MOF(Fe)的制备及其氧气还原催化性能

以硝酸铁为金属离子前驱体、均苯三甲酸为有机配体,采用水热法合成了金属有机骨架MOF（Fe）催化剂,应用X射线衍射、N₂吸附-脱附、透射电镜、红外光谱和热重等方法对催化剂的结构进行了表征,并采用循环伏安法测试了催化剂在碱性电解质中的氧气还原（ORR）催化性能,同时也采用旋转圆盘电极进一步研究了催化剂的ORR的动力学行为.?结果表明,所制MOF（Fe）具有很好的晶型结构、大比表面积、丰富的微孔以及较高的热稳定性. 且表现出很好的ORR催化活性. ORR的反应历程随电位的改变而改变：电位在-0.3到0.50 V范围内,ORR为2电子途径;随着电位从-0.50 V升至-0.95 V,ORR从2电子向4电子途径转变. 另外,该催化剂在碱性电解质中也表现出较好的氧气析出（OER）催化性能,这为制备用于ORR和OER的高效非贵金属催化剂提供了新的途径.     

高压锂离子电池电解液的研究进展

电极/电解液界面不稳定是高压锂离子电池发展的主要瓶颈.提高界面稳定性是高压锂离子电池得以应用的前提.本文综述了碳酸酯基电解液氧化分解反应机理、新型耐高压溶剂体系和新型成膜添加剂实验与理论的研究进展.     

咪唑类离子液体用作电解质对燃料电池性能的影响

为优化改善燃料电池的整体性能,在自由电解质燃料电池中,考察了五种咪唑类离子液体用作燃料电池电解质时对燃料电池性能的影响。结果表明,以氢气为燃料时,在相同电流密度下,电路电压和输出功率从高到低依次为1-丁基-3-甲基咪唑四氟硼酸盐 > 1-丁基-3-甲基咪唑六氟磷酸盐 > 氢氧化钠溶液 >> 氯化-1-丁基-3-甲基咪唑 > 溴化-1-丁基-3-甲基咪唑 > 1-丁基-3-甲基咪唑硫酸氢盐;以甲烷为燃料时,相同电流密度下,电路电压和输出功率从高到低则依次为溴化-1-丁基-3-甲基咪唑 > 1-丁基-3-甲基咪唑硫酸氢盐 > 氯化-1-丁基-3-甲基咪唑 > 氢氧化钠溶液> 1-丁基-3-甲基咪唑四氟硼酸盐 > 1-丁基-3-甲基咪唑六氟磷酸盐。以[Bmim]BF₄为氢气燃料电池电解质时,温度升高和离子液体中水含量增加,均会使燃料电池的性能减弱。     

Polymer electrolyte for lithium batteries based on photochemically crosslinked poly(ethylene oxide) and ionic liquid

Polymer/ionic liquid composites were investigated as solvent-free electrolytes for lithium batteries. Ternary electrolytes based upon poly(ethylene oxide), an ionic liquid and a conducting salt were UV crosslinked with benzophenone as the photoinitiator. Crosslinking leads to an increase in mechanical stability of the PEO composites. This straight-forward process provides a way to increase the content of ionic liquid and thus to raise ionic conductivity without loss of mechanical stability. Impedance measurements showed that the ionic conductivity of the composites is not affected by the UV curing process. Moreover, the UV curing process causes a decrease in the degree of crystallinity in the PEO composites which contributes to an increase in ionic conductivity. The present work is related to safety issues of lithium batteries.     

Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers

Ionic liquid monomer couples were prepared by the neutralization of 1‐vinylimidazole with vinylsulfonic acid or 3‐sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at ?83 °C and ?73 °C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10^?9 S cm^?1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium‐co‐vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4 × 10^?8 S cm^?1 at 30 °C. Advanced copolymer, poly(vinylimidazolium‐co‐3‐sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10^?6 S cm^?1 at 30 °C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd.     

Ionic liquids to the rescue? Overcoming the ionic conductivity limitations of polymer electrolytes

Polymer electrolytes – solid polymeric membranes with dissolved salts – are being intensively studied for use in all-solid-state lithium-metal-polymer (LMP) batteries to power consumer electronic devices. The low ionic conductivity at room temperature of existing polymer electrolytes, however, has seriously hindered the development of such batteries for many applications. The incorporation of salts molten at room temperature (room temperature ionic liquids or RTILs) into polymer electrolytes may be the necessary solution to overcoming the inherent ionic conductivity limitations of ‘dry’ polymer electrolytes.     

