When I was twelve, I went to spend the holidays at my cousin’s home in Rio; in that time one of his friends said that “during the World War II someone had invented an internal combustion engine powered by water … the unfortunate inventor having been killed by the oil companies … ” not knowing whether it was or was not a “talk to teens”, I immediately concluded that the hydrogen contained in water was the fuel element. Even knowing that it is necessary to consume more energy to remove the H2 of H2O, store somewhere, then release this element safely, etc…. when compared to the mechanical energy delivered to a car, for example, I still found the idea interesting.
Many decades have passed and the matter of extracting the H2 of H2O putting it to burn in an internal combustion engine, took shape in several technological proposals. Among them, the electrolysis of water in off-peak hours, when electricity is cheaper, with accumulation of hydrogen safely, in “solid state tanks” containing the powdered palladium (Pd) that is able to store hydrogen safely in interatomic interstices avoiding the risk of explosion, after all the H would have greater ability to enter the crystal lattice of Pd because it is a mere proton, to leave its electron elsewhere in the tank with only purpose to neutralize the total charge; a simple heating, even using the heat of the exhaust (water vapor) pipe would release H2 molecules that, by combining with oxygen in the air + spark, would produce the explosion to continue moving the motor.
The latest entry in this direction comes from a process developed by Sossina Haile, a researcher at Caltech, which uses a ceramic-based compound of cerium (CeO2) doped zirconium oxide, which is able to separate the H2 from H2O using solar energy! Although it has been working at laboratory level, it is quite simple and exciting: an optical system concentrates solar energy on a porous plate CeO2, leading to a temperature of ~ 1500C. At this temperature the CeO2 “expels” atoms “O” that migrate through the pores of the plate; cooling the plate with H2O vapor makes the ceramic to remove the atom “O” from water, to thereby recover the CeO2 original composition. The H2 that is left over can be used to move a combustion engine.