Proton exchange membrane fuel cells water management

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. 

Proper water management in proton exchange membrane fuel cells (PEMFCs) is critical to PEMFC performance and durability. PEMFC performance is impaired if the membrane has insufficient water for proton conduction or if the open pore space of the gas diffusion layer (GDL) and catalyst layer (CL) or the gas flow channels becomes saturated with liquid water, there is a reduction in reactant flow to the active catalyst sites. PEMFC durability is reduced if water is left in the CL during freeze/thaw cycling which can result in CL or GDL separation from the membrane,1 and excess water in contact with the membrane can result in accelerated membrane thinning.2... 

Nguyen, T.V. and White, R.E., A water and heat management model for proton-exchange-membrane fuel cells, J. Electrochem. Soc., 140, 2178, 1993. 

R. Mosdale and S. Srinivasan, Analysis of water and thermal management in proton exchange membrane fuel cells. Electrochemical Acta, 40(4) (1995) 413-424. 

Modroukas D, Calabrese Bartrai S, Modi V, Frechette LG (2005) Water management and mass transport studies. In Free convection proton-exchange membrane fuel cells. In 208th meeting of the electrochemical society, Los Angeles, 16-21 Oct 2005... 

Water management is one of the critical operation issues in proton exchange membrane fuel cells. Spatially varying concentrations of water in both vapor and liquid form are expected throughout the cell because of varying rates of production and transport. Water emanates from two sources the product water from the oxygen-reduction reaction in the cathode catalyst layer and the humidification water carried by the inlet streams or injected into the fuel cell. 

C.R.. Buie, J.D. Posner, T. Fabian, S.-W. Cha, D. Kim, F.B. Prinz, J.K. Eaton, J.G. Santiago, Water management in proton exchange membrane fuel cells using integrated electroosmotic pumping, J. Power Sources 161 (2006) 191-202. 

Song T-W, Choi K-H, Kim J-R et al (2011) Pumpless thermal management of water-cooled high-temperature proton exchange membrane fuel cells. J Power Sources 196 4671-4679... 

Ceballos, L., and Prat, M., 2010, Invasion percolation with inlet multiple injections and the water management problem in proton exchange membrane fuel cells , J. Power Sources, 195 (3) pp. 825. 

The main purpose of many investigations is to improve water management in proton-exchange membrane fuel cells (PEMFCs) and direct methanol fnel cells (DMFCs) operating at temperatures below 120°C, at which water is present in the liquid as well as in the gaseous state. 

High-temperature proton exchange membrane fuel cells (HT-PEM fuel cells), which use modified perfluorosulfonic acid (PFSA) polymers [1—3] or acid-base polymers as membranes [4—8], usually operate at temperatures from 90 to 200 °C with low or no humidity. The development of HT-PEM fuel cells has been pursued worldwide to solve some of the problems associated with current low-temperature PEM fuel cells (LT-PEM fuel cells, usually operated at <90 °C) these include sluggish electrode kinetics, low tolerance for contaminants (e.g. carbon monoxide (CO)), and complicated water and heat management [4,5]. However, operating a PEM fuel cell at >90 °C also accelerates degradation of the fuel cell components, especially the membranes and electrocatalysts [8]. 

St-Pierre, J. and Jia, N. (2002) Successful demonstration of Ballard PEMFCs for space shuttle applications. J. New Mater. Electrochem. Syst. 5, 263-271 St-Pierre, J., Jia, N. and Rahmani, R. (2008) Proton exchange membrane fuel cell contamination model - Competitive adsorption demonstrated with NO J. Electrochem. Soc. 155, B315-B320 St-Pierre, J., WrUdnson, D. P., Knights, S. and Bos, M. (2(XX)) Relationships between water management, contamination and Ufetime degradation in PEFC. J. New Mater. Electrochem. Syst. 3,99-106... 

In PEMFCs working at low temperatures (20-90 °C), several problems need to be solved before the technological development of fuel cell stacks for different applications. This concerns the properties of the components of the elementary cell, that is, the proton exchange membrane, the electrode (anode and cathode) catalysts, the membrane-electrode assemblies and the bipolar plates [19, 20]. This also concerns the overall system vdth its control and management equipment (circulation of reactants and water, heat exhaust, membrane humidification, etc.). 

It has been demonstrated that EIS can serve as a standard analytical diagnostic tool in the evaluation and characterization of fuel cells. Scientists and engineers have now realized that the entire frequency response spectrum can provide useful data on non-Faradaic mechanisms, water management, ohmic losses, and the ionic conductivity of proton exchange membranes. EIS can help to identify contributors to PEMFC performance. It also provides useful information for fuel cell optimization and for down-selection of the most appropriate operating conditions. In addition, EIS can assist in identifying problems or predicting the likelihood of failure within fuel cell components. 

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