Articles techniques et présentations

The rise in atmospheric CO2 needs the development of efficient conversion technologies. CO2 reduction reaction (CO2RR) emerges as a compelling solution, offering the transformation of CO2 into more energetic compounds, such as fuels (hydrocarbons, alcohols, etc.) and valuable chemicals, mainly, utilizing renewable electricity. The CO2RR can be pursued exploiting different types of electrolysers, where the flow cell reactor is the system on which the simulation will be implemented. In the proposed 1D designed scheme, the different CO2RRs occur at the cathode, together with the competitive Hydrogen Evolution Reaction (HER); while at the anode the Oxygen Evolution Reaction (OER) balance the cell. The anolyte and catholyte are separated by an Ionic Exchange Membrane (IEM), which prevents the electrolyte and produced gasses to mix, while allowing ion migration to compensate the charge unbalance. Flow cell reactor in CO2RR field exploits a Gas Diffusion Electrode (GDE) as cathode, a type of current collector characterized by a Gas Diffusion Layer (GDL) to let the gas passage close to the catalyst layer. The introduction of GDE allows to overcome the intrinsic mass transport limit of the substrate diffusion close to the electrode, being the CO2 solubility in water deeply limited. Thanks to the GDE, a three-phases system is created, allowing contact between the gaseous CO2 and the liquid electrolyte on the solid interface of the catalyst. Such equilibria is the most delicate aspect of GDE utilization, being the imposed voltage, the occurring reactions, pressure imbalance (and so on) aspect that alter such equilibria and the product efficiency. GDL represents the zone where the CO2 and products concentration profile deviates from bulk conditions due to mass transfer limitations. To optimize this region and prevent the flooding process is essential for maximizing product yield and selectivity. A key parameter influencing CO2RR performance is the GDL's pore saturation index (S). When S = 1 (flooding), the pores become solely occupied by the electrolyte, hindering CO2 diffusion and compromising reaction efficiency. This work utilizes COMSOL simulations to understand and optimize this parameter. By simulating the CO2RR process beforehand, we gain valuable insights into the reaction surface within the GDL. This allows for the optimization of pore saturation, preventing flooding and maximizing both electrode efficiency and operational useful life. Traditionally, CO2RR development relies heavily on experimental trial-and-error approaches. This method can be time-consuming, expensive, and generate vast amounts of waste. COMSOL simulations offer a powerful alternative. By constructing a digital model of the flow cell and incorporating relevant physical and chemical properties, we can virtually investigate the CO2RR process under various operating conditions. This allows us to explore different GDL designs, catalyst materials, and operating parameters to identify configurations that optimize pore saturation and achieve superior CO2 conversion efficiency.