Insight into photo-Fenton reaction mechanism on a magnetite-GO nanocomposite: Computational and experimental investigations

A necessary condition for an optimum photo-Fenton heterojunction photocatalyst is that its reduction part should be electron-rich and have a high affinity for H2O2 molecules. This study uses a combination of experimental investigations, classical molecular dynamics (MD), and density functional theory (DFT) calculations to elucidate the photo-Fenton degradation of p-nitrophenol (PNP) on a magnetite-GO composite from the above viewpoint. The magnetite nanostructures and the Graphene oxide (GO) for this composite had bandgaps in the visible range. Photo-Fenton experiments revealed that the composite had significantly better PNP degradation activity than magnetite nanoparticles. Large-scale molecular dynamics demarcated the affinity of the different parts of the composite towards H2O2 and PNP in an aqueous medium. Time-dependent DFT (TDDFT) calculations revealed that photo-excitation shifted the highest occupied molecular orbitals (HOMO) to the magnetite part of the composite. The photo-Fenton mechanism, proposed using computational and experimental pieces of evidence, gives a critical criterion for screening photocatalysts for a particular substrate.