How could this have a positive EROI? You start with H2O, radio energy then breaks the bonds and gives you 2H2 + 02, and the H2 burns and gives you back H20 + heat. But since you start with the same substance you end with, the amount of energy released as heat must be less than amount of energy added by the radio waves, right? Unless the salt is somehow involved...

Am I missing anything? Hydrocarbons have a positive EROI because the end products (CO2 and H20) have lower energy than the original fuel, and so the excess can be harnessed to do work. But electrolysis/fuel cells have only been proposed for energy storage (and portability) because you can't get out more energy than you put in...