Fuel Crossover Techniques in Development

In addition to the (almost) universally applied techniques outlined above, there are other ideas being tried that are more experimental or at a very early stage of development. Among these are the following  

The use of selective (non-platinum) catalysts on the air cathode. These will stop the fuel reacting on the cathode and so eliminate the voltage drop due to the mixed-potential . 

However, there are problems with this approach. The first is that all catalysts that do not promote the fuel oxidation tend only to very slowly promote the reaction of oxygen with the H+ ions. Thus, the activation losses on the cathode are made even worse than normal, and there is no increase in performance. Another problem is that although the mixed-potential problem may be solved, the fuel is still crossing over, and while it may not be reacting on the cathode, it will probably just evaporate instead. Thus, it will still be wasted. So, although it may be possible in the future to find selective cathode catalysts that amehorate the fuel crossover problem, this approach does not offer a complete solution. 

An interesting example (and special case) of the use of selective catalysts mentioned above is the possibility of abandoning any attempt to prevent crossover and of feeding all the reactants (methanol, air, water) as a mixture over both electrodes. Experiments with very small cells made in this way have been reported by Barton et al. (2001). 

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