Efficient photocatalytic degradation of tetracycline on lanthanum-doped BiOBr/g-C3N5 Z-scheme heterojunction under visible-light

In this study, Lanthanum ions (La 3 + )-doped BiOBr/g-C 3 N 5 (La 3+ @BiOBr/g-C 3 N 5 ) Z-scheme heterojunction photocatalyst was successfully synthesized via a facile solvothermal method. The composite structure was thoroughly characterized by XRD, FTIR, XPS, SEM, TEM, UV-Vis DRS, PL, and EIS analyses, confirming the successful incorporation of La 3+ into the BiOBr lattice and the effective integration of g-C 3 N 5 . The optimal composite with 5 wt% g-C 3 N 5 demonstrated superior photocatalytic performance in degrading tetracycline hydrochloride (TCH), achieving a removal efficiency of 95.9% within 180 min under visible light irradiation. The enhanced activity is attributed to the synergistic effects of increased specific surface area, improved visible light absorption, and more efficient photogenerated charge separation, as facilitated by La 3+ doping and Z-scheme charge transfer pathways. Scavenger experiments and Mott-Schottky analysis indicated that superoxide radicals (•O 2 - ) and photogenerated holes (h + ) are the main reactive species responsible for pollutant degradation. Furthermore, the composite exhibited excellent stability and reusability, maintaining over 87% degradation efficiency after five consecutive cycles with minimal structural change. This work provides a promising strategy for the design of high-efficiency rare-earth-modified photocatalysts for antibiotic pollutant removal in wastewater treatment applications.