Anode Reactions in the Alkaline DMFC

The anode and cathode reactions depend on the electrolyte used, and methanol can, in principle, be used in a fuel cell with any of the standard electrolytes. However, if we are to retain the simplicity of a liquid fuel system, then it is only the low-temperature electrolytes - alkaline and PEM - that are serious contenders. 

Methanol fuel works in both the alkaline FC considered in Chapter 5 and the PEMFC of Chapter 4. However, the reaction between the product carbon dioxide and the electrolyte of the alkaline (electrolyte) fuel cell (AFC) is a major problem, which would appear to be insoluble. The anode reaction of the alkaline DMFC is 

Here we see the six electrons produced for each molecule of methanol, which is why it is such an attractive fuel cell fuel. However, for this reaction to occur the reactants must interface with the alkaline electrolyte, and so the carbon dioxide will inevitably react with the hydroxide, forming carbonate  

The electrolyte thus inevitably and steadily loses its alkalinity, and has a very limited life. In alkaline DMFCs, it is not possible to see any product carbon dioxide, as it all reacts according to eqnation 6.3. For this reason the alkaline DMFC is not practical, even though it could have many advantages in terms of cost and performance in comparison with PEM-based systems. 

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