Polyvinylpyrrolidone-induced size-dependent catalytic behavior of Fe sites on N-doped carbon substrate and mechanism conversion in Fenton-like oxidation reaction

Fe-based N-doped carbon catalysts (Fe/NC-XPVP) are synthesized through a solvent-free and one-step pyrolysis strategy, allowing for the control of Fe active center sizes and the morphology of carbon substrates. The variable-sized Fe active centers in Fe/NC-XPVP exhibit size-dependent catalytic behavior in peroxymonosulfate (PMS) activation reaction, which indicates that downsizing Fe particles to atomic level achieves performance improvement and mechanism transformation from radical to non-radical pathway. The optimal Fe/NC-1.0PVP catalyst can realize nearly 100.0 % of tetracycline degradation efficiency within 30 min. Density functional theory calculations demonstrate that the strong adsorption of PMS onto Fe-N₄ sites can promote the formation of catalyst/PMS* complexes and induce the occurrence of electron transfer process, which performs great resistance to complex water environments during PMS activation. This work gives valuable insights into the precise design and regulation of metal active sites on N-doped carbon materials and provides a promising catalyst for wastewater remediation.