<>All these stories overlook the inconvenient fact that it takes energy to do all these things. It takes energy to split hydrogen out of water. It takes energy to synthesize it back into a hydrocarbon. And because of the Second Law of Thermodynamics, energy is always lost in the process. Consequently, you always end up with less energy than when you started.
Lots of folks don't understand the Second Law of Thermo.
Interestingly enough, though, when I mentioned this in one forum, someone pointed out this would also be the case with the original hydrocarbon-based fossil fuel -- ignoring the fact that fossil fuels represent energy stored over time, millions of years ago. Fossil fuels are useful only because something else stored all that energy that we're now tapping.