Bismuth oxyiodide coupled with bismuth nanodots for enhanced photocatalytic bisphenol A degradation: synergistic effects and mechanistic insight

Fe-MOFs nanosheets for photo-Fenton degradation of carbamazepine

Iron(II)-based metal organic framework (Fe(II)-MOF) nanosheets have emerged as promising candidates for photo-Fenton catalysis. However, efficiently synthesizing Fe(II)-MOF nanosheets remains a significant challenge. Here, a bottom-up synthesis strategy is proposed to prepare two-dimensional Fe-MOF nanosheets (TFMN) with micrometer lateral dimensions and nanometer thickness, featuring Fe(II) as the metal nodes. The application of TFMN in the photo-Fenton degradation of carbamazepine (CBZ) demonstrates remarkable CBZ degradation performance and excellent efficiency across a wide range of pH values. The electron density and density of states are further calculated by density functional theory. Mechanism analysis identifies h+, •OH and •O2- as the predominant active species contributing to the catalytic oxidation process in the Vis/TFMN/H2O2 system.

Enhanced photocatalytic degradation of bisphenol A by magnetically separable bismuth oxyiodide magnetite nanocomposites under solar light irradiation

Bismuth oxyiodide/magnetite (BiOI/Fe₃O₄) nanocomposites were synthesized by a hydrothermal reaction. The synthesized BiOI/Fe₃O₄ was used to remove bisphenol A (BPA) from an aqueous solution under simulated solar light. The molar ratio of Bi to Fe in BiOI/Fe₃O₄ significantly affected BPA degradation, with the optimal BiOI/Fe₃O₄ (2:1) ratio in the composites. Optimum operating conditions such as a catalyst dosage of 1.0 g/L, an initial BPA concentration of 10 mg/L, and pH 7 gave a complete degradation of completely removed BPA within 30 min. The primary reactive oxygen species were verified as superoxide radicals and holes in oxidative species experiments. The magnetic BiOI/Fe₃O₄ could be easily collected from an aqueous solution by an external magnet, and its reusability was successfully demonstrated through recycling experiments. Furthermore, the derivatives in BiOI/Fe₃O₄ photocatalytic reactions were investigated, and a possible BPA degradation pathway was proposed. These results show that BiOI/Fe₃O₄ nanocomposites have great potential for BPA removal from water and wastewater treatment systems.

Spatiotemporally Synchronous Oxygen Self-Supply and Reactive Oxygen Species Production on Z-Scheme Heterostructures for Hypoxic Tumor Therapy

Photodynamic therapy (PDT) efficacy has been severely limited by oxygen (O₂ ) deficiency in tumors and the electron-hole separation inefficiency in photosensitizers, especially the long-range diffusion of O₂ toward photosensitizers during the PDT process. Herein, novel bismuth sulfide (Bi₂ S₃ )@bismuth (Bi) Z-scheme heterostructured nanorods (NRs) are designed to realize the spatiotemporally synchronous O₂ self-supply and production of reactive oxygen species for hypoxic tumor therapy. Both narrow-bandgap Bi₂ S₃ and Bi components can be excited by a near-infrared laser to generate abundant electrons and holes. The Z-scheme heterostructure endows Bi₂ S₃ @Bi NRs with an efficient electron-hole separation ability and potent redox potentials, where the hole on the valence band of Bi₂ S₃ can react with water to supply O₂ for the electron on the conduction band of Bi to produce reactive oxygen species. The Bi₂ S₃ @Bi NRs overcome the major obstacles of conventional photosensitizers during the PDT process and exhibit a promising phototherapeutic effect, supplying a new strategy for hypoxic tumor elimination.

Heterojunctions of halogen-doped carbon nitride nanosheets and BiOI for sunlight-driven water-splitting

A fluorine-doped, chlorine-intercalated carbon nitride (CNF-Cl) photocatalyst has been synthesized for simultaneous improvements in light harvesting capability along with suppression of charge recombination in bulk g-C3N4. The formation of heterojunctions of these CNF-Cl nanosheets with low bandgap, earth abundant bismuth oxyiodide (BiOI) was achieved, and the synthesized heterojunctions were tested as active photoanodes in photoelectrochemical water splitting experiments. BiOI/CNF-Cl heterojunctions exhibited extended light harvesting with a band-edge of 680 nm and generated photocurrent densities approaching 1.3 mA cm-2 under AM1.5 G one sun illumination. Scanning Kelvin probe force microscopy under optical bias showed a surface potential of 207 mV for the 50% BiOI/CNF-Cl nanocomposite, while pristine CNF-Cl and BiOI had surface photopotential values of 83 mV and 98 mV, respectively, which in turn, provided direct evidence of superior charge separation in the heterojunction blends. Enhanced charge carrier separation and improved light harvesting capability in BiOI/CNF-Cl hybrids were found to be the dominant factors in increased photocurrent, compared to the pristine constituent materials.

