I am investigation how the concentration of a supporting electrolyte affects the rate of the electrolysis of otherwise pure water. Specifically it is the steady state electrolysis rate I’m interested in. That is, steady state rate of H2 & O2 production and therefore also the rate of the total DC current through the electrolysis cell.

I am looking for any previous experiments along these lines in order to see what experimental methods have been used and what the the results have been.

It would be most useful if the supporting electrolyte was not an acid or base, since those would change the concentration of H+/OH- ions and I'm trying to study the affect of the non-reactive supporting electrolyte on the current only from H+/OH- ions from auto-ionization. And in order to not have any side reactions, the supporting electrolyte should be inert in a voltage window of about 2V. For example Na2SO4.

I've seen many casual statements that a supporting electrolyte increases the rate of electrolysis. And also actual data where adding supporting electrolyte decreases the steady state current, for example copper refining with a Na2SO4 supporting electrolyte.

So, does anyone know of published results of experiments similar to what I'm planning to investigate?