Sort of. Put both ends of a normal AC supply into water and I think you'll get a mix of hydrogen and oxygen from both wires - you need to convert to DC first. Not sure about using ordinary sea water - I think there might be a risk of splitting the salt content as well as the water - and you probably don't want sodium or chlorine getting in the mix. Presuming the hydrogen is going to be burnt (or equivalent in say a hydrogen fuel cell) then it'll consume exactly the same amount of oxygen as was originally released - so overall no significant nett benefit either to fishes or the atmosphere. But yes, hydrogen is a plausible method of energy storage - some commercial applications already exist (e.g. https://www.gknhydrogen.com) - and once we get to the point of having substantial amounts of spare electricity from renewables to drive the electrolysis process, it could well be a very reasonable approach.

   - Andy.

The rise in the number of EVs will tend to balance out the drop in demand due to LEDs and possibly insulation. And will put more demands on the network distribution. So not sure where the surplus energy will come from.

It sounds like a win-win solution though, cleaner than burning natural gas

Burning hydrogen isn't necessarily pollution free either - if you burn it in ordinary air (rather than pure oxygen) - as boilers and IC vehicles would do - you end up heating up substantial amounts of nitrogen as well - producing oxides of nitrogen (NOx) as well as oxides of Hydrogen (H2O/water).

   - Andy.

This can be done, First the AC has to be stepped down to a lower DC, and  then under high pressure current is forced though thin layer of water between large are plates, with a semi permeable membrane between them to stop the gasses mixing. 

Siemens do it commercially, but it is rather more than wire ends in seawater, and not cheap link  Units of some gigawatts are in production now link

Mike

We used to split salt solution with a carbon rod anode inside a rough red flower pot and suck the chlorine gas off the anode inside the flower pot to chlorinate our swimming pool.  The hydrogen fizzed off the copper cathode at a copious rate. We used 24 volt DC and 10 amps.

However, this is a totally uneconomic way of producing hydrogen fuel.  Hebrides may have spare wind power but governments must look at total costs per kWh.  Same with solar; it would make little sense to heat water using electricity as a solar vacuum tube water heater is much more efficient way. Only 25% of he suns EM rays is absorbed by solar PV panels where as 80% by the direct method.

Hydrogen fuel for cars is not economical either as the gas is incompressible at room temperature unless it is combine with a expensive carbon catalyst.  Theoretically possible but uneconomical