Performance of CO<sub>2</sub> electrolysis using solid oxide electrolysis cell with Ni-YSZ as fuel electrode under different fuel atmospheres
Anqi Wu, Beibei Han, Liangzhu Zhu, Wanbing Guan, Subhash C. Singhal
Abstract
High efficiency conversion of CO2 can be realized in a solid oxide electrolysis cell. In this work, a flat-tube cell with symmetrical structure supported by Ni-YSZ fuel electrode was used to study the performance of high-temperature CO2 electrolysis under different reducing gas components in the fuel electrode. The results indicated that in the H2-CO2 fuel electrode atmosphere, the instantaneous performance of CO2 electrolysis is better, the polarization impedance is smaller, and the overpotential of CO2 electrolysis is lower under the same partial pressure of oxygen (i.e., with the same open-circuit voltage). Compared with CO as the protective gas, it is easier to achieve a stable electrolytic voltage for the electrolysis of CO2 under H2 protection. In the H2-CO2 reaction atmosphere, when the proportion of protective H2 increased from 25% to 75%, devastating irreversible degradation occurs at −300 mA/cm2, while in the CO-CO2 (71.7% CO-28.3% CO2) reaction atmosphere, the similar degradation occurs at – 200 mA/cm2. At – 200 mA/cm2 constant-current electrolysis, the highest energy conversion efficiency can reach 171% (disregarding energy consumption for heating the gas) and 81.6% (disregarding energy consumption for heating air). This work provides a useful reference for the selection of atmosphere protection in CO2 electrolysis based on Ni-YSZ electrode SOEC.