They don't work, don't waste your time.

You need a ton of power to split a water molecule, more than your car can provide. Thats one of the big problems yet to be solved with fuel cells, they have yet to figure out a way to get hydrogen easly. Splitting it from water is a good way, but it takes so much engery its not worth it.

The first person to figure out how to split a water molecule with little power is going to make a fortune...

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2006 CL500
1969 280SE
2023 Ram 1500
2026 Genesis GV70
2007 Tiara 3200