ADVANCED ALKALINE ELECTROLYSIS WITH POROUS POLYMERIC DIAPHRAGMS

In this work, microporous polymeric membranes for use as diaphragms in advanced alkaline electrolysis were produced from poly(ethersulfone)s UDEL(R), RADEL R(R), RADEL A(R) and VICTREX(R), and were tested as di aphragms in an electrolyzer cell. The membranes were produced by phase inversion precipitation. Different membrane morphologies have been ob tained by systematically varying the polymer and polymer additive cont ent, the type of solvent and nonsolvent, molecular mass of the additiv e, and the hydrophilicity of the polymer. The membranes were character ized by measurement of their electric resistance in an electrolysis ce ll, by scanning electron microscopy and by determination of their ''bu bble-point''. Furthermore the membranes have been tested in a ''zero g ap'' electrolyzer cell under intermittent conditions. The variation of gas purity with load factor has been determined by gas chromatography . With decreasing current density the H-2 content in O-2 increases sig nificantly but still stays below the safety threshold. In addition, th e internal Ohmic resistance of the diaphragm is promisingly low. The r esults show that the developed membranes meet all requirements as diap hragms, like low resistance connected with sufficiently high pressure stability to avoid gas intermixture in the electrolysis cell compartme nts.