Direct methanol fuel cell (DMFC) science

Hydrogen is a very active reducing agent (fuel). Thus, in hydrogen-oxygen fuel cells, very high operating currents and high specific power values per unit weight can be achieved. However, the handling, storage, and transportation of hydrogen fuel is complex. This is primarily a problem for relatively small portable power plants. For such a plant, liquid fuels are more realistic.
Methanol is a very promising fuel for small portable fuel cells. It is more convenient and less dangerous than gaseous hydrogen. Compared to petroleum products and other organic fuels, methanol has a fairly high electrochemical oxidation activity (although not as high as hydrogen). Its chemical energy ratio content is about 6 kWh/kg, which is lower than that of gasoline (10 kWh/kg), but quite satisfactory. For this reason, its application in fuel cells for power plants in electric vehicles and different portable devices is widely discussed today.

The operation of DMFCs has fundamental problems that do not exist in proton exchange membrane fuel cells. In the latter, the membrane is practically impermeable to reactants (hydrogen and oxygen), preventing them from mixing. In contrast, in DMFC, the membrane is partially permeable by methanol dissolved in an aqueous solution. For this reason, some methanol penetrates from the anode part of the battery through the membrane to the cathode part. This phenomenon is called cross-curium-crustic ethanol. This methanol is directly oxidized by gaseous oxygen on a platinum catalyst without producing useful electrons. This has two consequences: (i) a significant portion of the methanol is lost in the electrochemical reaction, and (ii) the potential of the oxygen electrode shifts to a lower positive value, so the operating voltage of the fuel cell decreases. Despite many investigations conducted so far, it has not been possible to fully address this issue.
One potential application area for DMFC is low-power (up to 20W) power supplies for electronic devices such as laptops, camcorders, DVD players, mobile phones, medical devices, and more. At present, the application of DMFC as a power source for electric vehicles is very far away. Despite a great deal of research, DMFCs are still not in commercial production or widely used in practical use compared to proton exchange membrane fuel cells.