Or you could skip the hydrolysis part and go straight to water injection. Which has been proven in the real world to give economy benefits, allowing you to lean out, produce more power, reduce particulates, etcetera. And on gasoline engines, it allows you to run lower octane, as well... producing extra savings in the form of cheaper gas.
Without the electrolytic middleman. And no hocus pocus.
The OEMs have experimented with water injection, and some (serious) research has been done into using it for fuel economy. But water injection has been dropped, partly because you can't trust people to remember to refill the extra tanks (or trust them to use pure distilled water), because the need for a hefty tank for longer range adds weight and complexity and because direct injection achieves much of the same benefits already.
I still don't get why people keep trying to go the extra energy-loss step when the raw material being used, dihydrogen monoxide (
), is already a very efficient octane booster...