hodges
National Hazard
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Registered: 17-12-2003
Location: Midwest
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Fuel Cell Questions
I have recnetly been reading about fuel cells. While I don't feel that fuel cells are going to be the answer to high oil prices, I do think that fuel
cells may soon be a practical replacement for batteries in some portable electronics applications. See this article on a fuel cell that weighs 8.5
grams and produces 100 mW of power from methanol.
http://www.dpreview.com/news/0406/04062401toshibafuel.asp
Anyway, it seems the simplest type is the alkaline fuel cell. This was used in the US space program as early as the 1960's. As I read about alkaline
fuel cells, though, there is something that is not clear to me. How do the electrodes allow H+ and OH- through to the electrolyte without shorting
out the cell? If you look (for example) at the diagram in the Wikipedia article on alkaline fuel cells (at http://en.wikipedia.org/wiki/Alkaline_fuel_cell), the electrodes are shown in contact with both the gasses and the electrolyte. Obviously the
electrodes must be porous to allow H+ and OH- to flow from the gasses to the electrolyte. They must also conduct electricity since the electricity is
drawn from them. I know that in modern (PEM membrane) fuel cells, there is a membrane which allows H+ protons to pass yet does not conduct
electricity. With such a membrane, the cell makes intuitive sense. But out of several diagrams I have found for an alkaline fuel cell online none of
them show a membrane. Furthermore, I'm sure the science of exotic membranes such as the modern PEM ones is a more recent development than the 1960's.
Can someone explain to me what is going on in regards to the electrodes and membrane in an alkaline fuel cell or point me to a source of this
information?
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Twospoons
International Hazard
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Mood: A trace of hope...
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I think the answer may be in this
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The catalyst required for the electrodes can be any of a number of different chemicals that are relatively inexpensive compared to those required for
other types of fuel cells.
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Different catalyst at each electrode? So it then looks a bit like a standard primary cell (like the old zinc/copper/electrolyte cell).
The use of selective catalysts is an area of intense research in direct methanol cells, where methanol crossing the membrane is seriously detrimental
to the efficiency of the cell. With selective catalysts this cross-over is not a problem.
[Edited on 15-6-2006 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
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hodges
National Hazard
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Registered: 17-12-2003
Location: Midwest
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| Quote: | Originally posted by Twospoons
I think the answer may be in this
| Quote: |
The catalyst required for the electrodes can be any of a number of different chemicals that are relatively inexpensive compared to those required for
other types of fuel cells.
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Different catalyst at each electrode? So it then looks a bit like a standard primary cell (like the old zinc/copper/electrolyte cell).
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Yeah that's one thing I'm trying to figure out - what might the catalysts be. The most information I have seen on the web from several different
sources says "a variety of materials". Okay, so like what I wonder?
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solo
International Hazard
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Registered: 9-12-2002
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Mood: ....getting old and drowning in a sea of knowledge
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There is a collection of fuel cell journals in the Micellaneous forum under full journals .....solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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