Oxygen-containing functional groups in Fe 3 O 4 @three-dimensional graphene nanocomposites for enhancing H 2 O 2 production and orientation to 1 O 2 in electro-Fenton.

In electro-Fenton (EF), development of a bifunctional electrocatalyst to realize simultaneous H2 O2 generation and activation efficiently for generating reactive species remains a challenge. In particular, a nonradical-mediated EF is more favorable for actual wastewater remediation, and deserves more attention. In this study, three-dimensional graphene loaded with Fe3 O4 nanoparticles (Fe3 O4 @3D-GNs) with abundant oxygen-containing functional groups (OFGs) was synchronously synthesized using a NaCl-template method and served as a cathode to establish a highly efficient and selective EF process for contaminant degradation. The amounts of OFGs can be effectively modulated via the pyrolysis temperature to regulate the 2e- oxygen reduction reaction activity and reactive oxygen species (ROS) production. The optimized Fe3 O4 @3D-GNs synthesized at 750 °C (Fe3 O4 @3D-GNs-750) with the highest -C-O-C and -C꞊O group ratios exhibited the maximum H2 O2 and 1 O2 yields during electrocatalysis, thus showing remarkable versatility for eliminating organic contaminants from surface water bodies. Experiments and theoretical calculations have demonstrated the dominant role of -C-O-C in generating H2 O2 and the positive influence of -C꞊O sites on the production of 1 O2 . Moreover, the surface-bound Fe(II) favors the generation of surface-bound •OH, which steers a more favorable oxidative conversion of H2 O2 to 1 O2 . Fe3 O4 @3D-GNs were proven to be less pH-dependent, low-energy, stable, and recyclable for practical applications in wastewater purification. This study provides an innovative strategy to engineer active sites to achieve the selective electrocatalysis for eliminating pollution and reveals a novel perspective for 1 O2 -generation mechanism in the Fenton reaction.