MODELING AND NUMERICAL INVESTIGATION OF THE GAS DIFFUSION ELECTRODE FOR THE ELECTROCHEMICAL ‎REDUCTION OF CARBON DIOXIDE INTO ALCOHOLS

Abstract

The application of gas ‎diffusion electrodes (GDEs), ‎as a solution to mass ‎transfer limitations for the ‎electrochemical reduction ‎of carbon dioxide into ‎value-added products ‎including ‎alcohols, is ‎gaining more attention. In ‎this study, a model was ‎built to investigate the role ‎of Cu2O-ZnO (1:1) based-GDE ‎in enhancing the ‎production rate of ‎alcohols inside an ‎‎electrochemical filter-press ‎cell. This two-dimensional, ‎steady-state, and ‎isothermal ‎model was simulated using ‎the commercial ‎software ‎COMSOL Multiphysics® v5.2.‎ ‎The electrode ‎electrochemical kinetics, ‎momentum, mass, and ‎charge transport were ‎‎incorporated in the model. ‎ In this work, the effect of ‎key process parameters; ‎current density (j = 5–10 ‎mA cm-2), gas flow rate ‎‎(Qg/A = 10–20 ml min-1 cm-‎‎2), electrolyte flow rate and ‎CO2 gas feed concentration ‎on the production rate and ‎faradic efficiency of ‎methanol and ethanol were ‎investigated. The ‎developed model was ‎validated against a set of ‎experimental results and ‎‎showed reasonable ‎agreement with an average ‎error of 6%. The results ‎showed that, ‎at low electrolyte flow rate, ‎the methanol production ‎rate was independent of ‎the electrolyte flow rate. ‎From the economic point of ‎view, it is recommended to ‎use a gas stream of 90% or ‎slightly lower CO2 ‎concentration at optimum ‎values of applied current ‎density of 9 mA cm-2, gas ‎flow rate of 17.5 ml min-1 ‎cm-2 and an electrolyte flow ‎rate as low as 2 ml min-1 ‎cm-2.