Polymer electrolyte fuel cells structure

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

Both temperature and pressure have a significant influence on cell performance the impact of these parameters will be described later. Present cells operate at 80°C, nominally, 0.285 MPa (30 psig) (5), and a range of 0.10 to 1.0 MPa (10 to 100 psig). Using appropriate current collectors and supporting structure, polymer electrolyte fuel cells and electrolysis cells should be capable of operating at pressures up to 3000 psi and differential pressures up to 500 psi (4). 

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. 

Passalacqua, E., Lufrano, R, Squadrito, G., Patti, A., and Giorgi, L. Influence of the structure in low-Pt loading electrodes for polymer electrolyte fuel cells. Electrochimica Acta 1998 43 3665-3673. 

Bolwin, K., Giilzow, E., Bevers, D., and Schnurnberger, W. Preparation of porous electrodes and laminated electrode-membrane structures for polymer electrolyte fuel cells (PEFCs). Solid State Ionics 1995 77 324-330. 

P. Sinha, P. Mukherjee, and C. Y. Wang. Impact of GDL structure and wettability on water management in polymer electrolyte fuel cells. Journal of Materials Chemistry 17 (2007) 3089-3103. 

Schematic depiction of seven-layer structure and basic processes in polymer electrolyte fuel cells under standard operation with hydrogen and oxygen.

Polymer electrolyte fuel cell (PEFC) is considered as one of the most promising power sources for futurist s hydrogen economy. As shown in Fig. 1, operation of a Nation-based PEFC is dictated by transport processes and electrochemical reactions at cat-alyst/polymer electrolyte interfaces and transport processes in the polymer electrolyte membrane (PEM), in the catalyst layers consisting of precious metal (Pt or Ru) catalysts on porous carbon support and polymer electrolyte clusters, in gas diffusion layers (GDLs), and in flow channels. Specifically, oxidants, fuel, and reaction products flow in channels of millimeter scale and diffuse in GDL with a structure of micrometer scale. Nation, a sulfonic acid tetrafluorethy-lene copolymer and the most commonly used polymer electrolyte, consists of nanoscale hydrophobic domains and proton conducting hydrophilic domains with a scale of 2-5 nm. The diffusivities of the reactants (02, H2, and methanol) and reaction products (water and C02) in Nation and proton conductivity of Nation strongly depend on the nanostructures and their responses to the presence of water. Polymer electrolyte clusters in the catalyst layers also play a critical... 

This review considers what we believe to be a suitable method to solve a range of electrochemical related problems in science and engineering, i.e., Adomian decomposition. The method is applied to several problems related to the analysis of three dimensional electrodes.4,5 The typical structure of three dimensional electrodes is shown schematically in Figure 1, in terms of two types of electrode. Figure la, is appropriate for electrodes connected by an electrolyte as typically used in synthesis or in batteries, while Figure lb is for electrodes as used in fuel cells, e.g., polymer electrolyte fuel cells (PEMFC). In general the models are concerned with determining the concentration and potential (and current) distributions in the structure. 

Yang, X.G. and Wang, C.Y., Nano structured tungsten carbide catalysts for polymer electrolyte fuel cells, Appl. Phys. Lett., 86, 224104, 2005. 

M. Uchida, Y. Fukuoka, Y. Sugawara, N. Eda, and A. Ohta, Effects of micro structure of carbon support in the catalyst layer on the performance of polymer-electrolyte fuel cells, J. Electrochem. Soc., 143, 2245 (1996). 

Abstract This article outlines some history of and recent progress in perfluorinated membranes for polymer electrolyte fuel cells (PEFCs). The structure, properties, synthesis, degradation problems, technology for high temperature membranes, reinforcement technology, and characterization methods of perfluorosulfonic acid (PFSA) membranes are reviewed. 

The application to fuel cells was reopened by Ballard stacks using a new Dow membrane that is characterized by short side chains. The extremely high power density of the polymer electrolyte fuel cell (PEFC) stacks was actiieved not only by the higher proton conductance of the membrane, but also by the usage of PFSA polymer dispersed solution, serpentine flow separators, the structure of the thin catalyst layer, and the gas diffusion layer. Although PFSA membranes remain the most commonly employed electrolyte up to now, their drawbacks, such as decrease in mechanical strength at elevated temperature and necessity for humidification to keep the proton conductance, caused the development of various types of new electrolytes and technologies [7], as shown in Fig. 2. 

Passalacqua E, Lufrano F, Squadrito G, Patti A, Gioigi L. Nafion content in the catalyst layer of polymer electrolyte fuel cells effects on structure and performance. Electrochim Acta 2001 46(6) 799—805. 

Y., and Minemoto, M. (2008) Development of simulated gas diffusion layer of polymer electrolyte fuel cells and evaluation of its structure. J. Power Sources, 175, 145-158. 

High-Temperature Polymer Electrolyte Fuel Cells, Fig. 1 Chemical structures of PBI and TPS variants (a) m-PBI,... 

Platinum-Based Cathode Catalysts for Polymer Electrolyte Fuel Cells, Fig. 3 Oxygen reduction on Pt(hkl) in 0.05 M H2SO4 lower part, disk currents upper part, ring currents. Top view of the surface structure of Pt(l 11), Pt(100),andPt(110)... 

Polymer Electrolyte Fuel Cells (PEFCs), Introduction, Fig. 2 Generalized structure ftumula of Nafitype membranes (DuPont) with m = 1, / = 1, fc = 5-7... 

Polymer Electrolyte Fuel Cells, Mass Transport, Fig. 4 Modeled catalyst layer cutout with a side length of 100 nm. The shown random structure includes 64 carbon particles with a diameter of 28 nm colored in blue. The ionomer coating has a thickness of 10 nm and is shown in colors from green to red... 

Polymer Electrolyte Fuel Cells, Membrane-Electrode Assemblies, Fig. 2 Chemical structure of perfluoro-sulfonic acid polymer... 

Figure 8.1. Outline of the general framework for structure-based modeling of catalyst layer operation in polymer electrolyte fuel cells [51], (Reprinted from Elecfrochimica Acta 53.13, Liu J, Eikerling M. Model of cathode catalyst layers for polymer electrolyte fuel cells The role of porous structure and water accumulation, 4435-46, 320 08, with permission from Elsevier.)...

Wakisaka, M., S. Mitsui, Y. Hirose, K. Kawashima, H. Uchida, and M. Watanabe. 2006. Electronic structures of Pt-Co and Pt-Ru alloys for CO-tolerant anode catalysts in polymer electrolyte fuel cells studied by EC-XPS. t. Phys. Chem. B 110 23489-23496. 

Arlt T, Maier W, Totzke C et al (2014) Synchrotron X-ray radioscopic in situ study of high-temperature polymer electrolyte fuel cells—effect of operation conditions on structure of membrane. J Power Sources 246 290-298... 

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