Name the type of cell which was used in Apollo space programme for providing electrical power.
One of the most successful fuel cells uses the reaction of hydrogen with oxygen to form water. This fuel cell was used for providing electrical power in the Apollo space programme. The water vapours produced during the reaction were condensed and added to the drinking water supply for the astronauts. In the cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous sodium hydroxide solution. Catalysts like finely divided platinum or palladium metal are incorporated into the electrodes for increasing the rate of electrode reactions. The electrode reactions are given below:
Cathode: O2(g) + 2H2O(l) + 4e- →4OH–(aq)
Anode: 2H2 (g) + 4OH–(aq) → 4H2O(l) + 4e–
Overall reaction being: 2H2(g) + O2(g)→ 2 H2O(l )