(535a) Improving Energy Efficiency of Electrochemical CO2 Capture Using Pulsed Current

Electrochemical CO2 separation is a compelling alternative to thermal methods, oVering
isothermal operation and the potential for reduced energy consumption. Among various
strategies, systems based on redox-active molecules are particularly promising due to their
tunable performance, enabled by modifying the physicochemical properties of the
molecular carriers. However, many redox-active molecules suVer from limited hydrophilicity,
resulting in poor solubility and sluggish transport in polar electrolytes. This transport
limitation often impedes capture kinetics and hinders initial electrochemical evaluation.
Synthetic modification to improve solubility can be time-consuming and costly, and the
tailored nature of such modifications makes them unsuitable as a general solution.
Therefore, a universal operational strategy to improve molecular transport is urgently needed
to accelerate both early-stage molecule screening and system-scale development.
This work introduces pulsed chronopotentiometry as an eVective technique to enhance
mass transport and redox cycling eViciency in electrochemical CO2 capture systems. We
focus on Neutral Red (NR), a redox-active carrier with favorable air stability and high
theoretical eViciency. Despite these advantages, practical implementation of NR has been
limited by high cell voltages (>2 V), primarily due to mass transport constraints at 50 mM
concentration, even with nicotinamide as a solubilizer. By applying alternating reduction and
rest currents, pulsed operation significantly enhances NR diVusion, reduces overpotentials,
and improves overall eViciency. Compared to constant current operation, pulsed
chronopotentiometry reduced the cell voltage by 57% from 2.07 V to 0.90 V at a current
density of 8 mA/cm2 under 15% CO2 with a 50% working capacity.
The 1D transport model will also be discussed to provide a quantitative framework for
understanding the interplay between diVusion limitations and pulsed operation. By
simulating NR concentration profiles under both steady and pulsed current conditions, the
model captures how rest periods enable replenishment of depleted reactants near the
electrode surface. The analysis reveals that pulse parameters—such as duration and current
density—can be tuned to optimize the redox reaction zone and minimize concentration
polarization. This mechanistic insight supports the experimental observation of voltage
reduction and provides a predictive tool for extending this strategy to other redox-active
systems with limited solubility.
The system employed a symmetric cyclic configuration with graphite felt electrodes
mounted in a custom nylon housing, separated by an anion exchange membrane. Surface
treatments were applied to improve electrode wettability, facilitating uniform current
distribution and more eVective electron transfer. Cyclic voltammetry confirmed enhanced
current response and lower internal resistance. Additional voltage reductions were achieved
through thermal modification of the electrode surfaces.
This study highlights pulsed chronopotentiometry as a broadly applicable method to lower
energy demands and improve operational stability in electrochemical carbon capture. The
approach oVers a generalizable framework for utilizing redox-active molecules with poor
solubility, paving the way for scalable, energy-eVicient CO2 separation technologies.