Comprehensive Structural Characterization of Charged Polymers Involved in Moisture-Driven Direct Air Capture

TL;DR

This study provides detailed structural insights into alkaline anion-exchange membrane polymers used in moisture-driven direct air capture, highlighting moisture effects and guiding the development of more efficient CO2 capture materials.

Contribution

It offers a comprehensive structural characterization of AEM polymers, revealing how moisture influences their properties for improved DAC performance.

Findings

Molecular ordering and structural organization in AEMs

Humidity causes significant structural changes and swelling

Structural features correlate with CO2 capture behavior

Abstract

The rise in atmospheric carbon dioxide (CO2) levels has led to urgent calls for effective carbon capture methods, with direct air capture (DAC) emerging as a promising solution. This study focuses on the structural characterization of commercially available alkaline anion-exchange membrane (AEM) polymers, Fumasep FAA-3 and IRA 900, for use in low-energy, moisture-driven DAC applications. A combination of X-ray diffraction, small and wide-angle X-ray scattering (SAXS/WAXS), atomic force microscopy (AFM), focused ion beam-scanning electron microscopy (FIB-SEM), and transmission electron microscopy (TEM) were employed to explore the structural features of these materials. X-ray scattering analysis revealed molecular ordering and large-scale structural organization in both materials, while humidity-induced changes highlighted the impact of moisture on structural properties. AFM surface analysis further indicated the presence of clustering, porosity, and swelling, which were corroborated by FIB-SEM and TEM imaging. These structural insights offer a deeper understanding of the behavior of AEM-DAC materials during CO2 capture and release, emphasizing the role of moisture in these processes. This work lays the foundation for the development of more energy-efficient DAC polymers, paving the way for improved CO2 capture technologies.