Influence of Electric Field and Current Distribution due to Electrode Geometry on CO2 Electroreduction

The electrode geometry significantly influences the selectivity and activity in CO2 electroreduction (CO2ER) even when the same materials are utilized. In order to obtain insight into why the electrode geometry impacts the CO2ER, a computational study using COMSOL Multiphysics software was conducted. A three-dimensional (3-D) simulation was performed to compare three electrodes with the same surface area (0.9 cm2) and different geometries: a two-dimensional (2-D) flag, a 3-D foil coil, and a 3-D wire coil, all composed of silver. The results showed that the edges and corners have a higher current density and stronger electric field compared with the flat regions. Therefore, the foil coil and wire coil, which have more edges and corners compared to the flag, had a higher total current, a stronger electric field, and a more uniform current distribution on the surface. The high current at the edges and corners can decrease the energy barrier needed for CO2ER. An enhanced electric field can also increase the concentration of cations at the interface, leading to stabilization of the intermediates such as CO2•– radicals and improvement in CO2ER. The interfacial properties in the electrode–electrolyte interface are also impacted by the electrode geometry. It was also observed that the edges and corners have a higher local pH and a lower CO2 concentration due to the enhanced CO2ER reactions at these sharp points. The calculations in this study can further explain the enhanced performance of foil coil and wire coil electrodes, which had been observed in our previous report. This work illustrates how important it is to include electric field and current distribution considerations in the design of electrochemical reactors.