Influence of the electrolyte conductivity on the critical current density and the breakdown voltage

The work investigates influence of the electrolyte conductivity on the onset of partial contact glow discharge electrolysis (CGDE) in a water electrolysis. Critical current density (CCD) and breakdown voltage were measured together with in situ observation of hydrogen bubble behavior, whose influence has not been focused on. For a fixed current during normal electrolysis, hydrogen coalescence adjacent to cathode surface was invigorated at a lower conductivity. Photographic analyses elucidated the hydrogen coalescence characteristics by quantifying size and population of detached hydrogen bubbles. The CCD increased about 104% within given range of conductivity (11.50–127.48 mS·cm^–1) due to impaired bubble coalescence, which delays hydrogen film formation on the cathode. Meanwhile, decreasing trend of breakdown voltage was measured with increased conductivity showing maximum drop of 74%. It is concluded that onset of partial CGDE is directly affected by hydrodynamic bubble behaviors, whereas the electrolyte conductivity affects the bubble formation characteristics adjacent to cathode electrode.