One-Dimensional/Two-Dimensional Core-Shell-Structured Bi2O4/BiO2- x Heterojunction for Highly Efficient Broad Spectrum Light-Driven Photocatalysis: Faster Interfacial Charge Transfer and Enhanced Molecular Oxygen Activation Mechanism.

Deliberate tuning of nanoparticles encapsulated with nanosheet shells can bring about fascinating photocatalytic properties because of the fast charge-transfer characteristics of a nanosized core-shell structure. Herein, a novel core-shell-structured Bi2O4/BiO2- x composite was fabricated through a one-step hydrothermal method. The core-shell Bi2O4/BiO2- x composite presented distinct optical absorption property, including UV, visible, and near-infrared (NIR) light regions. Compared to Bi2O4 and BiO2- x, the Bi2O4/BiO2- x composite revealed improved broad spectrum light-responsive molecular oxygen activation into •O2-, especially achieving •O2- generation under NIR light irradiation. The achievement that enhanced broad spectrum light-activated molecular oxygen activation could be ascribed to the faster electron transfer confirmed by the electron spin resonance (ESR) spectra, photoluminescence (PL) spectra, photoelectrochemical test, and quantitative analysis of •O2-. The strong interface effect of the Bi2O4/BiO2- x composite was confirmed by X-ray photoelectron spectroscopy analysis. Density functional theory calculated results suggested that the Bi2O4/BiO2- x composite revealed increased density of states near the Fermi level, suggesting that it possessed higher carrier mobility as compared to Bi2O4 and BiO2- x, contributing to the faster separation of photoinduced carriers and the generation of •O2-. Benefiting to the heterojunction, the Bi2O4/BiO2- x composite showed improved photocatalytic activity and anti-photocorrosion activity during rhodamine B (RhB) and ciprofloxacin (CIP) degradation with the irradiation of UV, visible, and NIR lights. Besides, the possible photocatalytic mechanism and transformation pathway of RhB and CIP degradation by the Bi2O4/BiO2- x composite were proposed by the analyses of the liquid chromatography-mass spectrometry. This study furnishes a new strategy for fabricating high-efficient and broad spectrum light-driven heterojunction photocatalysts for environment purification.