Properties of g-C3N4/ZnO composite photocatalyst

Abstract

In this study, g-C3N4/ZnO composite photocatalysts were synthesized through a one-step facile method at various annealing temperatures with diverse precursors. Thiourea, urea, and dicyandiamide (DCDA) were used as g-C3N4 precursors. The prepared photocatalysts were analyzed using several characterization methods to investigate the effect of annealing temperatures and precursors on the structural and optical properties and the role of ZnO during the thermal polycondensation process. Consequently, the higher annealing temperatures for DCDA-CNZ induced the stronger interaction between ZnO particles and g-C3N4 and each composite is composed of different morphological structures. The composite materials prepared from DCDA formed a core–shell structure with thin g-C3N4 layers caused by a strong interaction between DCDA and ZnO. The strong interaction in a core-shell g-C3N4/ZnO structure not only gradually decreased the electronic density of Zn but also proportionally inhibited the recombination of photo-generated electron-hole pairs, with increasing the annealing temperature. Meanwhile, thiourea and urea induced a segregated morphology of porous g-C3N4 and ZnO in the composites, which was ascribed to the weak interaction between them and gas generation during thermal polymerization. Furthermore, the photocatalysts prepared by DCDA at 500 ℃ exhibited the highest efficiency for the photocatalytic degradation of methylene blue under visible-light irradiation. Thus, in g-C3N4/ZnO composite materials, a core–shell morphology due to the efficient interaction between g-C3N4 and ZnO influenced photocatalytic activity.