Article
Direct visualization of electrochemical reactions and heterogeneous transport within porous electrodes in operando by fluorescence microscopy

https://doi.org/10.1016/j.xcrp.2021.100388Get rights and content
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Highlights

  • Operando electrolyte reaction-flow mapping within porous electrodes

  • Quantified local state of charge with micron- and sub-second resolution

  • 2D particle tracing measuring spatial flow profiles within tortuous structures

  • Coupled electrochemical concentration polarization with spatial state of charge maps

Summary

Optical fluorescence microscopy is shown to enable both high spatial and temporal resolution of redox-dependent fluorescence in flowing electrolytes. We report the use of fluorescence microscopy coupled with electrochemistry to directly observe the reaction and transport of redox-active quinones within porous carbon electrodes in operando. We observe surprising electrolyte channeling features within several porous electrodes, leading to spatially distinguishable advection-dominated and diffusion-dominated regions. These results challenge the common assumption that transport in porous electrodes can be approximated by a homogeneous Darcy-like permeability, particularly at the length scales relevant to many electrochemical systems such as redox flow batteries. This work presents a new platform to provide highly resolved spatial and temporal insight into electrolyte reactions and transport behavior within porous electrodes.

Keywords

fluorescence microscopy
electrochemistry
in operando imaging
heterogeneous flow
direct visualization

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2

Present address: Lawrence Livermore National Lab, Livermore, CA 94550, USA

3

Present address: The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

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