Visible-light-driven photocatalytic H2O2 activation for efficient tetracycline removal via a Z-scheme FeNi2S4/g-C3N4 nanoarchitecture

Tetracycline (TC) residues in the environment pose serious ecological and health risks, yet conventional treatment methods are often inefficient. Herein, a composite photocatalyst composed of porous graphitic carbon nitride nanosheets (CN) and FeNi 2 S 4 microspheres (FNS) was successfully synthesized via calcination, solvothermal, and electrostatic self-assembly methods. The as-prepared FNS/CN heterojunction exhibited outstanding performance in the visible-light-driven activation of H 2 O 2 for TC degradation, achieving a removal efficiency of 88.9% within 100 min, with a reaction rate constant (k) of 0.0202 min −1 , which is 2.4 and 8.1 times higher than that of pure CN and FNS, respectively. The enhanced activity was attributed to the Z-scheme heterojunction structure, which facilitated efficient charge separation, broadened visible-light absorption, and provided abundant active sites. Meanwhile, the introduction of FNS established an efficient photo-assisted Fenton-like system. Photogenerated electrons continuously accelerated the Fe 3+ /Fe 2+ and Ni 3+ /Ni 2+ redox cycles to in situ activate H 2 O 2 , significantly promoting hydroxyl radical generation. Mechanistic studies revealed that ·O 2 - , 1 O 2 and ·OH were the main active substances, and holes cooperatively promoted the degradation. The catalyst also demonstrated excellent stability and recyclability over five consecutive cycles. This work provides a promising strategy for designing efficient photocatalysts for antibiotic degradation via H 2 O 2 activation.