Membrane electrode assembly cell performance

HBP-SA, HBP-SA-Ac, HBP-PA and HBP-PA-Ac polymers, interpenetrated electrolyte membrane HBP-SA-co-HBP-Ac, and the crosslmked membranes CL-HBP-SA and CL-HBP-PA showed the VTF-type temperature dependence. These polymers and membranes are thermally stable up to 260 °C, and they had suitable thermal stability as an electrolyte in the polymer electrolyte fuel cell operating under non-humidified conditions. Fuel cell measurement using a single membrane electrode assembly cell with crosslinked membranes CL-HBP-SA and CL-HBP-PA was successfully performed under non-humidified conditions, and polarization curves were observed. The concept of the proton conduction coupled with the polymer chain motion was proposed as one possible approach toward high temperature fuel cells. 

Sol-gel techniques have been successfidly applied to form fuel cell components with enhanced microstructures for high-temperature fuel cells. The apphcations were recently extended to synthesis of hybrid electrolyte for PEMFC. Although die results look promising, the sol-gel processing needs further development to deposit micro-structured materials in a selective area such as the triple-phase boundary of a fuel cell. That is, in the case of PEMFC, the sol-gel techniques need to be expanded to form membrane-electrode-assembly with improved microstructures in addition to the synthesis of hybrid membranes to get higher fuel cell performance. 

Bose, A. B., Shaik, R., and Mawdsley, J. Optimization of the performance of polymer electrolyte fuel cell membrane electrode assemblies Roles of curing parameters on the catalyst and ionomer structures and morphology. Journal of Power Sources 2008 182 61-65. 

Bender, G., Zawodzinski, T. A., and Saab, A. P. Fabrication of high-precision PEFG membrane electrode assemblies. Journal of Power Sources 2003 124 114—117. Ihm, J. W., Ryu, H., Bae, J. S., Ghoo, W. K., and Ghoi, D. K. High performance of electrode with low Pt loading prepared by simplified direct screen printing process in PEM fuel cells. Journal of Materials Science 2004 39 4647--4649. 

T. Erey and M. Linardi. Effects of membrane electrode assembly preparation on the polymer electrolyte membrane fuel cell performance. Electrochimica Acta 50 (2004) 99-105. 

Advances in fuel cell technology over the last four decades have come primarily from improved electrocatalysts, membrane electrode assembly fabrication strategies, and cell/stack/system engineering. Apart from Nafion, new ion conducting polymeric materials have played only a minor role in significantly increasing cell performance. However, new materials... 

The membrane electrode assembly (MEA), which consists of three components (two gas diffusion electrodes with a proton exchange membrane in between), is the most important component of the PEMFC. The MEA exerts the largest influence on the performance of a fuel cell, and the properties of each of its parts in turn play significant roles in that performance. Although all the components in the MEA are important, the gas diffusion electrode attracts more attention because of its complexity and functions. In AC impedance spectra, the proton exchange membrane usually exhibits resistance characteristics the features of these spectra reflect the properties of the gas diffusion electrode. In order to better understand the behaviour of a gas diffusion electrode, we introduce the thin-film/flooded agglomerate model, which has been successfully applied by many researchers to... 

A publication by the Paul Scherrer Institute reports progress in preparing membrane/electrode assemblies for polymer electrolyte fuel cells based on radiation-grafted FEP PSSA membranes [95]. Hot-pressing with Nation was used to improve the interfaces. These improved MEAs showed performance data comparable to those of MEAs based on Nafion 112 (Figure 27.58) and an service-life in H2/O2 fuel cells of more than 200 h at 60°C and 500 mA cm. ... 

The catalyst can be bonded to the membrane surfaces by many different methods such as vacuum deposition (21). However, the performance of the membrane-electrode assembly produced by the vacuum deposition method is poor because a smooth metallic layer is formed while electrode material for an electrochemical cell should be rough (high surface area). 

Design and optimize membrane-electrode assemblies (MEAs) to enhance cell performance. 

Electrodes were fabricated with catalyst layers containing platinum-ruthenium alloys and platinum-ruthenium oxide. Membrane electrode assemblies were fabricated with such cells, and the performance was evaluated in a full cell configuration. Although ruthenium oxide is a proton conductor and is expected to enhance the rate of proton transport from the interface during methanol oxidation, no noticeable improvement in activity of the catalyst layer was observed by addition of ruthenium oxide. The role of other metal oxides such as tungsten oxide will be investigated next year, along with evaluation of non-noble metal catalysts based on nickel, titanium, and zirconium. 

Recently, taking advantage of the very narrow size distribution of the metal particles obtained, microemulsion has been used to prepare electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) Catalysts containing 40 % Pt Ru (1 1) and 40% Pt Pd (1 1) on charcoal were prepared by mixing aqueous solutions of chloroplatinic acid, ruthenium chloride and palladium chloride with Berol 050 as surfactant in iso-octane. Reduction of the metal salts was complete after addition of hydrazine. In order to support the particles, the microemulsion was destabilised with tetrahydrofurane in the presence of charcoal. Both isolated particles in the range of 2-5 nm and aggregates of about 20 nm were detected by transmission electron microscopy. The electrochemical performance of membrane electrode assemblies, MEAs, prepared using this catalyst was comparable to that of the MEAs prepared with a commercial catalyst. 

Further improvements to membrane and membrane-electrode-assembly fabrication techniques resulted in cells with superior electrical performance to those previously tested, as shown in Fig. 1.100. In attempt to improve the... 

Based on the Model 3, a 10-cell stack of microfuel cells was assembled. It was reported that an output of near 10 W was achieved, as shown in Fig. 8.23 [47]. Recently, through membrane electrode assembly (MEA) improvement, a power density 290 mW cm of the cell with an air cathode has been achieved. A 5-cell stack with effective area of 67 cm demonstrated that the power reached IlOW when the operating temperature reached 60 °C, though the stack started at room temperature without humidification. The performances of single ceU and 5-ceU stacks are shown in Fig. 8.24. 

Michel M, Taylor A, Sekol R, Podsiadlo P, Ho P, Kotov N, Thompson L, et al. (2(X)7) High-performance nanostructured membrane electrode assemblies for fuel cells made by layer-by-layer assembly of carbon nanocoUoids. Adv. Mater. 19 3859—3864. 

The earliest PEMFC system models [1,2] were for single cells at steady state, assuming isothermal and isobar conditions. Performance is averaged over the cross-channel direction, and transport in gas channels is decoupled from transport through the Membrane Electrode Assembly (MEA). The power of... 

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