(550b) Non-Solvent Induced Phase Separation for Designer Porous Carbon Electrodes

Porous carbon electrodes play an important role in many leading electrochemical systems by supporting a number of critical functions which include providing active catalyst sites to facilitate redox reactions, distributing liquid reactants and products, and conducting electrons and heat.^[1] This is particularly relevant for redox flow batteries (RFBs), wherein solubilized active species are forced through porous electrodes within a flow cell, oxidizing and reducing on the fiber surfaces during charge and discharge. Due to its decoupling of energy and power, scalability, and long service life, RFBs hold promise for long duration energy storage for the electric grid.^[2] However, current RFBs are prohibitively expensive, necessitating further cost reduction for widespread deployment. Lowering reactor cost by improving power output is a promising approach to bridging the economic gap. While commercial electrodes are functional, they possess suboptimal surface chemistry and microstructure for existent and emerging RFB chemistries.^[3] Deterministic fabrication of engineered porous materials would enable exploration of a wider electrode design space, further elucidating electrode-level performance descriptors.

In this presentation, we will describe a bottom-up synthesis method leveraging non-solvent induced phase separation (NIPS) for advancing porous electrodes with property sets suitable for RFBs.^[4] NIPS enables fabrication of high surface area, interconnected pore networks unattainable in conventional fibrous electrodes; further, the pore size, gradient, and structure are tunable via facile synthesis design parameters. We demonstrate the feasibility of NIPS to generate a family of electrodes that share similar but uniquely distinct microstructural characteristics. Combining spectroscopic, microscopic, and physicochemical characterization to flow cell performance in two common aqueous RFB redox couples (i.e., iron chloride and all-vanadium), we will show the viability of this synthetic platform for illuminating structure-function relations in porous materials for RFBs. Further, we will highlight opportunities for the development of high-performance and chemistry-specific NIPS-derived electrode material sets. While the efforts of these studies are primarily focused on RFBs, we envision that the methods and findings would be beneficial for convection-driven electrochemical devices that require highly engineered electrodes.

References:

[1] Kim et al., J. Mater. Chem. A., 3, (2015).

[2] Dunn et al., Science, 334, (2011)

[3] Forner-Cuenca et al., Current Opinion in Electrochemistry, 18, (2019).

[4] Wan & Jacquemond et al., Adv. Mat., (2021).