A novel ternary polymer electrolyte for LMP batteries based on thermal cross-linked poly(urethane acrylate) in presence of a lithium salt and an ionic liquid

A new ternary polymer electrolyte based on thermally cross-linked poly(urethane acrylate) (PUA), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-butyl-N-methylpyrrolidinium TFSI (PYR₁₄TFSI) was developed and tested for application in LMP batteries. The polymer electrolyte was a transparent yellow self-standing material with quite good mechanical properties, i.e., comparable to that of a flexible rubber. The room temperature ionic conductivity of the dry polymer electrolyte was found to be as high as 0.1 mS cm⁻¹ for the compound containing 40 wt% of ionic liquid (PYR₁₄TFSI) and a O/Li ratio of 15/1 (Li⁺ from LiTFSI). The thermal analysis of the new cross-linked electrolyte showed that it was homogeneous, amorphous and stable over a wide temperature range extending from −40 °C to 100 °C. The homogeneity of the polymer electrolyte was also confirmed by SEM analysis.     

Recent progress of composite solid polymer electrolytes for all-solid-state lithium metal batteries

In comparison with lithium-ion batteries (LIBs) with liquid electrolytes, all-solid-state lithium batteries (ASSLBs) have been considered as promising systems for future energy storage due to their safety and high energy density. As the pivotal component used in ASSLBs, composite solid polymer electrolytes (CSPEs), derived from the incorporation of inorganic fillers into solid polymer electrolytes (SPEs), exhibit higher ionic conductivity, better mechanical strength, and superior thermal/electrochemical stability compared to the single-component SPEs, which can significantly promote the electrochemical performance of ASSLBs. Herein, the recent advances of CSPEs applied in ASSLBs are presented. The effects of the category, morphology and concentration of inorganic fillers on the ionic conductivity, mechanical strength, electrochemical window, interfacial stability and possible Li⁺ transfer mechanism of CSPEs will be systematically discussed. Finally, the challenges and perspectives are proposed for the future development of high-performance CSPEs and ASSLBs.     

Asymmetric double-layer composite electrolyte with enhanced ionic conductivity and interface stability for all-solid-state lithium metal batteries

All-solid-state Li metal battery has been regarded as a promising battery technology due to its high energy density based on the high capacity of lithium metal anode and high safety based on the all solid state electrolyte without inflammable solvent.However,challenges still exist mainly in the poor contact and unstable interface between electrolyte and electrodes.Herein,we demonstrate an asymmetric design of the composite polymer electrolyte with two different layers to overcome the interface issues at both the cathode and the anode side simultaneously.At the cathode side,the polypropylene carbonate layer has enough viscosity and flexibility to reduce the inter-facial resistance,while at the Li anode side,the polyethylene oxide layer modified with hexagonal boron nitride has high mechanical strength to suppress the Li dendrite growth.Owing to the synergetic effect between different components,the asprepared double layer composite polymer electrolyte demonstrates a large electrochemical window of5.17 V,a high ionic conductivity of 6.1×10~(-4) S/cm,and a transfe rence number of 0.56,featuring excellent ion transport kinetics and good chemical stability.All-solid-state Li metal battery assembled with LiFePO_4 cathode and Li anode delivers a high capacity of 150.9 mAh/g at 25℃ and 0.1 C-rate,showing great potential for practical applications.     

石墨化氮化碳负载Cu纳米颗粒用作高效氧还原电催化剂

高活性低成本氧还原反应(ORR)电催化剂是燃料电池和金属/空气电池等可再生能源技术的关键组成部分.在离子液体[(C16mim)2CuCl4]和质子化的石墨化氮化碳(g-CN)的存在下,采用简易的水热反应制备了Cu/g-CN电催化剂用于ORR.与纯的g-CN相比,所制Cu/g-CN表现出高的ORR催化活性:起始电势正移99 mV,为2倍动力学电流密度.另外,Cu/g-CN还表现出比商用Pt/C(HiSPECTM 3000,20%)催化剂更好的稳定性和甲醇容忍性.因此,该催化剂作为廉价的高效ORR电催化剂有望应用于燃料电池中.     

