Electrodeposition of Sb2Se3 on indium-doped tin oxides substrate: Nucleation and growth

The mechanisms related to the initial stages of the nucleation and growth of antimony selenide (Sb₂Se₃) semiconductor compounds onto the indium-doped tin oxides (ITO) coated glass surface have been investigated using chronoamperometry (CA) technique. The fabrication was conducted from nitric acid bath containing both Sb³⁺ and SeO₂ species at ambient conditions. No underpotential deposition (UPD) of antimony and selenium onto ITO substrate was observed in the investigated systems indicating a weak precursor-substrate interaction. Deposition of antimony and selenium onto ITO substrate occurred with large overvoltage through 3D nucleation and growth mechanism followed by diffusion limited growth. FE-SEM and XRD results show that orthorhombic phase Sb₂Se₃ particles with their size between 90 and 125 nm were obtained and the atomic ratio for antimony and selenium was 2:2.63 according to the EDX results.     

熔体旋甩法合成n型(Bi_(0.85)Sb_(0.15))_2(Te_(1-x)Se_x)_3化合物的微结构及热电性能

采用熔体旋甩结合放电等离子烧结(MS-SPS)技术制备了单相n型四元(Bi0.85Sb0.15)2(Te1-xSex)3(x=0.15,0.17,0.19,0.21)化合物,并对所得样品的微结构和热电传输性能进行了系统研究.样品自由断裂面的场发射扫描电子显微镜及抛光面的背散射电子成分分析表明:块体材料晶粒细小,晶粒排列紧密,成分分布均匀且相结构单一,样品中存在大量10—100nm的层状结构.随着Se含量x的增加,样品的电导率和热导率逐渐增加,而Seebeck系数逐渐降低.相比商业应用的区熔材料,MS-SPS方法合成的高Se组成的样品均在425K后表现出更高的ZT值,其中(Bi0.85Sb0.15)2(Te0.83Se0.17)3样品具有最高的ZT值,在360K可达到0.96,并在320—500K均保持较高的ZT值,500K时其ZT值相比区熔材料提高了48%.此外,通过调节Se的含量,可以有效地调控材料的ZT峰值出现的温度段,这对多级或梯度热电器件的制备具有重要意义.     

Investigations on co-evaporated Cu2SnSe3 and Cu2SnSe3-ZnSe thin films

Cu₂SnSe₃ is an important precursor material for the growth of Cu₂ZnSnSe₄, an emerging solar cell absorber layer via solid state reaction of Cu₂SnSe₃ and ZnSe. In this study, we have grown Cu₂SnSe₃ (CTSe) and Cu₂SnSe₃-ZnSe (20%) films onto soda-lime glass substrates held at 573 K by co-evaporation technique. The effect of annealing of these films at 723 K for an hour in selenium atmosphere is also investigated. XRD studies of as-deposited Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films indicated SnSe as secondary phase which disappeared on annealing. The direct optical band gap of annealed Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films were found to be 0.90 eV and 0.94 eV respectively. Raman spectroscopy studies were used to understand the effect of ZnSe on the properties of Cu₂SnSe₃.     

X-ray spectroscopic study of zirconium and molybdenum diselenides

The K absorption spectra of zirconium, molybdenum and selenium in ZrSe₂ and MoSe₂ have been recorded photographically using a Cauchois type bent crystal (mica) spectrograph. The absorption edge shifts are used along with the data for NbSe₂ (Bhide and Bahl 1971J. Phys. Chem. Solids 32 1001) to propose bond schemes for these compounds.     

Charge fluctuation,charge ordering,and zero-gap state in organic conductors

We have carried out a series of measurements of angular dependence of solid-state NMR spectrum using single crystal samples on various organic molecular conductors, in order to investigate the natures of the electronic states at low temperatures. We confirmed a charge ordered insulating state in α-(BEDT-TTF)₂I₃ and large charge disproportionation in the metallic state of this salt. In another charge ordered system, θ-(BEDT-TTF)₂RbZn(SCN)₄, we observed unusual NMR line broadening, proportional to resonance shift, in the metallic state above the transition. We found that this broadening is due to charge disproportionation, or more correctly, due to the inhomogeneity of local susceptibility at nuclear sites and analyzed its dynamics. We observed similar broadening in various organic molecular conductors as well, such as θ-(BEDT-TTF)₂CsZn(SCN)₄, an exotic Bechgaad salt, (TMTSF)₂FSO₃, and λ-type BETS salts, λ-(BETS)₂(Fe,Ga)Cl₄. We found the mechanism of CD in each system is different, respectively.     

