Platinum-free catalysts for ethanol fuel cells to go commercial by 2006
Publication Date:31-May-2005
11:50 AM US Eastern Timezone
Source:Electronics Weekly
Low-cost, platinum-free catalysts for fuel cells running on ethanol, which were initially discovered during research into removing heavy metals from tannery waste water, should be inside commercial devices by the end of the year.
Ethanol is an attractive fuel since it offers a higher specific energy than methanol, and is easier to handle.
Italian manufacturer Acta said the Hypermec catalysts have already interested several large Far Eastern OEMs, and last week it announced an Asian distribution deal with a subsidiary of Japanese materials giant Sumitomo.
The catalysts, which use iron, cobalt and nickel supported on a polymer, offer a number of advantages over existing platinum-based alternatives. The amount of metal required is comparatively low; they are effective at room temperature; and unlike platinum, the anode catalyst is not poisoned by carbon monoxide.
Self-breathing ethanol fuel cells using Hypermec catalysts at 22°C have shown electrical efficiency of 42-45 per cent, and a power density of 65mW/cm2 at a voltage of 200-600mV. Maximum power output in a self-breathing cell was demonstrated at 142mW/cm2, achieved within four minutes of start up.
“Twenty five per cent of customers want to reduce the amount of platinum [they have to use], and 25 per cent want to try platinum-free catalysts with [existing] methanol cells,” said Bert. “However, 50 per cent, mainly those that are lagging a little bit behind in fuel cells, are interested in platinum free/ethanol technology.”
There are other benefits. The anode and cathode catalysts are selective for the specific reaction occurring at the particular electrode, so a simplified (unseparated) cell structure is possible. The catalysts are also effective with a wide range of fuels, including ethylene glycol and some solid fuels.
The Co, Fe and Ni metal particles have an average diameter of 0.3nm, which Acta says compares with 5-50nm in typical platinum catalysts. The fine dispersion on the Vulkan polymer means that densities of 0.2mg/cm2 are required to give the same activity as 4.0 to 8.0mg/cm2 of platinum.
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