How Mechanical Challenges Affect the Performance of Industrial Scale Carbon Dioxide Electrolyzer Cells?

One of the most important challenge of humanity in the mid-21st century is to maintain economic growth in an environmentally sustainable way. The European Green Deal addresses this issue, and it aims at making Europe climate neutral by 2050. To reach this aim, a promising technology is to convert a greenhouse gas, carbon dioxide into valuable chemicals (produce e.g., energy carriers, fine chemicals, pharmaceuticals) in an environmentally and economically sustainable manner, such as the utilization of renewable energy sources. The direct electrochemical reduction of carbon dioxide into carbon-monoxide (a high-value product which can be readily used in the chemical value chain) is a promising waste-to-wealth approach among the developed technologies and it can be easily coupled with carbon-free electricity sources to make the process completely sustainable. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance, as well as finding technological solutions that enable scale-up to reach industrially relevant dimensions. Zero-gap electrolyzer cell technology operates with high reaction rates and good efficiencies under ambient and near ambient conditions. In addition, its operation is simpler compared to other types of carbon-dioxide electrolyzer cell technologies (just one example: there is no need very precisely pressure control because no flowing catholyte inside the cell), and this allows the scale up of such architectures. Exploring the fundamentals and understanding of the chemistry in zero-gap electrochemical cells is carried out by many research groups, usually with small experimental test cells. These results provide a good scientific basis (e.g., to select the right catalysts, components, or to study long-term degradation, etc.), however, compared to the size of an industrial-scale electrolyzer, these experimental cells only measure a "one point" chemistry. The results cannot be transferred without careful consideration during scale-up, due to several additional challenges. These challenges are mainly of mechanical origin, and all of these create uneven conditions that can significantly affect the chemistry of the on given sections of the cells. Over the past several years, we have gone through the steps of scaling up electrochemical cells (for CO 2 -to-CO conversion) from a small experimental test cell (8 cm 2 ) to an industrial-sized cell stack (2500 cm 2 / cell). During the development journey we encountered many of the challenges outlined above. In this talk, I am going to present some of these challenges, their origins, what affects them and by them, and what principles can be used to find solutions.