Milestones in DMFC Development

Owing to the relatively low rate of methanol oxidation at platinum, considerable amounts of platinum catalyst had to be used in these models (up to 10 mg/cm ). Still, the specific power attained was qnite small (abont 20 mW/cm ). For this reason, interest gradually subsided. Just a few papers have since been published in the scientific and technical literature on this topic. 

A turning point in this area was reached in the mid-1990s after the considerable success achieved in the development of hydrogen-oxygen fuel cells with protonconducting membranes, PEMFCs, and when it had become possible to transfer these achievements to other types of fuel cells. 

At present, most work toward building methanol fuel cells reUes on technical and design principles developed previously for PEMFCs. In both types of fuel cells, it is common to use Pt-Ru catalysts at the anode and a catalyst of pure platinum at the cathode. In methanol fuel cells, the membrane conunonly used is of the same type as in hydrogen-oxygen fuel cells. The basic differences between these versions are considered in Section 4.7. 

Ionization of adsorbed hydrogen atoms and the anodic formation of species from water molecules are the steps actually producing the current  

Under certain conditions, as when the cell is temporarily at open circuit, when the formation of species OH ds is not possible, species COH ds age and change to species COads that are hard to oxidize and capable of inhibiting further methanol oxidation. 

The thermodynamic potential of the methanol electrode is +0.02 V, a value that is rather close to the hydrogen electrode potential. The steady-state potential of a platinum electrode in a methanol solution is about +0.3 V. The working potential of a steady-state methanol oxidation depends on the current density and varies within the range of 0.35-0.65 V. This means that the working voltage of a methanol-oxygen fuel cell will have values within the range of 0.4-0.7 V. 

In the beginning of the 1960s, repeated attempts were made to build test models of methanol/oxygen (air) fuel cells. In the first of these attempts, an alkaline electrolyte solution was used. On account of undesirable carbonate formation in this electrolyte, for later studies of anodic methanol oxidation solutions of methanol in aqueous sulfuric acid were used, and the same solutions were used when building the first models of methanol fuel cells, more particularly, by Shell in England and Hitachi in Japan. 

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