Optimisation of operating parameters for enhanced CO2 electrochemical reduction to ethylene in flow cell configuration: A study on catalytic performance

Significant research efforts have been directed toward developing efficient working electrodes for CO₂ electrochemical reduction reaction (CO₂RR), with copper-based electrodes as promising catalysts for reducing CO₂ to hydrocarbons. Herein, the electroreduction performance of a copper-based gas diffusion layer (Cu-based GDL) as a working electrode for CO₂ conversion to ethylene in a liquid flow cell configuration is investigated. Online gas product quantification was conducted using micro-gas chromatography. Analysis of the Cu-based GDL’s surface morphology and crystallinity before and after CO₂RR revealed significant structural changes, transitioning from microscale particles to a flowery-shaped configuration and shifting from pure copper (Cu) to a mixture of copper (Cu) and cupric oxide (Cu₂O). Optimisation of critical parameters, including half-cell potential, liquid flow rate, and gas flow rate, was performed to enhance CO₂ reduction efficiency. Ethylene production was most favourable at higher half-cell potentials, achieving a formation rate of 133.36 µmol/cm².h and a faradaic efficiency (FE) of 60.95 % at -1.25 V vs reversible hydrogen electrode (RHE), attributed to the 12-electron reduction pathway. The highest current density, 94.74 mA/cm², was observed at -1.50 V vs RHE; however, optimal operating conditions for ethylene production, considering both FE and formation rate, were determined to be -1.25 V vs RHE, despite a slightly lower current density of 70.36 mA/cm². While variations in liquid flow rate had minimal impact on FE and current density, an optimal gas flow rate of 3 mL/min was identified, maximising ethylene production.