(445a) Techno-Economic Optimization of Electrochemical Reactors for CO2 Reduction

The production of base chemicals, such as various hydrocarbons, by electrochemical conversion of CO₂paired with CO₂capture technologies has the potential to close the carbon cycle, thereby significantly contributing to the future energy transition. The feasibility of electrochemical CO₂conversion has been demonstrated at lab scale, leading researchers to optimize reactor designs based on performance targets derived from techno-economic analysis. However, these techno-economic analysis are commonly based on fixed performance metrics and therefore neglect the well studied interdependence of crucial performance parameters such as current density, faradaic efficiency and cell potential on the mechanistic level. This confines the techno-economic studies to univariate sensitivity analyses assuming that reactor performance parameters are independent of each other, thereby overestimating the solution space for feasible reactor designs.

This study, therefore, presents a multi-scale modelling approach spanning from a firstprinciple reactor model over the electrolyser-stack scale to the process scale, allowing us to assess the well described interdependencies on the reactor design level from an economic perspective. The first-principle model of a CO₂electrolyser is developed based on experimental data in literature for the production of ethylene and captures the interplay between CO₂conversion, consumption and faradaic efficiency for varying current densities and inlet velocities. This framework does not only show the propagation of interdependencies across scales it further enables us to perform the first techno-economic optimization for CO₂-electrolysis systems. The optimal performance targets are found to strongly deviate from previously reported targets, which manifests for the herein chosen reactor design, in an optimal current density of ≈ 100mAcm^−2in comparison to commonly reported values greater than 200mAcm^−2. This approach highlights the importance of including interdependencies on the reactor scale to asses the economic viability of a reactor design and presents a tool to evaluate reactor design choices. This study further shows that the accuracy of these predictions is highly dependent on the available data, which makes it important to a) move towards more holistic,multi-scale modelling approaches in the field of CO₂-electrolysis, and to b) communicate measured or targeted reactor performance with all applicable boundary conditions.