Steering Peroxymonosulfate Activation Toward Exclusive Singlet Oxygen Generation via Active Iron Carbides Nanoparticles

The conversion of peroxymonosulfate (PMS) to singlet oxygen ( 1 O 2 ) mediated by Fe-based nanoparticles is significant for environmental remediation. However, the selectivity of this process is often compromised by the apparent valence change of Fe during conventional redox activation. Herein, we report an unconventional PMS activation pathway catalyzed by iron carbide (Fe 2 C), which enables discriminative regulation of 1 O 2 generation from PMS decomposition. Unlike inert Fe 3 O 4 and Fe 2 O 3 catalysts, the surficial Fe 2+ and Fe 3+ sites bridged by carbon atoms in Fe 2 C are identified as the effective catalytic centers. These Fe–C sites achieve PMS activation via built-in electric fields and sustain long-term catalytic activity, thereby bypassing the pathway of full electron transfer that sacrifices low-valent Fe. Consequently, Fe 2 C exhibits a 661.3-fold higher efficiency in levofloxacin removal than Fe 3 O 4 and Fe 2 O 3 . Moreover, the non-radical degradation pathway via 1 O 2 oxidation achieves nearly 100% selectivity, facilitating the complete removal of various pollutants within 5 min. By rationally incorporating covalent coordination into the design of Fenton-like catalysts, this work overcomes the inherent trade-off between activity and durability. Thus, effective water purification is achieved through selective, nonradical reaction pathways.