(53d) Peptide-Controlled Assembly of Anion Exchange Ionomer Thin Films on Electrode Surfaces for Promoting Microphase Separation and Ionic Conductivity

In electrochemical devices such as water electrolyzers and fuel cells, the network and morphology of the conductive ionomers binders within electrodes are critical for ion delivery and mass transport, significantly influence the device performance. Most studies have investigated these materials as bulk polymer electrolyte membranes, while comparatively little attention has been given to their behavior on electrode surfaces as thin films. Anion exchange membrane fuel cells and water electrolyzers (AEMFCs and AEMWEs) would allow the use of non-precious group metals in alkaline environments, and enable low-cost systems. Yet, even less is known about thin films of anion exchange ionomer (AEI). Protein engineering is emerging as a powerful nanomanufacturing tool to control the organization of components on electrodes in bio-electrochemical technologies. Taking advantages of the ability to precisely define protein sequence to achieve multiple functions, can be organized into complex designed structures. In this work, we proposed the application of protein engineering for ionomer control, demonstrating that sequence defined elastin-like peptides assembled on electrode surface, an/or solvent vapor annealing processing, alters the microstructure configuration of assembled thin films of anion exchange ionomer. It is observed that peptides form a uniform monolayer on metal surface, and moderately sized microphase separated ionic domains of the AEI are obtained either by modifying the electrode with peptides, or solvent vapor annealing, increasing in-plane ionic conductivity of the thin film. Interestingly, the use of peptide modified electrodes in conjunction with solvent vapor annealing yields excessively large ionic grains that compromise ionic conductivity. Overall, we show that the sequence defined peptides could serve as a tool for controlling electrode architecture, and judicious use of the peptides adsorbed to electrode surfaces, or solvent vapor annealing, have the potential to control the microstructures of thin AEI films and lead to structure-function understanding.