Electric Potential Distribution Inside the Electrolyte During High Voltage Electrolysis

Applying an external potential difference between two electrodes leads to a voltage drop in an ion conducting electrolyte. This drop is particularly large in poorly conducting electrolytes and for high currents. Measuring the electrolyte potential is relevant in electrochemistry, e.g., bipolar electrochemistry, ohmic microscopy, or contact glow discharge electrolysis. Here we study the course of the electrolyte potential during high voltage electrolysis in an electrolysis cell using two reversible hydrogen electrodes as reference electrodes, placed at different positions in the electrolyte. The electrolysis is performed with a Pt working and stainless steel counter electrode in a KOH solution. A computational COMSOL® model is devised which supports the experimentally obtained potential distribution. The influence of the cell geometry on the electrolyte potentials is evaluated. Applying the knowledge of the potential distribution to the formation of a Au oxide surface structure produced during high voltage electrolysis, we find that the amount of oxide formed is related to the current rather than the applied voltage.