Why couldn’t this be run during off peak hours when most electricity generated goes unused and is simply lost? Storing H and O2 for use in maybe a peak demand generator should be easy.
Off-peak electrical energy could be stored in some form. But the H and O released by this process needs to be pressurized for storage/transportation, and that takes energy. Unless this device can work in a high-pressure environment, but you can’t get the pressure for free. Probably would operate at a lower efficiency. Also, for safety reasons you would probably want to separate the H and O, but if doesn’t seem that would be easy with this device.
Any method of off-peak storage would have some energy losses, but it is something to work on.