Boosting peroxidase-like activity of single-atom nanozymes <i>via</i> sulfur-doped Fe–N–C sites for rapid rhodamine B degradation at neutral pH

Rhodamine B (RhB), a persistent carcinogenic dye, poses critical challenges for environmental remediation. Herein, we report a sulfur-doped single-atom nanozyme (FeNC-SO_x SAzyme) with boosted peroxidase-mimetic activity for rapid RhB degradation. FeNC-SO_x, synthesized <i>via</i> pyrolysis and sulfur modification, features a sulfur-doped carbon network with atomically dispersed Fe-N-C-S active sites. Compared to undoped FeNC, sulfur doping significantly boosted peroxidase-like activity (20.83 U mg^-1, 12.39-fold enhancement) by tailoring Fe 3d-orbital electron density and lowered the Michaelis-Menten constants for H₂O₂ (31.6 mM) and TMB (0.047 mM), indicating superior substrate affinity. Leveraging its Fenton-like catalytic capability, FeNC-SO_x activated H₂O₂ to generate hydroxyl radicals (˙OH) under near-neutral conditions (pH 6.5), achieving over 96% RhB degradation within 15 min. The system demonstrated robust performance in real water samples (tap water: 84.57% degradation efficiency; Lijiang River water: 71.37% degradation efficiency) and maintained stability across a broad pH range (5.0-7.0). This sulfur doping approach provides an effective strategy to engineer SAzymes for neutral pH wastewater treatment and is particularly suitable for textile industries generating alkaline dye effluents (pH 6-8).