As the cell reaction is between hydrogen and oxygen, the continuous supply of these gases is vital.
Oxygen poses no problem, as it is freely available
from the air. The best way to provide hydrogen fuel
has not yet been resolved. Hydrogen reservoirs containing pressurised gas, or as liquid, have been considered.
One promising avenue seems to be the use
of non-stoichiometric metal hydrides which can
reversibly store hydrogen. In addition to this there is
much work on using methane, methanol, petrol