Au core-PtAu alloy shell nanowires for formic acid electrolysis

Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen(H2)production from acidic water electrolysis.Herein we report the one-pot precise synthesis of ultrafine Au core-Pt Au alloy shell nanowires(Au@PtxAu UFNWs).Among them,Au@Pt_0.077 Au UFNWs exhibit the best performance for formic acid oxidation reaction(FAOR)and hydrogen evolution reaction(HER),which only require applied potentials of 0.29 V and-22.6 m V to achieve a current density of 10 m A cm^-2,respectively.The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 m A cm^-2 current density.Density functional theory(DFT)calculations reveal that the Au-riched Pt Au alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt_0.077 Au UFNWs.This work provides meaningful insights into the electrochemical H₂ production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.     

Layered Ag-graphene films synthesized by Gamma ray irradiation for stable lithium metal anodes in carbonate-based electrolytes

Lithium metal batteries are considered as high energy density battery systems with very promising prospects and have bee n widely studied.However,The uncon trollable plating/strippi ng behavior,infinite volume change and den drites formation of lithium metal anode restrict the applicati on.The unc on trolled n ucleati on of lithium caused by the non uniform multi-physical field distributions,can lead to the undesirable lithium deposition.Herein,a graphene composite uniformly loaded with Ag nano-particles(Ag NPs)is prepared through a facile Gamma ray irradiation method and assembled into self-supported film with layered structure(Ag-rGO film).Whe n such film is used as a lithium metal an ode host,the uncontrolled deposition is converted into a highly nucleation-induced process.On one hand,the Ag NPs distributed between the in terlayers of graphe ne can preferentially induce lithium nu cleati on and en able uniform deposition morphology of lithium between interlayers.On the other hand,the stable layered graphene structure can accommodate volume change,stabilize the interface between anode and electrolyte and inhibit dendrites formation.Therefore,the layered Ag-rGO film as anode host can reach a high Coulombic efficiency over 93.3% for 200 cycle(786 h)at a current density of 1 mA cm^-2 for 2 mAh cm^-2 in carbonate-based electrolyte.This work proposes a facile Gamma ray irradiation method to prepare metal/3D-skeleton structure as lithium anode host and demonstrates the potential to regulate the lithium metal deposition behaviors via manipulating the distribution of lithiophilic metal(e.g.Ag)in 3D frameworks.This may offer a practicable thinking for the subsequent design of the lithium metal anode.     

中国纤维素乙醇技术的研究进展

中国面临着严重的能源短缺和环境污染问题,中国政府正在局部几个省份内政策性鼓励燃料乙醇生产和使用.尽管当前主要是用玉米和谷物作为生产乙醇的原料,然而中国具有大量潜在的低成本的纤维素生物质原料,可以极大地扩大乙醇的产量,降低原料成本.近20年来,由于技术的革命性进步,已使得纤维素乙醇的生产成本从4美元/加仑以上,降低至约1.2-1.5美元/加仑.其中,每吨生物质约44美元.因此,目前乙醇掺汽油具有十分强的市场竞争力.已有几个公司正在建造首批商业纤维素乙醇工厂,虽然这些刚起步的小型设施在合理利用和管理上风险较小,但规模经济需要较大型工厂.尽管配送生物质原料的成本会随需求的增加而增加,但在乙醇生产基础上的生物精炼技术的发展,尤其是化工产品和动力的协同生产,将会使全过程的经济可行性大大提高.进一步深入的基础研究,将解决低成本下实现纤维素的完全利用,以确保在无政策性补贴的前提下,真正使纤维素乙醇成为具有市场竞争力的低成本纯液体燃料.     

