Engineering interfacial band hole extraction on chemical-vapor-deposited MoS2/CdS core-shell heterojunction photoanode: The junction thickness effects on photoelectrochemical performance

Abstract

Heterojunction fabrication is a promising strategy that can greatly boost the charge carrier separation and improve the solar-to-hydrogen conversion efficiency of photoelectrochemical (PEC) cells. However, such technology still suffers from limited contact interfaces. In this study, the chemical vapor deposition (CVD) technique was for the first time used to construct the CdS/MoS2 heterojunction photoanode with a unique core-shell nanoarchitecture, in which a continuous crystalline MoS2 nanosheet layer was grown directly on one-dimensional (1D) oriented CdS nanorods (NRs) in a plane-to-plane stacking fashion. The optimization of junction thickness with adjustable MoS2 loading from mono to a few layers was achieved by experimental parameters variation. Systematic characterizations show that the MoS2 shell plays a dual role as an optical absorption booster for more photo-exciton generation and a surface passivator of trap states. Meanwhile, the formed heterojunction helps regulate the unidirectional charge migration for a significantly suppressed electron-hole recombination process, which synergistically contributes to higher quantum yield and efficiency. As a result, the optimized CdS/MoS2 heterojunction photoanode with 3-layered MoS2 wrapping exhibits the highest photocurrent density and photoconversion efficiency, over a two-fold increase, compared to those of pristine CdS and the previously reported CdS/MoS2 heterojunctions. Moreover, due to the rapid hole extraction from CdS and transferred surface oxidation sites, the present CdS/MoS2 heterostructure demonstrates better corrosion resistance and higher photostability. The present work is expected to provide a versatile platform for exploiting the CVD technique to develop other MoS2-based heterojunction photoelectrodes with extensive PEC applications.