Flower-like spherical ZnCdS/Bi2WO6/ZnAl-LDH with dual type II heterostructure as a photocatalyst for efficient photocatalytic degradation and hydrogen production

One of the effective strategies for improving the photocatalytic activity of composite materials is to construct a heterostructure using layered double hydroxide (LDH) as the main photocatalytic material in order to accelerate photogenerated charge transfer. We report herein the preparation of a novel flower-like spherical photocatalytic composite, ZnCdS/Bi2WO6/ZnAl-LDH, with a dual type II heterostructure, by a hydrothermal method. ZnAl-LDH in the composite has the characteristic structure of a good hydrotalcite-like compound, and ZnCdS and Bi2WO6 are loaded on its surface to form flower-like spherical particles of uniform size. Compared with ZnAl-LDH, a ZnCdS/Bi2WO6/ZnAl-LDH composite has a significantly broader light absorption range and a more uniform pore size distribution. Electrochemical impedance, transient photocurrent, and photoluminescence results for ZnCdS/ Bi2WO6/ZnAl-LDH composites have shown that the composition with 20% ZnCdS displayed the highest photocurrent density, the lowest electron-transfer resistance, and the lowest electron-hole recombination efficiency. Multi-mode photocatalytic degradation experiments showed all ZnCdS/Bi2WO6/ZnAl-LDH composites to exhibit good photocatalytic degradation ability. Meanwhile, ZnCdS/Bi2WO6/ZnAl-LDH showed enhanced hydrogen production of 79.20 mu mol g-1 h-1, more than eight times that for ZnAl-LDH, and its photocatalytic activity remained stable after three experimental cycles. Through trapping experiments, the active species involved in the photocatalytic reaction has been identified, and the presence of a dual type II heterostructure in the ZnCdS/Bi2WO6/ZnAl-LDH composite is postulated. Rapid separation and migration of photogenerated charge carriers in the composite is achieved due to the close association of ZnCdS, Bi2WO6, and ZnAl-LDH.

Automated summary

One effective strategy for improving the photocatalytic activity of composite materials is to construct a heterostructure using layered double hydroxide (LDH) as the main photocatalytic material. In this study, a novel flower-like spherical photocatalytic composite, ZnCdS/Bi2WO6/ZnAl-LDH, with a dual type II heterostructure, was prepared by a hydrothermal method. The composite exhibited a significantly broader light absorption range and a more uniform pore size distribution compared to ZnAl-LDH. It was found that a composition with 20% ZnCdS displayed the highest photocurrent density, the lowest electron-transfer resistance, and the lowest electron-hole recombination efficiency. The ZnCdS/Bi2WO6/ZnAl-LDH composite showed good photocatalytic degradation ability and enhanced hydrogen production, which remained stable after three experimental cycles. Trapping experiments identified the active species involved in the photocatalytic reaction and suggested the presence of a dual type II heterostructure in the composite.