Hydrogen Peroxide as an Ideal Electron Donor for Long-Lasting Fenton Chemistry: Strong Enhancement of Fe(III) Activity by Heteroatom-Doped Nanocarbons

Heteroatom doping has been demonstrated to be an effective strategy to improve the catalytic activity of carbon materials. Herein, heteroatom-doped nanocarbons were found to be environmental protection cocatalysts for promoting Fenton oxidation. Nitrogen-doped reduced graphene oxide (N-rGO) exhibited better catalytic activity than sulfur-, boron-, and phosphorus-doped rGO for enhancing Fenton oxidation. Unlike classical electron sacrificial agents, H2O2 was employed as an electron donor to enhance Fenton oxidation during the catalysis of N-rGO. Electrochemical analysis and nitrogen molecular model tests indicated the oxidation potential of Fe(III) increased with improvement in the N atom content (R2 = 0.97), revealing that the Fe atoms of FeOH2+ on the N-rGO surface are more likely to abstract electrons from H2O2. In addition, the delocalized π electron is one of the active sites in N-rGO-boosted Fenton oxidation, and N-rGO could facilitate electron transfer from H2O2 to Fe(III) along the C–C/C═C structures due to the improvement of the conductivity ability and the oxidation potential of Fe(III). Moreover, density functional theory (DFT) calculations suggest that the pyrrole N species of N-rGO is the best catalytic activity site, resulting from the pyrrole N species with higher adsorption energy stretching the Fe–O bond of FeOH2+ to increase the activity of Fe(III) species. Therefore, the study findings provide insight into designing stable and efficient metal-free catalysts to enhance Fe(III) reactivity in overcoming the inherent drawbacks of the Fenton system.