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

Abstract

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 μmol 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.