Direct membrane fuel cells

The concept of the reversed fuel cell, as shown schematically, consists of two parts. One is the already discussed direct oxidation fuel cell. The other consists of an electrochemical cell consisting of a membrane electrode assembly where the anode comprises Pt/C (or related) catalysts and the cathode, various metal catalysts on carbon. The membrane used is the new proton-conducting PEM-type membrane we developed, which minimizes crossover. 

Ren, X. Springer, T. E. and Gottesfeld, S. (1998). Direct Methanol Fuel Cell Transport Properties of the Polymer Electrolyte Membrane and Cell Performance. Vol. 98-27. Proc. 2nd International Symposium on Proton Conducting Membrane Euel Cells. Pennington, NJ Electrochemical Society. 

Ford Motor Company. (1997). Direct Ilydrogcn-Fuclcd Proton Exchange Membrane Fuel Cell System for Transportation Applications Hydrogen Vehicle... 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

Mustain WE, Kepler K, Prakash J. 2007. CoPd, oxygen reduction electrocatalysts for polymer electrolyte membrane and direct methanol fuel cells. Electrochim Acta 52 2102-2108. Nagy Z, You H. 2002. Applications of surface X-ray scattering to electrochemistry problems. Electrochim Acta 47 3037-3055. 

Matsuoka K, Iriyama Y, Abe T, Matsuoka M, Ogumi Z. 2005. Alkaline direct alcohol fuel cells using an anion exchange membrane. J Power Sources 150 27-31. 

Shen M, Roy S, Kuhlmann JW, Scott K, Lovell K, Horsfall JA. 2004. Grafted polymer electrolyte membrane for direct methanol fuel cells. J Memb Sci 251 121-130. 

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. 

Sanicharane S, Bo A, Sompalli B, Gurau B, Smotkin ES. 2002. In-situ 50 °C ETIR spectroscopy of Pt and PtRu direct methanol fuel cell membrane electrode assembly anodes. J Electrochem Soc 149 A554-A557. 

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. 

Direct methanol fuel cells use sulfuric acid or a polymer membrane as an electrolyte and have an OT of 80 to 130°C. 

This survey focuses on recent developments in catalysts for phosphoric acid fuel cells (PAFC), proton-exchange membrane fuel cells (PEMFC), and the direct methanol fuel cell (DMFC). In PAFC, operating at 160-220°C, orthophosphoric acid is used as the electrolyte, the anode catalyst is Pt and the cathode can be a bimetallic system like Pt/Cr/Co. For this purpose, a bimetallic colloidal precursor of the composition Pt50Co30Cr20 (size 3.8 nm) was prepared by the co-reduction of the corresponding metal salts [184-186], From XRD analysis, the bimetallic particles were found alloyed in an ordered fct-structure. The elecbocatalytic performance in a standard half-cell was compared with an industrial standard catalyst (bimetallic crystallites of 5.7 nm size) manufactured by co-precipitation and subsequent annealing to 900°C. The advantage of the bimetallic colloid catalysts lies in its improved durability, which is essential for PAFC applicabons. After 22 h it was found that the potential had decayed by less than 10 mV [187],... 

In addition to these smaller applications, fuel cells can be used in portable generators, such as those used to provide electricity for portable equipment. Thousands of portable fuel cell systems have been developed and operated worldwide, ranging from 1 watt to 1.5 kilowatts in power. The two primary technologies for portable applications are polymer electrolyte membrane (PEM) and direct methanol fuel cell (DMFC) designs. 

All fuel cells for use in vehicles are based on proton-exchange-membrane fuel cell (PEMFC) technology. The methanol fuel-processor fuel cell (FPFC) vehicle comprises an on-board fuel processor with downstream PEMFC. On-board methanol reforming was a development focus of industry for a number of years until around 2002. Direct-methanol fuel cells (DMFC) are no longer considered for the propulsion of commercial vehicles in the industry (see also Chapter 13). 

Direct-methanol fuel cell Proton- conducting polymer membrane H+ (proton) 80-100... 

