After careful evaluation of the obtained ex-situ data, STz25 was selected for single cell electrolysis testing in 15 wt% KOH at a temperature of 60 °C. An initial polarization curve and EIS data were recorded after an equilibration period of 24 h at a constant current density of 100 mA cm -2 . The cell was then operated at a constant current density of 100 mA cm -2 for a total duration of 588 h, where the cell suffered from dry-out due to electrolyte imbalance and was stopped. The cell voltage evolution over time is shown in Figure .