AgSbSe2 and AgSb(S,Se)2 thin films for photovoltaic applications

Silver antimony selenide (AgSbSe₂) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb₂S₃), silver selenide (Ag₂Se), selenium (Se) and silver (Ag). Sb₂S₃ thin film was prepared from a chemical bath containing SbCl₃ and Na₂S₂O₃, Ag₂Se from a solution containing AgNO₃ and Na₂SeSO₃ and Se thin films from an acidified solution of Na₂SeSO₃, at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350 °C in vacuum (10⁻³ Torr) for 1 h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe₂ or AgSb(S,Se)₂ depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV-visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe₂/Al was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this structure showed V_oc = 435 mV and J_sc = 0.08 mA/cm² under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe₂ as an absorber material by a non-toxic selenization process is achieved.     

Organic acid assisted solid-state synthesis of Li1.2Ni0.16Co0.08Mn0.56O2 nanoparticles as lithium ion battery cathodes

Lithium-rich layered oxide Li_1.2Ni_0.16Co_0.08Mn_0.56O₂ can be referred as a crystalline mixture of Li₂MnO₃ and LiNi_0.4Co_0.2Mn_0.4O₂ at equal molar ratio. In the paper, the solid state reaction of M(AC)₂·4H₂O (M = Mn, Co and Ni) and LiOH·H₂O has been performed to obtain nanocrystalline Li_1.2Ni_0.16Co_0.08Mn_0.56O₂ using a small molecular organic acid (i.e., oxalic acid (OA), citric acid (CA) or tartaric acid (TA)) as additive. The introduction of organic acids can help to improve the layered structure and inhibit the particle growth of Li_1.2Ni_0.16Co_0.08Mn_0.56O₂, and the different organic acids exert distinct influences on the structural and electrochemical properties of Li_1.2Ni_0.16Co_0.08Mn_0.56O₂. In detail, the nanoparticles obtained in the presence of OA have the smallest average size of 50–150 nm, which correspondingly exhibit the highest initial discharge capacity of 267.52 mAh g⁻¹ at 0.1C and the best high-rate capability (e.g., 152.22 mAh g⁻¹, 5C) when applied as a lithium ion battery cathode. Furthermore, the active substance obtained from TA shows the best cycling stability and a discharge capacity of 202.42 mAh g⁻¹ can be retained after 50 cycles at 0.5C.     

Mechanism study of selenium retention by iron minerals during coal combustion

The interactions between selenium vapors and coal accessory Ca/Fe-minerals favor selenium emission control by transferring selenium into fly ash during coal combustion. Considering the complicated effects of iron transformation on selenium retention, iron species in fly ashes from seven coal-fired power plants were distinguished and the associations between selenium and iron minerals were assessed. Iron oxides (including Fe₃O₄, γ-Fe₂O₃ and ɑ-Fe₂O₃) were determined as the main form of iron minerals in fly ash. The adsorption of selenium vapors by different iron oxides was conducted at temperatures ranging from 300 to 900 °C and the species of captured selenium were identified. Furthermore, reaction sites on the surfaces of fresh and reacted iron oxides were compared to investigate the mechanism regarding selenium adsorption over these iron oxides, which were further clarified through density functional theory study. The results showed that iron oxides were surely to play a significant role in selenium retention mainly through chemisorption and the reactions probably occurred at temperatures below 900 °C. At 300 °C, ɑ-Fe₂O₃ had better selenium adsorption performance than Fe₃O₄/γ-Fe₂O₃. Regardless of iron species, Fe atoms on iron oxides participated in the selenium adsorption by forming a Se–O–Fe Structure. With temperature increasing, selenium adsorption by Fe atoms was suppressed, which caused a drop off in selenium capture capacity of Fe₃O₄ and ɑ-Fe₂O₃. Differently, increasing temperature promoted selenium adsorption over γ-Fe₂O₃, which owned a high selenium adsorption capacity even at 700 °C. Further analysis confirmed that the presence of O₂/H₂O(g) in the flue gas contributed to the formation of oxygen vacancies on the surface of γ-Fe₂O₃ at high temperatures and facilitated selenium vapors to react with Fe atoms.     

Cu2ZnSnSe4 thin films prepared by selenization of co-electroplated Cu-Zn-Sn precursors

A novel technique for growth of high quality Cu₂ZnSnSe₄ (CZTSe) thin films is reported in our work. The CZTSe thin films were fabricated onto Mo layers by co-electroplating Cu-Zn-Sn precursors followed by annealing in the selenium vapors at the substrate temperature of 550 °C. The morphology and structure of CZTSe thin films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum, respectively. The results revealed that the single phase was in the CZTSe thin films, and the other impurities such as ZnSe and Cu₂SnSe₃ were not existed though they were difficult to distinguish both from EDS and XRD.     

