I have a fuel cell experiment kit. The instructions specify that distilled water must be use with it. I suspect this is because of mineral deposits that would build up with other water.Here in Ireland it is difficult to find distilled water. The auto parts store supply de-ionized water. The pharmacy supply purified water. I can't find any one who sells distilled water. I don't want to ruin the fuel cell.
use only distilled and enjoy the added cost for being green.
A true fuel cell wouldn't use water, just pure hydrogen and oxygen and it does have to be pure with PEM fuel cells. There are high temperature fuel cells that can tolerate carbon impurities but a 1500 C fuel cell is a bit dangerous to have in a car. The only place that water would be mentioned as a feedstock to a fuel cell would be one of those scams or in one of those scientific demonstration kits as the amount of power required to disassociate hydrogen from water is higher than that which can be recovered from hydrogen reacting with oxygen. In the scientific kits, the only reason why they include a water hydrolysis portion is that that's easier than trying to obtain commercial hydrogen and electrolysis is a scientific principle that can be taught with the kit. If it's a scientific demonstration kit that you wish to use the water in, the purified or the deionized water should be fine. De-ionized will be closer to distilled then the purified. De-ionization is effective because almost all subtances become ionic when dissolved in water because they become aqueous and suspended particles can be removed by physical filters. Even if the water wasn't pure, the hydrogen produced would still be pure so there's no danger to the fuel cell, just to the electrolysis equipment.
DI water only removes dissolved salts (the majority if impurities in water). It does not remove dissolved/suspended organic compounds, gasses, etc. For a hobby kit, I doubt it will make much difference- I expect that the electrolysis part of your experiment might have buildups after a while, but the minute amounts aren't going to affect you too badly. your mileage may vary, however.
