"By splitting water by electrolysis and creating hydrogen/oxygen gas"
http://waterpoweredcar.com/
"Electrolyzers (both alkaline and PEM) – Electrolyzers use electricity to split water and create hydrogen. These can be small for on-site generation or can leverage multiple stacks generating hydrogen from surplus hydroelectricity or other renewable energy sources."
https://investor.cummins.com/news/detail/493/cummins-leadership-shares-hydrogen-technology-strategy-and
"All the generator needed was an external energy source to start it up, after which it ran till someone stopped it or because of a mechanical failure. This Tesla mentions in his correspondence with Sava Kosanovic, March 1, 1941...
"I add that in the station one must have a small generator or battery of 30 volts for activation.""
https://nexusnewsfeed.com/article/science-futures/nikola-tesla-s-flying-saucer-electromagnetic-field-lift-experiments/
Alternator 220V & Motor generator 12V, charging system
How to make Alternator battery charging machine with electric motor