Cs3Bi2Br9/BiOBr S-scheme heterojunction for selective oxidation of benzylic C-H bonds

Converting hydrocarbons into aldehydes in a green and environmentally benign way is of great signif-icance in fine chemistry.In this work,all-inorganic Cs3Bi2Br9 perovskite nanoparticles were uniformly loaded on BiOBr nanosheets via an in-situ growth method,which can selectivity photoactivate aromatic C(sp3)-H bond of toluene to generate benzaldehyde.According to the in-situ X-ray photoelectron spec-troscopy characterization,the photogenerated electrons of BiOBr transfer to Cs3Bi2Br9 enforced by the in-ternal electric field under light irradiation,resulting in S-scheme heterojunction.Furthermore,theoretical calculations indicate that toluene molecules are inclined to adsorb on the BiOBr surface,subsequently in-volving the oxidation reaction to generate benzyl radical(PhCH2·)by using the energetic holes of BiOBr,while the remaining photoinduced electrons in the conduction band(CB)of Cs3Bi2Br9 with powerful reduction ability reduce O2 into·O2-,which is the vital oxidative active species working on toluene selective oxidation process.Such an unexceptionable charge carrier utilization mode and tendentious ad-sorption behavior of reactants contribute to the optimized Cs3Bi2Br9/BiOBr heterojunction with excellent photocatalytic performance,achieving a maximum of 22.5％toluene conversion and 96.2％selectivity to-wards benzaldehyde formation.This work provides a rational photocatalyst heterojunction construction protocol for the selective oxidation of saturated aromatic C-H bonds.     

Acoustooptic Properties of Cs3Bi2I9 Crystals

Cs₃Bi₂I₉ crystals were grown, and their longitudinal-wave acoustooptic properties were studied. The crystals were found to possess a large acoustooptic figure of merit and photoelastic constants.     

Biochar decorated Bi4O5Br2/g-C3N4 S-scheme heterojunction with enhanced photocatalytic activity for Norfloxacin degradation

In this work,a novel biochar decorated Bi4O5Br2/g-C3N4 S-scheme heterojunction was successfully pre-pared for Norfloxacin(NOR)degradation,and it was found that the 5％-Bi4O5Br2/g-C3N4/C heterojunction exhibited the excellent photocatalytic degradation activity toward NOR,degrading 92.5％of NOR within 72 min under visible light irradiation.The effects of pH,dosage,and concentration of the NOR on the photocatalytic activity were also systematically investigated.The mechanism studies revealed that the active species like hole(h+),hydroxyl radical(·OH),and superoxide radical(·O2-)play a predominant role in the NOR degradation,and the enhanced removal rate of Bi4O5Br2/g-C3N4/C heterojunction can be attributed to the synergistic effect of adsorption and photocatalytic process.In addition,an S-scheme transfer channel in the interface of the Bi4O5Br2/g-C3N4/C heterojunction is proposed,which can effec-tively improve the separation of the photogenerated carriers and enhance the photocatalytic performance.This research provides inspiration for designing S-scheme heterojunction for wastewater treatment.     

空间限域生长CsBi3I10无铅钙钛矿用于高质量、高灵敏度和高稳定性近红外光电探测器

因具有较高的耐热性和较长的电子扩散长度,无铅钙钛矿Cs Bi3I10备受关注.然而,由于二维结构Cs Bi3I(10)钙钛矿的表面极其粗糙且存在大量针孔,导致Cs Bi3I10钙钛矿器件性能不高.本文报道了一种利用空间限域生长(SCG)获得高平滑度、高结晶度和致密CsBi3I10钙钛矿薄膜的方法.相对于传统旋涂法制备的...     

Cs2TiI6:A potential lead-free all-inorganic perovskite material for ultrahigh-performance photovoltaic cells and alpha-particle detection

The lead contamination and long-term stability are the two important problems limiting the commercialization of organic-inorganic lead halide perovskites.In thi...     

