Visible light-driven ZnO/g-C3N4/carbon xerogel ternary photocatalyst with enhanced activity for 4-chlorophenol degradation

This work aims to synthesize visible light-driven photocatalysts based on zinc oxide, polymeric graphitic carbon nitride (g-C3N4) and carbon xerogel. The addition of g-C3N4 and carbon xerogel to the zinc oxide is expected to hinder electron-vacancy recombination, increase specific surface area and reduce bandgap energy. The Raman spectroscopy and X-ray diffractometry confirm the presence of the wurtzite phase of zinc oxide in the materials. Furthermore, the X-ray diffractometry results show that C and N were likely incorporated into the structure of the zinc oxide in the ternary and binary materials, due to the distortion observed in the crystal lattice of the composites. The XPS analysis corroborates the presence of the g-C3N4 in the composite developed, as well as the incorporation of the carbon xerogel into the wurtzite structure. The addition of g-C3N4 and carbon xerogel resulted in significant changes on the morphology of the prepared materials, causing an increase in surface area and textural modification. The optimized ternary composite, which contains 0.25% of g-C3N4 (% w/w), has the highest photocatalytic response among all materials tested, obtaining 92% of 4-chlorophenol degradation under solar radiation and 72% under visible radiation, after 5 h. The enhanced photocatalytic activity of the ternary material can be linked to a superior charge mobility and higher visible light response, as shown by chronoamperometry tests and diffuse reflectance spectroscopy.