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

Nanjing University of Science and Technology, School of Energy and Power Engineering, Nanjing, China

^* qqww1234562006@126.com;
^** liudong15@njust.edu.cn;
^*** liqiang@mail.njust.edu.cn

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 *CO₂^δ- 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.