TiO2 electron transport bilayer for all-inorganic perovskite photodetectors with remarkably improved UV stability toward imaging applications

High ultraviolet(UV)stability and low dark current(Idark)are necessary for high-quality perovskite photodetectors(PDs).TiO2 thin film is known as effective electron-transport-layer(ETL)for perovskite devices.However,common spin-coated TiO2 ETLs endow many surface defects and have strong UV pho-tocatalytic effect to decompose perovskite materials,resulting in inferior stability of devices.In this work,TiO2 bilayer film(Bi-TiO2)has been fabricated by combining spin-coating and atomic-layer-deposition process and its positive effects on UV stability and Idark of Cs2AgBiBr6-based PDs have been revealed for the first time.It is demonstrated that Bi-TiO2 possesses fewer surface defects and smoother morphology with type Ⅱ band alignment,which is beneficial to suppress photocatalytic activity of TiO2 and reduce carrier recombination at the interface.After accelerated strong UV aging treatment,the PD with Bi-TiO2 maintains excellent performance,whereas the PD with spin-coated TiO2 film dramatically deteriorate with on-off ratio drops from～102 to～2.Besides,the Idark of PD remarkably decreases from～10-8 A to～10-10 A after bilayer optimization.Furthermore,we have integrated the corresponding PDs into a self-built imaging system adopting diffuse reflection mode.This work suggests a feasible approach to fabricate TiO2/Cs2AgBiBr6-based PDs with remarkable UV tolerance for imaging applications.     

Novel Mo/Bi2MoO6/Bi3ClO4 heterojunction photocatalyst for ultra-deep desulfurization of thiophene under simulated sunlight irradiation

In the present work, a visible-light-driven Mo/Bi₂MoO₆/Bi₃ClO₄ heterojunction photocatalyst was fabricated via the Pechini sol–gel process. The type and amount of gelling agent, chelating agent and mole ratio of chelating agent to total metals were balanced to generate ultrafine nanoparticles. The Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite as a novel photocatalyst not only exhibited an excellent visible-light photocatalytic desulfurization performance of thiophene (~97%), but also had better photodesulfurization efficiency than Mo/Bi₂MoO₆ and Bi₃ClO₄ nanostructures. The ultra-deep photocatalytic desulfurization performance of the Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite can be attributed to the strong visible-light absorption, unique nanostructures, high separation and low recombination of electron–hole pairs due to the as-formed heterojunctions. Furthermore, a photocatalytic desulfurization mechanism was elucidated via radical trapping experiments, which revealed that the ^?O₂^? and ^?OH radicals play a key role in the photocatalytic desulfurization process.     

Dielectric relaxation in complex perovskite Ba(Bi1/2Ta1/2)O3

A new lead-free perovskite Ba(Bi_1/2Ta_1/2)O₃ was prepared by conventional ceramic fabrication technique at 1,200 °C/4 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. The crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm3m. EDAX and SEM studies were carried out in order to evaluate the quality and purity of the compound. Permittivity data showed a low temperature coefficient of capacitance (T _CC  < 4%) up to +125 °C. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. Electric modulus studies supported the hopping type of conduction in Ba(Bi_1/2Ta_1/2)O₃.     

Phase-transition temperatures and piezoelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2Li1/2)TiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics.

The phase-transition temperatures and piezoelectric properties of x(Bi(1/2)Na(1/2))TiO3-y(Bi(1/2)Li(1/2))TiO3-z(Bi(1/2)K(1/2))TiO3 [x + y + z = 1] (abbreviated as BNLKT100(y)-100(z)) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T(d), rhombohedraltetragonal phase transition temperature T(R-T), and dielectric-maximum temperature T(m) were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100(y)-100(z)) show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor k(33), piezoelectric constant d(33) and T(d) of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171 degrees C, and 0.590, 190 pC/N, and 115 degrees C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d(33), the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d(33) and T(d) of BNLKT4-28 were 135 pC/N and 218 degrees C, respectively. Moreover, this study revealed that the variation of T(d) is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

Construction of S-scheme heterojunction by doping Bi2WO6 into Bi2O3 for efficiently enhanced visible-light photocatalytic performance

Journal of Materials Science - The objective of this study was to construct the S-scheme Bi2WO6/α-Bi2O3 heterojunctions with high enhanced visible-light photocatalytic performance. The...     

