Fuel cells methanol

Fuel Cell Systems Explained, Second Edition James Larminie and Andrew Dicks 2003 John Wiley Sons, Ltd ISBN 0-470-84857-X 

Storage method Energy density of fuel Storage efficiency (%) Net energy density 

Section 6.5 will also consider the problems of storing and producing methanol, and how it compares with other alcohols such as ethanol. 

The most pressing problem associated with the DMFC is that the fuel anode reactions proceed so much more slowly than with hydrogen. The oxidation of hydrogen occurs readily - the oxidation of methanol is a much more complex reaction, and proceeds much more slowly. This results in a fuel cell that has a far lower power for a given size. The anode reactions of the DMFC will be explained in Section 6.2 

The second major problem is that of fuel crossover. This was discussed briefly in Section 3.5. It is particularly acute in the DMFC because the electrolyte used is usually a proton exchange membrane (PEM), as described in Chapter 4. These readily absorb methanol, which mixes well with water, and so quickly reaches the cathode. This shows itself as a reduced open circuit voltage but affects the performance of the fuel cell at all currents. DMFC electrolytes and this fuel crossover problem are further discussed in Section 6.3. 

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Direct Methane Conversion, Methanol Fuel Cell, and Chemical Recycling of Carbon Dioxide... 

The schematic diagram of the liquid-feed direct methanol fuel cell (DMFC) is shown in Figure 13.1. 

Figure 13.1. Liquid-feed direct methanol fuel cell.

Besides chemical catalytic reduction of carbon dioxide with hydrogen, which is already possible in the laboratory, we are exploring a new approach to recycling carbon dioxide into methyl alcohol or related oxygenates via aqueous eleetrocatalytic reduction using what can be called a regenerative fuel cell system. The direct methanol fuel cell... 

Fuel cells can run on fuels other than hydrogen. In the direct methanol fuel cell (DMFC), a dilute methanol solution ( 3%) is fed directly into the anode, and a multistep process causes the liberation of protons and electrons together with conversion to water and carbon dioxide. Because no fuel processor is required, the system is conceptually vei"y attractive. However, the multistep process is understandably less rapid than the simpler hydrogen reaction, and this causes the direct methanol fuel cell stack to produce less power and to need more catalyst. 

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. 

In a simple version of a fuel cell, a fuel such as hydrogen gas is passed over a platinum electrode, oxygen is passed over the other, similar electrode, and the electrolyte is aqueous potassium hydroxide. A porous membrane separates the two electrode compartments. Many varieties of fuel cells are possible, and in some the electrolyte is a solid polymer membrane or a ceramic (see Section 14.22). Three of the most promising fuel cells are the alkali fuel cell, the phosphoric acid fuel cell, and the methanol fuel cell. 

This proton exchange membrane is used in both hydrogen and methanol fuel cells, in which a catalyst at the anode produces hydrogen from the methanol. Because the membrane allows the protons, but not the electrons, to travel through it, the protons flow through the porous membrane to the cathode, where they combine with oxygen to form water, while the electrons flow through an external circuit. 

The dynamic behavior of fuel cells is of importance to insure the stable operation of the fuel cells under various operating conditions. Among a few different fuel cell types, the direct methanol fuel cell (DMFC) has been known to have advantages especially for portable... 

Interestingly, the PEMFC may also operate directly on methanol. Naturally, the problems associated with high coverage of various intermediates will be present, as mentioned above, as well as additional problems such as loss of methanol over the membrane. Nevertheless, it is possible to operate a methanol fuel cell with a voltage around 0.4 V and a reasonable current, to power small mobile devices such as portable computers and cell phones and make them independent of connection to the conventional power net. For more details on fuel cells we refer the reader to L. Carr-ette, K.A. Friedrich and U. Stimming, Fuel Cells 1(1) (2001) 5-39. 

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... 

Convert P, Countanceau C, Cromgneau P, Gloaguen F, Lamy C (2001) Electrodes modified by electrodeposition of CoTAA complexes as selective oxygen cathodes in a direct methanol fuel cell. J Appl Electrochem 31 945-952... 

Wasmus S, Kiiver A (1999) Methanol oxidation and direct methanol fuel cells a selective review. J Electroanal Chem 461 14-31... 

Lasch K, Hayn G, Jdrissen L, Garche J, Besenhardt O (2002) Mixed conducting catalyst support materials for the direct methanol fuel cell. J Power Sources 105 305-310... 

Direct Methanol Fuel Cells From a Twentieth Century Electrochemist s Dream to a Twenty-first Century Emerging Technology... 

A direct methanol fuel cell consists of two electrodes—a catalytic methanol anode and a catalytic oxygen cathode—separated by an ionic conduc-... 

Figure 3. Schematic diagram of a direct methanol fuel cell working in an acidic medium.

From the above discussion, it is clear that the main objectives of fundamental investigations on the direct methanol fuel cell are to ... 

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