High-efficiency 4-CP removal by CuFe₂S₃/H₂O₂ Fenton-like system: Unraveling the role of sulfur vacancies in H₂O₂ activation

The degradation of persistent organic pollutants like 4-chlorophenol (4-CP) remains a critical challenge in wastewater treatment. Transition-metal sulfides have emerged as promising Fenton-like catalysts owing to their tunable electronic structures and abundant redox-active sites. Herein, we report a highly efficient Fenton-like system using ternary copper-iron sulfide (Cu x Fe y S z ) nanocatalysts for 4-CP degradation. Three Cu x Fe y S z phases—CuFe₂S₃, CuFeS₂, and Cu₅FeS₄—were synthesized and systematically evaluated, with CuFe₂S₃ demonstrating superior catalytic activity, achieving complete degradation of 20 mg/L 4-CP within 7 min using 5 mmol/L H₂O₂. Mechanistic studies reveal that sulfur vacancies in CuFe₂S₃ serve as key features, enhancing H₂O₂ adsorption and activation, as evidenced by in situ Raman spectroscopy. Comparative studies with CuFe₂S₃ analogues (0.7-CuFe₂S₃, 0.9-CuFe₂S₃, Fe₃S₄, and Cu₈S₅) confirm the unique catalytic efficiency of stoichiometric CuFe₂S₃, attributed to its optimal electronic structure and vacancy density. This work not only presents CuFe₂S₃ as a cost-effective and high-performance Fenton-like catalyst but also lays a solid foundation for the application of naturally occurring copper-iron sulfide minerals in wastewater treatment.