Bacon cell

This electrode structure was also used in the Apollo mission fuel cells. Such structures may or may not be combined with catalysts. In the Apollo and Bacon cells, the anode was formed from the straightforward nickel powder as described above, whereas the cathode was partially lithiated and oxidised. ... 

The search for effective electrocatalysts led to investigations of the corrosive resistance and of the reactivity for the O2 reduction of compounds of metals with other elements like boron, carbon, nitrogen, oxygen, etc. The cathode [78] of the Bacon cell represents the classical example. The porous cathodes were made by pressing and sintering mixtures of carbonyl nickel and ammonium bicarbonate. Subsequently, they were coated with a layer of lithiated nickel oxide. 

Initially, it was called Bacon cell, by virtue of its inventor Francis Thomas Bacon. It operates at low temperature around 100 °C and it is able to achieve 60-70% efficiency. It uses an aqueous solution of potassium hydroxide (KOH) as electrolyte solution. This fuel cell has quidc startup speed, one of its great advantages. The main disadvantage is that it is very sensitive to CO2 (Farooque Maru, 2001). It needs an external system to remove CO2 from the air. Furthermore, the use of a liquid electrolyte is also a disadvantage because it reduces the cell lifetime and makes the assembly handling and transport more difficult. 

With efficient catalysts this reaction can give rise at ordinary temperatures to current densities of 100-150 mAcm at about 0.75 V. Medium-temperature cells operating at 370-470 K, such as the Bacon cell, can give up to 500-1000 mA cm at the same voltage and with less expensive catalysts. 

As already indicated, a flat, layer construction is normally used in fuel cell batteries, and an individual cell, usually not more than 1 cm thick, will be somewhat as shown in figure F.2. Low-temperature cells need the most effective catalyst, which is platinum, although silver can be used at the oxygen electrode. To prevent the cost being prohibitive, efforts are made to restrict the platinum coating to the actual region of contact between gas and liquid. In medium-temperature cells, such as the Bacon cell, which operate at about 470 K, nickel is used as catalyst... 

The difficulty is that these reactions are slow, and their useful application requires expensive catalysts and elevated temperatures. Also, an acid electrolyte must be used since CO2 is a product, and the formation of intermediate products such as formaldehyde must be prevented to avoid poisoning the catalyst. At present the disadvantages in the direct use of such fuels appear to be greater than those of employing them indirectly to provide the fuel for a Bacon cell. 

Temperature pressure and electrolyte concentration should be balanced to achieve maximum efficiency. For example, to obtain high performance for the Bacon cell, the pressure has to be reduced and temperature should be increased. Moreover, the electrolyte concentration of KOH should be increased by 75%, so that the electrolyte does not boil. Figure 2.7 depicts the variation of KOH electrolyte concentration with temperature and pressure. 

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