It turns out that electrolysis in zero-g is tricky, the bubbles tend to stick to the electrodes. I believe there are some nanomaterials in development now to prevent that, but it makes it more complex than you would initially think.

Then don't do it in zero g. Spin the chamber and siphon off the combined gasses from the center. It might not even need 'moving' parts. The contents of the tank could be stirred with magnets.