利用空间电荷限制电流方法确定三(8-羟基喹啉)铝的电子迁移率特性初步研究

材料的迁移率是其关键电学特性之一.有机材料迁移率的研究对于有机电致发光器件、 有机太阳电池、有机薄膜场效应晶体管性能的提高有重要的意义. 应用简单易行的空间电荷限制电流方法,对基于三(8-羟基喹啉)铝(Alq₃) 的四种单载流子器件电流密度-电压曲线特性进行研究, 根据空间电荷限制电流模型,拟合出Alq₃材料在四种器件中的零场电子迁移率和电场依赖因子,并且给出Alq₃电子迁移率随外加偏压的变化趋势. 实验结果表明,顶电极铝蒸镀到缓冲层氟化锂(1 nm)和Alq₃ (100 nm)的表面后, 可以明显改善Alq₃的零场迁移率和电场依赖因子. 认为产生这种现象的原因是氟化锂可以使铝和Alq₃发生络合反应, 形成Li⁺¹Alq^-1粒子,形成良好的欧姆接触,使得电子的注入效率大大提高.     

Novel catalysts: Indium implanted SiO2 thin films

Interactions of Indium (In) and silicon (Si) atoms are known to catalyze certain organic chemical reactions with high efficiency. In an attempt of creating a material that manifests the interactions, In implanted SiO₂ thin films were prepared by ion beam injection and their catalytic abilities for organic chemical reactions were examined. It has been found that, with an injection energy of approximately 0.5 keV, a thin In film is formed on a SiO₂ substrate surface and the In implanted SiO₂ thin film can catalyze an organic chemical reaction. It has been also shown that there is an optimal ion dose for the highest catalytic ability in the film preparation process. Thin-film-type catalyzing materials such as the one proposed here may open a new way to enhance surface chemical reaction rates.     

Sonochemical synthesis of silver, copper and lead selenides

Ag₂Se, CuSe and PbSe were prepared by irradiating the mixtures of AgNO₃, CuI or PbCl₂ with selenium in ethylenediamine (en) with ultrasound at 18 kHz, using a commercial ultrasonic cleaner, respectively. X-ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) images show that the products are orthorhombic Ag₂Se, hexagonal CuSe and cubic PbSe, respectively, and all are well crystallized in nanometers.     

Photocatalytic properties of porous C-doped TiO2 and Ag/C-doped TiO2 nanomaterials by eggshell membrane templating

Porous organic carbon-doped titania (C-TiO₂) nanomaterials and their composites with Ag nanoparticles (Ag/C-TiO₂) were synthesized by an eggshell membrane templating method, and their structural and photocatalytic properties were systematically characterized. These nanomaterials, exhibiting a macroscopic morphology of a thin film, are composed of interwoven tubes, and the tube wall consists of nanocrystals. The doped organic carbon was composed of the active carbon and carbonate species, which could form a layer around the surface of TiO₂ nanoparticles, while the silver was incorporated into Ag/C-TiO₂ composites as separated Ag nanoparticles. The degradation of methylene blue under visible light irradiation was employed to evaluate the photocatalytic activity of these as-prepared TiO₂-based materials. Both C-TiO₂ and Ag/C-TiO₂ nanomaterials showed higher photocatalytic activity than pure TiO₂ material–commercial Degussa P25. These results can be accounted for the coupling effect of the incorporation of carbon species and Ag nanoparticles.     

大规模合成具有氧空位的多孔Bi2O3用于有效降解亚甲基蓝

光催化降解有机污染物由于其具有低能耗和绿色环保的特点,已经成为研究的热点. 氧化铋纳米晶体的带隙在2.0∽2.8 eV之间,利用它催化可见光降解有机污染物具有较高的活性,从而引起了越来越多的关注. 尽管近年来已经开发了几种制备Bi₂O₃基半导体材料的方法,但是仍然难以用简单的方法大规模地制备高活性的Bi₂O₃催化剂. 因此,开发简单可行的大规模制备Bi₂O₃纳米晶体的方法对于工业废水处理的潜在应用具有重要意义. 本文通过蚀刻商用BiSn粉末,然后进行热处理,成功地大规模制备了多孔Bi₂O₃. 获得的多孔Bi₂O₃在亚甲基蓝(MB)的光催化降解中表现出优异的活性和稳定性. 对该机理的进一步研究表明,多孔Bi₂O₃合适的能带结构允许生成活性氧物种,例如O₂^-·和·OH,可有效降解MB.     

