Reading Wikipedia for electrolysis, it provides the information that a potential of 1.23V is required to electrolyze water. How was that calculated? My intuition tells me that it is the sum of the potential of the hydrogen and oxygen ions, but I am afraid that it is wrong. There's the other problem of electrolyzing a solution other than a molten electrolyte, when the potential is definitely different. I also know that a overpotential must be provided to prevent the solution from reaching an equilibrium, but how much exactly is that overpotential?