Lightest, simplest, most abundant element in the universe. Highest energy content of any common fuel by weight, but the lowest energy content by volume.
It takes about 15 volts to electrolyze pure water, but pure water is not the ideal fuel to begin with, water with electrolytes dissolved in it is. If you live near the ocean, the ideal fuel medium is plain sea water, which has the perfect level of salinity for electrolysis, and requires not 15 volts to separate the hydrogen from the oxygen, but only 1/2 of a volt.
Electrolysis
The volume of gas produced is proportional to the current passing through the water and the total surface area of the plates. To do this the spacing of the electrodes must be as close as possible while still having enough room for the gas to bubble out freely. A greater surface area also means less resistance and less heat.
Consider the distance between your plates, if water is an insulator, then the more water you have between two plates, the higher the resistance will be between the plates. The farther apart your plates are, the less amps your cell will draw through the water. The closer the plates are, the more amperage your cell will draw.
The metal chosen for the plates was special high grade stainless steel to reduce corrosion. Such metal is not as conductive as others like copper for instance, so a few more plates might be used.
If we add Electrolytes to the water, we will make the water conduct better by decreasing the Resistance between the plates. A decrease in resistance allows more current to flow thus increasing the possibility of producing more HHO. A cell that has wide spacing can be made to produce just as much HHO as a cell with close spacing. Note, see {https://en.wikipedia.org/wiki/Urea Urea}.
Chemical Generation
A mixture of water, aluminium strips and lye(sodium hydroxide) generates hydrogen. The lye mixture is best kept in High Density Polyethylene(HDPE#2) and Polypropylene(PP#5).
Fuel Cell
A fuel cell is a device that converts a fuel such as hydrogen, alcohol, gasoline, or methane into electricity directly. A hydrogen fuel cell produces electricity without any pollution, since pure water is the only byproduct.
In a 1976 U.S. Patent, Gutbier and Hohne indicated that hydrogen could be produced via the reaction of magnesium-aluminum mixtures with sea water.