Hydrogen Oxygen Fuel Cell

Introduction 

Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. In such plants, the chemical energy (heat of combustion) of fossil fuels (coal, gas or oil) is first used for converting water into high pressure steam. This is then used to run a turbine to produce electricity. A galvanic cell directly converts chemical energy into electricity and is highly efficient.  Galvanic cells are designed to convert the energy of combustion of fuels like hydrogen, methane, methanol, etc. directly into electrical energy are called fuel cells. It consists of an anode, cathode, catalysts and most often an electrolyte.  Fuel cells are different from batteries in that they consume reactant from an external source, which must be replenished.

Hydrogen Oxygen Fuel Cell and its Working Principle

It is one of the most successful fuel cell which uses the reaction of hydrogen with oxygen to form water. Hydrogen oxygen fuel cell was used for providing electrical power in the Apollo space programme. The water vapour produced during the reaction were condensed and added to the drinking water supply for the astronauts.  In the cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous sodium hydroxide solution. Catalysts like, finely divided platinum or palladium metals are incorporated into the electrodes for increasing the rate of electrode reactions.
Catalysis plays a very important role in Hydrogen oxygen fuel cell, separating the electrons and protons of the reactant fuel (at the anode), and forcing the electrons to travel though a circuit, generating electrical power.  At the cathode, another catalytic process takes the electrons back in, combining them with the protons, which have traveled across the electrolyte and the oxidant to form waste products (like carbon dioxide and water).

The electrode reactions of Hydrogen oxygen fuel cell are given below:
Reaction at Cathode:  O2 (g) + 2H₂ O(l ) + 4e⁺    4OH^–(aq)
Reaction at Anode:     2H₂ (g) + 4OH^–(aq)          4H₂O(l) + 4e^–
Overall reaction is:
2H₂(g) + O₂(g)         2 H₂O(l )
The cell runs continuously as long as the reactants are supplied. Fuel cells produce electricity with an efficiency of about 70 % compared to thermal plants whose efficiency is about 40%.

Applications of Hydrogen Oxygen Fuel Cell

Hydrogen oxygen fuel cells are used in wide range of applications, from producing electricity for the grid to powering portable devices, like lap tops. It is also been used in automobiles on an experimental basis as fuel cells are pollution free with high efficiency.