Membrane electrolyte assembly preparation

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. 

In earlier investigations by the authors (2,3) solid sulfonic acid resins containing polyarylether and cyano substituents, (II) and (III), respectively, were prepared and used as proton-conductive membranes, electrode electrolytes, electrode paste, and in membrane electrode assemblies. 

Membrane electrode assemblies (MEA) with AEM were prepared with a single-sided ELAT electrode (20% Pt on Vulcan XC-72 and 0.5 mg/cm2 Pt loading) on the cathode side and carbon only electrode on the anode side. The electrodes were assembled on both sides of a membrane without a press procedure and the assembly was sealed in the electrolytic cell. 

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. ... 

In Section 3, the slow rate of the ORR at the Pt/ionomer interface was described as a central performance limitation in PEFCs. The most effective solution to this limitation is to employ dispersed platinum catalysts and to maximize catalyst utilization by an effective design of the cathode catalyst layer and by the effective mode of incorporation of the catalyst layer between the polymeric membrane electrolyte and the gas distributor/current collector. The combination of catalyst layer and polymeric membrane has been referred to as the membrane/electrode (M E) assembly. However, in several recent modes of preparation of the catalyst layer in PEFCs, the catalyst layer is deposited onto the carbon cloth, or paper, in much the same way as in phosphoric acid fuel cell electrodes, and this catalyzed carbon paper is hot-pressed, in turn, to the polymeric membrane. Thus, two modes of application of the catalyst layer - to the polymeric membrane or to a carbon support - can be distinguished and the specific mode of preparation of the catalyst layer could further vary within these two general application approaches, as summarized in Table 4. 

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. 

Nafion 117 (purchased from DuPont) was used as electrolyte membrane for the DMFC single cell, which was pretreated in mildly boiling water with 3% H2O2 for 2 hours, then boiled in 2 M H2SO4 for 2 hours. For each treatment the membrane was washed in de-ionized water several times. After these treatments it was stored in water for preparation of membrane electrode assembly (MEA). Johnson Matthey s unsupported Pt black (2mg/cm ) and Pt-Ru... 

Aquivion E87-12S short-side chain perfluorosulfonic acid (SSC-PFSA) membrane with equivalent weight (EW) of 870 g eq and 120 pm thickness produced by Solvay Specialty Polymers was tested in a polymer electrolyte membrane water electrolyser (PEMWE) and compared to a benchmark Nation N115 membrane (EW 1100 g eq ) of similar thickness [27]. Both membranes were tested in conjunction with in-house prepared unsupported Ir02 anode and carbon-supported Pt cathode electrocatalyst. The electrocatalysts consisted of nanosized Ir02 and Pt particles (particle size 2-4 nm). The electrochemical tests showed better water splitting performance for the Aquivion membrane and ionomer-based membrane-electrode assembly (MEA) as compared to Nafion (Fig. 2.21). Lower ohmic drop constraints and smaller polarization resistance were observed for the electrocatalyst-Aquivion ionomer interface indicating a better catalyst-electrolyte interface. A current density of 3.2 A cm for water... 

The membrane electrode assembly (MEA) is a delicate component in low-temperature fuel cells based on polymer electrolyte membranes. Its condition is affected by many factors (1) selection and preparation of MEA materials (catalysts, supporting carbon powder, membrane materials, binder for MEA hot pressing, etc.), (2) history of MEA usage, (3) fuel cell operation parameters, and so on. The resulting MEA condition exerts a strong influence on the fuel cell performance, which is also a function of running time. 

Finally, Majda has investigated a novel inorganic membrane-modified electrode [32]. The membrane used was a microporous alumina prepared by anodizing metallic aluminum in an acidic electrolyte [33]. Majda et al. lined the pores of these membranes with polymers and self-assembled monolayers and studied electron and ion transfer down the modified pore walls to a substrate electrode surface [32]. Martin and his coworkers have used the pores in such membranes as templates to prepare nanoscopic metal, polymer, and semiconductor particles [34],... 

Concentration of HI over Hix solution by polymer electrolyte membrane electrodialysis was investigated using galvanodynamic and galvanostatic polarisation method. For this purpose, Hix solution with sub-azeotrope composition (HI L HjO = 1.0 0.5 5.8) was prepared. It was noticed that the electrical energy demand for electrodialysis of Hix solution decreases with increasing temperature. From the experimental results, it is concluded that the system resistance crucially affects the electrodialysis cell overpotential and hence the optimisation of cell assembly as well as the selection of low resistance materials should be carried out in order to obtain high performance electrodialysis cell. 

The aforementioned polymeric electrolytes have been effectively used in polymer electrolyte fuel cells operating up to In order to study the single cell performance and apart from the high ionic conductivity of the membrane, several parameters residing the MEA constmction must be taken into account in order to have optimum performance of the cell. Some of these parameters are the amount of the catalyst the ionomer-binder used at the electrodes and its percentage, electrode surface and the preparation method, pressure and the temperature of the MEA assembling and design and constmction parameters of the cell. ... 

In this section, PVA was blended with polyepichlorohydrin (PECH) in DMSO solution to prepare the PVA/PECH blend polymer membrane. The blend membrane was immersed in 6 M KOH aqueous solution to form the alkaline PVA/PECH SPE. It was improved in chemical, mechanical, and electrochemical properties [37]. The optimal blend ratio of PVA PECH was foimd to be 1 0.2. This polymer blend formed a imiform and homogeneous film. High PECH content, such as PVA PECH (1 1), resulted in phase separation morphology. The solid-state Zn/air batteries with PVA/PECH blend polymer electrolytes have been assembled and the test results are listed in Table 2. 

In Chapter 10, the authors will demonstrate the preparation techniques for ASPEM and the characterization results. The relationship between structure and properties will be discussed and compared. The double-layer carbon air cathodes were also prepared for solid-state alkaline metal fuel cell fabrication. The alkaline solid state electrochemical systems, sueh as Ni-MH, Zn-air fuel cells, Al-air fuel cells, Zn-Mn02 and Al-Mn02 cells, were assembled with anodes, cathodes and alkaline solid polymer electrolyte membranes. The electrochemical cells showed excellent cell power density and high electrode utilization. Therefore, these PVA-based solid polymer electrolyte membranes have great advantages in the applications for all-solid-state alkaline fuel cells. Some other potential applieations include small electrochemical devices, sueh as supercapacitors and 3C electronic products. 

A fuel cell reactor was designed for oxidation of ethylene with O2, as shown in Fig. 1. The cell was assembled using a membrane anode prepared from Pd-black supported carbon, a membrane cathode prepared from Pt-black supported carbon, and an electrolyte membrane of H3PO4/ Si02-wool. Selective oxidation of ethylene to acetaldehyde with a 95 % selectivity was performed using ethylene-02 fuel cell reaction at 373 K. Electrocatalysis of the Pd/C anode for the partial oxidation of ethylene is essential [1,4]. 

A gel polymer membrane based on P(MMA-AN-VAc) has been prepared by emulsion polymerization and phase inversion, and exhibits low crystallinity and Tg. Its ionic conductivity at room temperature is 3.48 x 10 g/cm, and its electrochemically stable voltage is above 5.0 V (vs. LP/Li). By further adding fumed silica, the semicrystalline state is changed into an amorphous porous structure. When 10 wt% fumed silica is added, the porosity of the polymer increases with an even distribution of pores. This intercoimected porous structure can improve the electrolyte retention ability and increase the ionic conductivity of the gel polymer from 3.48 x 10 g/cm to 5.13 x 10 3 S/cm. At the same time, the thermal and electrochemical stability of the membrane and the cycling performance of the assembled battery are improved. 

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