Fabrication of novel g-C3N4/nanocage ZnS composites with enhanced photocatalytic activities under visible light irradiation

Abstract

In order to develop efficient visible light-driven photocatalysts for environmental applications, novel g-C₃N₄/nanocage ZnS composites have been successfully fabricated via an anion exchange route using ZIF-8 as a self-sacrificing template. The as-prepared g-C₃N₄/ZnS composites were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and photoluminescence. In addition, the photocatalytic oxidation of organic contaminants in aqueous solution was investigated with the g-C₃N₄/ZnS composite system under visible light irradiation by using rhodamine B as a model compound. The results indicate that the g-C₃N₄/ZnS composite photocatalysts show higher photocatalytic activity than the single component (pure g-C₃N₄ or ZnS). More specifically, the optimum photocatalytic activity of the g-C₃N₄/ZnS composite was achieved with a weight ratio of 6 : 1, which is as high as 37.8 and 2.8 times those of individual ZnS and g-C₃N₄ under visible light irradiation. The enhanced photocatalytic activity of g-C₃N₄/ZnS is mainly attributed to an efficient electron–hole separation at the interface of the two semiconductors, as determined by photoluminescence spectroscopy. Moreover, it is observed that ˙O₂⁻ is the main active species in the photocatalytic oxidation of RhB solution using a g-C₃N₄/nanocage ZnS composite.