The electrochemical reduction of carbon dioxide (CO₂) to hydrocarbons provides storage of renewable electricity into energy dense molecules while also neutralizing CO₂ emissions. Last decade has shown an unprecedented development towards its industrial application by reaching CO₂ reduction reaction efficiencies (>95 % for CO and 87 % for C₂H₄) thanks to the fine engineering of novel catalyst and membrane types. In chorus, the gas diffusion electrodes (GDE) and flow-type reactors have played a key role to overcome mass transfer limitation and steer the current densities up to industrially relevant values, e.g. ~1 A/cm².

Currently, most of the gas diffusion layers forming the backbone of the GDEs have been adopted from the proven processes such as fuel-cell and chlor-alkali systems. However they are not ideal for the large scale implementation and long term stability of CO₂ electrolysis due to the diverse nature of the reaction. In this work, we will show the main advantages and limitations of the three most common gas diffusion layers employed in the field of CO₂ electrolysis which are; nonwoven-, paper and cloth-GDEs with an identical catalyst layer obtained by sputtering of 150 nm thin copper film. By using an operando IR-thermography technique (filed patent), we mapped the temperature distribution profile of the GDEs until their failure by flooding. Thermal imaging results showed a smaller gradient and uniform temperature profile along the Cloth-GDL, which was attributed to the continuous fiber structure forming a straight electron path. On the other hand, the agglomerated PTFE flakes, large pockets and cracks of Paper-GDL were found as failure points to flooding by electrowetting and displayed a resistance to the electron path, evident from the higher potential and temperature value at elevated current densities. Conversely, very compact form of carbon nanoparticle and fiber structure of Nonwoven-GDL underwent premature flooding by the salt deposits and blocked CO2 diffusion to the catalyst layer. Coupled with an advanced ex-situ electron microscopy for post-mortem analysis , we have localized and matched the failure mechanisms of each GDE with a focus on the changes observed in the operando analysis during an hour long electrolysis at 250 mA/cm². Our results will provide the strategies for inspection and improvement for better performing GDEs which would be beneficial not only to CO₂ electrolysis but also to the upscaling of electrical energy conversion and storage devices.