Synthesis of TiO2/Bi2S3 heterojunction with a nuclear-shell structure and its high photocatalytic activity

TiO₂/Bi₂S₃ heterojunctions with a nuclear-shell structure were prepared by the coprecipitation method. The products were characterized by X-ray diffraction analysis, Raman spectra, transmission electron microscope images and energy dispersion X-ray spectra. Results showed that as-prepared Bi₂S₃ was urchin-like, made from many nanorods, and TiO₂/Bi₂S₃ heterojunctions have a similar nuclear-shell structure, with Bi₂S₃ as the shell and TiO₂ as the nuclear. The photocatalytic experiments performed under UV irradiation using methyl orange as the pollutant revealed that the photocatalytic activity of TiO₂ could be improved by introduction of an appropriate amount of Bi₂S₃. However, excessive amount of Bi₂S₃ would result in the decrease of photocatalytic activity of TiO₂. The relative mechanism was proposed.     

Construction of hierarchical nanostructured TiO2/Bi2MoO6 heterojunction for improved visible light photocatalysis

In this study, Bi2MoO6 hollow microspheres were modified by depositing TiO2 nanoparticles through a simple hydrothermal method. The prepared TiO2/Bi2MoO6 photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of the heterostructured catalysts was evaluated by degradation of methylene blue (MB) under visible-light irradiation (lambda>420 nm). The photocatalysts based on nanostructured Bi2MoO6 and TiO2 exhibit much higher photocatalytic activity than the single-phase Bi2MoO6 or TiO2 and the mechanical mixture of Bi2MoO6 and TiO2 for degradation of MB under the same conditions. The results reported in this study provide insight into constructing other heterostructured photocatalysts.     

Multiple heterojunction system of Bi2MoO6/WO3/Ag3PO4 with enhanced visible-light photocatalytic performance towards dye degradation

Multiple heterojunction system of Bi₂MoO₆/WO₃/Ag₃PO₄ was designed via constructing binary heterojunction Bi₂MoO₆/WO₃, followed by the deposition of nano-Ag₃PO₄ on the surface of Bi₂MoO₆/WO₃. Various techniques were employed to characterize the properties of the as-prepared catalytic system. In this study, the decomposition efficiency of C.I. reactive blue 19 (RB-19) was used as a measure of photocatalytic activity and the Bi₂MoO₆/WO₃/Ag₃PO₄ composite exceeded its stand-alone components (pristine Ag₃PO₄, WO₃/Ag₃PO₄ and Bi₂MoO₆/Ag₃PO₄) by 3.16 times, 2.63 times and 1.75 times, respectively. The photocatalytic tests implied that the construction of multiple heterojunction could achieve efficient separation of photo-generated electrons and holes. A possible photocatalytic mechanism for Bi₂MoO₆/WO₃/Ag₃PO₄ system was also proposed according to the results of trapping experiments.     

Phase-transition temperatures and piezoelectric properties of (Bi/sub 1/2/Li/sub 1/2/)TiO/sub 3/-(Bi/sub 1/2/K/sub 1/2/)TiO/sub 3/ lead-free ferroelectric ceramics

The phase-transition temperatures and piezoelectric properties of x(Bi_1/2Na_1/2)TiO_3-y(Bi_1/2Li_1/2)TiO_3-z(Bi_1/2K_1/2)TiO₃ [x + y + z = 1] (abbreviated as BNLKT100y-100z) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T_d, rhombohedral-tetragonal phase transition temperature T_R-T, and dielectric-maximum temperature T_m were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100y-100z show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor &33, piezoelectric constant d₃₃ and T_d of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171degC, and 0.590, 190 pC/N, and 115degC, respectively. In addition, the relationship between d₃₃ and T_d of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high T_d and high d₃₃, the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d₃₃ and T_d of BNLKT4-28 were 135 pC/N and 218degC, respectively. Moreover, this study revealed that the variation of Td is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

