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

Abstract

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 via 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).