Carbon-Supported Nanostructured Core-Shell Catalysts for Low Temperature Fuel Cells
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The direct methanol fuel cell needs a catalyst with low overpotential and high current density for methanol oxidation to be commerically viable. The catalyst with highest performance at the moment is the PtRu-alloy catalyst, but this is unstable. A compromise is the core-shell catalyst with ruthenium core and platinum shell. This catalyst shows improvement for CO-oxidation, but for the overall methanol oxidation, this is not as high as expected. This is believed to be because the catalyst promotes the parallell pathway through the intermediary species formaldehyde and formic acid. A method to detect these species were investigated. A model was made to calculate the concentration on the ring electrode to see if this was feasible. A rotating ring-disk electrode setup with a gold ring electrode was used to try and detect these species on the ring when they where formed on the disk. Experiments for different concentrations for formic acid and formaldehyde showed that palladium was more sensitive for these species than gold. An attempt to make a palladium ring by electrodeposition was made, and a microcell was also used to try and detect formaldehyde and formic acid by getting a high enough concentration in the bulk after methanol oxidation. The results of these experiments were that the ring-disk experiment on gold was inconclusive, but the model and results from concentration experiments showed that it should be feasable. Most of the electrodeposited palladium electroded were shown to be active in methanol, and the microcell experiment were inconclusive.