Design of a CdS/CdSe Heterostructure for Efficient H2 Generation and Photovoltaic Applications

The design of nano-heterostructures for light-harvesting systems for photocatalysis and photovoltaic applications is an emerging area of research. Here, we report the synthesis of a one-dimensional quasi-type-II CdS/CdSe heterostructure where holes are confined in CdSe nanoparticles and electrons can delocalize throughout the conduction bands of both CdS nanorods and CdSe nanoparticles because of the smaller conduction band offset. By controlling the oxidation and reduction sites of the CdS/CdSe heterostructure, we achieved a maximum H2 generation of 5125 μmol/g/h for 27.5 wt % CdSe-loaded CdS heterostructure, which is found to be 44 times higher than that of bare CdS nanorods and 22 times higher than that of CdSe nanoparticles. Furthermore, this heterostructure exhibits a photovoltaic effect (Voc = 0.8 V, Jsc = 0.56 mA/cm2, FF = 40%, and η = 0.18), which could be useful for solar cell application. The bleaching recovery kinetics and hot electron cooling dynamics have been studied by using femtosecond transient spectroscopy, which confirms the efficient charge separation and long excited-state lifetime of 27.5% CdSe-loaded CdS heterostructure. Thus, the slow recombination process is the reason for efficient H2 generation and photovoltaic properties.