It seems like a thing, but:
a. it is fuel cell, one of many on the market,
b. it is not clean, unfortunately, because it "burns" carbon fuel, and that is not clean as it generates (CO2)
c. to be clean it needs hydrogen, but you have to generate it, so the overall efficiency drops.
He has a secret formula to replace the membrane in between ceramic plates. Nice because membranes are notorious for clogging and failing.
Unfortunately you need to get fuel to it, so if you are to disperse these among the people, it has to be where the gas lines are. Not much chop if you are away from city centres and suburbs.
Ok, the fuel cell efficiency is somewhere in 80% (from memory) efficient as opposed to 20-30 for petrol motors and 30% for diesel, however the saving is a factor of 2 to 5. That is nowhere near Nuc or fusion, but any little bit helps
Me thinks out loud