Tailoring the d-band center enables La doped ZnIn2S4 to be active for boosting photocatalytic activation of oxygen and degradation of antibiotics in wastewater

Abstract

Designing efficient photocatalysts for advanced oxidation processes is a promising approach to address the ever-increasing antibiotics in water pollution, but it remains a challenging task due to insufficient adsorption and activation of O₂, as well as hindered electron transfer over existing photocatalysts. In this study, a series of La-doped ZnIn₂S₄ (La_x-ZIS) compounds were constructed and used for efficient removal of antibiotics from wastewater. Experimental and theoretical calculations show that La partially replaces Zn in the ZIS lattice. The doping of La effectively broadens the absorption range of ZIS and induces an upward shift of its d-band center, enhancing the spatial separation of the HOMO–LUMO. This not only improves the adsorption and activation capacity for O₂ but also enhances the separation and transport of photogenerated carriers, thereby increasing the production of ˙O₂⁻ and h⁺ active species. The optimal sample, La_1.37-ZIS, exhibited degradation efficiency for high concentrations of metronidazole (MNZ) and tetracycline hydrochloride (TCH) that were 3.44 and 3.46 times higher than those of ZIS, respectively. This study offers profound insights into the rational manipulation and synthesis of photocatalysts, as well as their effective utilization in the process of photo-oxidation for wastewater treatment.