Engineering active Co-Co/Co-N sites in carbon nanotube catalyst for efficient Fenton-like removal of sulfamethoxazole

Development highly efficient and stable carbon-loaded cobalt-based catalysts holds great significance for Fenton-like wastewater purification. The incorporation of N atoms into the carbon substrate can effectively modulate the charge distribution of the catalyst and generate multiple active sites. Herein, using ZIF-9 and melamine as precursors, Co nanoparticles encapsulated N-doped carbon nanotubes (Co@NCNT) were constructed. In Fenton-like catalysis, Co@NCNT could efficiently activate peroxymonosulfate (PMS) to produce reactive oxygen species (ROS), and completely degrade sulfamethoxazole (SMX) within 5 min. Meanwhile, the Co@NCNT/PMS system shows good resistance to inorganic anions and natural organic matter and is highly adaptable to various organic pollutants. Continuous 10 h operation of SMX degradation indicates Co@NCNT has good cycling stability and practical application potential. Mechanism analysis reveals the synergistic effect between radicals (SO₄^•-) and non-radicals (¹O₂, Co(IV) = O). In addition, there are two active sites (Co-Co/Co-N) to propel PMS activation, CoCo bonds primarily contribute to the formation of ¹O₂, Co(IV) = O, and SO₄^•-, whereas CoN bonds generate a minor amount of ¹O₂, minimize Co leakage, and enhance electron transfer efficiency. In summary, this work provides a strategy for the simple fabrication of catalysts with dual active sites for efficient Fenton-like catalysis.