Abstract: Aiming at the problem of the widespread presence of antibiotics such as sulfamethoxazole （SMX） in water bodies, which posed a threat to the ecosystem and human health, and were difficult to effectively remove by using conventional wastewater treatment processes，  we prepared a few-layer carbon nitride catalyst (Ni@C₃N₄) loaded with single-atom nickel,  which could efficiently electrocatalytically degrade sulfamethoxazole by generating hydrogen peroxide (H₂O₂) via an oxygen reduction reaction (ORR). Structural characterization show that nickel is highly dispersed in the few-layer carbon nitride matrix in the form of single-atoms and significantly modulates the electronic structure of the few-layer carbon nitride to optimize the active site distribution. Electrochemical test results show that Ni@C₃N₄ has excellent two-electron selectivity and rapid reaction kinetics. Under acidic conditions (pH=3), Ni@C₃N₄ can generate H₂O₂ via the two-electron pathway,  and degradation rate of sulfamethoxazole can reach 81.3% within 120 min, which is significantly better than that of the undoped carbon nitride catalyst. Kinetic analysis results show that the degradation process conforms to a pseudo-first-order reaction model. The research results provide new ideas for the treatment of antibiotics in water bodies.

Key words: sulfamethoxazole, few-layer carbon nitride, single-atom catalyst, oxygen reduction reaction, hydrogen peroxide