As far as how to capture the gases, it's just a matter of proper design of the equipment. Here is a typical laboratory device used for demonstrations:
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The gas bubbles rise from the electrodes, and collect in the vertical glass tubes, where the gases can be drawn off via stopcocks. The basic design could easily be scaled up to whatever size you want.

[This message has been edited by NJwirenut (edited 08-12-2006).]

[This message has been edited by NJwirenut (edited 08-12-2006).]