[wamatt]

Very interesting.

Can someone who knows about this stuff comment on whether the energy required to extract the H2 from the water, is more than the energy contained in the chemical bonds of the H2 itself? (assume both sides of the comparison contain equal number of molecules)

I suspect it is.. otherwise they are potentially sitting on a much more important innovation, than mere jet fuel.

[jordanb]

Consider it from the perspective of the conservation of energy:

2H2 + O2 = 2H2O + energy

The energy is on the right because the reaction is exothermic.

The opposite reaction must be endothermic and must have the same amount of energy on the left:

2H2O + energy = 2H2 + O2

Otherwise, energy isn't conserved.

Because nothing is 100% efficient, there's also energy lost to inefficiencies. So the answer to your question is that yes, you need more energy to make the second reaction happen than is stored in the chemical bond.