. With same careful fiddling of the choke, and a fresh tank of gas, it ran happily for about a half hour, consuming surprisingly little fuel. Would make a nice hydrogen-fuel project it's not very picky to air/fuel ratios, reliable and simple as can be (carborated, and the fuel line is visible. I could remove the gas tank in 2 minutes if I wanted to, as well as the carborator), so I might try running it on hydrogen once I get a large enough system made. A small high-pressure tank could be fitted where the current gas tank goes, maybe a metal hydride tank (safer, but possibly pricey), with a refueling station in the garage.
Anyways...
When I first read "catalust" and "coating", platinum popped into my head as a commonly available catalyst, seen in catalytic convertors in cars in a honeycomb structure. To do its job, it needs a high temperature, provided by the exhaust gases, but I doubt we'll be reaching several hundred degree with this cell, unless we put it directly next to the exhaust.
From what I gather, the metal plates, made of the catalyst metal, are coated with a chemical, something cheap and plentiful, which reacts with water, to form hydrogen (?) and what is most likely an oxide or hydroxide compound with the water. This new compound is then broken down (not synthesised?) by the catalyst, to yield a fertilizer.
The fertilizer compound contains hydrogen, since it can be broken apart to yield it.
Ammonia, NH3 is a common ingredient in fertilizers, but I've no clue where we'd get the nitrogen for it... Maybe what the catalyst metal is covered with contains nitrogen? I haven't followed through on the clue about the product being used in hydroseeding, though.
Maybe it's just me, but the limiting reagent bit doesn't light that bulb in my head yet...
To my knowledge, a limiting reagent in a reaction is the chem of which you have the lowest amount of compared to ideal amounts for the reaction, it's what determines how much product you can make, it limits it, hence the name.
Hard to describe in writing, so I'll do an example, since I'm sure some folks here are scratching their heads at that last paragraph.
Ok... Let's take the burning of methane, CH4, since it's a fairly simple reaction.
methane + oxygen (and a spark, but that's not included) make carbon dioxide and water.
CH4 + 2O2 --> CO2 + 2H2O
That's the balanced equation for the combustion of methane. The numbers in front of the chems show moles of the chemical needed to fully react with the rest of the chems. Here, we need one mole (unit of measure) of methane, and 2 moles of oxygen to make a perfect reaction, with all of the reactants (left side of equation) used up, making one mole of carbon dioxide and 2 moles of water. Let's say we only have one mole of oxygen instead of two, so half of what we need for a perfect reaction. Since half as much oxygen is available, only half of the methane will burn, and the other helf will be left over. Likewise, only half the CO2 and H20 will be made. Since it limits how much of the reactants are made, and how much of the other reactant is used up, oxygen is our limiting reagent. The methane, since there's some left over, automatically becomes our excess reagent, since we have more than we needed for all of the oxygen to be used up.
If we had 4 moles of oxygen, or twice as much as ideally needed, then we'd be left with 2 moles after all of the methane burns, since only 2 moles are needed to burn the one mole of methane, and the excess is left over. The oxygen in this case is the excess reagent, and methane the limiting reagent.
I know that isn't the best explanation, but I'm trying to keep it a bit short.
So basically, in Alaska's cell, there is excess of the liquid (water, from what I gather) compared to the chem on the plate. I don't see how simply having a limiting reagent can cut costs. Hmm... the amount of chems, and in particular of the limiting reagent, can affect how fast the reaction happens. Less limiting reagent makes it faster, since there's less to use up, but makes for less production of the reactants. Opposite is true for a larger amount of the limiting reagent (until it meets the ideal amount needed, or exceeds it, becoming the excess reagent. But then we'd have more chem than water.) Still, there has to be something I'm missing with this, since there's a lot of bits that I haven't looked at in the right way, or that have gone right over my head.
Oh, and I tired downloading your video, Alaska, and it wouldn't play, after about a half hour of downloading
. Apparently one or more codecs needed to play it were missing (according to Windows Media Player). I clicked the first link you posted, not Geo's second corrected one, maybe that's it? 