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 H 2 O 2 generation and activation efficiently for generating reactive species remains a challenge. In particular, a nonradicalmediated EF is more favorable for actual wastewater remediation, and deserves more attention. In this study, three-dimensional graphene loaded with Fe 3 O 4 nanoparticles (Fe 3 O 4 @3D-GNs) with abundant oxygencontaining 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 Fe 3 O 4 @3D-GNs synthesized at 750 degrees C (Fe 3 O 4 @3D-GNs-750) with the highest -C-O-C and -C=O group ratios exhibited the maximum H 2 O 2 and 1 O 2 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 H 2 O 2 and the positive influence of -C=O sites on the production of 1 O 2 . Moreover, the surface -bound Fe(II) favors the generation of surface -bound center dot OH, which steers a more favorable oxidative conversion of H 2 O 2 to 1 O 2 . Fe 3 O 4 @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 O 2 -generation mechanism in the Fenton reaction.