Efficient Proton Conductor Based on Bismuth Oxide Clusters and Polyoxometalates

Developing new solid-state electrolyte materials for improving the proton conductivity remains an important challenge. Herein, a novel two-dimensional layered solid-state proton conductor Bi2O2-SiW12 nanocomposite, based on silicotungstic acid (H4SiW12O40) and Bi(NO3)3·5H2O, was synthesized and characterized. The composite consists of a layered cation framework [Bi2O2]2+ and interlayer-embedded counteranionic [SiW12O40]4-, which forms continuous hydrogen bond (O-H···O) networks through the interaction of adjacent oxygen atoms on the surface of the [Bi2O2]2+ and oxygen atoms of the H4SiW12O40. Facile proton transfer along these pathways endows the Bi2O2-SiW12 (30:1) nanocomposite with an excellent proton conductivity of 3.61 mS cm-1 at 90 °C and 95% relative humidity, indicating that the nanocomposite has good prospects as a highly efficient proton conductor.

Screen-printed p-n BiOCl/BiFeO3 heterojunctions for efficient photocatalytic degradation of Rhodamine B

Colloidal-free screen-printed p-n BiOCl/BiFeO3 heterojunctions are successfully synthesized to achieve photocatalytic degradation of Rhodamine B (RhB) using visible light (λ ≥ 400 nm). The crystalline structure of dense BiOCl nanosheets self-assembled with impressive aspect ratio atop BFO powders is confirmed by XRD, Raman and TEM measurements. Iron impurities inside these 10 ± 2 nm-thick BiOCl nanosheets increase visible light absorption. Fluorescent Rhodamine B (RhB) dye degradation is used to evaluate the photocatalytic performance of this unique heterojunction material. For optimal metal-enhanced RhB degradation, a few nanometers of platinum are deposited using the sputtering technique to act as a cocatalyst. This unique architecture yields an impressive 92% RhB degradation in only 150 min under visible light. Operating at near-neutral pH, the proposed approach also addresses the key issue of catalysis recovery, which remains one of the main drawbacks of current photocatalysis technologies.

Polymer-coated BiOCl nanosheets for safe and regioselective gastrointestinal X-ray imaging

Bismuth-based compounds are considered to be the best candidates for computed tomography (CT) imaging of gastrointestinal (GI) tract due to high X-ray absorption. Here, we report the introduction of polymer-coated bismuth oxychloride (BiOCl) nanosheets for highly efficient CT imaging in healthy mice and animal with colitis. We demonstrate simple, low cost and fast aqueous synthesis protocol which provides gram-quantity yield of chemically stable BiOCl nanosheets. The developed contrast gives 2.55-fold better CT enhancement compared to conventional contrast with negligible in vivo toxicity. As a major finding we report a regioselective CT imaging of GI tract by using nanoparticles coated with differentially charged polymers. Coating of nanoparticles with a positively charged polymer leads to their fast accumulation in small intestine, while the coating with negatively charged polymers stimulates prolonged stomach retention. We propose that this effect may be explained by a pH-controlled aggregation of nanoparticles in stomach. This feature may become the basis for advancement in clinical diagnosis of entire GI tract.

Optical and Photocatalytic Properties of Br-Doped BiOCl Nanosheets with Rich Oxygen Vacancies and Dominating {001} Facets

Crystal facet engineering and nonmetal doping are regarded as effective strategies for improving the separation of charge carriers and photocatalytic activity of semiconductor photocatalysts. In this paper, we developed a facial method for fabricating oxygen-deficient Br-doped BiOCl nanosheets with dominating {001} facets through a traditional hydrothermal reaction and explored the impact of the Br doping and specific facets on carrier separation and photocatalytic performance. The morphologies, structures, and optical and photocatalytic properties of the obtained products were characterized systematically. The BiOCl samples prepared by the hydrothermal reaction exhibited square-like shapes with dominating {001} facets. Photodeposition results indicated that photoinduced electrons preferred to transfer to {001} facets because of the strong internal static electric fields in BiOCl nanosheets with dominating {001} facets. Br doping not only contributed to the formation of impurity energy levels that could promote light absorption but introduced a large number of surface oxygen vacancies (VO) in BiOCl photocatalysts, which was beneficial for photocatalytic performance. Moreover, the photocatalytic activities of these products under visible light were tested by degradation of rhodamine B (RhB). Because of the synergistic effect of the dominating {001} facets, Br doping, and rich VO, oxygen-deficient Br-doped BiOCl nanosheets exhibited improved carrier separation, visible light absorption, and photocatalytic efficiency.

