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

Highlights: • Hierarchical Bi₂S₃/BiOCl microflowers with open hollow structures were achieved. • Bi-based heterostructures were constructed by a PVP-induced ion exchange method. • PVP amount determined the substitution degree and growth status of Bi₂S₃ nanoflakes. • The h-Bi₂S₃/BiOCl exhibited superior photocatalytic activity for CIP degradation. -- 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.