High ionic conductivity of all-solid polymer electrolytes based on polyorganophosphazenes

A series of all-solid polymer electrolytes were prepared by cross-linking new designed poly(organophosphazene) macromonomers. The ionic conductivities of these all-solid, dimensional steady polymer electrolytes were reported. The temperature dependence of ionic conductivity of the all-solid polymer electrolytes suggested that the ionic transport is correlated with the segmental motion of the polymer. The relationship between lithium salts content and ionic conductivity was discussed and investigated by Infrared spectrum. Furthermore, the polarity of the host materials was thought to be a key to the ionic conductivity of polymer electrolyte. The all-solid polymer electrolytes based on these poly(organophosphazenes) showed ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature.     

Highly porous LiMnPO4 in combination with an ionic liquid-based polymer gel electrolyte for lithium batteries

A porous well defined LiMnPO₄ cathode material is synthesized by a sol-gel method. The electrochemical performance of the cathode material is evaluated in a cell with an ionic liquid-based polymer electrolyte (0.5 M LITFSI in EMImTFSI) and a lithium metal electrode. The results are compared to a cell with a traditional organic carbonate-based electrolyte (1 M LiPF₆ in EC/DMC). The cell with the ionic liquid-based polymer electrolyte presents an enhanced electrochemical intercalation performance of lithium ions, a high electrochemical stability window of 5 V, and an excellent cycling ability as compared with the organic based counterpart. Furthermore, the ionic liquid-based polymer gel electrolyte effectively prevents the dissolution of manganese — otherwise a common problem.     

The preparation of ionic liquid based iron phosphate/CNTs composite via microwave radiation for hydrogen evolution reaction and oxygen evolution reaction

Water electrolysis is a promising method for hydrogen production, so the preparation of low-cost and efficient electrocatalysts with a quick and simple procedure is crucial. Herein, iron phosphate (Fe₇(PO₄)₆) was prepared via microwave radiation using ionic liquid (IL) as iron and phosphorus dual-source. This method is simple and rapid, and the product can be directly used as electrocatalysts without further treatment. The experimental results show that the IL can influence the morphology and electrocatalytic performance. Moreover, the addition of carbon nanotubes (CNTs) is favorable for formation of iron phosphate nanoparticles to improve the catalytic activities. As hydrogen evolution reaction (HER) catalyst, this iron phosphate/CNTs exhibits an onset overpotential of 120 mV, Tafel slope of 32.9 mV dec^-1, and current densities of 10 mA cm⁻² at overpotential of 185 mV. Then, it obtains a good activity for oxygen evolution reaction (OER) with a low onset potential of 1.48 V, Tafel slope of 73.3 mV dec^-1, and it only needs an overpotential of 300 mV to drive the 10 mA cm⁻². This bifunctional catalyst also shows good durability for HER and OER. This microwave-assisted method provides an outstanding strategy to prepare iron phosphate in a simple and fast process with good catalytic performance for water splitting.     

碳载氧化锰表面氧还原反应路径研究(英文)

氧还原反应(ORR)是一个复杂的过程,尤其在碱性电解液中,炭载型催化剂表面的ORR路径尤为复杂,因为碳本身可以催化ORR以二电子转移过程发生,产生过氧化氢,继而过氧化氢或者发生化学分解生成氧气(HODR),或者发生电化学还原生成OH(HORR).本文详细研究了ORR在常用氧化锰催化剂表面的反应路径.通过比较HODR和HORR的转换频率发现,尽管利用旋转环盘电极方法得到的表观电子转移数接近4,真实的ORR主要是2电子过程,反应生成的过氧化氢继而大部分发生化学分解生成氧气.该结果有助于理解碱性电解质中炭载型过渡金属氧化物电催化剂对ORR的催化行为.     

Recyclable organotungsten Lewis acid and microwave assisted Diels-Alder reactions in water and in ionic liquids

The water-soluble, organotungsten Lewis acid, [OP(2-py)₃W(CO)(NO)₂](BF₄)₂ (1), was synthesized and characterized. A series of 1-catalyzed Diels-Alder reactions were investigated under conventional heating or microwave heating conditions. The cycloaddition reactions were efficiently conducted in either water or in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate. The ionic liquid acts as a powerful medium not only for rate- and selectivity enhancements but also for facilitating catalyst recycling. Dramatic rate acceleration via microwave flash heating as compared to thermal heating was observed.     

