Construction of N-Fe-S bridge in atomic iron catalyst for boosting Fenton-like reactions

Constructing the coordination environment of single-atom catalysts (SACs) can be an attractive technical strategy to regulate the generation of reactive oxygen species for Fenton-like reactions. Herein, we have constructed an asymmetric coordination of Fe single-atom catalyst (Fe_SA-NS-PCNS) with abundant N-Fe-S bridge (Fe_SA-N₃S₁) for robust Fenton-like reactions. 82.5 % of singlet oxygen (¹O₂) selectivity and high turnover frequency of bisphenol A degradation (0.568 min⁻¹) were achieved at mild conditions. Experimental works and theoretical analyses illustrated that S doping breaks the inert environment of the original N-Fe-N symmetric coordination equilibrium and modulates the electron density of the atomic Fe center, which is beneficial for boosting PMS adsorption and reducing the energy barriers of vital *OH and *O intermediates. The coupling between the Fe_SA-N₃S₁ interface and peroxymonosulfate molecule boosts in-situ electron transfer through the N-Fe-S bridge, which induces more electron flow from the low valence Fe to OH* on the surface of Fe-*O-H, forming a high yield of ¹O₂. Moreover, we designed the Fenton-like reactions by Fe_SA-NS-PCNS membrane reactor for an efficient contaminant removal rate of over 90 % even after 11 cycles. This work provides a novel perspective on developing SACs with asymmetric coordination to regulate reactive oxygen species for the treatment of organic contaminants in water bodies.