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.     

合成介孔纳米晶体氧化锆的新方法(英文)

通过一种新颖的方法,即软模板-固液技术(CSSL)合成具有高比表面积的介孔纳米晶体氧化锆.首先,通过软模板法以1-十六烷基-3-甲基咪唑溴(C16mim+Br-)为结构导向剂,硫酸锆为无机前驱物合成了介观相氧化锆杂化物,然后该杂化物与固体硝酸铜无机盐研磨并进行热处理.在600℃焙烧后所得到的氧化锆材料具有蠕虫状介孔结构,且孔壁由尺寸约为2.50nm的四方相氧化锆纳米粒子组成.该材料的比表面积为240.0m2·g-1,孔径为4.10nm.与之对应,使用单一的软模板法在相同的温度焙烧后,所得到的氧化锆材料介孔结构坍塌,比表面积仅为9.5m·2g-1.     

Deposition of thin mesoporous silica films on glass substrates from basic solution

Transparent thin (ca. 100 nm) films of silica-surfactant mesostructured materials were deposited on borosilicate glass plates and soda-lime glass tubes from aqueous solutions containing tetraethoxysilane, alkyltrimethylammonium chloride, ammonia, and methanol. By calcination in air, the films became mesoporous (BET surface area of 700-900 m2 g-1) with pore diameter 2.0-2.8 nm.     

耐温高比表面氧化锡制备

对比了氨水或NaOH共沉淀和尿素水解均相沉淀三种不同的制备方法,以及NaOH沉淀不 同的老化条件下制备的SnO2粉体材料的比表面以及烧结特性.实验结果表明,减慢成核速度 及在母液中高温老化都有利于提高初始粒子的晶化程度和焙烧后样品的比表面.以NaOH共沉 淀,在100 ℃下回流老化48 h制备的SnO2具有最大的比表面和最好的烧结性能,在500、800 和1000 ℃焙烧后比表面分别为94、75和53 m2穏-1.初始粒子晶化程度的提高以及材料中 硬团聚的减小是改善SnO2烧结性能的主要原因.     

碱土金属对ZrO2-Al2O3及其负载Pd-Rh密偶催化剂的影响

采用胶溶法制备了一系列碱土金属改性的ZrO₂-Al₂O₃, 并以其为载体采用等体积浸渍法制备了Pd-Rh密偶催化剂. 采用低温N₂吸附-脱附、X射线衍射(XRD)、氨气程序升温脱附(NH3-TPD)对载体样品进行了表征. 结果表明, 碱土金属的添加增大了ZrO₂-Al₂O₃的比表面积, Sr-Zr-Al样品经1000 °C焙烧5 h后具有最大的比表面积, 为164 m²·g^-1. 对催化剂进行了H₂程序升温还原(H₂-TPR)、X射线光电子能谱(XPS)和活性表征, 考察了催化剂对C₃H₈的转化活性. 测试结果表明, 添加碱土金属能有效提高催化剂上丙烷的转化活性.     

胶溶法制备铈锆镧共改性氧化铝及催化性能

γ-Al2O3是机动车尾气净化催化剂的常用载体,其高温热稳定性、比表面积、孔容、孔径及表面酸性等对催化活性有很大影响.近年来,大量研究结果表明,铈、锆、镧和钡等元素的添加可以提高氧化铝的高温热稳定性和催化活性[1～3],然而这些研究大多致力于单组分或者双组分改性氧化铝,制备方法以浸渍法和溶胶-凝胶法为主.胶溶法制备三组分共同改性氧化铝的研究很少.本文利用胶溶法制备了系列铈、锆、镧改性氧化铝,讨论了三组分共同添加对氧化铝载体的性质以及催化剂活性的影响.     

