BiOBr_0.75I_0.25/BiOIO₃ as a Novel Heterojunctional Photocatalyst with Superior Visible-Light-Driven Photocatalytic Activity in Removing Diverse Industrial Pollutants

A series of novel heterojunctional photocatalysts BiOBr_0.75I_0.25/BiOIO₃ were synthesized by a facile deposition–precipitation method for the first time. In contrast to pristine BiOIO₃, the photoabsorption of BiOBr_0.75I_0.25/BiOIO₃ composites in visible light region is greatly promoted. All the BiOBr_0.75I_0.25/BiOIO₃ composite photocatalysts exhibit highly enhanced photocatalytic activity in decomposing bisphenol A under visible light (λ > 420 nm) illumination, and the 20% BiOIO₃-BiOBr_0.75I_0.25 sample possesses the optimal photoreactivity, which is 7.4, and 3.3 times higher than those of pure BiOIO₃ and BiOBr_0.75I_0.25. Moreover, the 20% BiOIO₃-BiOBr_0.75I_0.25 sample displays superior photocatalytic performance against diverse industrial contaminants and pharmaceuticals, including methyl orange, phenol, 2,4-dichlorophenol, chlortetracycline hydrochloride, and tetracycline hydrochloride. The enhancement of phototcatalytic activity is ascribed to the profoundly promoted transfer and separation of photoexcited charge carriers, which is verified by transient photocurrent response and photoluminescence emission. In addition, the photocatalytic mechanism over composite photocatalyst under visible light irradiation is systematically investigated by active species trapping experiment and •OH quantification experiment. This work may provide a new hint for fabrication of high-performance heterojunctions by combining the narrow-band gap and wide-band gap semiconductors

Multifunctional Bi₂O₂(OH)(NO₃) Nanosheets with {001} Active Exposing Facets: Efficient Photocatalysis, Dye-Sensitization, and Piezoelectric-Catalysis

Exploration for multiresponsive catalytic materials and synthesis of highly active exposing crystal facets are challenging subjects for catalysis research. In this work, well-defined Bi₂O₂(OH)­(NO₃) nanosheets (BON-S) with a dominantly exposed {001} active facet were synthesized by a sodium-dodecyl-benzenesulfonate-assisted (SDBS-assisted) soft-chemical route. BON-S presents far superior photocatalytic activity compared to bulk materials as well as a universal performance for degradation of contaminants and antibiotics under UV light. The profoundly enhanced photocatalytic activity basically stems from the largely shortened diffusion pathway of photogenerated electrons (e^–) and holes (h⁺), favoring their migration from bulk to the surface of the catalyst under the internal electric field between [Bi₂O₂(OH)]⁺ and NO₃^– layers along the [001] direction. The photocatalytic active species production rates of BON-S are determined to be 3.14 μmol L^–1 min^–1 for superoxide radicals (^•O₂^–) and 0.03 μmol L^–1 min^–1 for hydroxyl radicals (^•OH). BON-S also shows an enhanced visible-light-responsive dye-sensitization degradation activity with Rhodamine B (RhB) as a sensitized medium to provide photoinduced e^–. Moreover, for the first time we unearth that Bi₂O₂(OH)­(NO₃) demonstrates an ultrasonic-assisted piezoelectric-catalytic performance for decomposition of methyl orange, bisphenol A, and tetracycline hydrochloride, and ^•OH dominates the piezoelectric-catalytic process with an evolution rate of 7.13 μmol L^–1 h^–1, which far exceeds the photocatalytically induced one. This study may cast new inspiration on developing a new microstructure-design strategy for high photocatalytic/dye-sensitization performance, and furnishes a novel piezoelectric-catalytic material for environmental applications

Homogeneous {001}-BiOBr/Bi Heterojunctions: Facile Controllable Synthesis and Morphology-Dependent Photocatalytic Activity

The homogeneous BiOBr/Bi heterojunctions photocatalyst was synthesized from {001} facet dominated BiOBr flakes via a PVP-assisted in situ reduction reaction at room temperature. The high {001} facet exposure of BiOBr could induce the homogeneous distribution of metallic Bi on the surface of BiOBr. The introduction of PVP not only effectively protected the uniform structure but also largely promoted the photocatalysis properties. Compared to the bare BiOBr, an obviously enhanced photochemical performance was achieved over the homogeneous BiOBr/Bi pertaining to methyl orange (MO) degradation and photocurrent generation. The highly enhanced photocatalytic activity can be attributed not only to the surface plasmon resonance effect and efficient separation of electron–hole pairs by the metallic Bi but also to its uniform and regular structure. The present work provided a new approach to the development of attractive bismuth-based-photocatalysts/metallic Bi heterostructures with controllable structures and photocatalytic performance

