Slurry Electrodes Modulate Power Draw Beyond Mass Transfer Limits Through Synergistic Control of Faradaic and Capacitive Currents

Abstract

Despite their promise as scalable platforms for heterogeneous electrochemistry, slurry electrodes struggle with high power operation either due to their low conductivity, or the inherent kinetic and transport limitations of the supported electrochemical reaction. In this paper, we reveal order of magnitude improvements to flow cell power densities by leveraging capacitive effects in short residence time slurry electrodes. This outcome is sensitive to the residence time of electrode material and applied current density in the half cell due to the concerted interplay of capacitive double layer and faradaic currents. Using a 1D porous electrode model tied to Fe 2+ /Fe 3+ half-cell experiments, we deconvolve this interplay and map operating regimes of power draw versus residence time and applied current density. We experimentally find that short residence times (∼1–10 s) drive primarily capacitive discharge, enabling power densities up to an order of magnitude higher than pseudo-steady state (>1 min residence time), primarily faradaic, operation. Our findings suggest that distinguishing capacitive vs faradaic current contribution reframes performance improvements often ascribed to improved mass transfer instead as advection of double layer charge and shifts in charge transport timescales. These findings offer practitioners design criteria that can be applied directly in scaling high power density electrochemical cells and reactors employing slurry electrodes.

Identifiers

DOI

10.1149/1945-7111/ae5fde

Journal

Journal of The Electrochemical Society

Year

2026