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.
Bibliographical noteFunding Information:
This research was supported initially by US Department of Energy (DOE) award DE-AC05-76RL01830 through PNNL subcontract 428977 and subsequently by the US DOE Office of Basic Energy Sciences award DE-SC0020170 . Manuscript preparation was performed by A.A.W. under the auspices of the US DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 . The authors thank Anton Graf for helpful discussions.
© 2021 The Author(s)
- direct visualization
- fluorescence microscopy
- heterogeneous flow
- in operando imaging