Recyclable zinc (II) ionic liquid catalyzed synthesis of azides by direct azidation of alcohols using trimethylsilylazide at room temperature

A new efficient method has been reported for the synthesis of azides by direct azidation of alcohols with TMSN₃ in presence of recyclable task specific ionic liquid (TSIL) [bmim]ZnCl₃ as a catalyst in DCM at room temperature. Ionic liquid [bmim]ZnCl₃ was synthesized under solvent free conditions and characterized by IR, ¹H NMR, ¹³C NMR and HRMS. The Lewis acidity of catalyst was also examined using IR spectroscopy. The main features of this new methodology are high yields of products, recyclability of catalyst, scalability of reaction to gram scale and short reaction time.     

An in-depth look at the effect of Lewis acid catalysts on Diels-Alder cycloadditions in ionic liquids

The present work explores in detail the Diels-Alder reaction between cyclopentadiene and a series of dienophiles, performed in an innovative medium such as an ionic liquid. The potential activation of different Lewis acid catalysts and their load effect when used in combination with this solvent have been explored, in order to settle the improvement on rates and selectivities.     

聚苯胺衍生Fe-N-C催化剂在碱性电解质中对氧还原反应的催化性能

经过热解聚苯胺、碳和FeCl₃的混合物制备的Fe-N-C材料在酸性电解质中对氧还原反应表现出高的催化活性;由于材料中不存在任何贵金属, 因而被认为是一类新型非贵金属氧还原催化剂. 然而这类催化剂在碱性电解质中催化氧还原反应的性能如何尚不清楚. 本文使用旋转圆盘电极技术考察了制备的两个Fe-N-C催化剂在KOH水溶液中催化氧还原反应性能, 发现这两个催化剂表现出比无金属的N掺杂碳材料更高的活性. 与商业Pt/C催化剂相比, 它们催化氧还原反应的起始电势和半波电势分别仅低60和40 mV左右, 计时电流测试表明, 它们比Pt/C催化剂显示出更好的稳定性. 此外, 在这两个Fe-N-C催化剂上的氧还原反应主要遵循四电子途径. 本工作显示, Fe-N-C材料有望用于碱性燃料电池氧还原反应催化剂.     

Effect of simple electrolytes on the thermodynamic properties of room temperature ionic liquids in aqueous solutions

Density, sound velocity and conductivity measurements are carried out on 1-heptyl-3-methylimidazolium bromide ([C₇mim][Br]) in pure water and in aqueous solutions of sodium di-hydrogen citrate, di-sodium hydrogen citrate and tri-sodium citrate over a range of temperatures at atmospheric pressure. The experimental density and sound velocity data are used to calculate the apparent molar volume and isentropic compressibility as a function of temperature and concentration. The effects of temperature and charge on the anion of sodium citrate salts on the apparent molar volume and isentropic compressibility of [C₇mim][Br] are studied. It was found that both of the apparent molar volume and isentropic compressibility of [C₇mim][Br] in aqueous sodium citrate solutions are larger than those in pure water and increase by increasing temperature. The effects of temperature and charge on the anion of sodium citrate salts on the conductivity behavior of the investigated IL solutions are also studied.     

Development of an ionic liquid-based dispersive liquid-liquid micro-extraction method for the determination of phthalate esters in water samples

Ionic liquid-based dispersive liquid-liquid micro-extraction (IL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) for the determination of four phthalate esters, including butyl benzyl phthalate, di-n-butyl phthalate, dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate in water samples. The mixture of ionic liquid (IL) and dispersive solvent was rapidly injected into 10 mL aqueous sample. Then, IL phase was separated by centrifugation and was determined by high-performance liquid chromatography-ultraviolet. The factors influencing the extraction efficiency, such as type and volume of IL, disperse solvent, extraction time, centrifuging time and ionic strength, were investigated and optimized. Under the optimized conditions, the extraction recoveries by the proposed ionic liquid-based dispersive liquid-liquid micro-extraction for the four phthalates ranged from 83.0 to 91.7%. The relative standard deviations were between 7.8 and 15%. The limits of quantification for four phthalates were between 10.6 and 28.5 μg/L. The proposed method was successfully applied for the analysis of PAEs in tap, lake and treated wastewater samples.