Nitrogen-doped carbon matrix single-atom catalysts (SACs) for the efficient removal of organic pollutants have attracted widespread attention. However, the ligand structure and the origin of the high activity between nitrogen species and single-atoms remain elusive. Herein, nitrogen-doped carbon matrix iron single-atom catalysts (Fe/NC-SACs) that exhibit high catalytic reactivity (98.2% SMX degradation in 5 min), broad pH resistance (pH 3.0-11.1), high stability, and sustainable water treatment capacity are reported. High-valent iron (Fe ^IV=O) and singlet oxygen (¹O₂) were the reactive oxygen species observed. The electrochemical results demonstrated the generation of catalyst-PMS complexes. The DFT calculations revealed that Fe-pyrrolic N₄ was the best ligand for PMS, exhibiting the highest adsorption energy, bond length variation and electron transfer capacity. The central Fe single atom and the carbon electrons adjacent to the pyrrolic N were the reactive sites of the PMS. The main source of ¹O₂ was the oxidation of PMS. This work provides guidance for the discovery of high-performance catalysts and provides a single-atom catalyst that can be used for practical environmental purification.

Environmental Implication

This work demonstrates the synthesis of Fe single-atom catalysts by a simple template sacrifice method. The obtained Fe-NC-SACs exhibit excellent catalytic performance in the PMS-activated degradation of organic pollutants. In addition, the Fe/NC-SACs exhibit strong stability and sustainable water treatment in PMS activation transformation. The Fe/NC-SACs have good applicability and tolerance to interference in the treatment of target pollutants in real water environment. Fe/NC-SACs have potential and importance for application in persulfate-mediated remediation of polluted water. The environmental friendliness of Fe makes Fe/NC-SACs a green catalyst for catalytic oxidation reactions.