In Situ Composition-Transforming Fabrication of BiOI/BiOIO₃ Heterostructure: Semiconductor p–n Junction and Dominantly Exposed Reactive Facets

We for the first time disclose the integrated effects of a semiconductor p–n heterojunction and dominantly exposed reactive facets that are enabled in a facile way. Unlike most of the reported semiconductor heterojunctions that are constructed by compositing the individual components, in this work, we report the composition–transformation fabricating BiOI/BiOIO₃ heterostructure via an in situ reduction route by using thiourea as the reducing agent. This reducing process enables BiOIO₃ dominant exposure of the {010} reactive facet, and the exposed percentage can be effectively tuned by monocontrolling the thiourea concentration. The photocatalysis and photoelectrochemical properties of samples are assessed by surveying the decomposition of methyl blue (MB) and photocurrent generation under simulated solar light or visible light illumination. The heterostructured BiOI/BiOIO₃ nanocomposites unfold drastically strengthened photoreactivity, in which the MB degradation rate is over 85% for 1 h irradiation, and the photocurrent density rises more than 3 times higher than the pristine sample. This enhancement should be ascribed to the formation of a steady p–n junction between the n-type BiOIO₃ and p-type BiOI as well as dominantly exposed reactive facets. Separation and transfer of photoinduced charges are thereby greatly boosted as verified by the electrochemical and photoelectrochemical results. This work paves a novel way for fabrication of semiconductor p–n junction via composition transformation and furnishes a new perspective into the designing of crystal reactive facet

Ba₂AsGaSe₅: A New Quaternary Selenide with the Novel [AsGaSe₅]^4– Cluster and Interesting Photocatalytic Properties

The new zero-dimensional selenide Ba₂AsGaSe₅ was synthesized via a solid-state reaction at 900 °C. It belongs to the orthorhombic space group <i>Pnma</i> with <i>a</i> = 12.632(3) Å, <i>b</i> = 8.9726(18) Å, <i>c</i> = 9.2029(18) Å, and <i>Z</i> = 4. In the structure, the As atom adopts trigonal-pyramidal coordination owing to the stereochemically active 4s² lone pair electrons and the Ga atom is tetrahedrally coordinated with four Se atoms. The AsSe₃ trigonal pyramids share edges with GaSe₄ tetrahedra to form novel [AsGaSe₅]^4– clusters, which are further separated from each other by Ba²⁺ cations. The optical band gap was determined as 1.39 eV according to UV–vis–NIR diffuse reflectance spectroscopy. Interestingly, the photocatalytic behavior investigated by decomposing rhodamine B indicates that the compound displays a 6.5 times higher photocatalytic activity than does P25

Achieving Enhanced UV and Visible Light Photocatalytic Activity for Ternary Ag/AgBr/BiOIO₃: Decomposition for Diverse Industrial Contaminants with Distinct Mechanisms and Complete Mineralization Ability

Heterojunction fabrication and noble metal deposition serving as efficacious means for promoting photocatalytic activity attract huge interests. Here, a series of ternary Ag/AgBr/BiOIO₃ composite photocatalysts that integrate the above two aspects are prepared by in situ crystallization of Ag/AgBr on BiOIO₃. The photocatalytic performance is first investigated by degrading MO with visible light and UV light irradiation. The results indicate that Ag/AgBr/BiOIO₃ composites present strengthened photocatalytic activity compared with BiOIO₃ and Ag/AgBr under both light sources. Distinct activity enhancement levels corresponding to different mechanisms with UV and visible light illumination are uncovered, which are closely related to the applied light source. The universal catalytic activity of Ag/AgBr/BiOIO₃ is surveyed by decomposition of diverse antibiotics and phenols, including tetracycline hydrochloride, chlortetracycline hydrochloride, bisphenol A, phenol, and 2,4-dichlorophenol which discloses that this ternary heterojunction photocatalyst demonstrates unselective catalytic activity with universality. Importantly, Ag/AgBr/BiOIO₃ displays a strong mineralization ability, completely decomposing BPA into CO₂ and H₂O. This work affords a new reference for designing heterojunction photocatalyst with multiple advantageous effect and powerful capability for environmental purification

Easily and Synchronously Ameliorating Charge Separation and Band Energy Level in Porous g‑C₃N₄ for Boosting Photooxidation and Photoreduction Ability

