Electrochemical CO₂ conversion offers a direct strategy to transform captured CO₂ into renewable fuels and feedstock chemicals using electricity from renewable sources. This approach has the potential to decarbonize the chemical industry and aviation, where direct electrification is challenging, while also addressing the issue of seasonal storage of renewable energy. Despite substantial recent progress, electrochemical CO₂ conversion remains inefficient at scale due to the high energy demand of the conversion process, poor product selectivity yielding mixtures that are difficult to separate, and limited operational stability of the electrolysers. Key issues are dynamic phenomena such as (bi)carbonate precipitation, which clogs electrode pores and causes instability, and sharp local variation of CO₂ availability and pH that alter reaction pathways and affect selectivity. Understanding and controlling these phenomena is essential to make the technology ready for large scale deployment.
Our research focuses on solving these key issues by understanding and controlling transport phenomena and degradation inside gas diffusion electrodes, which are key components of CO₂ electrolysers [1-3]. To this end, we built a unique multi-channel electrochemical reactor platform with an open-source data pipeline to systematically evaluate gas diffusion electrode architectures under industrially relevant conditions [4]. We use it to investigate polymer-based gas diffusion electrodes fabricated in-house (a), which boast tunable microstructure and hydrophobicity, and can achieve high carbon product selectivity at industrially relevant current densities (b) [5]. Furthermore, we investigate gas diffusion electrode stability using synchrotron operando characterizations, tracking where and when (bi)carbonate salts precipitate and degrade gas diffusion electrodes (c) [6-7]. These insights lay the groundwork for more durable, selective, and efficient electrochemical CO₂ conversion devices.

(a) Cross section of a polymeric gas diffusion electrode made in-house. The electrode consists of an electrospun poly(vinylidene fluoride-co-hexafluoropropylene) fiber substrate (PVDF-HFP, darker contrast) coated with a layer of Cu catalyst (brighter contrast). (b) Influence of the substrate pore size on the product selectivity of polymeric gas diffusion electrodes as a function of applied current density, with smaller pore sizes showing a strongly enhanced selectivity for high value C₂ and C₃ carbon products compared to larger pore sizes. (c) Operando synchrotron wide angle X-ray scattering showing the position and extent of (bi)carbonate precipitation in polymeric Cu gas diffusion electrodes. (Bi)carbonate crystals precipitate close to the Cu catalyst within minutes from the start of the CO₂ reduction reaction.