Electronic Control of Traditional Iron–Carbon Electrodes to Regulate the Oxygen Reduction Route to Scale Up Water Purification

Shifting four-electron (4e–) oxygen reduction in fuel cell technology to a two-electron (2e–) pathway with traditional iron–carbon electrodes is a critical step for hydroxyl radical (HO•) generation. Here, we fabricated iron–carbon aerogels with desired dimensions (e.g., 40 cm × 40 cm) as working electrodes containing atomic Fe sites and Fe3C subnanoclusters. Electron-donating Fe3C provides electrons to FeN4 through long-range activation for achieving the ideal electronic configuration, thereby optimizing the binding energy of the *OOH intermediate. With an iron–carbon aerogel benefiting from finely tuned electronic density, the selectivity of 2e– oxygen reduction increased from 10 to 90%. The resultant electrode exhibited unexpectedly efficient HO• production and fast elimination of organics. Notably, the kinetic constant kM for sulfamethoxazole (SMX) removal is 60 times higher than that in a traditional iron–carbon electrode. A flow-through pilot device with the iron–carbon aerogel (SA-Fe0.4NCA) was built to scale up micropolluted water decontamination. The initial total organic carbon (TOC) value of micropolluted water was 4.02 mg L–1, and it declined and maintained at 2.14 mg L–1, meeting the standards for drinking water quality in China. Meanwhile, the generation of emerging aromatic nitrogenous disinfection byproducts (chlorophenylacetonitriles) declined by 99.2%, satisfying the public safety of domestic water. This work provides guidance for developing electrochemical technologies to satisfy the flexible and economic demand for water purification, especially in water-scarce areas.