Umicore AG & Co. KG (Hanau-Wolfgang, DE) garnered U.S. Patent 7,776,781 for a platinum/ruthenium catalyst for direct methanol fuel cells. The catalyst has a high catalytically active precious metal surface area ("dispersion"), displays very good performance in the anodic oxidation of methanol and accordingly overcome the disadvantages of the previous supported and unsupported PtRu catalyst systems
Developed by Marco Lopez and Peter Biberbach, the invention relates to a carbon-supported PtRu anode catalyst for direct methanol fuel cells (DMFC) which has a platinum/ruthenium content in the range from 85 to 95 wt. % (based on the total weight of the catalyst), on a carbon-based electrically conductive support material and has a mean particle size of less than 3 nm.
The catalyst is prepared using a carbon black support material having a specific surface area (measured by the BET method) in the range from 1000 to 2000 m2/g by means of a reduction process using chemical reducing agents with addition of organic acids. Electrodes and membrane-electrode units containing the catalyst according to the invention having a high precious metal loading have an electrode layer thickness of less than 80 microns at a PtRu loading per unit area of the electrode of from 6 to 12 mg of PtRu/cm2 and lead to improved electric power in direct methanol fuel cells.
Fuel cells convert a fuel and an oxidant in separate locations at two electrodes into electric power, heat and water. The fuel used can be hydrogen, methanol or a hydrogen-rich gas, and the oxidant can be oxygen or air. The energy conversion process in the fuel cell is largely free of pollutants and has a particularly high efficiency. For this reason, fuel cells are becoming increasingly important for alternative propulsion concepts, domestic energy supply plants and portable applications.
The direct methanol fuel cell (DMFC) converts the fuel methanol directly into electric energy. Owing to its low operating temperature, its compact construction and its power density, it is particularly suitable for portable applications, e.g. as replacement for accumulators and batteries.