Peptide-Modified Electrode Surfaces for Promoting Anion Exchange Ionomer Microphase Separation and Ionic Conductivity

Ionomer binders are critical materials for delivering ions to and from electrocatalyst surfaces in fuel cell and water electrolyzer technologies. Most studies examine these materials as bulk polymer electrolyte membranes, and comparatively little attention has been given to their behavior on electrode surfaces as thin films. This report demonstrates that sequence-defined peptides anchored to electrode surfaces, or the solvent vapor annealing processing, alters the microstructure configuration of anion exchange ionomers (AEIs). It is observed that moderately sized microphase-separated ionic domains of the AEI, obtained either by peptide-modified electrodes or solvent vapor annealing, give rise to a two- to three-fold increase in thin-film in-plane ionic conductivity. Interestingly, the use of peptide-modified electrodes, in conjunction with solvent vapor annealing, yields excessively large ionic grains that compromise ionic conductivity. Overall, the judicious use of sequence-defined peptides adsorbed to electrode surfaces, or solvent vapor annealing, encourage the appropriate microstructures of thin-film AEIs resulting in ameliorated ionic conductivity.