Visualizing degradation mechanisms in a gas-fed CO2 reduction cell via operando X-ray tomography

Abstract

We utilize operando X-ray computed tomography, coupled with real-time electrochemical analysis, to reveal the underlying failure mechanisms of membrane electrode assemblies (MEAs) for electrochemical CO₂ reduction (eCO₂R). Through operando imaging, we can obtain unprecedented insights into the dynamic behavior of the MEA under different operating conditions, revealing critical changes in interface interactions, phase distribution, and structural integrity over time. Our findings identify phenomena giving rise to the transition from CO₂R to the hydrogen evolution reaction (HER), as evidenced by shifts in cathode potential and CO₂R selectivity. The formation of inhomogeneous precipitates at the gas diffusion electrode disrupts the CO₂ supply and reduces the active sites for eCO₂R, resulting in a shift toward H₂ production during low current density operation. Additionally, under high current density conditions, rapid water crossover up to the microporous layer/gas diffusion layer promotes the transition from CO₂R to HER, further shifting cell potential toward anodic direction. Oscillating voltage conditions reveal the dissolution and regrowth of precipitates, providing direct visualization of the competing selectivity of CO₂R and HER. This work offers new insight into the degradation mechanisms of MEAs, with implications for the design of more durable CO₂R systems.