Layered nanostructured ferroelectric perovskite Bi5FeTi3O15 for visible light photodegradation of antibiotics

Abstract

Solar photocatalytic degradation of organic pollutants is a promising cheap way for waste water disinfection. There are two weaknesses in the photocatalytic process: inadequate utilization of light energy and fast charge recombination. Effective surface–interface control over morphological tailoring can provide a large surface area, and prevent quick recombination of carriers, resulting in efficiency enhancement. In this work, we focus on enhancing the critical elemental photocatalytic steps via innovation in material chemistry. A diverse series of nanostructured ferroelectric Bi₅FeTi₃O₁₅ with enhanced charge separation originating from their ferroelectric nature were synthesized by varying the pH value during the hydrothermal synthesis. Their photocatalytic properties can also be tailored to best fit the degradation of hazardous antibiotics (e.g. tetracycline) in aqueous solution, including light absorption in the solar spectrum, charge separation, structure and surface charge for effective mass transport. The photodegradation of tetracycline follows first-order kinetics, and a significantly enhanced photooxidation performance is observed for 3D flower-like Bi₅FeTi₃O₁₅ with a degradation rate constant of 1.97 × 10⁻¹ min⁻¹, much faster than that reported in the literature for Fe-based visible light active photocatalysts towards tetracycline degradation. Density functional theory calculations indicate that the higher electron densities in [Bi₃FeTi₃O₁₃]²⁻ layers can favor the transport of photogenerated electrons and holes in alternate layers, promoting a longer charge carrier lifetime from 3.4 ns to 7.1 ns, as revealed by time-resolved photoluminescence spectra. The photodegradation mechanism is supported by theoretical calculation and experimentally identified by free radical and spin trapping experiments, LC-MS, and reduced total organic carbon analysis with approximately 94.88% removal, all of which testify to the complete mineralization of the antibiotics.