Fuel cells
Batteries have a fixed amount of reactant present,
stored in the battery casing. Fuel cells are primary
cells with a continuous input of chemicals and a
continuous output of power. The reactants are stored
separately from the electrodes and electrolyte and
can be replenished when necessary. (The Li–air cell
is, in fact, a form of fuel cell with only one consumable chemical introduced.) There is much research
at present on fuel cells as a source of clean electricity. The reaction favoured is the production of water
from hydrogen gas and oxygen gas, giving a cell
voltage of about 1.2 V. The concept is simple (Figure 9.12), and early fuel cells, containing an alkaline
solution, typically potassium hydroxide solution, as
electrolyte, demonstrate the principle involved