新的稀土锂钒酸盐的合成,结构和发光

本文首次报道了在６００℃灼烧数小时合成出新的稀土锂钒醛盐Ｙ０．５－ｘＬｉ１．５ＶＯ４；ＲＥｘ（ＲＥ＝Ｓｍ＾３＋，Ｄｙ＾３＋，Ｈｏ＾３＋，Ｅｒ＾３＋，Ｔｍ＾３＋）（０．０１＜ｘ＜０．０１）多晶粉末。比通常钒酸盐的合成温度降低近４００℃。用Ｘ射线粉末法分析此多晶粉末的结构。     

Interfacing BiVO4 with Reduced Graphene Oxide for Enhanced Photoactivity: A Tale of Facet Dependence of Electron Shuttling

Efficient interfacial charge transfer is essential in graphene‐based semiconductors to realize their superior photoactivity. However, little is known about the factors (for example, semiconductor morphology) governing the charge interaction. Here, it is demonstrated that the electron transfer efficacy in reduced graphene oxide‐bismuth oxide (RGO/BiVO₄) composite is improved as the relative exposure extent of {010}/{110} facets on BiVO₄ increases, indicated by the greater extent of photocurrent enhancement. The dependence of charge transfer ability on the exposure degree of {010} relative to {110} is revealed to arise due to the difference in electronic structures of the graphene/BiVO₄{010} and graphene/BiVO₄{110} interfaces, as evidenced by the density functional theory calculations. The former interface is found to be metallic with higher binding energy and smaller Schottky barrier than that of the latter semiconducting interface. The facet‐dependent charge interaction elucidated in this study provides new aspect for design of graphene‐based semiconductor photocatalyst useful in manifold applications.     

Revealing Nanoscale Chemical Heterogeneities in Polycrystalline Mo‐BiVO4 Thin Films

The activity of polycrystalline thin film photoelectrodes is impacted by local variations of the material properties due to the exposure of different crystal facets and the presence of grain/domain boundaries. Here a multi‐modal approach is applied to correlate nanoscale heterogeneities in chemical composition and electronic structure with nanoscale morphology in polycrystalline Mo‐BiVO₄. By using scanning transmission X‐ray microscopy, the characteristic structure of polycrystalline film is used to disentangle the different X‐ray absorption spectra corresponding to grain centers and grain boundaries. Comparing both spectra reveals phase segregation of V₂O₅ at grain boundaries of Mo‐BiVO₄ thin films, which is further supported by X‐ray photoelectron spectroscopy and many‐body density functional theory calculations. Theoretical calculations also enable to predict the X‐ray absorption spectral fingerprint of polarons in Mo‐BiVO₄. After photo‐electrochemical operation, the degraded Mo‐BiVO₄ films show similar grain center and grain boundary spectra indicating V₂O₅ dissolution in the course of the reaction. Overall, these findings provide valuable insights into the degradation mechanism and the impact of material heterogeneities on the material performance and stability of polycrystalline photoelectrodes.     

铝合金2024上钒酸盐转化膜的研究

利用浸渍法在铝合金表面获得钒酸盐转化膜,应用交流阻抗技术(EIS)研究了NaVO3浓度及浸泡时间对铝合金2024表面钒酸盐转化膜成膜过程的影响,扫描电子显微镜(SEM)与能量散射能谱(EDS)分析膜表面形貌与成分.结果表明,EIS显示当转化液中NaVO3的浓度为0.1 M时处理3 min得到的转化膜的阻抗值最大,达到7.17×105Ω.cm2;SEM显示在该溶液浓度下表面所形成的转化膜均匀致密,其成分主要由Al,V,Mg元素组成.钒酸盐转化膜工艺简单,对环境无污染,膜的耐蚀性强,具有一定的应用前景.     

热电池钒酸铜Cu_3V_2O_8的制备

通过沉淀法合成钒酸铜正极材料,采用X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、差热分析(DTA)和粒度分析方法对钒酸铜材料进行了表征。采用粉末压片工艺制备单体电池,研究合成条件对其性能的影响。研究表明,合成的Cu_3V_2O_8单体电池具有较高的放电电压和放电比容量。     

Photoinduced Absorption Spectroscopy of CoPi on BiVO4: The Function of CoPi during Water Oxidation

This paper employs photoinduced absorption and electrochemical techniques to analyze the charge carrier dynamics that drive photoelectrochemical water oxidation on bismuth vanadate (BiVO₄), both with and without cobalt phosphate (CoPi) co‐catalyst. These results are correlated with spectroelectrochemical measurements of Co^II oxidation to Co^III in a CoPi/FTO (fluorine doped tin oxide) electrode during dark electrocatalytic water oxidation. Electrocatalytic water oxidation exhibits a non‐linear dependence on Co^III density, with a sharp onset at 1 × 10¹⁷ Co^III cm^?2. These results are compared quantitatively with the degree of CoPi oxidation observed under conditions of photoinduced water oxidation on CoPi–BiVO₄ photoanodes. For the CoPi–BiVO₄ photoanodes studied herein, ≤5% of water oxidation proceeds from CoPi sites, making the BiVO₄ surface the predominant water oxidation site. This study highlights two key factors that limit the ability of CoPi to improve the catalytic performance of BiVO₄: 1) the kinetics of hole transfer from the BiVO₄ to the CoPi layer are too slow to effectively compete with direct water oxidation from BiVO₄; 2) the slow water oxidation kinetics of CoPi result in a large accumulation of Co^III states, causing an increase in recombination. Addressing these factors will be essential for improving the performance of CoPi on photoanodes for solar‐driven water oxidation.     

