Fuel cells are those cells in which the energy produced from the combustion of fuels such as H₂, CO, CH₄ etc. is directly converted into electrical energy.

Working of a fuel cell. Anode and cathode are graphite electrodes containing suitable NaOH of KOH is placed between the electrodes as electrolyte. H₂ gas and O₂ gas are bubbled through the porous electrodes into the electrolyte.

Reactions involved.

At anode : 2H₂(g) + 4OH^- (aq) → 4 H₂O(l) + 4e^-

At cathode : O₂(g) + 2H₂O (l) + 4e- → 4OH^- (aq) _______________________________________

Overall cell reaction : 2H₂(g) + O₂(g) → 2H₂ (l) _______________________________________