Direct-methanol fuel cells (DMFCs) have attracted considerable attention for certain mobile and portable applications, because of their high specific energy density, low poison emissions, easy fuel handling, and miniaturization [129,130], However, the methanol permeation through electrolyte membranes (usually called methanol cross-over) in DMFCs still is one of the critical problems hindering the commercialization [131,132], Nafion , a... 

The effect of annealing temperatures (65 - 250 °C) and blend composition of Nafion 117, solution-cast Nafion , poly(vinyl alcohol) (PVA) and Nafion /PVAblend membranes for application to the direct methanol fuel cell is reported in [148], These authors have found that a Nafion /PVAblend membrane at 5 wt% PVA (annealed at 230 °C) show a similar proton conductivity of that found to Nafion 117, but with a three times lower methanol permeability compared to Nafion 117. They also found that for Nafion /PVA (50 wt% PVA) blend membranes, the methanol permeability decreases by approximately one order of magnitude, whilst the proton conductivity remained relatively constant, with increasing annealing temperature. The Nafion /PVA blend membrane at 5 wt% PVA and 230 °C annealing temperature had a similar proton conductivity, but three times lower methanol permeability compared to unannealed Nafion 117 (benchmark in PEM fuel cells). 

R. X. Liu, and E. S. Smotkin, Array membrane electrode assemblies for high throughput screening of direct methanol fuel cell anode catalysts, J. Electroanal. Chem. 535, 49-55 (2002). 

FIGURE 15.9. Performance comparison of RSn anode based direct ethanol fuel cells at 90°C. Anode catalysts Carbon supported PtSn with a R loading of 1.5 mg/cm, ethanol concentration 1.0 mol/L, flow rate 1.0 mL/min. Cathode (20 Pt wt.%, Johnson Matthey Inc.) with a R loading of 1.0 mg/cm, Pq2 = 2 bar. Electrolyte Naflon -115 membrane. 

Cha, S. Y., and Lee, W. M. Performance of proton exchange membrane fuel cell electrodes prepared by direct deposition of ultrathin platinum on the membrane surface. Journal of the Electrochemical Society 1999 146 4055 060. 

Scott, K., Taama, W. M. and Argyropoulos, R 2000. Performance of the direct methanol fuel cell with radiation-grafted polymer membranes. Journal of Membrane Science 171 119-130. 

Hatanaka, T., Hasegawa, N., Kamiya, A., Kawasumi, M., Morimoto, Y. and Kawahara, K. 2002. Cell performances of direct methanol fuel cells with grafted membranes. Fuel 81 2173-2176. 

Ren, X., Henderson, W. and Gottesfeld, S. 1997. Electro-osmotic drag of water in ionomeric membranes—New measurements employing a direct methanol fuel cell. Journal of the Electrochemical Society 144 L267-L270. 

Carter, R., Wycisk, R., Yoo, H. and Pintauro, P. N. 2002. Blended polyphosphazene/polyacrylonitrile membranes for direct methanol fuel cells. Electrochemical and Solid-State Letters 5 A195-A197. 

Elabd, Y. A., Walker, C. W. and Beyer, F. L. 2004. Triblock copolymer ionomer membranes. Part 11. Structure characterization and its effects on transport properties and direct methanol fuel cell performance. Journal of Membrane Science 231 181-188. 

Cho, K.-Y, Jung, H.-Y., Choi, N.-S., Sung, S.-H., Park, J.-K., Choi, J.-H. and Sung, Y.-E. 2005. A coated Nafion membrane with a PVdF copolymer/ Nafion blend for direct methanol fuel cells (DMFCs). Solid State Ionics 176 3027-3030. 

Sauk, J., Byun, J. and Kim, H. J. 2005. Composite Nafion/polyphenylene oxide (PPO) membranes with phosphomolybdic acid (PMA) for direct methanol fuel cells. Journal of Power Sources 143 136-141. 

Manea, C. and Mulder, M. 2002. Characterization of polymer blends of poly-ethersulfone/sulfonated polysulfone and polyethersulfone/sulfonated poly-etheretherketone for direct methanol fuel cell applications. Journal of Membrane Science 206 443-453. 

Jung, B., Kim, B. and Yang, J. M. 2004. Transport of methanol and protons through partially sulfonated polymer blend membranes for direct methanol fuel cell. Journal of Membrane Science 245 61-69. 

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