Comparative study of metal oxides and phosphate modification with different mechanisms over g-C3N4 for visible-light photocatalytic degradation of metribuzin

In this work, a comparative study of three frequently employed modification techniques to g-C3N4 (CN) nanosheets for the photocatalytic degradation of metribuzin (MET) under visible-light irradiation has been carried out in detail. The modification methods were coupling TiO2 nanoparticles (TO) as electron acceptors, nano-sized Fe2O3 (FO) to construct a Z-scheme nanocomposite, and phosphate (HP) modification to promote O-2 adsorption. The steady-state and transient-state surface photovoltage spectra and transient photoluminescence (PL) spectra confirmed that all the three modification techniques enhanced the charge separation with prolonged lifetimes and presented degradation activities in the order of TO/CN > FO/CN > HP/CN. The TO/CN nanocomposite showed the highest photocatalytic activity for MET degradation, with a sixfold higher rate than bulk CN. Liquid chromatography-tandem mass spectrometry and radical trapping experiments indicated that the increased activity was related to the synergetic effect of two radicals (center dot O-2(-) and center dot OH) involved in the photocatalytic degradation pathway, which was different from the center dot OH radical-dominated pathway of bulk CN. This work reveals the importance of charge separation and the influence of the radical pathway and provides guidance for the design of high-efficiency photocatalysts.

Automated summary

A comparative study of three modification techniques for g-C3N4 nanosheets for the photocatalytic degradation of MET was conducted. The TO/CN nanocomposite showed the highest photocatalytic activity for MET degradation.