Iron carbide nanoparticles encapsulated in guanine-derived carbon for peroxymonosulfate activation

Iron and nitrogen co-doped carbon-based catalysts have garnered significant attention for their efficacy in the degradation of Rhodamine B (RhB), Tetracycline (TC) and other organic pollutants through peroxymonosulfate (PMS) activation. However, designing catalysts with both high activity and abundant active sites has proven challenging, primarily due to the limited understanding of the structure-activity relationship. Herein, we present a straightforward synthesis of iron and nitrogen co-doped carbon nanosheets (FeNC) that exhibit exceptional activity in activating PMS for degradation of RhB and TC. The FeNC material shows robust resistance to interference across a wide pH of 1.5 to 10, resistance to inorganic anions and humic acid (HA). More importantly, the Fe3C nanoparticles are uniformly anchored within the carbon layer, effectively prevent metal leaching. Unlike the traditional sulfate radical-based advanced oxidation processes, our study reveals that non-radical singlet oxygen (1O2) serves as the main reactive oxygen species (ROS) responsible for the degradation processes through quenching tests and electron paramagnetic resonance (EPR) analysis. Structural characterizations and spectroscopic study indicate that the potential active sites on FeNC, namely CO, graphitic and pyridinic nitrogen play an important role in this degradation. Particularly noteworthy is the discovery that Fe3C species, present in the FeNC-900/PMS system, also contribute significantly to the degradation of TC. Moreover, we have proposed potential degradation pathways for RhB and TC based on the results of liquid chromatograph mass spectrometer (LC-MS) measurement. Overall, this study offers novel insights into the development of heterogeneous iron and nitrogen co-doped carbon-based catalysts for advanced oxidation processes (AOPs) via PMS activation.