Burning hydrogen produces dangerous nitric oxides, it also causes other
problems like embitterment.
What you really want is a Fuel Cell. You can see a .GIF animation of
how one works at http://www.hpower.com as well as a couple of other
places. The 'exhaust' of a Fuel Cell is water. In other words a Fuel
Cell is electrolysis in reverse from which you get electricity as the
output.
If things go as planed, and so far they have not, there will be a detailed
page on Fuel Cell's at http://www.circuitcellar.com/online in October.
http://www.biogate.com/bpaddock/