MoS2/CdS Heterojunction with High Photoelectrochemical Activity for H2 Evolution under Visible Light: The Role of MoS2

MoS2/CdS p-n heterojunction films with high photoelectrochemical activity for H2 evolution under visible light were successfully prepared by electrodeposition followed by chemical bath deposition. The films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible absorption, X-ray photoemission spectroscopy, photoluminescence, and photoelectrochemical response. The MoS2/CdS heterostructure shows much higher visible-light photoelectrocatalytic activity and higher stability toward the water splitting than pure CdS film. The MoS2/CdS film with an optimal ratio of 0.14% exhibits the highest photocurrent of 28 mA/cm2 and the highest IPCE of ca. 28% at 420 nm at 0 V vs Ag/AgCl. The critical role of MoS2 in the MoS2/CdS film was investigated. The improved photoelectrochemical performance of the MoS2/CdS heterojunction film was attributed to the visible light absorption enhanced by MoS2 and the formation of a p-n junction between CdS and MoS2, which accelerates the effective separation of photogenerated carriers by the internal electrostatic field in the junction region.