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.     

THF/H~2O二元团簇中“幻数”现象研究

利用分子束、同步辐射光源和飞行时间质谱研究了HF/H~2O二元团簇体系,观察到了一系列组成为(THF)~n·(H~2O)~mH^+(n=2～5,m=0～n-1)离子峰,其中(THF)~n(H~2O)~n~-~2H^+(n=2～5)离子峰强为“幻数”峰。运用从头算(abinitio)分子轨道法,在HF/3-21G基组水平上对(THF)~n(H~2O)~n~-~2H^+(n=2～4)团簇几何构型进行了优化,计算结果表明团簇离子(THF)~n(H~2O)~n~-~2H^+具有较大的稳定性,解释了实验中观察到的“幻数”现象。     

Hydration and dissociation of hydrogen fluoric acid (HF)

The hydration and dissociation phenomena of HF(H(2)O)(n)() (n < or = 10) clusters have been studied by using both the density functional theory with the 6-311++G[sp] basis set and the M?ller-Plesset second-order perturbation theory with the aug-cc-pVDZ+(2s2p/2s) basis set. The structures for n > or = 8 are first reported here. The dissociated form of the hydrogen-fluoric acid in HF(H(2)O)(n) clusters is found to be less stable at 0 K than the undissociated form until n = 10. HF may not be dissociated at 0 K solely by water molecules because the HF H bond is stronger than the OH H bond, against the expectation that the dissociated HF(H(2)O)(n) would be more stable than the undissociated one in the presence of a number of water molecules. The dissociation would be possible for only a fraction of a number of hydrated HF clusters by the Boltzmann distribution at finite temperatures. This is in sharp contrast to other hydrogen halide acids (HCl, HBr, HI) showing the dissociation phenomena at 0 K for n > or = 4. The IR spectra of dissociated and undissociated structures of HF(H(2)O)(n) are compared. The structures and binding energies of HF(H(2)O)(n) are found to be similar to those of (H(2)O)(n+1). It is interesting that HF(H(2)O)(n=5,6,10) are slightly less stable compared with other sizes of clusters, just like the fact that (H(2)O)(n=6,7,11) are slightly less stable. The present study would be useful for the experimental/spectroscopic investigation of not only the dissociation phenomena of HF but also the similarity of the HF-water clusters to the water clusters.     

样品价态对激光气化产生Cu/Cl团簇的组成和稳定性的影响

研究团控的形成条件、形成机理是目前团簇科学中的一个热点领域［‘］．产生气相团簇的方法主要有Knudsen高温炉扩散法、粒子溅射法、激光气化／分子束法、直接激光气化法·因为不需要另加缓冲气体，直接激光气化法【刀具有对体系真空要求较低，装置简单，容易和飞行时间质谱结     

Mid-infrared characterization of the NH4 +(H2O)n clusters in the neighborhood of the n=20 "magic" number

Vibrational predissociation spectra are reported for size-selected NH4+ (H2O)n clusters (n=5-22) in the 2500-3900 cm(-1) region. We concentrate on the sharp free OH stretching bands to deduce the local H-bonding configurations of water molecules on the cluster surface. As in the spectra of the protonated water clusters, the free OH bands in NH4+ (H2O)n evolve from a quartet at small sizes (n<7), to a doublet around n=9, and then to a single peak at the n=20 magic number cluster, before the doublet re-emerges at larger sizes. This spectral simplification at the magic number cluster mirrors that found earlier in the H+(H2O)n clusters. We characterize the likely structures at play for the n=19 and 20 clusters with electronic structure calculations. The most stable form of the n=20 cluster is predicted to have a surface-solvated NH4+ ion that lies considerably lower in energy than isomers with the NH4+ in the interior.     

