Dear Edward,

Thanks for your response.

Both of mentioned reactions are governed by movement of protons in electrolyte. If pH of electrolyte is more than 7, then OH- will be in majority and will rule the reaction. Typical water splitting reaction in basic medium is as follows:

at cathode (reduction)

2H2O + 2e --------- 2OH- + H2        E = -0.8V vs NHE

at anode (oxidation)

4OH-    ---------- 2H2O + O2 + 4e        E = 0.4V vs NHE

I am wondering if we can find out which ion (proton or OH-) movement in electrolyte will govern the electrolysis at pH = 7 where both ions are in equal concentration.

Article Advances in electrocatalysts for oxygen evolution reaction o...

In neutral conditions (pH 7), the reactions are

4H2O + 4e- --> 2H2 + 4OH- Eoc=0:413 V

2H2O --> O2 + 4H+ + 4e- Eoa=0:817 V