Advances in facet-dependent photocatalytic properties of BiOCl catalyst for environmental remediation

Bismuth chloride oxide (BiOCl) is a typical V-VI-VII ternary oxide material, which is one of the widely studied metal oxides due to its unique surface, electronic and photocatalytic properties. However, the broad bandgap and the large number of photogenerated electron-hole pair complexes of BiOCl limit its photocatalytic efficiency. Since the photocatalytic performance of BiOCl is highly dependent on its exposed crystallographic facets, research attention has increasingly focused on the different structures and properties possessed by different crystallographic facets of BiOCl. This article reviews the basic principles of using different crystalline surfaces of BiOCl materials to enhance photocatalytic activity, summarizes the applications of BiOCl single-crystal catalysts and composite catalysts in the environmental field, and provides an outlook on the challenges and new research directions for future development in this emerging frontier area. It is hoped that the crystalline surface-related photocatalysis of BiOCl can be used to provide new guidance for the rational design of novel catalysts for various energy and environment-related applications.

Facile fabrication of BiOCl nanoplates with high exposure {001} facets for efficient photocatalytic degradation of nitro explosives

BiOCl nanoplates with highly exposed {001} facets displayed excellent photocatalytic activity on the degradation of nitro explosives.

Control of Photocarrier Separation and Recombination at Bismuth Oxyhalide Interface for Nitrogen Fixation

Developing high-efficiency photocatalysts for clean energy generation is a grand challenge, which requires simultaneously steering photocarrier dynamics and chemical activity for a specific reaction. To this end, here for the first time, we explore the real-time photocarrier transport property and catalytic mechanism of nitrogen reduction reaction (NRR) at the interface of bismuth oxyhalides (BiOX, X = Cl, Br, and I), an inexpensive and green semiconductor. By time-dependent ab initio non-adiabatic molecular dynamics simulations, we show that the separation and recombination processes of excited carriers as well as the catalytic activity can be concurrently optimized by precise band structure engineering. The exact influence of impurity states and heterojunction on the reduction power and lifetime of photogenerated carriers, light absorbance, and NRR activity/selectivity of BiOX are clearly unveiled, to provide essential physical insights for improving the photocatalytic efficiency of semiconductors for practical solar energy conversion and hydrogen fuel storage.

Novel B-doped BiOCl nanosheets with exposed (001) facets and photocatalytic mechanism of enhanced degradation efficiency for organic pollutants

Novel B doped BiOCl nanocrystals (B-BiOCl) with exposed (001) facets were fabricated via a facile solvothermal route. The characterization methods of XRD, BET, SEM, TEM, UV-vis DRS, PL, EIS, ESR and photocurrent measurement were performed to investigate the physicochemical properties of the B-BiOCl samples. The results indicated that doping B into BiOCl could regulate and control the growth of (001) crystal facet, increase the specific surface areas and enhance the efficiency of charge separation. Hence, the optimal B_1.0-BiOCl (atomic ratio of Bi:O:Cl: B is around 27.41: 28.27:25.43:3.55) exhibited significant promoting effect for the degradation of phenol, bisphenol A and rhodamine B than that of pure of BiOCl. The results of radical capturing and ESR analysis confirmed that the O₂^- radicals played a fatal role in the degradation of organic pollutants. This work could be expected to offer a new insight into design and synthesis of highly efficient photocatalyst with specific exposed facets by doping non-metallic elements.

