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

Abstract

Heteroatom doping has been demonstrated to be an effective strategy to improve the catalytic activity of carbon materials. Herein, heteroatomdoped 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, H 2 O 2 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 (R 2 = 0.97), revealing that the Fe atoms of FeOH 2+ on the N-rGO surface are more likely to abstract electrons from H 2 O 2 . 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 H 2 O 2 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 FeOH 2+ 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.