燃料电池聚合物电解质膜的研究进展

本文根据聚合物电解质膜燃料电池操作温度、使用的电解质和燃料的不同,将其分为高温质子交换膜燃料电池、低温质子换膜燃料电池、直接甲醇燃料电池和阴离子交换膜燃料电池,综述了它们所用电解质膜的最新进展.第一部分简要介绍了这4种燃料电池的优点和不足.第二部分首先介绍了Nafion膜的结构模型,并对平行柱状纳米水通道模型在介观尺度上进行了修正;接着分别对应用于不同燃料电池的改性膜的改性思路作了分析;最后讨论了用于不同燃料电池的新型质子交换膜的研究,同时列举了性能突出的改性膜和新型质子交换膜.第三部分介绍了阴离子交换膜的研究现状.第四部分对未来聚合物电解质膜的研究作了展望.     

Polyaromatic-terminated iron(ii) clathrochelates as electrocatalysts for efficient hydrogen production in water electrolysis cells with polymer electrolyte membrane

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Improving protonic conduction of membranes for polymer electrolyte fuel cells

Method for the modification of proton-conducting Nafion membranes by using a zirconium citrate one-substituted salt, aimed at the improving of characteristics of membranes for polymer-electrolyte-based fuel cells, is suggested. In the method, the membrane is impregnated first with zirconyl chloride and then with citric acid; an insoluble sol is thus formed in the membrane pores. The impregnation is carried out in ultrasound bath, using an isopropyl alcohol-water solvent, to make it more rapid and uniform. It is shown that the impregnation lowers the real component of the membrane impedance. The discharge characteristics of the impregnated and nonimpregnated membranes are compared.     

Active layer of the cathode of a fuel cell with a solid polymer electrolyte: The effect of the Nafion concentration on the overall characteristics

A computer-aided simulation of the structure of the active layer of the cathode of a fuel cell with a solid polymer electrolyte (Nafion) is performed under the assumption about equidimensionalness of dimensions of grains of the substrate (with platinum crystallites in them) and grains (agglomerates of molecules) of Nafion. It is analyzed how the Nafion concentration affects principal parameters, which include the specific surface area, in the vicinity of which electrochemical process goes on; the effective ionic electroconductivity, and the effective diffusion coefficient of a gas. It is demonstrated how one can determine the Nafion concentration at which the overall current takes on a maximum value. Dependences of the optimum value of the overall current and the thickness of the active layer and the weight of platinum, which correspond to it, on the Nafion concentration are calculated. It is demonstrated that there in principle cannot exist one individual optimum concentration of Nafion, which is suitable for all techniques used for the preparation of the active layer. The mutual relationship between values of the effective diffusion coefficient of a gas and the effective ionic electroconductivity of Nafion determines the value of the optimum of the Nafion concentration.     

Mass transfer in porous systems, flooded in part with water, of gas diffusion and catalytic layers of the cathode of a fuel cell with a solid polymer electrolyte

Mass transfer in porous gas diffusion and catalytic layers of the cathode of a hydrogen-air fuel cell with a solid polymer electrolyte is considered. The transport processes are considered with allowance made for the partial flooding of porous systems of these layers with water, which forms during the fuel cell operation. The consideration also allows for the influence of the diluent gas present when air oxygen is used as the oxidant. The fraction of water-flooded pores is calculated within percolation theory as a function of structural parameters of the porous system. Conditions leading to the beginning of the gas diffusion layer flooding are presented.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

Gas diffusion electrodes for polymer electrolyte fuel cell using sulfonated polyimide

Gas diffusion electrodes for high temperature polymer electrolyte fuel cells (PEFCs) have been prepared by using a novel proton conductive sulfonated polyimide (SPI) electrolyte. The catalyst layer was composed of Pt-loaded carbon black (Pt-CB) and SPI ionomer. The polarization properties and the microstructure of the catalyst layer were investigated as a function of the SPI/CB weight ratio. The anodic polarization was found to be negligibly small for all the compositions examined. The highest cathode performance was obtained at SPI/CB = 0.5 (by weight), where the best balance of high catalyst utilization and oxygen gas diffusion rate through the ionomer was obtained.     

