I saw a video on the www a couple of years ago, but haven't been able to find it since.

There was a small motor (lawn mower motor I think) that was powered by hydrogen gas. The motor drove an alternator which powered a small welder and it turned an aluminium drum. The drum was submerged in a tank of water and the welder electrode touched the aluminium drum and arced. The spinning drum stopped the electrode from sticking to the aluminium. The arc bound O2 to the aluminium, falling to the bottom of the tank as an aluminium oxide residue, and the liberated hydrogen bubbled to the top and powered the motor.

Was it real? I don't know.