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16/07/2022

Direct Methanol Fuel Cell

Introduction of DMFC Fuel Cell

  • The DMFC is similar to polymer electrolyte membrane ( PEM ) cell in that both fuel cells use a polymer membrane as the electrolyte. 
  • However, the anode of DMFC draws hydrogen from the liquid methanol, eliminating the need of fuel reformer.

Direct Methanol Fuel Cells ( DMFC )

  • The direct methanol fuel cells are powered by pure methanol which is mixed with water and fed directly to the fuel cell anode. 
  • The methanol has higher energy density as compared to hydrogen therefore it has not any fuel storage problem. 
  • The density of methanol is less than gasoline or diesel fuel. It is easy to transport and supply to public in the liquid form.


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DMFC: Chemical reaction 

The methanol is directly oxidized to carbon dioxide at the anode. At the cathode, oxygen gas combines with the protons and electrons, reduces to water.

  • Anode : CH3CH + H2O → CO2 + 6H+ + 6e-
  • Cathode : 3/2O2 + 6H+ + 6e- → 3H2O
  • Overall chemical reaction : CH3CH + 3/2O2 → 2H2O + CO2

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FCT - DMFC


DMFC: Advantages 

  • Light weight
  • Easy to transport
  • Methanol is inexpensive, it can be supplied to fuel cell from liquid reservoir.
  • No fuel storage problem
  • Higher density as compared to hydrogen
  • Supply to public through current infrastructure ( no additional cost )

DMFC: Disadvantages / Limitations

  • Methanol cross over from anode to cathode across membrane separator.

Methanol crossover

  • Excess methanol is supplied to anode side of the membrane electrode assembly. 
  • It is desirable that most of methanol to diffuse into anode and react. 
  • This phenomenon is called as methanol crossover in which some of methanol diffuses through polymer electrolyte membrane from anode to cathode. 
  • The dilute methanol is supplied to the anode electrode which diffuses into anode and partially reacts. 
  • The remaining methanol leaves electrodes and moves to cathode which result in reduce fuel efficiency and reduce cathode performance. 
  • The potential efficiency of DMFC for operating cell of 0.5 V is about 40% at temperature of 40 – 90 0C. Higher efficiency is achieved at higher temperatures.

DMFC: Application

  • As a portable fuel cell for laptop computers or cell phone
  • Defense and military
  • Mobile homes and marine application

 

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