Visible light induced electron transfer from a semiconductor to an insulator enables efficient photocatalytic activity on insulator-based heterojunctions

Photogenerated electrons play a vital role in photocatalysis as they can induce the formation of radicals participating in the reaction or recombine with holes preventing them from the subsequent redox reaction. In this work, we explore an Earth-abundant insulator coupled with a semiconductor and construct insulator-semiconductor heterojunctions to effectively realize the efficient electron transfer from the semiconductor to the insulator and thus the enhanced charge carrier separation on the semiconductor. This result will challenge the traditional opinion that free electrons cannot be transferred onto insulators. Taking the BaCO3 insulator as a case study, the combined experimental and theoretical evidence indicates that the photogenerated electrons from the BiOI semiconductor could transfer directly to the BaCO3 insulator through a preformed electron delivery channel when they are coupled to form BaCO3/BiOI heterojunctions. The potential difference between the Bi layer of BiOI (5.03 eV) and the carbonate layer of BaCO3 (12.37 eV) would drive the transfer of excited electrons from Bi atoms across the energy barrier to the adjacent carbonate layer under visible light irradiation. Consequently, the free electrons on BaCO3 can be utilized to produce the oxidative radicals (˙OH, ˙O2- and 1O2) participating in the photocatalytic oxidation reaction. The in situ FT-IR spectra illustrate that the visible light induced active species in the heterojunctions could react with NO, leading to its oxidation to high valence state intermediates (NO+ and NO2+) first and then conversion to the final product of nitrates. This research offers new perspectives to explore insulator-based photocatalysts and unravel the gas-phase photocatalytic reaction mechanism.

Time-dependent synthesis of BiO2-x/Bi composites with efficient visible-light induced photocatalytic activity

A series of BiO_2-x/Bi nanocomposites were prepared via a time-dependent aqueous method, with the induction of lactic acid. The interaction of Bi³⁺ and C₃H₆O₃ in stock solution determined the formation of nonstoichiometric BiO_2-x as the precursor, subsequent reduction reaction at acid circumstance (pH = 3) produced combined composition of BiO_2-x nanosheets and Bi particles. Multiple valence states of Bi element (Bi⁰, Bi³⁺ and Bi⁵⁺) in the composite sample make it possible to manipulate the band structures of photocatalysts. The BiO_2-x/Bi composites with appropriate composition exhibited superior photocatalytic performance in the degradation of colorless bisphenol A (BPA) under visible-light irradiation. The O₂^- and OH radicals were detected as valid active species in the degradation process from ESR analysis. The photocatalytic mechanism over BiO_2-x/Bi composites was proposed on the consideration of electron-hole separation and the interfacial charge transfer.

Milling-Induced Synthesis of BiOCl1-x Brx Solid Solution and Their Adsorptive and Photocatalytic Performance

CH₃ COO(BiO) (denoted as BiOAc) is one of the most easily obtained bismuth compounds and was for the first time proposed by our group as an effective UV light photocatalyst. Herein, BiOCl_{1- x} Br_x (x refers to the feeding atomic ratio) were obtained using a facile solid state milling and subsequent water washing. More importantly, all of the as-prepared BiOCl_{1- x} Br_x possessed better visible light photocatalytic activity to the corresponding ones obtained by previously reported solution route. Especially at an optimal x value of 0.5, the solid solution showed the highest photodegradation efficiency (~100%) for rhodamine B (RhB) with a concentration of 30 mg L^-1 , whereas the degradation efficiency was only 63% over that obtained by solution route. Furthermore, the as-prepared BiOCl_0.5 Br_0.5 also exhibited excellent photodegradation activity for malachite green (MG). The superior photocatalytic performance of the as-prepared BiOCl_0.5 Br_0.5 could be attributed to its thinner sheetlike structures and highly exposed (001) facets, which enable effective separation of the photogenerated electrons and holes along the [001] direction. In addition, the as-prepared BiOCl_0.5 Br_0.5 revealed dramatic adsorption capacity for cationic dyes like MG, RhB and methylene violet (MV), as well as anion (Cr₂ O₇ )^2- owing to electrostatic interaction between cationic dyes and negatively charged surface of BiOCl_0.5 Br_0.5 , and positively charged surface in K₂ Cr₂ O₇ solution (pH ≈ 3).

Novel two-dimensional Bi4V2O11 nanosheets: controllable synthesis, characterization and insight into the band structure

Novel two-dimensional Bi₄V₂O₁₁ nanosheets were controllably prepared using a stable [Bi(EDTA)]⁻ complex, and their band structures were investigated as well.