Water is made out of hydrogen and oxygen.
And the byproducts combine to form deadly dihydrous monoxide, known to cause millions of dollars worth of damage every year and to claim thousands of lives.
Did you take high school chemistry?
Hydrogen [’water forming’] burns [’oxidizes’] to form water. They can’t go any further chemically.
2H2 + O2 > 2(H20) + energy ! oxidation
2(H20) + energy > 2H2 + O2 ! electrosis, for instance
The energy was given off forming water, you have to put just as much energy back in to get molecular hydrogen and oxygen. Some energy is invarably lost in the transaction. Hydrogen is more of an energy storage medium than a primary source. (Except when it’s converted to Helium in a star or a nuclear weapon. That’s high school physics.)