Proton-exchange membrane fuel cell temperature

Membrane-type fuel cells. The electrolyte is a polymeric ion-exchange membrane the working temperatures are 60 to 100°C. Such systems were first used in Gemini spaceships. These fuel cells subsequently saw a rather broad development and are known as (solid) polymer electrolyte or proton-exchange membrane fuel cells (PEMFCs). 

Ambient temperature catalysis of O2 reduction at low overpotentials is a challenge in development of conventional proton exchange membrane fuel cells (pol5mer electrolyte membrane fuel cells, PEMFCs) [Ralph and Hogarth, 2002]. In this chapter, we discuss two classes of enz5mes that catalyze the complete reduction of O2 to H2O multi-copper oxidases and heme iron-containing quinol oxidases. 

There are six different types of fuel cells (Table 1.6) (1) alkaline fuel cell (AFC), (2) direct methanol fuel cell (DMFC), (3) molten carbonate fuel cell (MCFC), (4) phosphoric acid fuel cell (PAFC), (5) proton exchange membrane fuel cell (PEMFC), and (6) the solid oxide fuel cell (SOFC). They all differ in applications, operating temperatures, cost, and efficiency. 

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable types of fuel cells. Moreover, the electrolyte membrane and other cell components can be manufactured very thin, allowing for high power production to be achieved within a small volume of space. Thus, the combination of small size and fast start-up makes PEMFCs an excellent candidate for use in mobile power applications, such as laptop computers, cell phones, and automobiles. 

Would the preferential CO oxidation reaction be needed if the proton-exchange membrane fuel cell (PEMFC) with Pt anode catalyst were able to work at temperatures higher than about 403 K ... 

Song, Y, Wei, Y, Xu, H., Williams, M., Liu, Y., Bonville, L. J., Kunz, H. R., and Fenton, J. M. Improvement in high-temperature proton exchange membrane fuel cells cathode performance with ammonium carbonate. Journal of Power Sources 2005 141 250-257. 

Yang, C., Costamagna, R, Srinivasan, S., Benzieger, J. and Bocarsly, A. B. 2001. Approaches and technical challenges to high-temperature operation of proton exchange membrane fuel cells. Journal of Power Sources 103 1-9. 

C. H. Liu, T. H. Ko, and Y. K. Liao. Effect of carbon black concentration in carbon fiber paper on the performance of low-temperature proton exchange membrane fuel cells. Journal of Power Sources 178 (2008) 80-85. 

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. 

Figure 29. Conductivity of some intermediate-temperature proton conductors, compared to the conductivity of Nafion and the oxide ion conductivity of YSZ (yttria-stabilized zirconia), the standard electrolyte materials for low- and high-temperature fuel cells, proton exchange membrane fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). 

After rehearsing the working principles and presenting the different kinds of fuel cells, the proton exchange membrane fuel cell (PEMFC), which can operate from ambient temperature to 70-80 °C, and the direct ethanol fuel cell (DEFC), which has to work at higher temperatures (up to 120-150 °C) to improve its electric performance, will be particularly discussed. Finally, the solid alkaline membrane fuel cell (SAMFC) will be presented in more detail, including the electrochemical reactions involved. 

Fuel cells can be broadly classified into two types high temperature fuel cells such as molten carbonate fuel cells (MCFCs) and solid oxide polymer fuel cells (SOFCs), which operate at temperatures above 923 K and low temperature fuel cells such as proton exchange membrane fuel cells (PEMs), alkaline fuel cells (AFCs) and phosphoric acid fuel cells (PAFCs), which operate at temperatures lower than 523 K. Because of their higher operating temperatures, MCFCs and SOFCs have a high tolerance for commonly encountered impurities such as CO and CO2 (CO c)- However, the high temperatures also impose problems in their maintenance and operation and thus, increase the difficulty in their effective utilization in vehicular and small-scale applications. Hence, a major part of the research has been directed towards low temperature fuel cells. The low temperature fuel cells unfortunately, have a very low tolerance for impurities such as CO , PAFCs can tolerate up to 2% CO, PEMs only a few ppm, whereas the AFCs have a stringent (ppm level) CO2 tolerance. 

However, the superiority of batteries over fuel cells in respect to specific power is gradually being ceded to fuel cells. A well-catalyzed proton exchange membrane fuel cell can reach up to 1 kW kg-1. Only batteries involving high temperatures can do as well. 

An important possible future use for pure hydrogen is in proton-exchange-membrane fuel cells (PEMFCs) the basic source for the hydrogen could be either a hydrocarbon or an alcohol, either of which can be steam-reformed to produce water-gas.16,17 As explained above, the equilibrium concentration of carbon monoxide decreases as the temperature falls (Figure 10.1), but as little as 1% is detrimental to the operation of platinum-based catalysts in a fuel cell. Excess water, which is commonly used,18 serves to move the... 

Baker R (2008) Substituted iron phthalocyanines electrocatalytic activity towards 02 reduction in a proton exchange membrane fuel cell cathode environment as a function of temperature. M.A.Sc. diss. The University of British Columbia, Canada... 

PEMFC (Proton Exchange Membrane Fuel Cell) and SPFC (Solid Polymer Fuel Cell) are the two competing mnemonics of a low-temperature fuel cell type originated for use in space by General Electric, USA. To reflect present practice, the author will use PEFC (Proton Exchange Fuel Cell). The DMFC (Direct Methanol Fuel Cell) also uses proton exchange membranes, but is referred to by its own mnemonic. Proton exchange between polar water molecules is discussed by Koryta (1991 1993) and in the introduction to this book. 

Malhotra, S. Datta, R., Membrane-Supported Nonvolatile Acidic Electrolytes Allow Higher Temperature Operation of Proton-Exchange Membrane Fuel Cells. Journal of The Electrochemical Society 1997, 144, (2), L23-L26. 

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