A veritable can of worms here, Jack.
Back in the late 70s and early 80s, there was a definite fad for quasi-electrical systems to prevent "osmosis". (AKA rising damp.) I used to do a lot of hacking off and re-plastering after installation by "specialists."
Rentokil had a single wire system that supposedly prevented damp rising by somehow persuading the damp to stop at the wire barrier.
(No, it didn't last.)
McCoy-Hill had a "positive" system that needed two wires and a transformer connected to the mains. The idea being that this electrical barrier also prevented rising.
(No, that didn't last either.)
I've worked with chemical injection. Holes drilled... a solution of silicone in white spirit injected... then re-plastered.
There is some evidence that this, being an actual barrier, could be effective. Variations of this are still being used.
Then there were clay inserts stuffed into walls to wick out any moisture. Can work fine, but there's often remaining local spots where it is not effective.
In my humble opinion, there are two main solutions remaining.
1."Tanking". Either old-fashioned bitumen tank (several coats of painted-on bitumen) or a much more modern solution... such as "Vandex". Vandex is a cementitious painted or sprayed on coating. This can be very effective, especially underground.
2. Back-to-basics with lime plaster. I've done several old cob buildings, some of which had had various tanking attempts made unsuccessfully. (Not by me I should add.)
Hack off, and re-plaster with lime plaster, and finish with fine lime skim.
Believe me, it works well. You know the theory. The lime lets the walls breathe out any moisture, even if the external face is hard cement render.
I think I should stop there, at the risk that I'm sending you to sleep. ;o)