Multiscale simulation on electrochemical CO2 reduction in gas-diffusion-electrode-based flow electrolyzer

Abstract

To respond to the goal of "carbon peaking and carbon neutrality", this paper establishes a multiphysics macroscopic model of a flow electrolyzer based on a gas diffusion electrode in the context of electrocatalytic CO2 reduction and combines the established microscopic model of Ag-based catalytic surface density function theory and mesoscopic model of transition state theory to realize the multiscale coupling of electroreduction of CO2 in a flow electrolyzer. The experimental system of CO2 reduction in a flow electrolyzer is designed and built to verify the reliability of the theoretical calculations. In the range designed by the model, the CO faradaic efficiency is maintained at a high level, and the CO2 conversion increases rapidly with the increase of the cell voltage; the coverage of intermediates *CO2δ- and **COOH increases continuously with the rise of the cell voltage, and the coverage of *CO intermediates decreases continuously, which indicate that the increase of CO production leads to the rise of CO2 conversion; the excessive inlet flow rate leads to the rapid dilution of CO2; the rise of inlet CO2 concentration significantly enhances the reduction reaction rate, but the relatively higher CO2 concentration in the gas channel leads to a decrease in the conversion. The optimal operating parameters are: flow rate of 5 to 10 sccm, cell voltage of 2.8 V to 3.2 V, and inlet CO2 molar fraction of 10% to 20%, where the CO2 conversion and CO faradaic efficiency can exceed 10% and 90%, respectively.