Could cars run on water?

Tweet

I know there are advancements which now enable cars to be run with the assistance of steam with hydrogen from gas bottles, but is it too obvious a question to wonder-can hydrogen be separated from regular water so to power an internal combustion engine?Separate the hydrogen from the oxygen, then combine a bit of the oxygen with the hydrogen and "bang"you end the whole oil problem. The "waste" gas would be oxygen? The question is probably simplistic, or else this method of fueling would surely be already used.