This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the Xinjiang Technical Institute of Physics and Chemistry (XTIPC) of the Chinese Academy of Sciences (CAS) have developed a core-shell confined iron-based single-atom catalyst that combines high Fenton-like catalytic activity with structural stability, enabling nearly complete removal of 2,4-dichlorophenol (2,4-DCP) within 20 minutes under mildly acidic conditions. Iron-based single-atom catalysts (Fe-SACs) hold great promise for heterogeneous Fenton-like water remediation, yet their practical deployment is severely hampered by the intrinsic activity-stability trade-off.
Under harsh acidic oxidative environments, isolated Fe atoms tend to leach from carbon supports and trigger rapid deactivation. Rational modulation of local coordination environments to reconcile high catalytic activity and structural robustness remains a critical challenge for designing advanced single-atom Fenton catalysts. In a recent study published in the Journal of Catalysis, professors Yang Liping and Yin Jiao's team at the Research Center for Energy and Chemical Engineering at XTIPC carried out comparative structure-performance investigations between Fe-N₄ and Fe-N₄O₂ single-atom moieties.
Taking mesoporous MCM-41 as a confined support and o-phenylenediamine as a ligand, polymerizable monomer and nitrogen source, the group fabricated a core-shell confined Fe-N₄ single-atom catalyst denoted SiO₂@Fe-N-C via an in situ polymerization-pyrolysis route. Using advanced imaging and X-ray techniques, the researchers confirmed that individual iron atoms were dispersed within nitrogen-doped carbon shells, with each iron atom surrounded by four nitrogen atoms. The catalyst also retained the ordered porous structure of the MCM-41 support.
The as-synthesized SiO₂@Fe-N-C delivers outstanding Fenton-like catalytic performance. Under mildly acidic conditions, nearly complete removal of 2,4-dichlorophenol (2,4-DCP) is achieved within 20 minutes with an apparent rate constant of 0.70 min⁻¹ and a mineralization efficiency of 62%. The catalyst maintained more than 95% pollutant-removal efficiency over 10 successive reuse cycles, with negligible iron leaching into the water.
Further experiments indicated that hydroxyl radicals were the main reactive species responsible for breaking down the pollutant, with singlet oxygen also contributing. The proposed degradation pathway involves removing chlorine atoms, adding hydroxyl groups and opening the pollutant's ring structure, ultimately leading toward mineralization. Computer calculations and measurements taken after the reaction helped explain how the catalyst combines activity with stability.
The researchers compared two types of active sites: symmetric Fe-N₄ sites, where each iron atom is surrounded by four nitrogen atoms, and asymmetric Fe-N₄O₂ sites, which also contain two oxygen atoms. Their results suggest that the symmetric sites bind reactants effectively while undergoing very little change in their electronic structure during catalysis. This combination could allow the catalyst to remain highly active without compromising the stability of its iron sites.
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