I saw on the television on one of the Science type channels a person who developed a car which ran on water by pumping the water to the engine which then comes into contact with a metal which would strip the hydrogen from the water and power the vehicle. The super thing about this process was that its exhaust was oxygen with water and it could get reclaimed by the fuel tank. The bad part of this was that it was powered by water and in much of the Earth water has a tendency to freeze during the winter months.