Harnessing Fe–Mo Atomic Interfaces for Boosted Electron Transfer and ROS Generation in Sustainable Pollutant Degradation

Developing efficient and sustainable catalytic systems for persistent organic pollutant degradation remains a critical challenge in wastewater treatment. Herein, we present a novel FeMo_0.5-OCN catalyst integrating iron clusters and molybdenum single atoms with oxygen coordination, which synergistically activates peroxymonosulfate (PMS) to generate reactive oxygen species (ROS), including sulfate radicals (SO₄^•-) and singlet oxygen (¹O₂), for enhanced pollutant degradation. Density functional theory (DFT) calculations and experimental studies reveal that Mo single atoms facilitate pollutant adsorption via oxygen coordination, while Fe clusters drive PMS activation, enabling efficient electron transfer and ROS generation. The FeMo_0.5-OCN/PMS system achieves rapid degradation (>90% within 1 min) and high mineralization (73% TOC removal) of phenol, along with robust stability over 30 reaction cycles and broad pH adaptability (pH 2-11). Apart from phenol, this system demonstrates outstanding degradation efficiency for other phenolic contaminants as well. The practical applicability of the system is demonstrated by chemical oxygen demand (COD) removal efficiencies of 91, 44, and 33% for phenolic, high-salinity, and alcohol-containing wastewaters, respectively, outperforming conventional Fe²⁺/H₂O₂ systems and activated carbon treatments. Heterogeneous catalytic model quantifies the contribution of ROS and the mass transfer behaviors of pollutants at the solid-liquid interface. Sensitivity analysis confirms that the ¹O₂-facilitated generation of p-benzoquinone (p-BQ) is the rate-determining step in the overall reaction pathway. Life cycle assessment (LCA) confirms the system's superior environmental sustainability and cost-effectiveness compared to conventional Fenton systems (Fe²⁺/H₂O₂ and Fe²⁺/PMS), with minimal metal leaching. This work highlights the critical role of interfacial electronic interactions in catalytic design and provides a scalable strategy for durable, eco-friendly wastewater remediation.