What exactly is the defenition of a catalyst? How do I recognize one? All in all, I'm trying to replace Platinum as the catalyst in my fuel cell... it makes it a little pricey...

IIRC, they lower the activation energy of a reaction.

Pt...That can usually be replaced with rainey Ni, no?

I'm also wondering is there something in specific that will allow you to tell if something is a catalyst. Some property that is commonly found in things that are catalysts.

Would enzymes in our bodies be considered catalysts?

We have to consider the operating temperature of the fuel cell and the mechanism in order to use enzyme as the catalyst. Given the high temperature of most (industiral) fuel cells, I am pretty sure the enzyme will denature before it would be useful.

Btw I am curious what role does this Pt catalyst play. Does it suppose to help in stripping hydrogen to prepare for fuel cell redox reaction? Or it aids the redox processes directly.

hey, p-man, so how is the fuel cell coming along?
The reason that Pt. is used over other elements such as Ni. is that it would work more efficiently, while it is true you would get a current reading if you were to use Nickel wire it would be significantly lower then when you would be using Pt.

about the industrial fuel cells, read carefully they will probably say that they use something like propane or methane or some kind of a fuel, that is what would increase the temperature.  

fuel cells that work by getting hydrogen and combining it with oxygen, such as a PEM (Proton Exchange Membrane) fuel cell, do not in any way combust the hydrogen to generate the energy.  Instead how these fuel cells works is quite interesting, the Hydrogen enters through the cathode and exits through the anode, but while this is taking place the electrons from the hydrogen molecules gets striper while passing through the cathode and go through a wire and directly to the appliance or what every you are using, such as a small motor, and then the electrons will come back through the negative wire and meet the Hydrogen when it will combine with the Oxygen to form H₂O.  the problem is getting the H₂ because if i am not mistaken you would need about 66 kilojoules to break apart 1 mole of H₂O.  But a catalyst is supposed to make that process faster and more efficient such that you would need less than the 66 kilojoules.  

now back again to the industrial fuel cells, well how those work is by using the fuel, propane most likely (since it is the most used residentially and allready has a pipe system in many cities), to heat the water and break them apart into H₂ and Oxygen molecules.  Right here we see another reason to use Platinum, generally when you heat the water to break it apart, you will find that the Hydrogen collected, if you had used another metal, would contain impurities, such as CO and CO₂, these would decrease the efficiency of the fuel cell and probably cause some expensive to fix problems in the future.  The efficiency of such industrial systems makes it a point of interest to get such a system, since the efficiency of such systems has been rated to be above 70%.  

which brings us to another point, fuel cells are amongst the most efficient sources of energy we have in current existence.  according to my Solar Energy class teacher, 1 Liter of Hydrogen would power a small car, about 6 inches by 4 inches by 3 inches, (of those small cars you build yourself from education kits) to go from Florida to New York.  She was probably talking about 1 liter in a liquid or something, i still see it as pretty hard to believe, maybe it was 1 Liter in a regenerative fuel cell    :-?

The world of fuel cells is quite an interesting area, they have allready made a micro fuel cell that would weight about 2 kilograms, is placed on a bike, and could release enough energy to drive the bike at about 40 miles per hour for a distance of about 20 miles, which is incredebly good considering the size of the bike.  if you want to research more on this the company that made the fuel cell was NOVar and they have 4 fuel cells ranging from 80 watts to 460 watts to 3000 watts to 5000 watts.  think about the possibilities when you have a system that rivals generators weighting 100 pounds and still weight less than 5%.  

the problem that is not pushing a hydrogen industry at the current moment is something which would generally be very possible if you were able to somehow guarantee that you would get the hydrogen to the place where it is intended to go.  Fuel cells generally would make the materials used for pipelines very brittle and prone to damage, that and the fact that it would go highly compressed could mean danger if you are not careful.  I have a question if anyone could perhaps answer it, is there anything that could solve this problem, i was thinking of plastic and rubber but then rememmber that the particles sould just effuse through the rubber, however, i do not know much about plastics and if they could diffuse through?

Yeah, they do that to store the hydrogen.

Anyways I'm not building the fuel cell just doing some of my ideas. How do I get a bit of Nafion? Where?

Yeah but still, all those cars are the biggest polluters out there, so if we don't find an alternative, we're pretty screwed.