Metal-free graphitic carbon nitride (g-C₃N₄) shows benign photocatalytic abilities concerning contaminant decomposition and hydrogen evolution under visible light irradiation. Developing facile modification tactics for promoted activity of g-C₃N₄ has always been desirable and worth pursuing. Herein, we report the integration of multiple (three-in-one) advantageous effects in g-C₃N₄ photocatalyst by a simple co-pyrolyzation of co-precursors melamine and NH₄HCO₃. This strategy utilizing NH₄HCO₃ as a bubble soft template not only endows g-C₃N₄ with porous structure with enhanced specific surface area, but also renders highly promoted separation and transfer of charge carriers and up-shifted conduction band. Given these benefits, the modified g-C₃N₄ unfolds remarkably improved photocatalytic performance toward RhB degradation, NO removal, and hydrogen evolution. Additionally, the exploration on active radicals has also corroborated the ameliorated band structure and illustrates the photocatalytic mechanism. Our present work may open up a new avenue for ameliorating the photocatalytic property of g-C₃N₄ and also further our understanding of design of high-performance photoelectric materials

A General and Facile Approach to Heterostructured Core/Shell BiVO₄/BiOI <i>p–n</i> Junction: Room-Temperature <i>in Situ</i> Assembly and Highly Boosted Visible-Light Photocatalysis

Development of core/shell heterostructures and semiconductor <i>p–n</i> junctions is of great concern for environmental and energy applications. Herein, we develop a facile <i>in situ</i> deposition route for fabrication of a BiVO₄/BiOI composite integrating both the core/shell heterostructure and semiconductor <i>p–n</i> junction at room temperature. In the BiVO₄/BiOI core/shell heterostructure, the BiOI nanosheets are evenly assembled on the surface of the BiVO₄ cores. The photocatalytic performance is evaluated by monitoring the degradation of the dye model Rhodamine B (RhB), colorless contaminant phenol, and photocurrent generation under visible-light irradiation. The heterostructured BiVO₄/BiOI core/shell photocatalyst shows drastically enhanced photocatalysis properties compared to the pristine BiVO₄ and BiOI. This remarkable enhancement is attributed to the intimate interfacial interactions derived from the core/shell heterostructure and formation of the <i>p–n </i>junction between the <i>p</i>-type BiOI and <i>n</i>-type BiVO₄. Separation and transfer of photogenerated electron–hole pairs are hence greatly facilitated, thereby resulting in the improved photocatalytic performance as confirmed by electrochemical, photoelectrochemical, radicals trapping, and superoxide radical (•O₂^–) quantification results. Moreover, the core/shell BiVO₄/BiOI also displays high photochemical stability. This work sheds new light on the construction of high-performance photocatalysts with core/shell heterostructures and matchable band structures in a simple and efficient way

Deep-Ultraviolet Nonlinear Optical Materials: Na₂Be₄B₄O₁₁ and LiNa₅Be₁₂B₁₂O₃₃

Deep-UV coherent light generated by nonlinear optical (NLO) materials possesses highly important applications in photonic technologies. Beryllium borates comprising anionic planar layers have been shown to be the most promising deep UV NLO materials. Here, two novel NLO beryllium borates Na₂Be₄B₄O₁₁ and LiNa₅Be₁₂B₁₂O₃₃ have been developed through cationic structural engineering. The most closely arranged [Be₂BO₅]_∞ planar layers, connected by the flexible [B₂O₅] groups, have been found in their structures. This structural regulation strategy successfully resulted in the largest second harmonic generation (SHG) effects in the layered beryllium borates, which is ∼1.3 and 1.4 times that of KDP for Na₂Be₄B₄O₁₁ and LiNa₅Be₁₂B₁₂O₃₃, respectively. The deep-UV optical transmittance spectra based on single crystals indicated their short-wavelength cut-offs are down to ∼170 nm. These results demonstrated that Na₂Be₄B₄O₁₁ and LiNa₅Be₁₂B₁₂O₃₃ possess very promising application as deep-UV NLO crystals

Y(IO₃)₃ as a Novel Photocatalyst: Synthesis, Characterization, and Highly Efficient Photocatalytic Activity

Nonbonding layer-structured Y­(IO₃)₃ was successfully prepared by a simple hydrothermal route and investigated as a novel photocatalyst for the first time. Its crystal structure was characterized by X-ray diffraction, high-resolution transmission electron microscopy, and scanning electron microscopy. The optical absorption edge and band gap of Y­(IO₃)₃ have been determined by UV–vis diffuse reflectance spectra. Theoretical calculations of the electronic structure of Y­(IO₃)₃ confirmed its direct optical transition property near the absorption edge region, and the orbital components of the conduction band and valence band (VB) were also analyzed. The photocatalytic performance of Y­(IO₃)₃ was evaluated by photooxidative decomposition of rhodamine B under ultraviolet light irradiation. It demonstrated that Y­(IO₃)₃ exhibits highly efficient photocatalytic activity, which is much better than those of commercial TiO₂ (P25) and important UV photocatalysts BiOCl and BiIO₄. The origin of the excellent photocatalytic performance of Y­(IO₃)₃ was investigated by electron spin resonance and terephthalic acid photoluminescence techniques. The results revealed that the highly strong photooxidation ability that resulted from its very positive VB position should be responsible for the excellent photocatalytic performance