Start-Stop Cyclic Durability Analysis of Membrane-Electrode Assemblies Using Polyflourene-Based Electrolytes for an Anion-Exchange Membrane Water Electrolyzer

Abstract

Highly durable anion-exchange membranes and ionomers are essential for developing cost-effective green hydrogen generation. The anion-exchange membrane and ionomer must withstand chemical attacks by OH- ions as well as nonlinear mechanical stress caused by irregular bubble formation when the electrolyzer is coupled with intermittent power sources. Herein, we examined the durability of a trimethylammonium-modified poly(fluorene-alt-tetrafluorophenylene) (PFT-C10-TMA)-based membrane and ionomer under dynamic operation to evaluate its competency to couple with intermittent power sources. The durability of membrane-electrode assembly (MEA) prepared using these polymer membrane and ionomer was evaluated by performing 1000 start-stop voltage cycles in 1 M KOH solution at 80 °C while varying the applied cell voltage. The electrochemical performances of the MEA and electrodes were simultaneously evaluated using an electrolyzer with reference electrodes, and the chemical structure of the polymer was examined before and after the durability test using NMR techniques. The MEA based on a commercial Sustainion XB-7 ionomer and X37-50 RT anion-exchange membranes showed the catalyst leaching during start-stop cycles, resulting in reduced cell performance. On the other hand, the MEAs with the PFT-C10-TMA membrane and ionomer demonstrated promising high chemical and mechanical durability under dynamic start-stop operation, encouraging the development of electrolyzers that can function with intermittent renewable power sources.