Solvothermal synthesis of Bi2O3/BiVO4 heterojunction with enhanced visible-light photocatalytic performances

Novel, three-dimensional, flower-like Bi2O3/BiVO4 heterojunction photocatalysts have been prepared by the combination of homogeneous precipitation and two-step solvothermal method followed by thermal solution of NaOH etching process. The as-obtained samples were fully characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Brunauer-Emmett-Teller surface area, and UV-vis diffusereflectance spectroscopy in detail. The crystallinity, microstructure, specific surface area, optical property and photocatalytic activity of samples greatly changed depending on solvothermal reaction time. The photocatalytic activities of samples were evaluated on the degradation of methyl orange (MO) under visible-light irradiation. The Bi2O3/BiVO4 exhibited much higher photocatalytic activities than pure BiVO4 and conventional TiO2 (P25). The result revealed that the three-dimensional heterojunction played a critical role in the separation of the electron and hole pairs and enhancement of the interfacial charge transfer efficiency, which was responsible for the enhanced photocatalytic activity.     

Three phase boundaries and electrochemically active zones of lanthanum strontium vanadate–yttria-stabilized zirconia anodes in solid oxide fuel cells

Electrochemical reactions in solid oxide fuel cells take place around three-phase boundaries (TPBs). The electrochemically active zones (EAZs) are generated in three-dimensions around the TPBs of on-running SOFCs. This work discusses the behaviours of TPBs and EAZs via a case study on lanthanum strontium vanadate (LSV)–yttria-stabilized zirconia (YSZ) composite anode. A percolating binary particle aggregate, based on geometric random loose packing model and traditional sintering theory, is constructed to represent the LSV–YSZ anode. The TPB lengths of LSV–YSZ anodes are evaluated from the coordination numbers and sintering necks of the particles in the particle aggregate. Empirical interrelations among TPBs, EAZs, active electrode thickness, in-depth penetration of electrocatalysts of polarized LSV–YSZ anode are established.     

A review on copper vanadate‐based nanostructures for photocatalysis energy production

The economic, social, and environmental aspects are important that should be notable before the selection of a method for the production of energy. Various renewable energy sources are used like hydropower, biomass, biofuel, geothermal energy, and wind energy for the production of sustainable energy that are excellent approaches to fulfill energy environmental energy demands. Renewable sources of energy give an excellent chance to extenuate the gas emission in greenhouse and reduction of global warming with the help of renewable sources of energy. The importance and utilization of the variety of renewable sources of energy are elaborated in this article. The emerging and exploring technique for the production of energy is the photocatalysis. In photocatalysis, solar spectrum is the extraneous source that is used with water to produce hydrogen energy (green energy) by the water splitting under the shower of the solar spectrum. The solar spectrum contains heat and intensity of light from which light spectrum is the abundantly used for the splitting of water. The photocatalyst is the key factor to initiate the reaction depending upon the energy band gap by absorbing the energy from the spectrum of the sun. Semiconducting materials having lower forbidden energy band gap are the basic requirements to use them as a photocatalyst for photocatalysis. Copper vanadate and their composites are the promising materials that are used as photocatalyst for the production of hydrogen energy. Copper vanadate is the focusing material that can be used as photocatalyst. It is an n‐type semiconducting material with 2 eV indirect energy band gap having monoclinic structural phase which is tuned by the doping of metals like chromium, molybdenum, and silver to reduce the grain size and energy band gap and increase the surface area and optical absorption of solar light only to enhance the photocatalytic performance towards the production of hydrogen energy by water splitting in the presence of solar light.     

Development of deep red–emitting CaBiVO5:Pr3+ phosphor for multifunctional optoelectronic applications

Orthorhombic Pr³⁺-doped calcium bismuth vanadate (CBV: Pr³⁺) phosphors have been synthesized successfully via a citrate-gel method. The single-phase formation of CBV: Pr³⁺ phosphor has been endorsed by X-ray diffraction (XRD) analysis. The scanning electron microscopy (SEM) image reveals dense-particle packaging with the quasi-spherical shape for the prepared CBV: Pr³⁺ phosphors. Under blue light excitation, CBV: Pr³⁺ phosphors exhibit intense red emission bands located at 608 and 656 nm wavelengths, overlapping with the absorption spectrum of P_R phytochrome, which is present in plants. To achieve the maximum red intensity, the Pr³⁺ ion concentration is optimized to be 1.25 mol% in the CBV host, after which the emission intensity ceases due to concentration quenching. Dexter's theory disclosed the possibility of d-d multipolar interaction among Pr³⁺ ions at higher concentrations of Pr³⁺ ions in the CBV host. The CIE coordinates are found to be positioned in the pure red region for CBV: Pr³⁺ phosphor and in the proximity of red-emitting commercial phosphor. The temperature-dependent spectral studies manifest substantial thermal stability of the as-synthesized phosphor. All the studies mentioned above specify the tremendous potentiality of thermally stable CBV: Pr³⁺ phosphor in agricultural lighting and w-LED applications.