Oxygen vacancy-engineered Bi2O2CO3 nanosheets for enhanced photodegradation of pharmaceuticals and personal care products in water†

Abstract

Defect engineering has emerged as a versatile approach for tailoring the properties of materials to meet specific functional applications and improve their properties. In the context of environmental remediation, the introduction of surface oxygen vacancies in semiconductor materials has demonstrated to be a highly effective strategy to enhance molecular adsorption and contaminants' degradation. Herein, we reported the synthesis of Bi₂O₂CO₃ nanosheets with surface oxygen vacancies (OVs) via the controlled addition of an accessible, non-toxic and versatile ionic liquid, choline hydroxide. The presence of OVs was confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemical techniques, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Upon optimizing the concentration of choline hydroxide, it was found that the addition of 10% of choline hydroxide yielded a material, Chol10%-Bi₂O₂CO₃, with significantly enhanced adsorptive and photocatalytic performance. This material efficiently removed not only antibiotics such as ciprofloxacin (97.5% in 20 min) and sulfamethoxazole (98.5% in 60 min), but also a UV filter compound, benzophenone-4 (92.4% in 180 min), which are representative of pharmaceuticals and personal care products (PPCPs) of high environmental concern. Mechanistic studies into reactive oxygen species involved in the photocatalytic process, together with a thorough study of the energy band structure, revealed that Chol10%-Bi₂O₂CO₃ generates both hydroxyl (OH·) and superoxide (·O₂⁻) radicals, which are essential for the efficient degradation of the recalcitrant UV filter compound, showing the potential of oxygen vacancy-engineered Bi₂O₂CO₃ nanosheets as promising platforms for water purification and environmental remediation applications.