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Nanoscale Probing of Interfaces Within Bipolar and Graphene-sandwich Membranes for Electrochemical Energy Conversion
Monday, March 08, 2021: 2:05 PM - 2:40 PM
Speaker(s)
Description
The techniques of confocal Raman microscopy and neutron reflectometry are being adapted as non-destructive probes of interfaces within ion conductive membranes that have application as anode/cathode separators in fuel cells and devices for solar-fuels production. In the study of ionomer-graphene composites, the ability to measure within membranes formed by sandwiching single layer graphene (SLG) between two Nafion layers has been demonstrated. These graphene-sandwich membranes show high selectivity for proton transport across electrochemical cells. Using a microscope equipped with an oil-immersion objective, the graphene layer is readily detected in confocal Raman microscopy depth-profiles of composite membranes. Spectra are sensitive to defects and stress within the buried graphene layer. Building on the ability to depth-profile through a membrane-supported SLG phase, SLG adsorbed to a glass microscope coverslip (SLG/SiO2) has been adapted as a platform for confocal aperture alignment and probe volume characterization. Using SLG/SiO2 to estimate the limiting axial spatial resolution, the junction separating the AEM/CEM (anion exchange membrane / cation exchange membrane) phases of bipolar polymer membrane was probed and shown to be consistent with roughness at the boundary on the order of a few micrometers. Continuing studies are adapting neutron reflectometry to investigate nanoscale structure at bipolar AEM/CEM interfaces. The ability to spatially map the ion-depleted, water-enriched interfacial region as a function of applied bias voltage is of special interest as it affects efficiency in electrochemical solar energy conversion devices. Spin-casting techniques are being used to construct model AEM/CEM interfaces on single crystal-Si neutron reflectometry substrates. The stability and performance of the bilayer polymer films is being assessed through observation of rectification behavior in linear scan voltammograms using redox active ions as probes.
Additional Info
Keywords: Please select up to 4 keywords ONLY:
Materials Characterization,Microscopy,Spectroelectrochemistry,Nanoscience
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