Binary ligand strategy toward interweaved encapsulation-nanotubes structured electrocatalyst for proton exchange membrane fuel cell

Hierarchically porous architecture of ir on-nitroge n-carb on(Fe-N-C)for oxyge n reducti on reaction(ORR)is highly desired towards efficient mass transfer in the fuel cell device manner.Herein,we reported a binary ligand strategy to prepare zeolitic imidazolate frameworks(ZIFs)-derived precursors,wherein the addition of secondary ligand endows precursors with the capabilities to transform into porously interweaved encapsulation-nanotubes structured composites after calcination.The optimal catalyst,i.e.,termed as Fe₆-M/C-3,exhibits excellent durability with 88.8%current retention after 50,000 seconds in 0.1 M HClO₄solution by virtue of nanoparticles-encapsulation features,which is more positive than the benchmark commercial 20 wt%Pt/C catalyst.Moreover,a promising maximum power density of Fe₆-M/C-3 as cathode catalyst was also dem on strated in proton exchange membrane fuel cells(PEMFCs)measurements.Therefore,this binary ligand approach to the fabrication of hierarchically porous structures would also have significant implications for various other electrochemical reactions.     

Molten salt as ultrastrong polar solvent enables the most straightforward pyrolysis towards highly efficient and stable single-atom electrocatalyst

Currently,pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts(C-SACs),e.g.,the sintering of metal atoms at high temperature as well as the high cost and complicated preparations of precursors.In this report,molten salts are demonstrated to be marvellous medium for preparation of C-SACs by pyrolysis of small molecular precursors(ionic liquid).The ultrastrong polarity on one hand establishes robust interaction with precursor and enables better carbonization,resulting in largely enhanced yield.On the other hand,the aggregation of metal atoms is effectively refrained while no nanoparticle or cluster is formed.By this strategy,a C-SAC with atomically dispersed Fe-N₄ sites and a high specific area over 2000 m² g^-1 is obtained,which illustrates high ORR activity in both acid and alkaline media.Moreover,this SAC exhibits superior methanol tolerance and stability after acid soaking at 85℃ for 48 h.It is believed that the molten-salts-assisted pyrolysis can be developed into a routine strategy as it not only can largely simply the synthesis of C-SACs,but also can be extended to prepare other types of SACs.     

镧对Mg-Si合金中Mg2Si相变质的影响

研究了Mg-5Si合金中La的添加对初生Mg2Si相变质的影响。结果表明,适量的La能够有效地变质初生Mg2Si相。基于本文的研究,在添加约0.5%La时,获得了最佳的变质效果,此时,初生Mg2Si相的尺寸减小到25μm以下,其形态从粗大的树枝形状变为多面体形状。然而,当La增加到0.8%或者更高时,初生Mg2Si相又生长为粗大的树枝形态。而且,在凝固过程中发现形成了一些LaSi2化合物,这些化合物的数量随着La的增加而呈现逐渐增加的趋势。     

电感耦合等离子体质谱法测定天然水体中19种元素

建立STD/KED模式-电感耦合等离子体质谱（ICP-MS）法同时测定天然水体中铍、硼、钛、钒、铬、锰、钴、镍、铜、锌、钼、镉、锑、钡、铊、铅、铁、砷和硒19种元素的分析方法。仪器调谐校准后,样品在线加入锂、钪、铑、铋校准溶液校正,以标准曲线内标法定量分析。标准曲线相关系数均大于0.999,样品加标回收率为92.6%～103.6%,质控样品测定值相对标准偏差为0.20%～2.6%(n=6),方法检出限为0.01～0.70μg/L。该方法灵敏度高,操作简便,节省人力,能满足天然水体中19种元素的同时检测需要。     

电解质-非电解质混合溶液活度系数的关联及溶解的推算 II:NH3-NaCl-Na2SO4-H2O体系的液固平衡热力学

由于在研究的体系中, Na2SO4是非对称电解质, 且能生成水合盐, 故推导了由非对称型电解质与非电解质所构成的混合溶液的各组分的活度系数关联通式, 并在此基础上讨论了水合盐液固平衡的计算方法.     

