Aluminum-doped cadmium sulfide homojunction photoelectrode with optimal film quality and water-splitting performance

Abstract

The electronic band configuration and film quality are two crucial factors of photoelectrodes for conducting photoelectrocatalytic reactions with high efficiency and stability; thus, they need to be rationally designed. In this work, a CdS/CdS:Al-based photoanode is prepared to simultaneously enhance the optimized band structure and film quality. In this architecture, the migration of holes from the light-harvesting component (CdS) to the reduction sites (counter electrode) is inhibited, accompanied with the construction of a desirable transport path for photogenerated electrons to the reduction sites. These features consequently result in the following characteristics: rapid charge separation, a low resistance, a suppressed dark current, and an optimized onset potential. In addition, in the presence of a CdS:Al layer, the in situ grown CdS presents a reduced crystal size, enhanced hydrophilicity, and optimized film continuity. Meanwhile, density functional theory calculations (DFT) reveal that the hydrogen evolution reaction (HER) activity is enhanced after adding CdS:Al as an insertion layer. Thus, an improved MoS₂/CdS:Al/CdS photoanode with high promise is achieved, demonstrating a photocurrent density in the electrolyte with a sacrificial agent of up to 7.9 mA cm⁻² (at 0 V vs. V_Ag/AgCl), an on-set potential of −1.23 V (vs. V_Ag/AgCl), good stability, and an almost totally suppressed dark current.