Solution-processed synthesis of ZnO/CdS heterostructure photoanode for efficient photoelectrochemical water splitting

A promising method for producing hydrogen from solar energy and transforming it into chemical fuel is photoelectrochemical (PEC) water splitting. This ecologically friendly process can also avoid energy crises. Herein, we present the electrodeposition and chemical bath deposition methods used to create ZnO-nanorod/CdS nanoparticle (ZnO/CdS) heterostructures. The structural, optical, morphological, and PEC properties are investigated. UV–Visible spectroscopy analysis reveals the ZnO/CdS films have absorption edges in the visible and ultraviolet regions. The CdS loading directly impacts the PEC result of ZnO/CdS photoanodes. The M-S plots show a positive slope, indicating the n-type nature of ZnO and CdS. Under illumination intensity of 100 mW cm⁻², the ideal photocurrent density reaches 4.90 mA/cm² at a bias of 1.35 V versus reversible hydrogen electrode (vs. RHE) and is five times greater than the pristine ZnO nanorods. The maximum applied bias photon to the current conversion efficiency of 0.23 % at 0.26 V vs. RHE is observed in the pristine ZnO photoanodes. In contrast, the ZnO/CdS photoanode has achieved 3.02 % at 0.26 V vs. RHE, almost 13 times greater than the pristine ZnO photoanode. Finally, the hydrogen evolution process and the mechanism of charge transfer in ZnO/CdS heterostructure are discussed.