黄花棘豆化学成分的研究II:两种三萜皂苷的结构

从黄花棘豆的总皂苷中分离出两个新皂苷1和2.经光谱分析及化学方法确证,1为3-O-[α-L-鼠李吡喃糖基(1→2)-β-D-葡萄吡喃糖基(1→4)-β-D-葡萄吡喃糖醛酸基]-黄豆醇B;2为3-O-[α-L-鼠李吡喃糖基(1→2)-α-L-阿拉伯吡喃糖基(1→4)-β-D-葡萄吡喃糖醛酸基]-黄豆醇B.     

二氧化钛纳米管的研究进展

二氧化钛纳米管由于其新奇的光电、催化、气敏等性能引起了广泛的关注,在太阳能电池、光催化、环境净化、气体传感器等领域有潜在的应用价值.本文概述了近年来在制备方法、反应机理和组成、晶型和形貌及掺杂和应用方面的进展,并讨论了今后可能的研究发展方向.     

Investigation on the electron-beam curing of vinylester resin

A typical vinylester resin, Derakane 411-350, was electron-beam (EB) cured without initiators. The curing process was investigated by gel-fraction testing, FTIR and Raman spectroscopies. Both dynamic numerical analysis and positron annihilation life spectroscopy were utilized to analyze the microstructure of resin samples irradiated with different doses and dose rates. Resin irradiated with the same dose at a low dose rate achieved a higher degree of cure than those samples irradiated with a high dose rate. Resin irradiated with low dose rates had a lower free-volume fraction with smaller interstices and a more uniform microstructure. The glass-transition temperature of the resin increased with increasing irradiation dose. The mechanical properties of the EB-cured resin confirmed the analysis of changes in microstructure arising from irradiation.     

Electron irradiation induced microstructural modifications in BaCl2 doped PVA: A positron annihilation study

Thin films of pure and 10 wt% BaCl₂ doped poly(vinyl alcohol) (PVA) were prepared by solution casting method. These films were subjected to electron irradiation for different doses ranging from 0 to 400 kGy in air at room temperature. The effect of electron irradiation on the optical and free volume related microstructures of these polymer films was studied using positron annihilation lifetime spectroscopy, FTIR and UV-vis techniques. The FTIR spectral studies indicate that the electron irradiation induces chemical modifications within the doped PVA, which results in chain scission as well as cross-linking of the polymer. The positron lifetime study on these irradiated polymers shows that the chain scissions and cross-linking within the polymer matrix affect the free volume content and hence the microstructure. The UV-vis optical absorption studies show that the induced microstructural change by electron irradiation also modifies the optical properties. Using UV-vis spectra, the optical energy band gap was estimated and it decreases with increase in electron dose. A correlation between positron results and optical results is obtained and electron irradiation induced microstructure modifications within the doped polymer are understood. The results highlight the usefulness of positron annihilation technique in the study of the microstructure of irradiated polymers.     

Positron lifetime spectroscopy as a probe of nanoporosity of cement-based materials

Hydrating cement pastes prepared with water-to-cement ratio equal to 0.5 in weight were investigated through positron annihilation lifetime spectroscopy over a period of 4 weeks. Two series of samples were prepared using different pre-treatment procedures, in order to assess the influence of sample manipulations on positron annihilation measurements. The technique is sensitive to changes in the pore structure with ageing time. Moreover, from the positron data an estimate of the first two moments of radii distribution of the nanopores was obtained.     

The effect of plasticizer on the ageing of Metolose films

The film-forming material, Metolose, was studied by positron annihilation spectroscopy. It is known that above a given concentration the plasticizer (PEG) forms a separate phase. The controlled ageing of the films showed that there is a difference between the ageing processes of the monophase and that of the separated phase films. The ageing consists of a fast and a slow step in both cases. Our PAS measurements showed that this slow process is hindered in the phase-separated samples.     

