(64f) Traversing the Design Space of Redox-Mediated Electrochemical Systems Via a Continuum Model Framework

Electrochemical systems offer a pathway toward directly harnessing sustainable electricity to manage intermittency in renewable power production, decarbonize transportation, and unlock new routes for chemical and material production. However, many electrochemical processes of interest need to achieve lower system costs, higher efficiencies, and longer operating lifetimes to compete with their thermochemical counterparts. Redox-mediated systems are an emerging technology concept that show promise in addressing these challenges by simultaneously enabling new reactor designs and novel materials. These devices utilize a chemical looping approach, where a soluble mediator species is circulated between an electrochemical reactor – where it is activated – and a chemical reactor – where the activated mediator drives an “off-electrode” chemical redox reaction.^1,2 Mediated processes have been demonstrated to improve the energy density of redox flow batteries,² catalyze impractical or inefficient electrochemical transformations,³ increase selectivity and efficiency of separations and recycling,^4,5 and facilitate spatial and temporal flexibility in chemical manufacturing.⁶ However, the complex interplay of the reactors and active species obfuscate the underlying behavior of these systems, hindering efforts to understand, improve, and scale.

In this presentation, we will describe a continuum model framework capable of capturing and rationalizing the thermodynamics, reaction kinetics, and transport phenomena that govern the performance dynamics of redox-mediated systems for energy storage and conversion.⁷ Leveraging (electro)chemical engineering principles and drawing upon theories used to describe metallic corrosion, the framework provides new avenues to probe questions related to system design and operation. Specifically, we have been able to relate physical and operating parameters to system-level performance trends, including revealing performance regimes and a dimensionless “collapsed relationship” for solid utilization in redox-mediated flow batteries. The framework has also enabled rapid, yet detailed, exploration of lesser-studied design features, such as how pressure drop losses, conductive additives, thermodynamic non-idealities, active material degradation, and variable charging protocol. These analyses also serve as a hypothesis generation tool, supporting targeted collaborative experiments, as opposed to iterative trial-and-error approaches. Ultimately, we seek to translate these findings into general design principles that guide component design, system integration, and operating protocols enabling high-performing redox-mediated systems.

Acknowledgements

N.J.M gratefully acknowledges the NSF Graduate Research Fellowship Program under Grant Number 2141064. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.

References

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