Alkaline fuel cells DAFCs

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). 

The research and development of nanostructured electrode materials for improved performance of the direct alcohol fuel cells (DAFCs) in alkaline electrolytes has continued to grow. Palladium-based nanocatalysts, in particular, have continued to receive much research attention because of their unique properties in alcohol electrooxidation in alkaline media compared to their platinum-based counterparts [1]. 

Direct Alcohol Fuel Cell (DAFC) and Direct Alcohol Alkaline Fuel Cell (DAAFC)... 

The Portable power supply to electronic equipment from DAFC (direct alcohol fuel cell) and DAAFC (direct alcohol alkaline fuel cell) should have minimum recharging interval of 10-12 hours. Recharging means changing of methanol and ethanol fuel cartridges. Cost targets are (a) stack cost US 150-200/kW, (b) fuel cost US 1-1.5/kg. Fuel Efficiency is 30-40%. 

The less corrosive nature of an alkaline environment ensures a longer durability of the ADAFC, and the faster kinetics of the ORR allows the use of non-noble, low-cost, metal electrocatalysts. Thus, ADAFC meets a number of potential advantages compared to PEM DAFC, which in turn triggers the resurgence of interest in this kind of fuel cell technology. 

The faster kinetics of alcohol oxidation and oxygen reduction reactions in alkaline direct alcohol fuel cells opens up the possibility of using less expensive Pt-free catalysts, as nickel, gold, palladium and their alloys [30]. Thus, the cost of ADAFC could be potentially lower compared to the acid DAFC technology if non-precious metal alloys are used for the alcohol electrooxidation, being the nanoparticulated Ni-Fe-Co alloys developed by Acta (Italy) with the trade name of HYPERMEC a good example. 

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