Free-standing boron doped CVD diamond films grown on partially stabilized zirconia substrates

Boron doped diamond films have been grown adhered to silicon substrates by chemical vapor deposition using boron containing gases. In this work it was shown that it is possible to grow free-standing boron doped CVD diamond films on partially stabilized zirconia substrates using boron powder as the source for doping. Results from Raman spectroscopy confirmed the boron incorporation with concentration up to ∼10²⁰ cm⁻³. X-ray diffraction and scanning electron microscopy showed that the effect of boron incorporation in the microstructure of the diamond film is negligible. The measurement of the resistivity as a function of temperature confirmed the semiconductor behavior, as expected for p-type diamond.     

不锈钢上液相电沉积类金刚石薄膜

以甲醇有机溶液作碳源,应用直流脉冲电化学沉积方法,在不锈钢表面制备了类金刚石碳薄膜.用原子力显微镜、扫描电镜、拉曼光谱仪和傅立叶红外吸收光谱表征该薄膜的表面形貌和结构.结果表明:经电化学沉积的含氢类金刚石碳薄膜均匀、致密,表面粗糙度小;Raman光谱在1 332.51cm-1处有一强的谱峰,与金刚石的特征谱峰相重合.加入活性添加剂,增加了电流密度,使沉积速率提高到0.5μm/h.     

掺硼多晶金刚石膜的电化学性能研究

采用EACVD(Electron Assisted Chemical Vapor Deposition)方法制备了掺硼金刚石膜, 并用扫描电镜、拉曼光谱及霍尔效应等测试方法对其表面形貌、生长特性、载流子浓度以及导电性能进行了分析. 测试结果表明, 掺硼金刚石膜是由微米级晶粒组成的多晶膜, 其载流子浓度为4.88×1020 cm-3, 电阻率为0.03 Ω·cm, 是高品质金刚石膜. 用该金刚石膜制作电化学电极, 利用循环伏安法分别测量了金刚石膜电极在氯化钾空白底液、亚铁氰化钾溶液和左旋半胱氨酸溶液中的循环伏安曲线, 发现该金刚石膜电极在水溶液中具有宽的电化学窗口(约为3.7 V)和接近零的背景电流, 在生物制剂的检测中具有很高的灵敏度和良好的稳定性, 是一种理想的电化学电极材料.     

Study of structural changes for STS 316L using the positron annihilation lifetime spectroscopy

The defects due to extrusion strengths and the temperature dependent deformities for low carbon stainless steel (STS 316L) were investigated using positron annihilation spectroscopy. The defects were restored after tempering at 700 °C. The gradients of the peak on the positron annihilation lifetime spectrum for a sample annealed at 700 °C is increased compared to the as extruded sample. In addition, we calculated the trapping rate and bulk lifetime based on the theoretical model. Both values are decreased, as the extrusion strengths are reduced. All annealed samples showed reduced trapping rate and bulk lifetime, comparing with as extruded samples.

     

正电子湮没技术在纳米材料中的应

纳米材料在现实应用中表现出越来越优异的性能,其微结构往往对宏观性能有着重要影响。从正电子湮没技术基本原理出发,结合正电子湮没技术在材料微观结构领域的独特优势,介绍了其在纳米金属、合金以及纳米半导体等材料中的微结构研究工作,阐述了纳米材料微结构对基础学科和实际应用的重要意义。     

Characterization of the surface layer of LB-films using a slow positron beam

Langmuir–Blodgett films were studied using a variable energy slow-positron beam. We measured the energy spectra of positron annihilation radiation for Cd and Mg eicosanoid films and obtained the V- and S-parameters as a function of the incident positron energy, E. In the V-E curves of Cd eicosanoid films, there were dips at the positron energy whose mean implantation depth corresponding to the first and second Cd²⁺ layers from the surface. These dips are interpreted as the result of inhibition of Ps formation by the Cd²⁺ ions. The S-parameter was found to be sensitive to chemical composition of the film and also to possible structural change due to heat treatment. Our results suggest that positron beams provide valuable information about the microstructure of the Langmuir-Blodgett films.