Photo-induced nonthermal melting of amorphous chalcogenides observed by pump and probe x-ray absorption spectroscopy

A new kind of melting phenomenon which is not based on thermal excitation has been observed. X-ray absorption spectroscopy (XAS) experiments under optical pumping provide a “snap-shot” information on the local structure under excitation. We have studied the local structure of chalcogenide glasses such as vitrious selenium and As₂Se₃ under optical excitation and confirmed the local melting phenomenon under light illumination at low temperature. The photo-induced nonthermal melting (PNM) in chalcogenide glasses is interpreted as the result of pairing of excited lone pair electrons during the illumination. Trapped states in this photo-assisted metastable phase result in a local structural disorder which is partially quenched at room temperature. The increased short-range disorder causing Coulomb repulsion is the origin of red shift of the absorption coefficient known as the photodarkening effect. We found that the bond alternation of chalcogens occurs during the photo-excitation.     

有机金属化学气相沉积法制备的Ni/Al2O3纳米复合材料的氢吸附

研究了通过有机金属化学气相沉积技术及单源分子前躯体方法制备的Ni/Al₂O₃纳米复合材料的氢吸附(存储). 在冷壁的有机金属化学气相沉积反应器中,通过降解Ni(acac)₂粉末基底上的[H₂Al(OtBu)]₂制备的Ni/Al₂O₃纳米复合材料. 通过X射线粉末衍射、扫描电镜、透射电镜以及能量色散型X射线荧光光谱等技术表征该复合材料. 采用自制Sievert's设备研究该复合材料的氢吸附(存储),可以储存约2.9%(重量比)的氢.     

Preparation and characterization of Li2CoMn3O8 thin film cathodes for high energy lithium batteries

An ion layer gas reaction (ILGAR) dip-coating process for the deposition of homogeneous spinel structured Li₂CoMn₃O₈ thin layers has been developed. Thin film cathodes for use in high-energy density lithium batteries with thicknesses of about 200 nm have been prepared. The films were found to be X-ray amorphous after preparation. After annealing at 700°C in air for 2 h, the spinel structure of Li₂CoMn₃O₈ was observed by X-ray diffraction analysis. The composition of the surface was studied by XPS, which indicated enhanced Li and Mn concentrations as a result of the rinsing process and different solubilities of the precursor salts. The electrochemical behavior was investigated by separating the annealed electrode sample from a conventional organic lithium ion-conducting electrolyte by a layer of LiPON solid electrolyte and using elemental lithium as counter electrode. A capacity of 110.8 mAh/g was observed which is related to the valence changes of Mn and Co in the spinel structure.     

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO₂ was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO₂ was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO₂ nanotubes could be up to four times as compared to TiO₂ powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO₂ nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO₂ nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO₂ nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO₂ nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.     

The high pressure synthesis of the graphitic form of C3N4

Abstract

Basing on “ab-initio” calculations, C₃N₄ was claimed to be an ultra-hard material with a bulk-modulus close to that of diamond. Five different structural varieties were announced: the graphitic form, the zinc blende structure, the α and β forms of Si₃N₄ and another form, isostructural with the high pressure variety of Zn₂Si0₄.

Using the same strategy as that developed for diamond or c-BN synthesis, it appears that the graphitic form could be an appropriate precursor for preparing the 3D varieties. Two main problems characterize the C₃N₄ synthesis: (-) the temperature should be reduced in order to prevent nitrogen loss, (-) the reactivity of the precursors should be improved.

Consequently, we have developed a new process using the solvothermal decomposition of organic precursors containing carbon and nitrogen in the presence of a nitriding solvent. The resulting material, with a composition close to C₃N₄, has been characterized by different physico-chemical techniques.     

生物油及生物质炭电催化制氢

报道了以生物质热裂解产物-生物油和生物质炭为原料,利用双固定床反应器和电催化水蒸气重整方法高效制氢过程研究．获得的最大绝对氢产率达到110.9 g H₂/1 kg干生物质,气相产物包括72%H₂、26%CO₂、1.9%CO和痕量的CH₄．研究了添加生物质炭对生物油制氢效果的影响,以及重整反应温度、通入催化床的电流等反应条件对生物油和生物质炭制氢效果的影响．结果表明,生物质炭的添加使绝对氢产率增加了大约20%～45%,提