12/02/2025
By Danielle Fretwell

The Francis College of Engineering, Department of Energy Engineering - Renewable, invites you to attend a Doctoral Dissertation Proposal defense by Daniel Rourke on: "Enabling Deep Decarbonization through Redox-Mediated Electrochemical Energy Storage and Conversion Systems."

Candidate Name: Daniel Rourke
Degree: Doctoral
Defense Date: Thursday, Dec. 4, 2025
Time: 2 - 4 p.m.
Location: Emerging Technologies and Innovation Center (ETIC) Conference Room 245

Committee:

  • Advisor: Ertan Agar, Associate Professor, Department of Mechanical and Industrial Engineering, UMass Lowell
  • Fuqiang Liu, Associate Professor, Department of Mechanical and Industrial Engineering, UMass Lowell
  • Juan Pablo Trelles, Professor, Department of Mechanical and Industrial Engineering, UMass Lowell
  • Patrick Cappillino, Associate Professor, Department of Chemistry and Biochemistry, UMass Dartmouth

Abstract:
Redox-mediation offers a solution to improve the performance of a number of different electrochemical systems which will be necessary for deep decarbonization. The two systems which will be explored in this doctoral research dissertation are redox-mediated flow batteries (RMFBs) and redox-mediated metal-air fuel cells (RMMAFCs). RMFBs offer the possibility of increasing the energy density of redox flow batteries (RFBs) which are otherwise excellent candidates for long-duration grid-scale energy storage. Previous research has shown that including an appropriate solid active material (the “booster”) in the electrolyte reservoir can decouple the energy density of the system from the solubility of the dissolved active material (the “mediator”), while maintaining the scalability inherent to the architecture of RFBs. The mechanism enabling this system is the indirect reaction between the mediator and the booster which is driven by Nernst potential changes in the mediator as it is oxidized and reduced at the electrode. This research aims to gain a deeper understanding of the fundamental processes occurring in the solid-mediator reaction and how they are affected by various parameters related to the structure of the booster and the operation of the flow cell. The first two tasks were accomplished using a compositionally-symmetric volumetrically-asymmetric flow cell in order to isolate the impact of the desired variables. First, the booster itself was examined through a study regarding the internal microstructure of the pellet, the selection of the conductive additive, and the mass loading of the booster relative to electrolyte volume. Next, we investigated the interplay between the two reactions occurring on each side of the RMFB: the redox reaction of the mediator at the electrode driven by the applied current, and the indirect solid-mediator reaction occurring in the external reservoir. With this improved understanding of the reactions driving the system, we plan to apply these findings to develop a model which can be used to determine a data-driven design for a full cell RMFB. Finally, the redox-mediation concept will be explored using a similar technology, RMMAFCs. These systems operate similar to RMFBs, but the solid material on the anodic side is used as fuel, being consumed during discharge then manually “recharged” (i.e., replaced), and the solid material on the cathodic side is substituted with oxygen bubbled into the electrolyte reservoir. The physical infrastructure, the flow cell, will remain the same, but the new cell chemistry will allow us to investigate the redox-mediation reactions between the metal and the anodic mediator and between the oxygen and the cathodic mediator. Altogether, this work will advance the fundamental understanding and practical design of redox-mediated electrochemical systems, helping enable their deployment as critical technologies for deep decarbonization.