One-Dimensional/Two-Dimensional Core–Shell-Structured Bi₂O₄/BiO_2–x Heterojunction for Highly Efficient Broad Spectrum Light-Driven Photocatalysis: Faster Interfacial Charge Transfer and Enhanced Molecular Oxygen Activation Mechanism

Abstract

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 Bi 2 O 4 /BiO 2−x composite was fabricated through a one-step hydrothermal method. The core−shell Bi 2 O 4 /BiO 2−x composite presented distinct optical absorption property, including UV, visible, and near-infrared (NIR) light regions. Compared to Bi 2 O 4 and BiO 2−x , the Bi 2 O 4 /BiO 2−x composite revealed improved broad spectrum light-responsive molecular oxygen activation into • O 2 − , especially achieving • O 2 − 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 • O 2 − . The strong interface effect of the Bi 2 O 4 /BiO 2−x composite was confirmed by X-ray photoelectron spectroscopy analysis. Density functional theory calculated results suggested that the Bi 2 O 4 /BiO 2−x composite revealed increased density of states near the Fermi level, suggesting that it possessed higher carrier mobility as compared to Bi 2 O 4 and BiO 2−x , contributing to the faster separation of photoinduced carriers and the generation of • O 2 − . Benefiting to the heterojunction, the Bi 2 O 4 /BiO 2−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 Bi 2 O 4 /BiO 2−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. KEYWORDS: core−shell, Bi 2 O 4 /BiO 2−x composite, anti-photocorrosion, near-infrared light, molecular oxygen activation, DFT study

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