Electrolyte membrane Micro

Because of its lower temperature and special polymer electrolyte membrane, the proton exchange membrane fuel cell (PEMFC) is well-suited for transportation, portable, and micro fuel cell applications. But the performance of these fuel cells critically depends on the materials used for the various cell components. Durability, water management, and reducing catalyst poisoning are important factors when selecting PEMFC materials. 

Keywords polymer electrolyte membrane fuel cell (PEMFC), porous silicon, silicon electrodes, micro fuel cells. 

Fuel cell researchers have also investigated other reference electrodes, such as a pseudo-reference electrode constructed by inserting a micro-sized carbon filament between two polymer electrolyte membranes [73], The main advantage of pseudoreference electrodes is their easy implementation, although one disadvantage is that their DC potential is unknown. However, this DC potential may not be that critical because EIS measurements mainly rely on the AC perturbation signal from which the impedance is calculated. 

The fuel solution is fed into the anode side channel. Methanol reacts at the anode and releases electrons, protons, and carbon dioxide. At the cathode, molecnlar oxygen reacts with proton being transported throngh the PEM (Polymer Electrolyte Membrane) from the anode and prodnces water. The electrons travel throngh the external circnit to the cathode. Power generation is performed by the above oxidation-rednction reaction principles. In order to realize micro-mini power sonrces, large nnmbers of DMFC shonld be integrated serially on a substrate. The structure of the proposed DMFC is suitable for this application. 

Solid polymer electrolyte FCs (SPEFCs) were developed last, but, paradoxically, they were the first to have a "commercial" application they powered the on-board instrumentation of the Gemini spacecraft and still power that of the biosatellite. Their acid electrolyte is micro-encapsxilated or laminated onto a proton-exchange membrane. The working temperature is a little above r. t (60-90 C) [7]. 

Looking back, the only unequivocal membrane improvement, in spite of all these efforts, has been the reduction of thickness from 200 jjim in 1995 to <50 (jun in 2005. In terms of chemical or morphological modifications at the microstructural level, no definite recommendations could be discerned so far. The focus of the works reviewed herein has been exploring the fundamental relations between micromorphology and transport from micro- to macroscales for prototypical polymer electrolyte membranes and the understanding of their major principles of operation. 

Soboleva T, Zhao X, Malek K, Xie Z, Navessin T, Holdcroft S (2010) On the micro-, meso-, and macroporous structures of polymer electrolyte membrane fuel cell catalyst layers. ACS Appl Mater Interfaces 2 375-384... 

Micro fuel cells Polymer electrolyte membrane fuel cells Proton exchange membrane fuel cells pPEMFC... 

Micro-Polymer Electrolyte Membrane Fuel Cells ([JI.PEMFC) and Their Challenges... 

Chisaka M, Daiguji H. Effect of glycerol on micro/nano structures of catalyst layers in polymer electrolyte membrane fuel cells. Electrochim Acta 2006 51(23) 4828-33. 

Fabrication and structural characterization of self supporting electrolyte membranes for a micro solid-oxide fuel cell, J. Mater. Res.,... 

The electrolyte membrane is an oxide ion conductive ceramic, whose thickness depends on the cell design. One may distinguish electrolyte-supported cell from electrode-supported cell (Fig. 15.6). In the first case, anode and cathode are deposited onto both faces of the electrolyte membrane. As a direct consequence, the membrane must be mechanically strong, and a minimal thickness of 100 pm is required. In the case of the electrode-supported cell, the anode is actually the mechanical support of the electrolyte first, and next the cathode on the top. Thus, the electrolyte thickness can be greatly reduced, down to 8 pm for classical SOFC devices. More recently, with the development of micro-SOFC, it can reach 100 nm to 1 pm. 

M. Wang, K.W. Feindel, S.H. Bergens, R.E. Wasybshen, In situ quantibcation of the in-plane water content in the NAFION membrane of an operating polymer-electrolyte membrane fuel cell using H micro-magnetic resonance imaging experiments, J. Power Sources 195 (2010) 7316—7322. 

Fig. 1 Schematic of a typical micro-fuel cell stracture with a sohd electrolyte membrane, catalysts, and gas diffusion layers on both sides. The structure is sandwiched by the two current collector bipolar plates acting also as the flow fields (After Morse 2007)...

Metal foam (see, for example. Figure 3.5) has already been discussed in the context of heat exchangers. Micro-reactors, highly relevant to the subject of small fuel cells, have also been introduced in earlier chapters. The construction of metal foam based methanol steam micro-reformers to generate hydrogen for polymer electrolyte membrane fuel cells (PEMFCs) has been reported and in Guangzhou, Chinese researchers have looked at laminated micro-reactors in which copper-based catalysts have been supported by metal foams (see Figure 11.11 Yu et al., 2007). 

Fig. 19.4 An example of a micro-planar SOFC produced by micro-fabrication methods, (a) The sequence of fabrication steps, (b) the corrugated electrolyte membrane before deposition of the electrodes, and (c) the electrochemical performance [12], Reproduced with permission...

Tang H, Wang S, Pan M, Yuan R. Porosity-graded micro-porous layers for potymer electrolyte membrane fuel cells. J Power Sources 2007 166(l) 41-6. 

In this chapter, the electrode construction of a high temperature (HT) polymer electrolyte membrane (PEM) electrode assembly (MEA) will be explained. The different functionalities of the electrode layers like the gas diffusion layer (GDL), the micro porous layer (MPL), and the... 

James JP (2012) Micro-computed tomography reconstruction and analysis of the porous transport layer in polymer electrolyte membrane fuel cells. Master, Queen s University, Kingston... 

We begin with the discussion of cell thermodynamics and electrochemistry basics (Chapter 1). This chapter may serve as an introduction to the field and we hope it would be useful for the general reader interested in the problem. Chapter 2 is devoted to basic principles of structure and operation of the polymer electrolyte membrane. Chapter 3 discusses micro- and mesoscale phenomena in catalyst layers. Chapter 4 presents recent results in performance modeling of catalyst layers, and in Chapter 5 the reader will find several applications of the modeling approaches developed in the preceding chapters. 

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