measurement (IPCE). The results showed that the CdS NRAs with optimal morphology can be synthesised when the S/Cd mole ratio in the precursor solution is 4/1 and a reaction time of 4 h. With SILAR deposition cycles at 4, Ag2S/CdS thin films exhibit the highest photocurrent density which is approximately three times higher compare to that of bare CdS NRAs. The efficiency improvement is understood by better charge carrier separation at the heterojunctions.