One-Dimensional/Two-Dimensional\nCore–Shell-Structured\nBi<sub>2</sub>O<sub>4</sub>/BiO<sub>2–<i>x</i></sub> Heterojunction for Highly Efficient Broad Spectrum Light-Driven\nPhotocatalysis: Faster Interfacial Charge Transfer and Enhanced Molecular\nOxygen Activation Mechanism

Deliberate\ntuning of nanoparticles encapsulated with nanosheet\nshells can bring about fascinating photocatalytic properties because\nof the fast charge-transfer characteristics of a nanosized core–shell\nstructure. Herein, a novel core–shell-structured Bi₂O₄/BiO_2–<i>x</i> composite\nwas fabricated through a one-step hydrothermal method. The core–shell\nBi₂O₄/BiO_2–<i>x</i> composite presented distinct optical absorption property, including\nUV, visible, and near-infrared (NIR) light regions. Compared to Bi₂O₄ and BiO_2–<i>x</i>, the Bi₂O₄/BiO_2–<i>x</i> composite revealed improved broad spectrum light-responsive\nmolecular oxygen activation into ^•O₂^–, especially achieving ^•O₂^– generation under NIR light irradiation. The achievement\nthat enhanced broad spectrum light-activated molecular oxygen activation\ncould be ascribed to the faster electron transfer confirmed by the\nelectron spin resonance (ESR) spectra, photoluminescence (PL) spectra,\nphotoelectrochemical test, and quantitative analysis of ^•O₂^–. The strong interface effect of\nthe Bi₂O₄/BiO_2–<i>x</i> composite was confirmed by X-ray photoelectron spectroscopy\nanalysis. Density functional theory calculated results suggested that\nthe Bi₂O₄/BiO_2–<i>x</i> composite revealed increased density of states near the Fermi\nlevel, suggesting that it possessed higher carrier mobility as compared\nto Bi₂O₄ and BiO_2–<i>x</i>, contributing to the faster separation of photoinduced carriers\nand the generation of ^•O₂^–. Benefiting to the heterojunction, the Bi₂O₄/BiO_2–<i>x</i> composite showed improved\nphotocatalytic activity and anti-photocorrosion activity during rhodamine\nB (RhB) and ciprofloxacin (CIP) degradation with the irradiation of\nUV, visible, and NIR lights. Besides, the possible photocatalytic\nmechanism and transformation pathway of RhB and CIP degradation by\nthe Bi₂O₄/BiO_2–<i>x</i> composite were proposed by the analyses of the liquid chromatography-mass\nspectrometry. This study furnishes a new strategy for fabricating\nhigh-efficient and broad spectrum light-driven heterojunction photocatalysts\nfor environment purification.