Nice, but it’s not an energy source! It's not even magical, like Flubber.
The efficiency of each step in the entire system must be evaluated...
I hope it proves to be better than the existing system (extract crude oil from
the ground, refine it into gasoline, fill up the fuel tank, start up the engine
and drive the car away).
Eventually we will run out of countries to invade, economically viable oil
to extract and breathable air. Nuclear power to hydrogen should be
sustainable ('till meltdown or waste produced by the nuke power plants
wipes out too many neighbors).
Hydrogen looks like a "clean" way to run the car engine. How it's produced
is the bigger unanswered question. Is it efficient enough?
For now, it simply comes down to dollars. Even evaluating efficiency gets
mucked up by government subsidies where true cost and efficiency is obscured.
If there's a way to "crack" water using only home solar power panels, that's
fantastic! It's unlikely those solar panels will "charg 'er up overnight, lol.