Paul
The Methane (CH4) is a way more dense method of storing Hydrogen, but you'll need to get rid of the carbon.... Liquid is 0.4 T per cubic meter, of which 1/4 is hydrogen (4 of 16 atomic mass units).. for 0.1T per cubic meter, as opposed to 0.07T per cubic meter as LHyd. 1.4T per Td as liquid methane.
Water is 1/9 hydrogen.... which puts it at 0.11T Hydrogen per cubic meter. 50% improvement over L-Hyd, but at a high extraction cost.
and the carbon is a basic building block for all kinds of things so it sells as well at the other end ..as to hydrogen and oxygen extraction thats pretty cheap ..ie hook up a junk solar panel then run the browns gas thru a centrifuge to seperate the hydrogen from the oxygen) (very little power required)