Does your statement apply to a hydrogen fuel cell?
If so count me as a doubter of the laws of physics.
If you use electrolysis to separate the Hydrogen from the Oxygen in the first place, you are not going to get more energy putting it back together than you spent taking it apart, storing and transporting it. Plus the heat of the equation is not recovered in fuel cells.
If this were not so, you could build a perpetual motion machine. I assume you don't believe in those.