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

Highlydurable trimethylammonium-modified poly(fluorene-alt-tetrafluorophenylene)polymer membrane and ionomer-based membrane electrode assembly foran anion-exchange water electrolyzer coupled with intermittent powersources. Highly durable anion-exchangemembranes and ionomersare essentialfor developing cost-effective green hydrogen generation. The anion-exchangemembrane and ionomer must withstand chemical attacks by OH- ions as well as nonlinear mechanical stress caused by irregularbubble formation when the electrolyzer is coupled with intermittentpower sources. Herein, we examined the durability of a trimethylammonium-modifiedpoly(fluorene-alt-tetrafluorophenylene) (PFT-C-10-TMA)-basedmembrane and ionomer under dynamic operation to evaluate its competencyto couple with intermittent power sources. The durability of membrane-electrodeassembly (MEA) prepared using these polymer membrane and ionomer wasevaluated by performing 1000 start-stop voltage cycles in 1M KOH solution at 80 degrees C while varying the applied cell voltage.The electrochemical performances of the MEA and electrodes were simultaneouslyevaluated using an electrolyzer with reference electrodes, and thechemical structure of the polymer was examined before and after thedurability test using NMR techniques. The MEA based on a commercialSustainion XB-7 ionomer and X37-50 RT anion-exchange membranes showedthe catalyst leaching during start-stop cycles, resulting inreduced cell performance. On the other hand, the MEAs with the PFT-C-10-TMA membrane and ionomer demonstrated promising high chemicaland mechanical durability under dynamic start-stop operation,encouraging the development of electrolyzers that can function withintermittent renewable power sources.