ZIF-8-coated CdS popcorn-like photocatalyst with enhanced visible-light-driven photocatalytic activity for degradation of toluene

Abstract In this paper, a visible-light-driven ZIF-8-coated CdS popcorn-like photocatalyst that can degrade toluene continuously and stably was successfully synthesized by controlling the preferential construction of 2-methylimidazole ligands on the PVP-coated CdS surface. A structural and morphological analysis showed that a popcorn-like photocatalyst with rich porosity and increased specific surface area was formed by self-assembly ZIF-8 around CdS. The photocatalytic efficiency of the ZIF-8-coated CdS popcorn-like photocatalysts remained at 81.44% after five photocatalytic cycles. In the process of photocatalytic degradation, the degradation efficiency was influenced by the flow velocity, relative humidity and initial concentration. Among these factors, the relative humidity played a crucial role because toluene was easily oxidized by the ⋅OH radicals contributed by water. Analysis of the Mott-Schottky (M-S) plots suggested that the formation of an n-n-type structure between CdS and ZIF-8 facilitated the conversion of toluene gas under visible light illumination.