Direct Methanol Fuel Cells – DMFC
The direct methanol fuel cell -DMFC is the only cell which is not using hydrogen but methanol for the eduction.
There are no reformers needed because the cell on its own converts methanol into hydrogen protons, free electrons and CO2. Because of the missing reformer it is best suited for the use in motorcars by coming closest to the ideal of an energy source as simple as possible.
A proton exchange membrane serves as electrolyte.
The function of the DMFC:
- Step 1
There are two supply circuits. At the cathode side is the oxygene supply and at the anode side methanol and water is supplied. The substances move into the gas area and the catalyzer.
- Step 2
The methanol reacts with water to carbon dioxide and hydrogen. After this the hydrogen is devided into two H+ atoms (protons). Each atom sets free one electron.
- Step 3
The protons move through the electrolyte (a proton transmitting membrane) to the cathode.
- Step 4
The electrons move from the anode to the cathode and cause an electric current. This electric current supplies an electric capacitor with electric power.
- Step 5
Respectively four electrons recombine with one oxygene molecule.
Remark: In this animation there is one oxigene atom "too much" at the cathode. In reality this atom will also absorbe two electrons and paticipate in the reaction.
- Step 6
The now generated oxygene ions are negative loaded and react with the protons to water.
Direct Methanol Fuel Cells - DMFC
At the moment the direct methanol fuel cell for portable applications is just before commercialisation. Some products are already available e.g. for professional video cameras. The DMFC extends the operation range of portable applications by a factor of seven to ten. The methanol cartridge can be changed during operation and within seconds the system is recharged.
By 2005 many companies have announced commercial DMFC products.
The motivation for working on DMFCs is the fact that methanol can be more easily stored in liquid form than hydrogen.
In the past DMFC have also been developed for vehicle drive trains. But after methanol is not the favoured fuel strategy of the big automotive companies anymore no further development can be seen in this area.