Orbital Modulation and Coupled Redox Cycling in Fe–Mn Dual-Atom Catalysts for Efficient Fenton-like Water Purification

Abstract

Single-atom catalysts (SACs) offer ideal active sites for advanced oxidation processes, yet their practical applications are hindered by synthetic complexity, isolated centers, and limited redox and charge-transfer dynamics. Here, we report a scalable synthesis of a Fe–Mn dual-atom catalyst (Fe–Mn/N–C) featuring a symmetric Fe–Mn–N6 coordination structure. This unique configuration establishes a sustainable bimetallic redox cycle that enables efficient activation of peracetic acid (PAA) for pollutant degradation. The catalyst achieves nearly complete removal of sulfamethoxazole (99.9%) with an apparent rate constant of 0.3226 min–1—7.7 and 8.5 times higher than those of Fe/N–C and Mn/N–C counterparts, respectively. Density functional theory calculations reveal that Mn–N coordination promotes electronic delocalization and fine-tunes the electronic structure of adjacent Fe centers, leading to distinct PAA adsorption geometries on Mn and Fe sites that favor the selective formation of hydroxyl radicals (•OH) and singlet oxygen (1O2) species. The optimized Mn d-band center further lowers the energy barrier for 1O2 generation. Moreover, the Fe3+/Fe2+ and Mn4+/Mn3+ redox cycles are coupled through electron transfer between Fe and Mn centers, ensuring self-regeneration of active sites and sustained catalytic stability. The Fe–Mn/N–C catalyst exhibits outstanding activity across a wide pH range, strong tolerance to competing inorganic ions, excellent recyclability, and broad substrate applicability. Collectively, this work establishes a durable bimetallic redox-coupling strategy that leverages electronic structure modulation to realize synergistic oxidation and provides insights for the rational design of robust Fenton-like catalysts for complex environments.