Measurements of breakdown voltage and critical current density in a water electrolysis varying area and shape of working electrode

This work investigated the influence of the working electrode on the partial contact glow discharge electrolysis (CGDE) using disk and rectangle shaped cathodes in a water electrolysis. The breakdown voltage and the critical current density (CCD), which are due to the initial formation of partial hydrogen film were measured together with in situ observation of hydrogen bubble behaviors. As the cathode area increased, the breakdown voltage increased regardless of shape of the cathode as the active area increased. By contrast, the CCD decreased at different rates depending on the cathode shape. The formation of the hydrogen bubble layer adjacent to the cathode surface elucidates this result. In case of the disk, the thickness of the bubble layer remarkably increased with increased cathode area, resulting in the CCD decrease since the partial hydrogen film was readily formed, while a trivial change of the bubble layer was observed in case of the rectangle. Thus, a milder decreasing trend of CCD was measured in case of rectangle cases than that of disk cases. The wetted perimeter per area (P/A) was introduced as a more generalized parameter affecting the CCD.