Fuel Cell Electrochemistry

Introduction :
What is fuel cell in electrochemistry:

Fuel cells are galvanic cells in which chemical energy of fuels is directly converted into electrical energy.(In the conventional electricity generators, the fuel is burn and the heat energy produced is used to boil water. The steam produced is made to spin the turbines connected with the electricity generators)
Hydrogen - oxygen fuel cell is a common type of fuel cell based on the combustion of hydrogen to form water.
                    2H₂(g) + O₂(g)  `rarr` 2H₂O(l)

Construction of Fuel Cell of Electrochemistry:

It consists of two porous  graphite electrodes impregnated with a catalyst namely silver, platinum or a metal oxide. The electrodes are kept in an electrolyte ie an aqueous solution of NaOH or KOH. Oxygen  and hydrogen are continuously fed into the cell under a pressure of about 50 atmospheres and the cell is maintained at a temperature above 100⁰C. The gases as well as the electrolyte diffuse into the pores of the electrodes.

Working and Uses of Fuel Cell Electrochemistry:

The following electrode reactions taking place in fuel cell electrochemistry:

• Oxidation electrode reaction:

            2H₂(g) + 4OH^-(aq) `rarr` 4H₂O(l) + 4e^-

• Reduction electrode reaction:

   O₂(g) +2H₂O(l) +4e^- `rarr` 4OH^-

The overall fuel cell reaction is the sum of the above two equations .
              2H₂(g) + O₂(g) `rarr` 2H₂O (l)
The emf of the cell is found to be 1 Volt. Since the temperature of the cell is more than 100⁰C, water produced vaporizes and leaves the cell along with the unused hydrogen
Advantages of fuel cell electrochemistry:

• When compared with the conventional electical energy generators the fuel cells are more efficient.The efficiency is about 75%.

• Since the product of combustion of the two fuel gases is water, it proves to be pollution-free source of power.


• The fuel cell can be made a perennial source of electrical energy by maintaining a continuous supply of fuel.


• The fuel cells are employed in spacecrafts.


• They seem to be the promising substitute for the internal combustion engines in automobiles in the very near future, reducing pollution and enhancing efficiency. Unlike the heavy lead-acid batteries used in vehicles at present , the fuel cells are very light in weight and so many individual cells can be arranged in series connection to generate very high voltages.