The cell, thus assembled, was then placed on a stand in a large beaker that was onethird filled with aqueous 6 M KOH (which we called a 'reservoir beaker'). This allowed the bottom end of the 8 m PES separator membrane to dip into the KOH solution while the rest of the cell remained above the liquid level. Figure schematically illustrates this arrangement. water electrolysis within the cell; that is, it formed the primary electrochemical system during operation of the cell. uptake by the KOH electrolyte, the beaker headspace was maintained and filled with an inert Ar atmosphere.