Distinct CO2-run-out regime from steric effect of electric double layer in electrochemical CO2 reduction

LF Chen and H Feng and Y Zhang and D Liu and Q Li, APPLIED PHYSICS REVIEWS, 11, 031406 (2024).

DOI: 10.1063/5.0214255

The field of electrochemical CO2 reduction reaction (eCO(2)RR) is pursuing high operating current densities, eventually controlled by CO2 transport. Here, we develop a new multiscale modeling approach that is able to more generally describe the effects of the electric double layer (EDL) on CO2 transport over a wide potential window extending to utmost potentials. By leveraging it, we identify a distinct CO2-run-out regime where the supply of CO2 runs out due to the EDL steric effect from a dense layer of solvated cations with the maximum layer thickness equal to the solvated cation size. Consequently, CO2RR current density drops at a relatively negative transition potential generating a bell-shaped polarization curve, which is in contrast to the CO2-transport-limited regime where the current density reaches a plateau. Furthermore, we develop a graphical method, verified by experimental data, to generally predict the transition to the CO2-run-out regime. This work sheds new light on the EDL effects for catalyst design and electrolyzer engineering.

Return to Publications page