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Modeling of ion conductivity in Nafion membranes

YANG Zhen, PENG Xiaofeng, WANG Buxuan, DUAN Yuanyuan, LEE Duujong

《能源前沿（英文）》 2007年第1卷第1期页码 58-66 doi: 10.1007/s11708-007-0005-y

摘要： A theoretical investigation was conducted to describe the ion transport behavior in a Nafion Membrane of proton exchange membrane fuel cells (PEMFC). By analyzing the surface energy configuration of the ionic clusters in a Nafion membrane, an equivalent field intensity, , was introduced to facilitate the analysis of surface resistance against ion conduction in the central region of clusters. An expression was derived for ionic conductivity incorporating the influence of surface resistance. A face-centered cubic (FCC) lattice model for a spatial cluster distribution was used to modify the effect of water content on ionic conductivity in the polymeric matrix, i.e., the regions between clusters. Compared with the available empirical correlations, the new expression showed much better agreement with the available experimental results, which indicates the rationality to consider the structural influence on ion conduction in water-swollen Nafion membranes.

关键词： face-centered polymeric theoretical investigation conduction equivalent

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Preparation and performance of soft actuator based on IPMC with silver electrodes

Qi CHEN, Ke XIONG, Kan BIAN, Ning JIN, Bangfeng WANG,

《机械工程前沿（英文）》 2009年第4卷第4期页码 436-440 doi: 10.1007/s11465-009-0054-5

摘要： The surface electrodes of traditional ionic polymer-metal composites (IPMC) are made of platinum. To reduce the production cost, nonprecious metals such as silver is proposed. A new approach of electroless silver plating based on chemical deposition method is adopted, getting two types of IPMCs, Pt-Ag IPMC, and Ag-Ag IPMC. The microscopic analysis, driving abilities tests, and their surface-electrode resistance analysis show that Ag and Pt particles penetrate inside Nafion membrane with gradient distribution throughout the membrane. The maximum electro-active bending deformation angles of the specimens, which are obtained under the same specimen dimension and constrains, are about 60° for Pt-Pt IPMC and Pt-Ag IPMC and 90° for the Ag-Ag IPMC, respectively, corresponding to the driving voltage of 3 V, 4 V, and 1.5 V. The surface-electrode resistance of Ag-Ag IPMC is the lowest and the most stable, which shows that the proposed approach is valid. The experiments show that the IPMC technology based on the silver electrode is feasible.

关键词： ionic polymer-metal composites (IPMC) Nafion intelligent material soft actuators electroless silver plating

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Sulfonated poly(ether ether ketone)/zirconium tricarboxybutylphosphonate composite proton-exchange membranes for direct methanol fuel cells

GAO Qijun, HUANG Mianyan, WANG Yuxin, CAI Yuquan, XU Li

《化学科学与工程前沿（英文）》 2008年第2卷第1期页码 95-101 doi: 10.1007/s11705-008-0012-5

摘要： Sulfonated poly(ether ether ketone) (SPEEK) is a very promising alternative membrane material for direct methanol fuel cells. However, with a fairly high degree of sulfonation (DS), SPEEK membranes can swell excessively and even dissolve at high temperature. This restricts membranes from working above a high tolerable temperature to get high proton conductivity. To deal with this contradictory situation, insolvable zirconium tricarboxybutylphosphonate (Zr(PBTC)) powder was employed to make a composite with SPEEK polymer in an attempt to improve temperature tolerance of the membranes. SPEEK/Zr(PBTC) composite membranes were obtained by casting a homogeneous mixture of Zr(PBTC) and SPEEK in N,N-dimethylacetamide on a glass plate and then evaporating the solvent at 60°C. Many characteristics were investigated, including thermal stability, liquid uptake, methanol permeability and proton conductivity. Results showed significant improvement not only in temperature tolerance, but also in methanol resistance of the SPEEK/Zr(PBTC) composite membranes. The membranes containing 30 wt-% ∼ 40 wt-% of Zr(PBTC) had their methanol permeability around 10 cm·s at room temperature to 80°C, which was one order of magnitude lower than that of Nafion115. High proton conductivity of the composite membranes, however, could also be achieved from higher temperature applied. At 100% relative humidity, above 90°C the conductivity of the composite membrane containing 40 wt-% of Zr(PBTC) exceeded that of the Nafion115 membrane and even reached a high value of 0.36 S·cm at 160°C. Improved applicable temperature and high conductivity of the composite membrane indicated its promising application in DMFC operations at high temperature.

关键词： homogeneous mixture PBTC zirconium tricarboxybutylphosphonate Nafion115 DMFC