焙烧温度对甲醇水蒸气重整制氢Ce/Cu/Zn-Al水滑石衍生催化剂的影响

采用原位合成法在γ-Al_2O_3载体表面上合成了Zn-Al水滑石,再采用顺序浸渍法制备了一系列Ce/Cu/Zn-Al催化剂,并采用XRD、BET、H_2-TPR和XPS等手段对催化剂进行了表征,考察了焙烧温度对Ce/Cu/Zn-Al催化剂表面结构及其催化甲醇水蒸气重整制氢性能的影响。结果表明,焙烧温度主要影响了催化剂的Cu比表面积、表面氧空穴含量和Cu-Ce间相互作用。当焙烧温度为500℃时,催化剂Cu的比表面积较大,表面氧空穴含量较多,Cu-Ce间相互作用较强,因此,催化甲醇水蒸气重整制氢活性较好。当焙烧温度升高到700℃时,Cu物种主要以稳定的CuAl_2O_4尖晶石形式存在,不利于甲醇水蒸气重整制氢反应的进行,因此,催化活性较差。     

载体对Pt/WO_3-ZrO_2催化临氢异构反应性能的影响

以平衡吸附过氧钨酸的水合氧化锆为前驱体,经焙烧得到WO_3-ZrO_2固体酸,并采用XRD、UV-vis、NH_3-TPD等手段考察了过氧钨酸吸附液浓度及焙烧温度对WO_3-ZrO_2固体酸组成、结构及酸性的影响。通过BET、H_2-TPR、H_2-TPD等表征手段和正戊烷临氢异构反应,考察了负载铂后相应催化剂的结构、还原与氢吸附性质及其催化正戊烷临氢异构反应的性能。结果表明,焙烧温度为700℃时,随着吸附液浓度的增加,所得载体酸度及相应催化剂比表面积均先增加后减小,且在吸附液浓度为82 mmol W/L时达到最大值。吸附液浓度为59 mmol W/L时,随着焙烧温度的升高,所得载体四方相氧化锆含量、酸度及相应催化剂比表面积均降低。吸附液浓度为82 mmol W/L、焙烧温度为700℃所得载体负载0.5%(质量分数)铂后催化活性最高。该催化剂在250℃常压临氢操作、n(H_2)/n(n-C_5H_(12))为3、WHSV为1.0 h~(-1)的条件下,催化正戊烷异构反应中异戊烷收率可达57.7%。     

制备方法对锰Mn掺杂钾六铝酸盐催化剂催化甲烷燃烧性能的影响

以甲烷催化燃烧为目标反应,通过共沉淀法、溶胶凝胶法和反相微乳液法制备了Mn掺杂六铝酸盐催化剂,用XRD和TG-DTA技术对催化剂进行了物理性能表征,通过BET模型计算了其比表面积。结果说明3种方法所制备催化剂经1 200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中反相微乳液法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性,起燃温度T10%为458℃,至676℃甲烷完全转化。     

La2-xCexCu1-yZnyO4 perovskites for high temperature water-gas shift reaction

The performance of La2-xCexCu1-yZnyO4 perovskites as catalysts for the high temperature water-gas shift reaction (HT-WGSR) was inves-tigated. The catalysts were characterized by EDS, XRD, BET surface area, TPR, and XANES. The results showed that all the perovskites exhibited the La2CuO4 orthorhombic structure, so the Pechini method is suitable for the preparation of pure perovskite. However, the La1.90Ce0.10CuO4 perovskite alone, when calcined at 350/700℃, also showed a (La0.935Ce0.065)2CuO4 perovskite with tetragonal struc-ture, which produced a surface area higher than the other perovskites. The perovskites that exhibited the best catalytic performance were those calcined at 350/700 ℃ and, among these, La1.90Ce0.10CuO4 was outstanding, probably because of the high surface area associated with the presence of the (La0.935Ce0.065) 2CuO4 perovskite with tetragonal structure and orthorhombic La2CuO4 phase.     

耐高温高比表面氧化铬/氧化锆体系的制备和表征

采用浸渍法和共沉淀法制备了CrOx/ZrO2样品.制备过程中所得沉淀都经100 ℃碱液回流老化24 h.通过X射线衍射、X射线光电子能谱、氮吸附、差热-热重分析等手段对样品进行了表征.结果证实,碱液回流过程中会有SiO2从所用的玻璃器皿进入样品， SiO2的表面修饰作用提高了载体的热稳定性.氧化铬的引入进一步提高了所得样品的比表面和热稳定性.与浸渍法相比，共沉淀法制备的样品具有更好的性能.其中铬锆摩尔比为0.15时，用NaOH作沉淀剂， pH值为13的条件下制备的样品在1000 ℃焙烧后比表面仍达到121 m2•g－1.