Comparative operando XPS and SEM spatiotemporal potential mapping of ionic liquid polarization in a coplanar electrochemical device
Date
2021-09-21Source Title
Analytical Chemistry
Print ISSN
0003-2700
Electronic ISSN
1520-6882
Publisher
American Chemical Society
Volume
93
Issue
39
Pages
13268 - 13273
Language
English
Type
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Abstract
The polarization response of a coplanar electrochemical capacitor covered with an ionic liquid as the electrolyte has been examined using a combination of two powerful analytic techniques, X-ray photoelectron spectroscopy (XPS) and scanning electron microcopy (SEM). Spatiotemporal distribution of the ionic liquid surface potential, upon DC or AC (square wave) biasing, has been monitored via chemical element binding energy shifts using XPS and secondary electron intensity variations using SEM. SEM’s high spatial resolution and speedy imaging together with application of a data mining algorithm made mapping of the surface potential distribution across the capacitor possible. Interestingly, despite the differences in the detection principles, both techniques yield similar polarization relaxation time constants. The results demonstrate the power of a synergistic combination of the two techniques with complementary capabilities and pave the way to a deeper understanding of liquid/solid interfaces and for performance evaluation and diagnostics of electrochemical devices.