Surface-iodine-grafting-induced local electric field drives charge separation of CdBiO2Br for excellent photocatalytic antibiotic degradation

Abstract

Photocatalytic technology has demonstrated immense potential in environmental purification, particularly in the degradation of antibiotics that pose serious health risks. However, the rapid recombination of photogenerated charge carriers and the limited light absorption capacity, which are major obstacles, severely hinder the photocatalytic degradation activity. Herein, the surface halogen-grafting strategy is introduced to address these issues in a Sillén-related layer-structured photocatalyst, CdBiO2Br (CBOB). The iodine-grafted CBOB nanosheets deliver a superb tetracycline hydrochloride photodegradation efficiency of 72.36 % within one hour, which is 2.44 times higher than that of the original CBOB. Additionally, they demonstrated a broad-spectrum degradation capability against various antibiotics and phenolic pollutants, such as ciprofloxacin, chloramphenicol hydrochloride, bisphenol A, highlighting their practical and industrial value. Mechanistic studies indicated that the high electronegativity of iodine could induce a surface dipole polarization effect to form localized electric fields that efficiently drive the separation of photogenerated electrons and holes, and, on the other hand, improve light absorption, which profoundly boosts the photocatalytic degradation process, as corroborated by experimental and theoretical results collectively. This work provides a foundation for understanding the highly electronegative halogen grafting-induced surface local electric field and offers new insights for the future design of high-performance environmental purification materials.