Enhanced oxygen activation in antibiotic degradation using N-doped carbon skeleton encapsulated high-entropy alloy catalysts

The catalyst employed for activating molecular oxygen to degrade organic pollutants in water environments encounters great challenges, such as facile agglomeration, leaching of metal ions, and a sluggish redox cycle. These factors lead to low catalytic activity and inadequate stability, thereby severely restricting its viability for industrial use. A high-entropy alloy (HEA) catalyst, FeCoNiCuZn@CN, was synthesized via a hydrothermal-pyrolysis method and employed to facilitate the degradation of norfloxacin (NOR) by activating molecular oxygen. The FeCoNiCuZn@CN is a face-centered cubic (FCC) structured FeCoNiCuZn HEA embedded within a nitrogen-doped carbon framework, as proved by XRD, Raman, SEM, XPS, and TEM. The optimized FeCoNiCuZn@CN6–800 demonstrates efficient degradation of NOR, achieving a removal rate exceeding 95 % within 40 min across a broad pH range of 3–11. The catalyst exhibits a maximum mineralization rate of 72.4 %, surpassing recently reported catalysts. Moreover, it exhibits universal degradation properties toward diverse antibiotics and demonstrates strong interference-resistance against prevalent inorganic ions, making it well-suited for treating intricate water matrices. Even after five cycles, the removal efficiency remains at 78.4 %, thanks to the exceptional stability of the HEA and the encapsulation of the carbon skeleton. The intrinsic nature of the synergistic effect caused by the formed HEA and carbon-metal (C-M) bonds between HEA and CN was revealed, which was responsible for the prominent molecular oxygen activation capacity. The reaction mechanism was proposed through reactive oxygen species (ROS) scavenging experiment, electron paramagnetic resonance (EPR), molecular probing experiment, and density functional theory (DFT) calculations. Finally, three degradation pathways were proposed by analyzing degradation intermediates, and the toxicity of intermediate products was predicted by T.E.S.T toxicity estimation software. This study opens new perspectives for the design and preparation of high-entropy-based catalysts that have an excellent ability to activate molecular oxygen in the field of wastewater treatment.