Construction of an in-situ Fenton-like system based on a g-C₃N₄ composite photocatalyst

In this study, g-C₃N₄/PDI/Fe (gCPF) composite material was prepared by incorporating Fe ion on the composite catalyst of g-C₃N₄/PDI (gCP). X-ray photoelectron spectroscopy (XPS) showed that the Fe was successfully incorporated on the pristine g-C₃N₄/PDI. UV-vis diffuse reflectance spectrometry (UV-vis DRS) and Photoluminescence spectral (PL) analysis confirmed the enhancement of the visible absorption band following a decline in the photoelectron/hole recombination rate with gCPF. A preparatory experiment was performed on photocatalytic degradation of p-nitrophenol (PNP) to examine the activity of gCPF. Results obtained in the radical quenching and the electron paramagnetic resonance (EPR) spectroscopic studies indicated that an in-situ Fenton-like system has been successfully established and the main reactive oxygen species (ROS) changed from O₂- to both O₂- and OH in the gCPF system. However, a competition toward conduction band electrons between Fe³⁺ and O₂ caused an inhibitory effect on PNP degradation. To overcome the effect, nitrilotriacetic acid (NTA) was introduced as a reducing agent for Fe³⁺. Upon adding NTA, the efficiency of PNP degradation greatly enhanced from 33 to 80%. The effect of initial pH, dosage of NTA and content of dissolved O₂ on PNP degradation was also studied. The photocatalytic stability was confirmed by recycling experiments.