DMFC - Direct Methanol Fuel Cell

The DMFC converts liquid Methanol (CH₃OH) into electrical power. The direct conversion of Methanol without external reformers makes the DMFC very unique, because a liquid fuel rather than gaseous hydrogen can be used. The structure of the DMFC is very similar to the PEMFC, only different catalysts are used to trigger certain chemical reactions.

The following picture shows the electrochemical reactions that are taking place in a DMFC. On the anode, liquid Methanol is oxidized with water and Carbondioxide (CO₂) is generated which is not needed and therefore removed from the fuel cell. As a result of this reaction free electrons e^- and Hydrogen ions H⁺ are generated . Similar to the PEMFC, Hydrogen ions pass thru the PEM while the free electrons generate electrical power when passing thru the external electrical circuit. On the cathode, the Hydrogen ions H⁺, the free electrons e^- and oxygen from the air react to water (H₂O).

DMFC fuctional diagram (Source: www.smartfuelcell.com)

The big advantage of the DMFC is the fact that liquid Methanol rather than gaseous Hydrogen can be used as a fuel. Since a liquid is much easier to store and handle than the gaseous hydrogen this is a significant advantage especially for mobile and portable applications.

The disadvantages of the DMFC today are caused by some technical problems which need to be solved. First the so called crossover of Methanol thru the PEM is a major problems since it does reduce the cell voltage as well as removes part of the Methanol fuel from the anode side of the cell. Secondly, the currently achieved power densities of the DMFC are still significantly below the PEMFC and other fuel cell types. This is mainly related to the relatively slow reaction speed of the electrochemical reaction described above. Therefore more research and development is needed to optimize these shortcomings.

In summary the DMFC today is a very exciting technology especially for portable applications in the power range of mWs to a view kWs and has the potential to become a key technology for mobile applications when further breakthroughs in this technology can be achieved.