Polymer electrolyte fuel cells microporous layer

H. Nakajima, T. Konomi, and T. Kitahara. Direct water balance analysis on a polymer electrolyte fuel cell (PEFC) Effects of hydrophobic treatment and microporous layer addition to the gas diffusion layer of a PEFC on its performance during a simulated start-up operation. Journal of Power Sources 171 (2007) 457-463. 

A. Z. Weber and J. Newman. Effects of microporous layers in polymer electrolyte fuel cells. Journal of the Electrochemical Society 152 (2005) A677-A688. 

U. Pasaogullari and C. Y. Wang. Two-phase transport and the role of microporous layer in polymer electrolyte fuel cells. Electrochimica Acta 49 (2004) 4359-4369. 

Figure 6.5. Impedance spectra for the oxygen reduction reaction at three different electrode potentials a 0.8 V b 0.7 V c 0.6 V. The microporous layer (loading 3.5 mg/cm2) of the electrode has varying PTFE content ( ) 10 ( ) 20 (A) 30 (+) 40 wt% [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.)...

Kitahara, T., Konomi, T., and Nakajima, H. (2010) Microporous layer coated gas diffusion layers for enhanced performance of polymer electrolyte fuel cells. J. Power Sources, 195 (8), 2202 2211. 

Weber A Z and Newman J (2005), Effects of Microporous Layers in Polymer Electrolyte Fuel Cells , Journal of The Electrochemical Society, 152(4), A677-A688. 

Abstract The polymer electrolyte fuel cell (PEFC) consists of disparate porous media microstructures, e.g. catalyst layer, microporous layer, gas diffusion layer, as the key components for achieving the desired performance attributes. The microstmcture-transport interactions are of paramount importance to the performance and durability of the PEFC. In this chapter, a systematic description of the stochastic micro structure reconstmction techniques along with the numerical methods to estimate effective transport properties and to study the influence of the porous structures on the underlying transport behavior is presented. 

Akey performance limitation in the polymer electrolyte fuel cell (PEFC) originates from the multiple, coupled and competing, transport interactions in the constituent porous components. The suboptimal transport behavior resulting from the underlying complex and multifunctional microstmctures in the catalyst layer (CL), gas diffusion layer (GDL) and microporous layer (MPL) leads to water and thermal management issues and undesirable performance loss. Therefore, it is imperative to understand the profoimd influence of the disparate porous microstmctures on the transport characteristics. In this chapter, we highhght the stochastic microstmcture reconstmction technique and direct transport simulation in the CL, GDL and MPL porous stmctmes in order to estimate the effective transport properties and imderstand the microstmctural impact on the imderlying transport behavior in the PEFC. 

Wood, D. L. and Borup, R. L. 2009. Diuabihiy aspects of gas-diffusion and microporous layers. In Polymer Electrolyte Fuel Cell Durability, eds. F. N. Biichi, M. Inaba, and T. J. Schmidt, eds. New York, NY Springer. 

FIGURE 11.10 Single fiber contact angles of Toray TGP-H materials (hydrophobized to 17 wt% fluorinated ethylene propylene, FEP) aged in accelerated fashion in different liquid-water environments. (With kind permission from Springer Science+Business Media Polymer Electrolyte Fuel Cell Durability, Durability aspects of gas-diffusion and microporous layers, 2009, pp. 159-195, Wood, D.L. and Borup R.L.)... 

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... 

Spemjak D, Fairweather J, Mukundan R et al (2012) Influence of the microporous layer on carbmt corrosion in the catalyst layer of a polymer electrolyte membrane fuel cell. J Power Sources 214 386-398... 

HT-PEM fuel cells operate with phosphoric acid doped polymer membrane as electrolyte. The acid is physically adsorbed to the membrane. The phosphoric acid distribution within the fuel cell components, such as membrane, catalyst layers, microporous layer, gas diffusion layers, and bipolar plates, is known to be a critical parameter for performance and life time of this type of fuel cells [10]. There are no defined specifications about phosphoric acid uptake of the bipolar plate because its impact on the fuel cell performance strongly depends on several parameters and always has to be considered in a context of the overall fuel cell design. 

The general layout of a cell includes a proton-conducting polymer electrolyte membrane (PEM), sandwiched between the anode and the cathode. Each electrode compartment is composed of (i) an active catalyst layer (CL), which accommodates finely dispersed nanoparticles of Pt that are attached to the surface of a highly porous and electronically conductive support, (ii) a gas diffusion layer (GDL), and (iii) a flow field (FF) plate that serves at the same time as a current collector (CC) and a bipolar plate (BP). This plate conducts current between neighboring cells in a fuel cell stack. At the cathode side, usually a strongly hydrophobic microporous layer (MPL) is inserted between CL and GDL, which facilitates the removal of product water from the cathode CL. The central unit including PEM and porous electrode layers, excluding the bipolar plates, is called the membrane electrode assembly (MEA). 

---