Few-Layered MoS2/ZnCdS/ZnS Heterostructures with an Enhanced Photocatalytic Hydrogen Evolution

Studies on highly efficient noble-metal-free catalysts are regarded as an important task for H-2 production by water-splitting. MoS2/ZnCdS/ZnS dual heterostructures were successfully prepared with respective supernatant MoS2 colloidal solutions (called M/ZC/Z) and MoS2 precipitates (M(p)/ZC/Z). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the M/ZC/Z sample showed that ZnS nanosheets were decorated with ZnCdS nanorods and few-layered MoS2. Then, photocatalytic hydrogen production study was performed and the results showed that the M/ZC/Z sample has a H-2 evolution rate of up to 79.3 mmol g(-1) h(-1) under visible light irradiation with an apparent quantum efficiency of 47.9% at 420 nm with noble-metal-free catalysts, which is nearly 5 times that of the M(p)/ZC/Z sample (15.7 mmol g(-1) h(-1)) and approximately 9 times that of the ZC/Z sample (8.98 mmol g(-1) h(-1)). Cycle tests showed that M/ZC/Z is stable and reusable. Without sacrificial agents, the production rates for hydrogen and oxygen evolution were obtained as 3.15 and 1.55 mmol g(-1) h(-1), respectively. Time-resolved photoluminescence spectra revealed that the well-matched structure is effective in the separation and transfer of photogenerated electron and hole pairs, leading to the enhancement of the photocatalytic H-2 production activity.