During HV electrolysis, a Au oxide film forms on the Au POSCs. This Au oxide film acts as a precursor for the formation of a NPG film via electrochemical reduction discussed below. We study the Au oxide growth at 300 V (before the breakdown of NE -average current density between 2.70 and 3.76 A•cm -2 ) and at 540 V (in the aCGDE region -average current density between 0.24 and 6.39 A•cm -2 ) for different electrolysis times. Note, for the Au oxide formation, the current density is a more meaningful parameter since the applied voltage strongly depends on the electrodes' geometry, electrodes position, and the cell geometry. Nevertheless, in this article we use the voltages to discern between the NE and aCGDE region. During the Au oxide growth at 300 V, vivid bubble formation is observed, and hence the electrode is only partially in contact with the electrolyte. The current is slightly increasing with increasing electrolysis time (see the red curve in Fig. ). This is related to an increase in electrolyte temperature, which increases the electrolytes' conductivity. At 540 V the electrode is surrounded by a gas sheath in which a plasma can be ignited. During HV electrolysis at 540 V the current is high and almost constant for short times until it breaks down to a lower constant value (see blue curve in Fig. ). This marks the point when a plasma is formed within the gas sheath. Note that for short electrolysis times, the plasma is not al- ways perfectly discernable by the naked eye.