Boron-Doped Carbon Material Modulated Highly Reactive Near-Free Fe(III) for Accelerated and Long-Lasting Fenton Oxidation with Hydrogen Peroxide as a Green Electron Donor

Heteroatom doping has been applied as an excellent method for mediating the catalytic reactivity of carbon materials. To overcome the inherent defect of slow Fe(III) reduction in Fenton chemistry, this work finds that boron-doped carbon materials demonstrate high cocatalytic activity in boosting Fenton oxidation. During Fenton chain reactions catalyzed by boron-doped reduced graphene oxide (B-rGO, the typical boron-doped carbon material), highly reactive near-free Fe(III) formed on the B-rGO surface can dramatically promote H₂O₂ mediated Fe(III) reduction, which strongly accelerates the rate-determining reaction in Fenton chain reactions to generate hydroxyl radicals. The results of DFT calculations, electrochemical analysis, characterizations (XAFS, in situ Raman, and HAADF-STEM), and pH-dependent performance reveal that doped boron atoms can modulate the electron-deficient iron atom of FeOH²⁺ by stretching the Fe-O bond (from 163.6 to 179.2 pm), which forms near-free Fe(III) on the B-rGO surface with higher oxidation capability than free Fe(III), and the Fe(III) oxidation potential is positively and linearly related to the boron content of B-rGO (R² = 0.96). Moreover, near-free Fe(III) can dramatically oxidize H₂O₂ (a green electron donor) to accelerate Fe(II) regeneration, thereby promoting Fenton chain reactions for long-lasting Fenton oxidation. These discoveries afford a strategy for designing green and sustainable cocatalysts to overcome the intrinsic weaknesses of classical Fenton chemistry.