Carbon Capture and Utilization (CCU) has recently gained attention as a sustainable process to mitigate the rising CO₂ level in the atmosphere. Among the various CCU processes, electrocatalytic CO₂ reduction offers a potential means of producing fuels or commodity chemicals (such as CO, formic acid, methanol, ethanol) from flue gases or atmospheric CO₂. When integrated with renewable electricity, this process facilitates a closing of the carbon cycle. Ethanol is regarded as a highly desirable product of CO₂ electroreduction, primarily due to the large market size of ethanol, thereby contributing significantly to the global CO₂ emissions. However, owing to the challenges associated with electrode and reactor design, the production of ethanol by CO₂ electroreduction is still at lab scale. Furthermore, there is a lack of understanding of the rate controlling mechanisms involved in the conversion of CO₂ to ethanol via electroreduction processes.

In this work, a mathematical model was developed to understand the fundamental processes and the polarization behaviour of CO₂ electroreduction to ethanol, with the emphasis on the cathode side. The model considers the mass balance of ions in the electrolyte using Nernst-Planck equation and the charge balance using Faradays law. Electrode reactions were represented using the Butler-Volmer equation, in order to obtain the relation between rate of reaction and potential. OH^- ions are transported from cathode to anode through electrolyte and membrane. The Donnan potential is used to relate the electrolyte potential and membrane potential. These equations are solved using COMSOL in tertiary current distribution and secondary current distribution physics.

Figure 1a represents the governing equations and boundary conditions used in the catholyte, the membrane and the anolyte domains and Figure 1 b represents the polarization curve simulated using the model. The applied potential at cathode is varied from -1.2 V to -1.5 V and average current density is computed and plotted against applied potential. As applied potential increases the average current density also increases.

There are several ongoing studies to find effective catalysts for electrochemical reduction of CO₂ to ethanol. Some of the efficient electrocatalysts are Boron and Nitrogen Co-Doped Diamond (BND)^[1], carbon nano spikes on copper nanoparticles (Cu/CNS)^[2], Cu₃Ag₁^[3] ,a carbon supported Cu catalyst prepared by Amalgamated Cu-Li method (Cu/C) ^[4] and a CoO-anchored N-doped carbon material composed of mesoporous carbon and carbon nanotubes (MC-CNT) ^[5]. All these catalysts give a faradaic efficiency more than 45% and some even more than 90%. In addition, we have to achieve a reasonable current density value. So, considering the faradaic efficiency for ethanol, current density, ease of fabrication and cost, we have selected Cu₃Ag₁^[3] as the catalyst material for electro-reduction of CO₂ to ethanol.

The polarization curves simulated using the model developed will be validated against the experimental data using H cell. The experimental setup includes H-Cell, anion exchange membrane (AEM), Ag/AgCl reference electrode, electrodes, 0.5 M KHCO₃ as electrolyte.