Soluble Graphene Nanosheets for the Sunlight-Induced Photodegradation of the Mixture of Dyes and its Environmental Assessment

Currently, the air and water pollutions are presenting the most serious global concerns. Despite the well known tremendous efforts, it could be a promising sustainability if the black carbon (BC) soot can be utilized for the practical and sustainable applications. For this, the almost complete aqueous phase photodegradation of the three well-known organic pollutant dyes as crystal violet (CV); rhodamine B (RhB); methylene blue (MB) and their mixture (CV + RhB + MB), by using water-soluble graphene nanosheets (wsGNS) isolated from the BC soot under the influence of natural sunlight is described. The plausible mechanism behind the photocatalytic degradation of dyes and their mixture has been critically analyzed via the trapping of active species and structural analysis of photodegraded products. The impact of diverse interfering ions like Ca2+, Fe3+, SO42-, HPO42-, NO3-, and Cl- on the photodegradation efficiency of wsGNS was also investigated. Importantly, the environmental assessment of the whole process has been evaluated towards the growth of wheat plants using the treated wastewater. The initial studies for the fifteen days confirmed that growth of wheat plants was almost the same in the photodegraded wastewater as being noticed in the control sample, while in case of dyes contaminated water it showed the retarded growth. Using the natural sunlight, the overall sustainability of the presented work holds the potential for the utilization of pollutant soot in real-practical applications related to the wastewater remediation and further the practical uses of treated water.

Application of BiOX Photocatalysts in Remediation of Persistent Organic Pollutants

Bismuth oxyhalides have recently gained attention for their promise as photocatalysts. Due to their layered structure, these materials present fascinating and highly desirable physicochemical properties including visible light photocatalytic capability and improved charge separation. While bismuth oxyhalides have been rigorously evaluated for the photocatalytic degradation of dyes and many synthesis strategies have been employed to enhance this property, relatively little work has been done to test them against pharmaceuticals and pesticides. These persistent organic pollutants are identified as emerging concerns by the EPA and effective strategies must be developed to combat them. Here, we review recent work directed at characterizing the nature of the interactions between bismuth oxyhalides and persistent organic pollutants using techniques including LC-MS/MS for the determination of photocatalytic degradation intermediates and radical scavenging to determine active species during photocatalytic degradation. The reported investigations indicate that the high activity of bismuth oxyhalides for the breakdown of persistent organic pollutants from water can be largely attributed to the strong oxidizing power of electron holes in the valence band. Unlike conventional catalysts like TiO2, these catalysts can also function in ambient solar conditions. This suggests a much wider potential use for these materials as green catalysts for industrial photocatalytic transformation, particularly in flow chemistry applications.

One dimensional hierarchical BiOCl microrods: their synthesis and their photocatalytic performance

One dimensional hierarchical BiOCl microrods are controlled synthesized via hydrothermal method using sodium citrate as structure-agent. These hierarchical BiOCl architectures exhibit outstanding photocatalytic activity for degrading organic dyes and phenol.

Controllable synthesis and photoreduction performance towards Cr(vi) of BiOCl microrods with exposed (110) crystal facets

BiOCl microrod exposed (110) facets was synthesized via a simple hydrothermal method using sodium citrate as capping agent. It exhibits outstanding photoreduction performance towards Cr(vi) at neutral and acid condition.

Constructing Bi24O31Cl10/BiOCl heterojunction via a simple thermal annealing route for achieving enhanced photocatalytic activity and selectivity

This work reports on the construction of a Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction via a simple thermal annealing method. The X-ray diffraction (XRD) results indicated that the phase transformation from BiOCl to Bi₂₄O₃₁Cl₁₀ could be realized during the thermal annealing process. The high-resolution transmission electron microscopy (HRTEM) images, X-ray photoelectron spectroscopy (XPS) binding energy shifts, Raman spectra and Fouier transform infrared spectroscopy (FT-IR) spectra confirmed the formation of the Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction. The obtained Bi₂₄O₃₁Cl₁₀/BiOCl photocatalyst showed excellent conversion efficiency and selectivity toward photocatalytic conversion of benzyl alcohol to benzaldehyde under visible light irradiation. The radical scavengers and electron spin resonance (ESR) results suggested that the photogenerated holes were the dominant reactive species responsible for the photocatalytic oxidation of benzyl alcohol and superoxide radicals were not involved in the photocatalytic process. The in-situ generation of Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction may own superior interfacial contact than the two-step synthesized heterojunctions, which promotes the transfer of photogenerated charge carriers and is favorable for excellent photocatalytic activities.

