Hþ ions; molten carbonate fuel cell(MCFC), with
molten Li2CO3 as electrolyte in a LiAlO2 matrix,
transporting CO32
ions; and solid oxide fuel cell
(SOFC), with solid yttria-stabilised zirconia electrolytes that allow O2
transport. The majority of cells
use a catalyst to speed up the reactions taking place.
These are mostly platinum-based, and are deposited
upon the electrodes as small highly dispersed particles, but the molten carbonate cell has an advantage
in that it uses a cheaper nickel catalyst.
As the cell reaction is between hydrogen and oxygen, the continuous supply of these gases is vital.
Oxygenposesnoproblem,asitisfreelyavailable
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