Analyzing the electrochemical reduction of CO and CO2 as reactants to C1 and C2 products on copper-based flow-through gas diffusion electrodes

Abstract

Electrochemical CO2 reduction (eCO2R) into useful chemicals and fuels is extensively studied, but it faces challenges such as high activation energy, carbonation, lower reaction rate, and unstable operation in alkaline conditions. In contrast, electrochemical CO reduction (eCOR) can efficiently produce C2+ products through a two-step conversion process without requiring high activation energy and involving complex reaction routes like CO2 electroreduction. Therefore, Converting CO2 to CO and then to C2+ products can be a strategic approach to enhance activity, selectivity, and economic viability. However, eCOR demonstrates lower reaction rates and sluggish kinetic with planar electrodes due to its lower solubility and poor mass transport to the electrode surface, therefore, industrially relevant current densities are still far to reach. Flow-through gas diffusion electrodes (FTGDEs) can potentially solve the issue of poor mass transport due to their abundant surface area, porous structure, and improved triple-phase interface. Herein, electrochemical CO reduction to C2+ products is investigated using Cu-based FTGDEs. A comparison of eCOR with eCO2R is also carried out to study the catalytic activity, selectivity, and stability. To demonstrate the influence of particle size, FTGDEs are designed using varying Cu particle sizes i.e. 10 nm, 100 nm, and 10 µm. The eCOR produced C2+ products with ethylene being the main product achieving 474 mA/cm2 current density and 72% faradaic efficiency at − 0.9 V vs. RHE, while eCO2R yielded more C1 products with lower catalytic activity and selectivity. Compared to gas diffusion configuration, the poor catalytic activity and selectivity of eCOR are observed in non-gas diffusion configuration which signifies that, due to higher local CO concentration and improved triple-phase generation, higher performance of FTGDEs can be obtained from gas diffusion configuration. Finally, the stable operation of Cu electrodes during eCOR highlights its promise as a highly suitable candidate for enhancing eCOR towards higher carbon products.