Facile hydrothermal synthesis and improved photocatalytic activities of Zn2+ doped Bi2MoO6 nanosheets

A novel sheet-like Zn²⁺ doped Bi₂MoO₆ photocatalyst with excellent UV-visible-light induced photocatalytic ability was successfully fabricated through a facile hydrothermal synthesis strategy.

Novel nanoparticle-assembled Bi12GeO20 hierarchical structures: facile hydrothermal synthesis and excellent photocatalytic activity

Novel nanoparticle-assembled Bi₁₂GeO₂₀ hierarchical structures with excellent UV-visible light driven photocatalytic performance have been successfully prepared via a facile hydrothermal route.

Mild synthesis of {001} facet predominated Bi2O2CO3 clusters with outstanding simulated sunlight photocatalytic activities

Bi₂O₂CO₃ clusters built up of ultrathin nanosheets with predominated {001} facets were facilely synthesized via a template-free hydrothermal strategy at a mild temperature of 60 °C and exhibit excellent photocatalytic activity.

Controlled exfoliation of monodispersed MoS2 layered nanostructures by a ligand-assisted hydrothermal approach for the realization of ultrafast degradation of an organic pollutant

Molybdenum disulfide (MoS₂) layered nanosheets were synthesized by the hydrothermal method.

Enhanced photocatalytic activity of Bi25FeO40–Bi2WO6 heterostructures based on the rational design of the heterojunction interface

Based on the rational design of heterojunction interface, a novel and efficient Bi₂₅FeO₄₀–Bi₂WO₆ heterostructure photocatalyst was successfully constructed by a facile hydrothermal process.

A {110} facet predominated Bi6O6(OH)3(NO3)3·1.5H2O photocatalyst: selective hydrothermal synthesis and its superior photocatalytic activity for degradation of phenol

A Bi₆O₆(OH)₃(NO₃)₃·1.5H₂O photocatalyst with predominant {110} facets but a low BET surface area was selectively prepared. It exhibits high photocatalytic activities for degradation of phenol.

Controlled synthesis of thin BiOCl nanosheets with exposed {001} facets and enhanced photocatalytic activities

Thin BiOCl nanosheets with exposed {001} facets were synthesized by controlling the concentration of hydrochloric acid.

Novel Bi12ZnO20–Bi2WO6 heterostructures: facile synthesis and excellent visible-light-driven photocatalytic activities

Sillenite-type Bi₁₂ZnO₂₀–Bi₂WO₆ heterostructure were prepared via a controllable partial precipitate conversion strategy and they exhibited excellent visible-light-driven photocatalytic activity.

Synthesis and characterization of micro/nano-structured BaHPO4/Ba3(PO4)2/Ba5(PO4)3OH phases and their luminescence

Microspheres covered with microcuboids/nanorods and nanoparticles of BaHPO₄/Ba₃(PO₄)₂/Ba₅(PO₄)₃OH phases were synthesized by a hydrothermal method, using the citric acid as a surfactant at different pH values.

Epitaxial growth of silver chloride crystals on bismuth oxychloride

AgCl crystals precipitating on the surface of bismuth oxychloride crystals show orientation ordering with the (001)_BiOCl||(100)_AgCl.

Synthesis of a highly efficient BiOCl single-crystal nanodisk photocatalyst with exposing {001} facets

BiOCl is known as a highly efficient photocatalyst for degradation of pollutants. However, effective methods for fabricating BiOCl nanomaterials with well-defined facets are still lacking. In this work, a facile synthetic method was developed for the fabrication of BiOCl nanodisks with exposed {001} facets. The central feature of this approach was the use of water as the hydrolysis agent and ethylene glycol as the crystal growth inhibitor agent to tune the growth of BiOCl nanomaterial. With this approach, the size and shape of BiOCl nanostructures could be effectively tuned through adjusting the volume ratio of ethylene glycol/H2O. In addition, the mechanism of the crystal growth in this fabrication process was elucidated. The as-prepared BiOCl nanodisks with exposed {001} facets exhibited an excellent photocatalytic activity towards Rhodamine B degradation under both ultraviolet and visible light irradiations. These findings shed light on the deep understanding of formation mechanisms of BiOCl nanodisks and provide an efficient and facile method for the synthesis of high active photocatalyst.