Novel flower-like (Bi(Bi2S3)9I3)2/3 nanostructure as efficient photocatalyst for photocatalytic desulfurization of benzothiophene under visible light irradiation

Here, we report the preparation of hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures that acts as a strong photocatalyst in the desulfurization of benzothiophene. We optimized the reaction time, type of capping agent and reflux temperature to tune the shape of porous flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures to achieve the highest desulfurization performance. We investigated the characteristic shape, size, purity, and optical response of the flower-shape nanostructures using XRD, EDS, FESEM, UV–Vis-DRS analysis. The flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures showed a significant photocatalytic property in desulfurization of benzothiophene as a model fuel. The hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 photocatalyst with an energy gap of 1.15 eV, exhibits a 92% photocatalytic desulfurization performance after 2 h of visible light irradiation. The (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures show a high photocatalytic reproducibility after 4 rounds of exposure. We proposed a photo-oxidation mechanism based on the active species scavenging, which revealed the role of photo-produced h⁺ and O₂^? species as essential in the photocatalytic desulfurization process. These findings provide a new prospect and design strategy for the development of efficient photocatalysts in desulfurization process.     

2D/2D layered BiOIO3/g-C3N4 S-scheme heterojunction for photocatalytic NO oxidation

It is essential to promote interfacial separation and charge migration in heterojunctions for effectively driving surface photocatalytic reactions.In this work,we report the construction of a 2D/2D layered BiOIO3/g-C3N4(BIO/CN)heterojunction for photocatalytic NO removal.The BIO/CN heterojunction exhibits a remarkably higher NO photo-oxidation removal rate(46.9％)compared to pristine BIO(20.1％)and CN(25.9％)under visible-light irradiation.Additionally,it effectively suppresses the formation of toxic NO2 intermediates during photocatalytic reaction.The improved photocatalytic performance of BIO/CN com-posite is caused by its S-scheme charge carrier transport mechanism,which is supported by Density Functional Theory simulations of work function and electron density difference,along with in-situ irra-diated X-ray Photoelectron Spectroscopy and Electron Paramagnetic Resonance analyses.This S-scheme structure improves the interfacial carrier separation efficiency and retains the strong photo-redox ability.Our study demonstrates that construction of a S-scheme heterojunction is significant in the design and preparation of highly efficient photocatalysts for air purification.     

Synthesis of Z-scheme g-C3N4/Gd-doped Bi2WO6 heterojunction with enhanced visible-light photodegradation of organic dyes

Herein, we prepared the g-C₃N₄/Gd-doped Bi₂WO₆ Z-scheme heterojunction (BCN) composites by a simple hydrothermal method. The composites were investigated by SEM (EDX), TEM, XRD, XPS, UV–Vis DRS and PL analysis. The photocatalytic performance of composites was envaulted by degrading methylene blue (MB) under the irradiation of a 300 W mercury lamp. The results demonstrated that coupling g-C₃N₄ and doping Gd ³⁺ effectively enhanced the photocatalytic efficiency of pure Bi₂WO₆. The 92% of MB was degraded within 120 min by optimal 0.15–100 BCN sample, being 1.61 times as that of Bi₂WO₆. The greatly enhanced performance of 0.15–100 BCN was due to the synergistic effect of Gd ³⁺ doping and g-C₃N₄ coupling, which maintained high redox capacity. According to the experiment of capture active species, Z-scheme charge transfer mechanism was also deduced. This study may provide an efficient and green method for the treatment of dyestuff industrial wastewater.

     

Effect of oxygen on the dielectric and energy storage performances of lead-free Bi2Mg2/3Nb4/3O7 thin films prepared by magnetron sputtering

Journal of Materials Science: Materials in Electronics - Bi2Mg2/3Nb4/3O7 (BMN) thin films are prepared on Pt–Si substrates by magnetron sputtering, the influence of oxygen on dielectric and...