Visible-light-assisted generation of high-valent iron-oxo species anchored axially on g-C3N4 for efficient degradation of organic pollutants

Abstract

As highly active species, in theory, hydroxyl radicals (OH) can move freely and destroy almost all organic compounds, including catalysts with a conjugate structure. Therefore, a system that can generate oxidative species with a high activity, but where the active species is anchored to avoid autooxidation, is urgently required. In this work, we fabricated a novel visible-light-assisted advanced oxidation process based on high-valent iron species (Fe(IV)O) over graphitic carbon nitride (g-C3N4) that was coordinated to iron hexadecachlorophthalocyanine (FePcCl16) through imidazole ligands (IMD). Under visible-light excitation, the phthalocyanine ring of the g-C3N4-IMD-FePcCl16/hydrogen peroxide (H2O2) can be motivated to an excited state FePcCl16∗, in which active H2O2 and the generation of anchored Fe(IV)O species are used for the degradation of carbamazepine (CBZ). Because the molecular movement of transient Fe(IV)O species is restricted, the possibility of oxidative collision is minimized, which provides good stability. An analysis of the electron paramagnetic resonance, gas chromatography/mass spectrometry, photoluminescence spectra, periodic on/off photocurrent density response and the photo-assisted catalytic active experiments, indicates that the rapid generation of Fe(IV)O species occurs as the catalyst contacts the H2O2, which inhibits the conduction-band electrons of the g-C3N4 from reacting with H2O2 and generating OH. This study provides insight into the construction of suitable structures that will enhance visible-light-assisted catalytic oxidation activity and allow for the fabrication of an anchored highly active species.