Nitrogen Doping-Induced Weak Metal–Support Interaction Regulating the Interfacial Behavior of Hydroxyl Radicals in the Electro-Fenton Process

Metal–support interaction critically influences the activity and stability of heterogeneous catalysts, yet its role in heterogeneous electro-Fenton (HEF) processes─which involve strong oxidizing conditions and multielectron transfer reactions─remains poorly understood. In this study, we synthesized a FeCo dual-atom catalyst via intermolecular interactions between the model molecule FePc/CoPc and a nitrogen-rich carbon substrate (FeCo-DAC -N ), delivering efficient catalytic performance for the HEF process. To elucidate the role of this weak metal–support interaction, a control catalyst (FeCo-DAC- C ) was prepared by pyrolyzing FeCo-DAC -N under N 2, thereby anchoring the metal sites directly into the carbon matrix. Despite having identical metal content, FeCo-DAC -N with this weak metal–support interaction outperformed in all dimensions, including RhB removal, H 2 O 2 activation, H 2 O 2 accumulation, and •OH generation. Cycling tests, metal leaching quantification, and in situ Raman characterization collectively suggested the improved stability of FeCo-DAC -N . Shell-isolated nanoparticle-enhanced Raman spectroscopy disclosed distinct peaks belonging to the adsorbed •OH (Fe–OH*, 563 cm –1 ) and OH – (Fe–OH, 445–450 cm –1 ) on the Fe site in FeCo-DAC- C -catalyzed HEF, respectively. Surprisingly, this typical Fe–OH* signal cannot be recognized in that of FeCo-DAC- N . Instead, a high-intensity and broad peak with a vacillating peak location (457–468 cm –1 ) under different electrode potentials was observed, which can be attributed to the overlap of Fe–OH* and Fe–OH peaks. The altered interfacial behavior of Fe–OH* was corroboratively evidenced by quenching experiments in which n -butanol caused more significant inhibition of RhB degradation. Furthermore, density functional theory calculations confirmed a lower energy barrier for H 2 O 2 activation and stronger Fe–OH adsorption when Fe–N sites interact with the nitrogen support, which is consistent with experimental observations. This work presents a primary effort to elucidate the role of the weak metal–support interaction in regulating the interfacial behavior of •OH in the HEF process, which should deepen the understanding of the electro-Fenton process and inspire the rational design of next-generation catalysts.