Early Warning for the Electrolyzer: Monitoring CO₂ Reduction via In‐Line Electrochemical Impedance Spectroscopy

Abstract

The electrochemical CO2 reduction reaction (CO2RR) to fuels and feedstocks presents an opportunity to decarbonize the chemical industry, and current electrolyzer performance levels approach commercial viability. However, stability remains below that required, in part because of the challenge of probing these electrolyzer systems in real time and the challenge of determining the root cause of failure. Failure can result from initial conditions (e.g. the over‐ or under‐compression of the electrolyzer), gradual degradation of components (e.g. cathode or anode catalysts), the accumulation of products or by‐products, or immediate changes such as the development of a hole in the membrane or a short circuit. Identifying and mitigating these assembly‐related, gradual, and immediate failure modes would increase both electrolyzer lifetime and economic viability of CO2RR. We demonstrate the continuous monitoring of CO2RR electrolyzers during operation via non‐disruptive, real‐time electrochemical impedance spectroscopy (EIS) analysis. Using this technique, we characterise common failure modes ‐ compression, salt formation, and membrane short circuits ‐ and identify electrochemical parameter signatures for each. We further propose a framework to identify, predict, and prevent failures in CO2RR electrolyzers. This framework allowed for the prediction of anode degradation ~11 hours before other indicators such as selectivity or voltage.

A brief review of in situ spectroscopic methods and electrochemical sensors as essential evaluation tools for the electrochemical reduction of CO2 (ElRC)

“…49 It is considered a non-destructive analytical method to assess the impedance of an ElRC system in response to its activation in a voltage signal by the potentiostatic method or the current signal by the galvanostatic method can be employed to induce the activation. 96 Nyquist and Bode plots are employed in EIS investigations using ElRC electrolyzers to examine how the cell changes in response to various experimental settings; however, the full long-term stability study in ElRC is yet to be widely implemented using EIS (Fig. 8).…”

Advances and challenges in membrane electrode assembly electrolyzers for CO2 reduction

“…This framework effectively predicted anode degradation nearly 11 hours prior to the observation of cell voltage or FE, presenting a potentially valuable tool for monitoring and estimating the lifespan of large-scale MEA cells or stacks. 111…”