Preparation of microtubular solid oxide fuel cells based on highly asymmetric structured electrolyte hollow fibers

A simple and cost-effective method has been developed for the fabrication of microtubular solid oxide fuel cells (MT-SOFCs). Highly asymmetric electrolyte hollow fibers composed of a thin dense skin layer and a thick porous substrate are first prepared by a modified phase inversion/sintering technique. The porous substrate is then formed into the anode by deposition of a Ni catalyst via an electroless plating method inside the pores while the thin dense skin layer serves directly as the electrolyte film of ...     

基于高度非对称结构电解质中空纤维的微管式固体氧化物燃料电池制备

提出了一种简单而方便的微管式固体氧化物燃料电池(MT-SOFCs)的制备新方法.首先应用改进相转化-烧结技术制备由致密电解质表皮薄层和多孔支撑层构成的高度非对称结构电解质中空纤维膜(微管),在电解质中空纤维膜的多孔支撑层内通过化学镀法沉积Ni催化剂作为电池阳极,而致密电解质表皮层直接作为电解质膜,在电解质微管外表面用浆料涂层法制备电池的多孔阴极,烧结后即得到完整的MT-SOFC.应用该方法制备了Ni-YSZ|YSZ|LSCF微管式电池,该电池以H2/空气作原料气,在800℃时最大输出功率达到159.6mWcm-2.     

Alkaline polymer electrolyte fuel cells: Principle, challenges, and recent progress

Polymer electrolyte membrane fuel cells (PEMFC) have been recognized as a significant power source in future energy systems based on hydrogen. The current PEMFC technology features the employment of acidic polymer electrolytes which, albeit superior to electrolyte solutions, have intrinsically limited the catalysts to noble metals, fundamentally preventing PEMFC from widespread deployment. An effective solution to this problem is to develop fuel cells based on alkaline polymer electrolytes (APEFC), which no...     

Preparation of electrolyte membranes for micro tubular solid oxide fuel cells

Yttria-stabilized zirconia (YSZ) micro tubular electrolyte membranes for solid oxide fuel cells (SOFCs) were prepared via the combined wet phase inversion and sintering technique. The as-derived YSZ mi- cro tubes consist of a thin dense skin layer and a thick porous layer that can serve as the electrode of fuel cells. The dense and the porous electrolyte layers have the thickness of 3-5 μm and 70-90 μm, respectively, while the inner surface porosity of the porous layer is higher than 28.1%. The two layers are perfectly integrated together to preclude the crack or flake of electrolyte film from the electrode. The presented method possesses distinct advantages such as technological simplicity, low cost and high reliability, and thus provides a new route for the preparation of micro tubular SOFCs.     

Model for the multicomponent gas diffusion in a fuel cell porous electrode

A simple analytically solvable model for the diffusion of a multicomponent vapor-air mixture is proposed. The model, which accurately accounts for the oxygen and water balance on the gas diffusion cathode of a fuel cell, is used for computing polarization characteristics of a fuel cell with a polymer electrolyte. An analytical solution for the cathodic overvoltage in the extreme cases of high and low current densities is derived. The results are compared with the available theoretical and experimental data. It is shown that the solutions of the proposed model coincide with the solutions provided by the Bernardi-Verbrugge model, which is far more involved.     

Cathode of a fuel cell with a solid polymer electrolyte: Calculating overall currents in the presence of a gas-diffusion layer

Mathematical apparatus, which makes it possible to perform calculations of the current-voltage characteristics of cathodes of fuel cells with a solid polymer electrolyte in conditions where there are present extraneous diffusion restrictions is proposed. In so doing, the partial pressure of oxygen and the absolute pressure of gas in the gas chamber may assume any values. First of all presented are the results of calculations of the current-voltage characteristics intrinsic to active layers of the air and oxygen cathodes, which are performed under the assumption that the extraneous diffusion restrictions are absent altogether. Thereafter, in the same conditions (at the same parameters that characterize the active layer of a cathode), obtained are results of a calculation of the current-voltage characteristics inherent in the air and oxygen cathodes in the presence of extraneous diffusion restrictions. Afterward there is performed an analysis of the way a gas-diffusion layer restricts the process of generation of current in a cathode and of what measures should be taken in order for the extraneous diffusion restrictions to become less significant.     

X-ray absorption fine structure and scanning transmission electron microscopic analysis of polymer electrolyte fuel cells

We introduce nano-X-ray absorption fine structure and scanning transmission electron microscope-energy dispersive X-ray spectroscopy, which are identical location measurement methods that can provide complementary information on the various constituents of polymer electrolyte fuel cells. In these methods, the membrane electrode assembly samples were measured ex situ in conditions as close as possible to those in fuel cells under humid N₂. The sample preparation and measurement optimization are important. Herein, we mainly reported on these identical location measurement methods, that is, the nano-X-ray absorption fine structure and scanning transmission electron microscope-energy dispersive X-ray spectroscopy and then discuss the results that could be obtained.     

