Boosting photoelectrochemical water splitting activity of zinc oxide by fabrication of ZnO/CdS heterostructure for hydrogen production

Abstract

We have investigated the effect of CdS loading on ZnO nanoparticles for photoelectrochemical (PEC) water splitting. ZnO nanoparticles were coated on the substrate to form a film of ZnO nanoparticles. The CdS layer was coated on the ZnO thin film using the Successive Ionic Layer Adsorption and Reaction (SILAR) approach, at different cycles. The synthesized samples were then studied for structural, morphological, optical, and photoelectrochemical (PEC) properties. X-ray diffraction (XRD), Raman spectroscopy, ultraviolet spectroscopy (UV), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) analysis confirm the existence of CdS and ZnO nanoparticles and the formation of ZnO/CdS heterostructure on the substrate. The UV–visible absorption spectrum reveals that the ZnO/CdS composite has significantly higher visible light absorption than bare ZnO. The low bandgap of CdS drives the absorption spectra of ZnO/CdS heterostructure to stretch into the visible range. Additionally, the composite samples exhibit significantly greater photocurrents than bare ZnO. The S-40 sample (40 SILAR cycles of CdS) of ZnO/CdS heterostructure film shows the highest photocurrent density of 5.36 mA/cm² at 0.96 V vs. RHE. The applied bias photoconversion efficiency (ABPE) of the S-40 sample is 4.15% at 0.33 V vs. RHE which is more than bare ZnO.