Apropos electrolysis and water, way back in the day in high-school, my chem istry teacher showed us how to make Hydrogen peroxide using electrolysis. I t was crude and not very efficient, and wasteful of resources.
Today, not so much.
Under controlled conditions, other products are also possible. I suspect th at is what Tennant was doing.
Side Note: This teacher partnered with several of the history teachers. He had us collect 'night soil' to make gunpowder when we were studying the Civ il War, we had to learn the 'secret code' whereby one could identify an Ame rican anywhere, any time (this _was_ the 1960s, remember), and we had to le arn the ten (10) reindeer. In any case, a lot of very basic and very useful chemistry and applied science has stuck with me over the years.
Peter Wieck Melrose Park, PA