PVP-induced Bi2S3/BiOCl photocatalyst with open hollow structures for the removal of ciprofloxacin under visible-light irradiation

Abstract

Hierarchical Bi2S3/BiOCl microflowers with open hollow structures were synthesized under PVP-induced anion exchange process. Thioacetamide (TAA), an organic sulfidation agent, was used in the aqueous solution to perform surface substitution on the early-formed BiOCl spheres to outreach Bi2S3 nanoflakes. The amount of PVP molecules (PVP–K30/Bi = 2–20 wt%) controlled the reaction speed and determined the growth status of Bi2S3 nanoflakes on microsphere surface. More PVP-K30 feeding resulted in honeycomb-like heterostructures with abundant open hollow structures (h-Bi2S3/BiOCl), while less PVP introduction led to densely packed microspheres (d-Bi2S3/BiOCl). The h-Bi2S3/BiOCl microflowers possess high surface area and efficient visible-light harvesting to gain good utilization of photogenerated electron-holes for evolving enhanced photocatalytic activity. The removal efficiency of ciprofloxacin (CIP, a typical antibiotic) over h-Bi2S3/BiOCl can reach ∼70.0% under visible-light irradiation of 120 min, nearly 2 times higher than that of d-Bi2S3/BiOCl. The trapping results revealed valid active species of ·O2− and ·OH in the process of colorless CIP degradation, and the superior photocatalytic behavior and good cycling stability would benefit from the valid separation of photogenerated carriers over open hollow structures of Bi2S3/BiOCl microspheres.