Polymer electrolyte fuel cell cathode side

Polymer Electrolyte Fuel Cells (PEFCs), Introduction, Fig. 4 Electrode layer (interphase) with three phase boundary (schematic) of a polymer electrolyte fuel cell (cathode side). Blue, polymer electrolyte black, carbon particles grey, platinum nanoparticles (Adopted from L. Gubler)... 

Figure 6.6. Polarization curves of fuel cells with electrodes containing 40 wt% PTFE in the gas diffusion layer. The temperature of the humidifier on the cathode side was maintained at ( ) 65°C and ( ) 80°C. For comparison, the polarization curve of the fuel cell with the electrode containing 30 wt% PTFE in the gas diffusion layer is shown at the cathode humidification temperature of 65°C (A) [5], (Reprinted from Journal of Power Sources, 94(1), Song JM, Cha SY, Lee WM. Optimal composition of polymer electrolyte fuel cell electrodes determined by the AC impedance method, 78-84, 2001, with permission from Elsevier and the authors.)...

Okada, T. Theory for water management in membranes for polymer electrolyte fuel cells part 2. The effect of impurity ions at the cathode side on the membrane performances. J. Electro-anal. Chem. 1999, 465 (1), 18-29. 

As illustrated in Figure 1.2, one side of the cathode GDL facing to the catalyst layer is generally provided with a micro-porous layer (MPL) of polytetrafluoroethylene (PTFE) with hydrophobic characteristics. It has much smaller pores and a much smoother surface than the GDL. The MPL plays an important role in the water management of polymer electrolyte fuel cells however, details of the meehanism that works to suppress water flooding are not fully understood. Questions still remain about whether the water transfer in the MPL occurs in the liquid or vapor phase. 

The polymer electrolyte membrane fuel cell (PEMFC) also known as proton exchange membrane fuel cell, polymer electrolyte fuel cell (PEFC) and solid polymer fuel cell (SPFC) was first developed by General Electric in the USA in the 1960 s for use by NASA in their initial space applications. The electrolyte is an ion conducting polymer membrane, described in more details in Section 2.2. Anode and cathode are bonded to either side of the membrane. This assembly is normally called membrane electrode assembly (MEA) or EMA which is placed between the two flow field plates (bipolar plates) (Section 2.5) to form what is known as stack . The basic operation of the PEMFC is the same as that of an acid electrolyte cell as the mobile ions in the polymer are or proton. 

Figure 4.1 shows a schematic of a typical polymer electrolyte membrane fuel cell (PEMFC). A typical membrane electrode assembly (MEA) consists of a proton exchange membrane that is in contact with a cathode catalyst layer (CL) on one side and an anode CL on the other side they are sandwiched together between two diffusion layers (DLs). These layers are usually treated (coated) with a hydrophobic agent such as polytetrafluoroethylene (PTFE) in order to improve the water removal within the DL and the fuel cell. It is also common to have a catalyst-backing layer or microporous layer (MPL) between the CL and DL. Usually, bipolar plates with flow field (FF) channels are located on each side of the MFA in order to transport reactants to the... 

Another characteristic of the proton-conducting membrane is that it has low permeability to oxygen and hydrogen in the gas phase so that a high coulombic efficiency exists [7], In addition, in this fuel cell type, the electrodes are normally formed on a thin layer on each side of a protonconducting polymer membrane used as an electrolyte, and platinum catalysts are required for both the anode and the cathode for the proper operation of this fuel cell [9],... 

In a H2/air fuel cell, the protons produced at the anode side need to be transferred to the cathode side to react with 02. This requires a proton transport electrolyte. Nafion membranes, composed of a perfluorosulfonated polymer, are the most commonly used polymer electrolyte membranes to conduct protons. The structure of the Nafion membrane is shown in Figure 1.5. Nafion can take on a... 

In proton exchange membrane fuel cells, perhaps the most divulgate type of fuel cells, a proton-conducting polymer membrane acts as the electrolyte separating the anode and cathode sides. Porous anaodic alumina (Bocchetta et al., 2007) and mesoporous anastase ceramic membranes have been recently introduced in this field (Mioc et al., 1997 Colomer and Anderson, 2001 Colomer, 2006). 

As is the case with fuel cells, depolarized cathodes have been considered for years but have not yet found wide commercial use in the chlor-alkali indusby. Reports of work in the 1970s and 1980s [117,118] described the use of solid-polymer electrolyte systems. Microporous electrodes are necessary for electrical continuity in these cells, and the cathode reaction takes place in the interior of the gas-diffiision electrode. Operating deficiencies include the gradual penetration of gas channels by caustic solution and the possibility of bulk flow of catholyte into the gas side of the electrodes. Section 17.2.2.2 describes more recent work that addresses these deficiencies. The first conunercial applications are beginning to appear. 

Fig.l (a) Principal layout of a PEM fuel cell with the main functional components, viz. proton-conducting polymer-electrolyte membrane (PEM), catalyst layers on anode (ACL) and cathode sides (CCL), gas-diffusion layers (CDL) and flow fields (FF). (b) Disciplines in fuel cell research and how they are connected by the theory. 

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