Wednesday, May 13, 2009

Hydrogen Fuel Cell

The hydrogen fuel cell works on the basis of electrolysis process. It generates electricity with fuel on the anode side and the oxidant on the cathode side and they react in the presence of electrolyte. The reactants which are the input flows into the cells and the reactant products flow out of it while the electrolyte remains inside it. The hydrogen fuel cell is just like the water fuel cell which was a failure. However the hydrogen fuel cell is a success. The fuel cells can run continuously if the input is maintained properly.

Hence the hydrogen fuel cell is just like the petrol engine and I must tell you that it works fine as well. However the fuel cells are different from the electrolytic cells as they consume the reactant from the external source, which requires a thermodynamically open system. Many combinations of the fuel and the oxidants are possible. For example the hydrogen cell uses the hydrogen as the fuel and oxygen as the oxidant. The other combinations are hydrocarbon and alcohol as well as chlorine and chlorine dioxide.

The fuel cell works with the help of electrolysis. Up till now you must have understood the use of reactant as well as oxidants. However you will have to understand one more thing and that is catalysis. The fuel cell works with the help of catalysis which helps in separating the electrons and protons. Now you must know that the electric current flows in the direction opposite to the flow of the electron. I must say that the electron flow is maintained with the help of catalysis which separates the electron and proton and hence the electrons start moving in one direction and hence the electricity is generated.

A typical hydrogen fuel cell produces about 0.6 to 0.7 volts of voltage. However this cell does not obey the ohms law. You must know that according to Ohms law the voltage is directly proportional to the current. However this is not the case with the hydrogen fuel cell. In case of the hydrogen fuel cell the voltage is found to go o decreasing as the current starts increasing.

The reason behind the decrease in the voltage is because of the facts that are as follows:
  1. Activation loss
  2. Ohmic loss: (due to the resistance of the cell components and interconnect.)
  3. Mass transport loss (due to the depletion of the reactants at the catalyst site.)
Hence it is a general observation that the hydrogen fuel cell do not obeys Ohms law. In fact all the electrolytic cells do not obey the ohms law and hence hydrogen fuel cell which is also a kind of electrolytic cell does not obey the ohms law.

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