Doing it directly in the car doesn't make much sense.  You need a big battery to power the electrolysis that generates the hydrogen.  But if you have a big battery, you might as well use an electric motor and have an electric car.


Doing it indirectly, using mains electricity to make hydrogen, then using the hydrogen to power a vehicle, is possible and lots of people have tried it.  But it's never caught on.  It's less efficient than a battery vehicle, and we don't have the infrastructure in place to transport the hydrogen.

Doing it directly in the car doesn't make much sense.  You need a big battery to power the electrolysis that generates the hydrogen.  But if you have a big battery, you might as well use an electric motor and have an electric car.


Doing it indirectly, using mains electricity to make hydrogen, then using the hydrogen to power a vehicle, is possible and lots of people have tried it.  But it's never caught on.  It's less efficient than a battery vehicle, and we don't have the infrastructure in place to transport the hydrogen.