系列同三核铬、锰、铁羧酸配合物的FAB-MS研究

进行了系列同三核羧酸配合物〔Ｍ３Ｏ（Ｏ２ＣＲ）６Ｐｙ３〕Ｘ（Ｍ＝Ｃｒ,Ｍｎ,Ｆｅ;Ｒ＝ＣＨ３,Ｃ２Ｈ５,Ｃ６Ｈ５;Ｘ＝Ｃｌ－,ＣｌＯ４－;Ｐｙ为吡啶）的快原子轰击质谱（ＦＡＢ－ＭＳ）研究。获得了包括配位吡啶在内的完整阳离子峰。在研究其断裂规律时,主要观察到４个系列碎片离子：Ⅰ．〔Ｍ３Ｏ（Ｏ２ＣＲ）ｎ〕＋,ｎ＝６～２;Ⅱ．〔Ｍ３Ｏ（Ｏ２ＣＲ）ｎＯ〕＋,ｎ＝５～１;Ⅲ．〔Ｍ２Ｏ（Ｏ２ＣＲ）ｎ〕＋,ｎ＝３～１;Ⅳ．〔Ｍ２（Ｏ２ＣＲ）ｎ〕＋,ｎ＝４～２。通过对该系列配合物质谱断裂过程的比较和分析,获得了配合物稳定性随金属离子及配体的变化如下：金属离子,Ｃｒ＞Ｍｎ＞Ｆｅ;桥配基,－ＣＨ３ＣＯ２＞－Ｃ２Ｈ５ＣＯ２＞－Ｃ６Ｈ５ＣＯ２;端配基,Ｐｙ＞Ｈ２Ｏ。本研究及先前的工作〔１,８〕还为某些三核铬,铁羧酸配合物在以乙炔加水或加氢为探针反应中存在活性物种：〔Ｃｒ３Ｏ（Ｏ２ＣＲ）３～４〕,〔Ｆｅ３Ｏ（Ｏ２ＣＲ）３〕和〔Ｆｅ３Ｏ－（Ｏ２ＣＲ）Ｏ〕～〔Ｆｅ３Ｏ４〕提供了佐证     

Mimicking solvent shells in the gas phase. II. Solvation of K+

The observed gas-phase coordination number of K+ in K+(H2O)m clusters is smaller than that observed in bulk solution, where the coordination number has been reported to be between 6 and 8. Both theoretical and gas-phase studies of K+(H2O)m cluster ions point to a coordination number closer to 4. In the gas phase, the coordination number is determined by a variety of factors-the most critical being the magnitude of the K+...ligand pairwise interaction. Decreasing the magnitude of the ion...ligand interaction allows more ligands to directly interact with the cation. One method for decreasing the ion...ligand interaction in K+(H2O)m clusters is to systematically substitute weakly bound ligands for the more strongly bound water molecules. The systematic introduction of para-difluorobenzene (DFB) to K+(H2O)m clusters was monitored using infrared photodissociation spectroscopy in the OH stretching region. By varying the ratio of DFB molecules to water molecules present in K+(H2O)m(DFB)n clusters, the observed coordination number of gas-phase K+ was increased to 8, similar to that reported for bulk solution.     

Experimental and theoretical study of the reactions between neutral vanadium oxide clusters and ethane, ethylene, and acetylene

Reactions of neutral vanadium oxide clusters with small hydrocarbons, namely C2H6, C2H4, and C2H2, are investigated by experiment and density functional theory (DFT) calculations. Single photon ionization through extreme ultraviolet (EUV, 46.9 nm, 26.5 eV) and vacuum ultraviolet (VUV, 118 nm, 10.5 eV) lasers is used to detect neutral cluster distributions and reaction products. The most stable vanadium oxide clusters VO2, V2O5, V3O7, V4O10, etc. tend to associate with C2H4 generating products V(m)O(n)C2H4. Oxygen-rich clusters VO3(V2O5)(n=0,1,2...), (e.g., VO3, V3O8, and V5O13) react with C2H4 molecules to cause a cleavage of the C=C bond of C2H4 to produce (V2O5)(n)VO2CH2 clusters. For the reactions of vanadium oxide clusters (V(m)O(n)) with C2H2 molecules, V(m)O(n)C2H2 are assigned as the major products of the association reactions. Additionally, a dehydration reaction for VO3 + C2H2 to produce VO2C2 is also identified. C2H6 molecules are quite stable toward reaction with neutral vanadium oxide clusters. Density functional theory calculations are employed to investigate association reactions for V2O5 + C2H(x). The observed relative reactivity of C2 hydrocarbons toward neutral vanadium oxide clusters is well interpreted by using the DFT calculated binding energies. DFT calculations of the pathways for VO3+C2H4 and VO3+C2H2 reaction systems indicate that the reactions VO3+C2H4 --> VO2CH2 + H2CO and VO3+C2H2 --> VO2C2 + H2O are thermodynamically favorable and overall barrierless at room temperature, in good agreement with the experimental observations.     

