Oxidation Process of Ni Cathode in CO2 Electrolysis in SOEC: X-Ray and DFT Study

Abstract

CO2 oxidation of Ni cathode in CO2 electrolysis in solid oxide electrolysis cell (SOEC) was studied experimentally and through first-principles density functional theory (DFT) calculation. Ex-situ analyses of Ni/YSZ surface after CO2 electrolysis were performed using SEM and XRD. As a result, less oxidation of Ni was found in CO2 electrolysis mode at high current density (-280 mA/cm2), whereas Ni was oxidized at low current density (-140 mA/cm2). DFT calculation showed CO2 reduction was more stable than Ni oxidation at the Ni/YSZ interface. The electrolysis mode can enhance the oxidation tolerance of the Ni electrode due to the oxygen transfer. It was also implied that the electrolyte structure could improve the oxidation tolerance.