The chemical bond in water is very stable so breaking it into H and O using electrolysis works but isn’t efficient. An energy source is still needed to produce the hydrogen gas, which can then be combined in a fuel cell with the oxygen in the ambient air to generate a DC current and generate a pure water exhaust.
Recharging such a car would be pretty fast, but the volume of stored hydrogen is large. Liquid fuel is more compact than hydrogen. Also hydrogen storage leaks because hydrogen atoms are tiny and tanks have to be under great pressure.
Kevin at Engineering Explained has a number of vids about the science, engineering, approaches, and pitfalls. Contrary to what you may have seen here from trolls here and elsewhere, he isn’t an electric car fanatic, he likes cars and he likes facts, rather than kneejerk responses and agendas.
https://www.youtube.com/@EngineeringExplained/search?query=hydrogen
Thanks. I like facts, too.
We humans NEED the oxygen in the 'air' to continue to live!!
It's already down to 21% - so I sure don't want LESS of it to breathe!!