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.

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