Effect of the fuel electrode composition and structure on the performance of the direct methanol fuel cell

The effect the composition and structure of the active layer of the anode exerts on the performance of the solid-polymer direct methanol fuel cell is studied experimentally. It is shown that the ohmic voltage losses in the layer and the content of the solid polymer electrolyte (SPE) play an important role. The performance of the fuel cells is the best at 20–25 vol % SPE in the layer.     

Cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte: The effect of the flooding of pores by water on the characteristics of the active layer

A computer model of the active layer of the cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte is studied. The active mass of the electrode consists of equidimensional grains of the substrate (agglomerates of carbon particles with platinum particles embedded in them) and a solid polymer electrolyte (Nafion). The flooding by water can be experienced by both the pores in the substrate grains, which facilitate the oxygen penetration into the active layer of the electrode, and the voids between the grains. All possible versions of the flooding of these pores by water are considered. A calculation of the optimum, at a given polarization of the electrode, value of electrochemical activity, the thickness of the active layer, and the weight of platinum is performed. The major parameters of the system are the concentrations of grains of the substrate and solid polymer electrolyte, the size of these grains, the platinum concentration in the substrate grains, the average diameter of pores in the substrate grains, and the polarization of electrodes. The ultimate aim of the work is to estimate how the flooding of pores of the active layer of the cathode by water affects the magnitude of the optimum current, the effective thickness of the active layer, and the weight of platinum.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 35–47.Original Russian Text Copyright © 2005 by Chirkov, Rostokin.     

LSM-infiltrated LSCF cathodes for solid oxide fuel cells

Mixed ionic-electronic conductors in the family of La_xSr_1–xCo_yFe_1–yO_3–δ have been widely studied as cathode materials for solid oxide fuel cells (SOFCs). However, the long-term stability was a concern. Here we report our findings on the effect of a thin film coating of La_0.85Sr_0.15MnO_3–δ (LSM) on the performance of a porous La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) cathode. When the thicknesses of the LSM coatings are appropriate, an LSM-coated LSCF electrode showed better stability and lower polarization (or higher activity) than the blank LSCF cathode without LSM infiltration. An anode-supported cell with an LSM-infiltrated LSCF cathode demonstrated at 825 °C a peak power density of ～1.07 W/cm², about 24% higher than that of the same cell without LSM infiltration (～0.86 W/cm²). Further, the LSM coating enhanced the stability of the electrode; there was little degradation in performance for the cell with an LSM-infiltrated LSCF cathode during 100 h operation.     

不同含钴阴极在YSZ薄膜电解质固体氧化物燃料电池中的性能

固体氧化物燃料电池阴极材料的阻抗对固体氧化物燃料电池的性能有较大影响.我们通过XRD、对称电池以及单电池性能测试等方法比较系统地研究了4种最为常用的含钴阴极材料直接用于钇稳定化氧化锆（YSZ）电解质薄膜与通过引入SDC夹层后用于YSZ电解质薄膜后的性能.我们发现,不同的含钴阴极材料与YSZ材料之间都不同程度地发生相反应,在应用于YSZ电解质薄膜上时,相反应大大降低了含钴阴极材料的性能,在使用了SDC夹层后,单电池的功率输出显著提高.     

聚合物固态电解质–高电压正极界面稳定性研究进展

聚合物固态电解质相比于液态电解质表现出更良好的热稳定性,并且对比无机固态电解质具有机械性能好、耐候性好和易加工成型等特点,因此在下一代高能量密度储能装置中极具应用潜能.然而,固态电解质与正负极材料之间的界面稳定性问题阻碍了其实际应用.本文总结了锂离子聚合物固态电解质的关键特性,讨论了聚合物固态电解质与高电压正极的普遍界面问题,包括界面接触不良与界面不稳定问题.分析了导致高电压富镍氧化物正极材料与聚合物固态电解质严重界面问题的主要因素,针对相关因素总结了缓解界面问题的有效策略,并展望了未来聚合物固态电解质与富镍层状氧化物的界面性能提升的研究方向,为基于聚合物固态电解质与高电压正极材料固态锂电池的研究提供参考.