Exploring CO₂ reduction and crossover in membrane electrode assemblies

Electrochemical CO₂ reduction (CO₂R) using renewable electricity is a key pathway toward synthesizing fuels and chemicals. In this study, multi-physics modeling is used to interpret experimental data obtained for CO₂R to CO using Ag catalysts in a membrane electrode assembly. The one-dimensional model is validated using measured CO₂ crossover and product formation rates. The kinetics of CO formation are described by Marcus–Hush–Chidsey kinetics, which enables accurate prediction of the experimental data by accounting for the reorganization of the solvent during CO₂R. The results show how the performance is dictated by competing phenomena including ion formation and transport, CO₂ solubility, and water management. The model shows that increasing the ion-exchange capacity of the membrane and surface area of the catalyst increases CO formation rates by >100 mA cm^–2 without negatively impacting CO₂ utilization. Here we provide insights into how to manage the trade-off between productivity and CO₂ utilization in CO₂ electrolyzers.