Natural Gas Power Density> 0.044 - 0.0562 /b/ft3
But you have to have a supply of natural gas. Hydrogen you can get anywhere.
I think this thing might make economic sense in some circumstances. I've been reading lately that the Navy now has the means to process ocean water into Aviation Fuel on their nuclear powered aircraft carriers. I think the fuel costs them something like $18.00 a gallon, but it become economically feasible as a result of their having the ability to make it whenever and wherever they need it instead of relying on logistical support to bring it.
Hydrogen splitting and storage would have to be used for some sort of similar need to make it economically viable, but I can see circumstances in which this could be true.
Also, your power densities for Hydrogen and for Natural Gas are at what pressures? Ambient?
What do they look like when pressurized to 3,600 psi as Natural Gas is normally?
Also is that energy density from burning or from Ionic transfer as with the Hydrogen?
Pressure on both figures were in lb/ft3
cubic lbs per ft.