Empowering solar-driven degradation: advancements in lanthanum-doped Bi2O3/g-C3N4 heterojunctions for high-performance photocatalysis

Abstract

The lanthanum-doped bismuth oxide (La-Bi₂O₃) anchored g-C₃N₄ (g-CN) heterojunction-based photocatalyst (La-Bi₂O₃/g-CN) has been designed with visible-light activation and prompt interfacial charge transfer. Pure and La-doped bismuth oxide nanomaterials were prepared via a hydrothermal method, while g-CN was obtained by thermal polymerization of melamine. The doped material was anchored over the 2D g-CN to make the heterojunction (Type-II) by prolonged ultrasonication. As-synthesized samples were characterized via XRD, FT-IR, TGA, SEM, TEM, UV-vis, PL spectroscopy, Mott–Schottky plots, EIS, and photocurrent response to investigate the structural features, thermal endurance, topography, optical response, and interfacial charge mobility. The photocatalyst's efficiency was determined by degrading methylene blue (MB) and ciprofloxacin (CPF) as representative pollutants under visible-light irradiation. The heterojunction material displayed promising photocatalytic activity compared to its pure counterparts and photodegraded 97% of MB and 84% of CPF, following 1st-order kinetics. This remarkable efficiency was due to the band structure tuning of bismuth oxide by La-doping and architecting heterojunction La-Bi₂O₃/g-CN with g-CN, which promotes the interfacial charge transfer, delaying recombination of the separated charges. The scavenging results revealed that the hydroxide radicals (HO˙) and holes (h⁺) correspondingly facilitated the MB and CPF degradation.