(Invited) Impact of Phenyl Adsorption of Various Ionomers on the Performance of Anion Exchange Membrane Water Electrolyzers

Abstract

In this presentation, design principals of ionomeric binders for anion exchange membrane water electrolysis (AEMWE) will be discussed. The crucial impact of phenyl adsorption on AEMWE performance is highlighted with poly(terphenylene), poly(fluorene), poly(aryl piperidinium), or polynorbonene ionomers. Adsorption energies to hydrogen oxidation catalyst surfaces, calculated by density functional theory, demonstrate the utility in the phenyl free ionomer structure wherein lower adsorption energies yield improved AEMWE performance.1,2 Polarization curves with higher adsorption energy ionomers show a nonlinear transition to mass transport limited behavior at cell potentials above 1.68 V. Alternatively, mass transport limitations are absent when using the phenyl free ionomer, polynorbonene.3 Furthermore, polarization curves in 1 M NaOH of all studied systems begin to overlap suggesting that the phenyl oxidation on the oxygen evolution catalyst may be a primary influence on the transition to mass transport limits in AEMWE. Recent progress in both ionomer and AEM development at LANL for improved performance and durability of AEMWE, specifically with regard to limiting phenyl oxidation, will be discussed.1 Matanovic, I. et al. Adsorption of Polyaromatic Backbone Impacts the Performance of Anion Exchange Membrane Fuel Cells. Chemistry of Materials 31, 4195-4204, doi:10.1021/acs.chemmater.9b01092 (2019).2 Motz, A. R. et al. Performance and durability of anion exchange membrane water electrolyzers using down-selected polymer electrolytes. Journal of Materials Chemistry A 9, 22670-22683, doi:10.1039/D1TA06869E (2021).3 Huang, G. et al. Ionomer Optimization for Water Uptake and Swelling in Anion Exchange Membrane Electrolyzer: Oxygen Evolution Electrode. Journal of The Electrochemical Society 167, 164514, doi:10.1149/1945-7111/abcde3 (2020).