Alkaline membranes

Alkaline solutions are generally known to lead to better catal5Tic activities than acidic solutions for many relevant electrode reactions. However, owing to the paucity in the development of suitable electrolyte materials, such as alkaline membranes, there has been much less fundamental work in the area of fuel cell catalysis in alkaline media. Nevertheless, there are a few hopeful developments in new alkaline polymer membranes [Varcoe and Slade, 2005] that are currently stirring up interest in smdying fuel cell catalytic reactions in alkalme solution. 

Solid alkaline membrane fuel cells (SAMECs) can be a good alternative to PEMFCs. The activation of the oxidation of alcohols and reduction of oxygen occurring in fuel cells is easier in alkaline media than in acid media [Wang et al., 2003 Yang, 2004]. Therefore, less Pt or even non-noble metals can be used owing to the improved electrode kinetics. Eor example, Ag/C catalytic powder can be used as an efficient cathode material [Demarconnay et al., 2004 Lamy et al., 2006]. It has also... 

Lamy C, Demarconnay L, Coutanceau C, Leger JM. 2006. Development of electrocatalysts for the solid alkaline membrane fuel cell (SAMEC). ECS Trans 3(1) 1351-1360. 

Wang Y, Li L, Hu L, Zhuang L, Lu J, Xu B. 2003. A feasibility analysis for alkaline membrane direct methanol fuel cell Thermodynamic disadvantages versus kinetic advantages. Electrochem Commun 5 662. 

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. 

SOFC = solid oxide fuel cell MCFC = molten carbonate fuel cell PAFC = phosphoric acid fuel cell AFC = alkaline fuel cell PEMFC = proton exchange membrane fuel cell DMFC = direct methanol fuel cell SAMFC = Solid alkaline membrane fuel cell. 

Solid alkaline membrane fuel cell (SAMFC) working at moderate temperatures (20-80 °C) for which an anion-exchange membrane (AEM) is the electrolyte, electrically conducting by, for example, hydroxyl ions (OH ). 

Solid Alkaline Membrane Fuel Cell (SAMFQ 29... 

Development of a Solid Alkaline Membrane for Fuel Cell Application... 

The first methanol-fed PEM EC working with an AEM was conceived by Hunger in 1960 [15,45]. This system contained an AEM with porous catalytic electrodes pressed on both sides and led to relatively poor electrical performance (1 mA cm at 0.25 Vat room temperature with methanol and air as the reactants). Since this first attempt, many studies have been carried out to develop alkaline membranes. 

A second class of fuel cells employs hydroxide-conducting (alkaline) electrolytes, again either in form of a solid membrane (alkaline membrane fuel cells) or a liquid electrolyte (alkaline fuel cells). While the modem era of fuel cells began with the latter type, the former type is under intense research today because a stable, highly conducting alkaline membrane with good C02 tolerance has remained elusive to date. 

Alkaline membrane fuel cell Solid polymer OH" 50°C-100°C Pure H2, liquid small organics (limited C02 tolerance) <35% Portable, under research... 

Alkaline membrane Potassium solution in water Hydrogen oxygen Pure oxygen <80°C 50%-70% 177, 181... 

This section is devoted to a brief description of the main comptments of DAFC as an introduction to the most exhaustive analysis in Chaps. 2, 3,4, and 5 for electrocatalysts for methanol, ethanol, and higher alcohols, in Chap. 6 for proton exchange and alkaline membranes, and Chap. 7 for carbonous materials used as catalysts support, gas diffusion layers and bipolar plates. 

Hie A, Simoes M, Baranton S, Coutanceau C, Martemianov S (2011) Influence of operational parameters and of catalytic materials on electrical performance of direct glycerol solid alkaline membrane fuel cells. J Power Sources 196 4965-4971... 

Simoes M (2011) Development of multimetallic nanostructured electrocatalysts for an application in a solid alkaline membrane fuel cell (SAMFC). Thesis, Universite de Poitiers, Poitiers... 

Table 6.10 Performance of ADMFC with different alkaline membranes... 

Zhou J, Unlii M, Anestis-Richard I, Kohl PA (2010) Crosslinked, epoxy-based anion conductive membranes for alkaline membrane fuel cells. J Membr Sci 350 286-292... 

Yan X, He G, Gu S, Wu X, Du L, Wang Y (2012) Imidazolium-functionalized polysulfone hydroxide exchange membranes for potential applications in alkaline membrane direct alcohol fuel cells. Int J Hydrogen Energ 37 5216-5224... 

Triphati BP, Kumar M, Shahi VK (2010) Organic-inorganic hybrid alkaline membranes by epoxide ring opening for direct methanol fuel cell applications. J Membr Sci 230 90-101... 

Scott K, Yu EH, Vlachogiannopoulos G, Shivare M, Duteanu N (2008) Performance of a direct methanol alkaline membrane fuel cell. J Power Source 175 452-457... 

Bunazawa H, Yamazaki Y (2008) Influence of anion ionomer content and silver cathode catalyst on the performance of alkaline membrane electrode assemblies (MEAs) for direct methanol fuel cells (DMFCs). J Power Sources 182(1) 48-51... 

Tamain C, Poynton SD, Slade RCT, Carroll B, Varcoe JR (2007) Development of cathode architectures customized for H2/O2 metal-cation-free alkaline membrane fuel cells. J Phys ChemC 111(49) 18423-18430... 

Piana M, Boccia M, Filpi A, Flammia E, Miller HA, Orsini M, Salusti F, Santiccioli S, Ciardelli F, Pucci A (2010) H2/air alkaline membrane fuel cell performance and durability, using novel ionomer and non-platinum group metal cathode catalyst. J Power Sources 195(18) 5875-5881... 

Varcoe JR, Slade RCT, Wright GL, Chen Y (2006) Steady-state dc and impedance investigations of H2/O2 alkaline membrane fuel cells with commercial Pt/C, Ag/C, and Au/C cathodes. J Phys Chem B 110(42) 21041-21049... 

Qiao J, et al. (2013) Carbon-supported co-pyridine as non-platinum cathode catalyst for alkaline membrane fuel cells. Electrochim Acta 96 298-305. doi 10.1016/j. electacta.2013.02.030... 

This chapter reviews a new type of solid electrolyte low-temperature fuel cell, the alkaline membrane fuel cell. The principles and main components of this fuel cell technology are described, with a major focus on the electrocatalysts for both electrodes. Finally, the latest published results on operation of the first developed alkaline membrane fuel cells are reviewed. 

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