Ultrahigh surface area of single-atom iron nanosheets assists in the efficient utilization of reactive oxygen species in the peroxymonosulfate activation process for pollutant removal

Abstract

Iron-based single-atom catalysts (SACs) have exhibited remarkable performance for persistent pollutant removal through activating peroxymonosulfate (PMS) to generate reactive oxygen species (ROS). However, the broad practical application of SACs has been restricted by the inefficient utilization of the as-activated ROS due to their ultrafast self-quenching. Herein, single-atom Fe loaded N-doped carbon nanosheets (SAFe/CNS) were synthesized via a cocoon silk chemistry strategy. SAFe/CNS exhibited ultrahigh specific surface area (1970 m² g⁻¹) which brought out a large adsorption capacity for organic pollutants, thereby effectively utilizing the vicinal as-generated active species. The degradation rate was 1.925 min⁻¹, which is superior to those of most reported Fe-based SACs and representative PMS activation methods. Theoretical and experimental results revealed that the electron transfer from Fe–N₄ sites to PMS made PMS a nucleophilic agent, which makes it prone to attacking another PMS molecule, arousing the formation of O₂˙⁻, and consequently generating ¹O₂ through disproportionation. Besides, SAFe/CNS is applicable for remediation of various actual wastewaters with ultralow PMS dosage. This work provides a novel strategy for efficient utilization of the as-generated ROS on SACs.