One of the most modern electrochemical technologies for producing electricity is a fuel cell. The fuel cell may be of different types. Although by principle all the fuel cells are the same. But different fuel cells use different fuels. Among them, the hydrogen-oxygen fuel cell is a popular one. Here, hydrogen and oxygen are the fuels for the cell.
Construction of Hydrogen Oxygen Fuel Cell
The construction of a hydrogen-oxygen fuel cell is not very complicated. In its most basic constructional structure, there are two inlets. One is for H2 and the other is for O2. There are two electrodes. The electrodes are made of porous graphite or any other similar materials. The electrodes serve as barriers. Such as the barriers prevent hydrogen gas and oxygen gas to mix up. The barrier like electrode towards the hydrogen inlet is the anode. On the other hand, the electrode toward the oxygen inlet is the cathode. The space available in between the electrodes contains aqua NaOH electrolyte.
Working Principle of Hydrogen Oxygen Fuel Cell
Because of the porous nature of anode, it remains wet with electrolyte. The hydrogen gas enters through the hydrogen inlet comes in contact with the electrolyte in the porous anode. Here the hydrogen molecules react with OH- ions of electrolyte. This is the oxidation reaction of hydrogen. This reaction forms water molecules and free electrons.
2H2 + 4OH– = 4H2O + 4e
These free electrons come to the cathode through the external load circuit. In the porous cathode, these electrons participate in the reduction reaction. Because of that, oxygen reacts with water and forms OH– ions. This half-reaction makes up the deficit of OH– ions of NaOH electrolyte occurred during oxidation reaction in the anode.
O2 + 2H2O + 4e = 4OH–
Full Reaction of Hydrogen Oxygen Fuel Cell
4OH– = 4H2O + 4e
O2 + 2H2O +
4e = 4OH–
2H2 + O2 = 2H2O
Advantages of Oxygen-Hydrogen Fuel Cell
- Both hydrogen and oxygen are easily available as fuel.
- The out come of oxygen-hydrogen fuel cells is pure water. This water is so pure that we can drink it directly. Hence these cells do not create any pollution in the atmosphere.
- The efficiency of this fuel cell is about 60-70% which is much more than that of convectional thermal power generating plant (40-50%).
Standard e.m.f of H2 –O2 Fuel Cell
The standard e.m.f of a hydrogen-oxygen fuel cell is 0.9V.
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