Sr2+和Ba2+水分子体系结构和结合能的从头算和ABEEM/MM研究

应用从头算方法和ABEEM/MM浮动电荷分子力场, 研究了水合碱土离子团簇Sr²⁺/Ba²⁺(H₂O)_n (n=1-6), 构建了离子-水相互作用的ABEEM/MM势能函数, 获得了水合离子团簇的稳定结构, 计算了结合能. 计算结果表明, ABEEM/MM方法的结果和从头算方法的结果有很好的一致性. 进一步应用ABEEM/MM对Sr²⁺和Ba²⁺水溶液进行了分子动力学模拟. 对Sr²⁺水溶液, 得到的Sr²⁺-水中氧原子的径向分布函数的第一和第二最高峰分别位于0.257和0.464 nm处, 第一和第二水合层的配位水分子数分别为9.2和11.4; 对Ba²⁺水溶液, 得到的Ba²⁺与水中氧原子的径向分布函数的第一和第二最高峰分别位于0.269和0.467 nm处, 第一和第二水合层的配位水分子数分别为9.9和12.4. 这与实验值或其它理论模拟结果有较好的一致性. 对比外层的水分子, 金属离子的极化作用使得溶液中第一水合层中水分子的O―H键长增长, HOH键角减小.     

Investigation of Structures and Stabilities of AlmPn and AlmP(m+n=2～6)Clusters by DFT

The geometries,electronic states and energies of Alm Pn （ m + n = 2 ～ 6）neutral and anionic clusters have been investigated using the density functional theory（DFT）method of Becke’s three-parameter hybrid exchange functional with the nonlocal correlation of B3LYP. Structural optimization and frequency analyses are performed with the basis of 6-311G（ d）. The calculations predict the existence of a number of previously unknown isomers（i. e. ,Al3P_ and AlmPn （ m + n.5））. The calculations have also predicted that small AlP and（AlP）2 clusters adopt two-and three-dimensional structures characteristic of Si2 and Si4 clusters,while the structures of the larger AlP clusters are different completely from those of Sin clusters with the same electrons. The results show that the structures with the singlet have higher symmetries,while those with the doublet have lower symmetries. The vertical detachment energy of AlmPn （ m + n = 2 ～ 6）are also discused and the adiabatic electron affinities of AlmPn（m + n = 2 ～ 6）and also discussed at the same level. The results agree satisfactorily with the anion photoelectron spectroscopy of aluminum phosphide clusters reported recently by Gomez et al.     

线性变位极谱研究 V:碲的吸附电流方程式

The mechanism of the electroreduction of Te(IV) has been studied, it is (TeO3)2- + 3H2O + 4e = (Teads)0 + 6OH- (1) (Teads)0 + H2O + 2e = (Hte)- + OH- (Teads)0 + 2e = Te2- The reaction scheme can generally be expressed as follows: ACcordingly, the equation of adsorptive current is give: i = 0.629 n2**2F**i/RT \n\(D0)1/2m2/3t7/6 \Pn\/(1+\Pn\)**2 (C0)* where \Pn\ = bAtA,7exp n2F/RT (E-E0)/& When \Pn\ = 1 the current reaches the maximum, ip = 0.157 n2**2F**2/RT \n\(D0)1/2m2/3t7/6(C0)* This equation shows that the peak current ip is proportional to m2/3t7/6, the ratio of potential change v and the concentration of the substance O being reduced. The half wave width, w1/2, can be obtained from the equation (6) in the form of the following expression W1/2 = 3.52RT/n2F The theoretical conclusions are in good agreement with experimental data for the adsorptive wave of tellurium in 0.25M NH3-NH4cl solution. The diffusion coefficient value determined agrees with that obtained by other polarographic method reported in the literature.