Optimization of the membrane electrode assembly for an alkaline water electrolyser based on the catalyst-coated membrane

Abstract

This study deals with the preparation and characterisation of catalyst-coated membranes for an alkaline water electrolysis process. For this purpose, a chloromethylated anion-selective block copolymer of styrene-ethylene-butylene-styrene with 1,4-diazabicyclo[2.2.2]octane functional groups was used both as an alkaline polymer electrolyte membrane and as an ionomer binder. Non-PGM catalysts (platinum group metals), specifically NiCo2O4 and NiFe2O4, were used on the anode and cathode side of the membrane, respectively. Air-brush deposition or computer-controlled ultrasonic dispersion of the catalytic ink were used to deposit the catalyst layers. The influence of the composition of the catalyst layer on its stability and the resulting electrolysis cell performance was investigated under typical membrane alkaline water electrolysis conditions (1–15 wt.% KOH, 45 °C). The optimal catalyst-to-binder ratio in the catalyst layer was identified as 93/7 using a catalyst loading of 2.5 mg cm-2 on each side of the membrane. The membrane electrode assembly prepared under optimal conditions showed high stability over 140 h at a current density of 250 mA cm-2. At this current load, the cell exhibited a voltage of 2.025 ± 0.010 V. The increase in cell voltage observed during the stability test did not exceed 1 μV h-1.