A critical review of CO₂ electrolysis by solid oxide electrolysis cells

Solid oxide electrolysis cells (SOECs) represent a highly efficient, high-temperature electrochemical technology with significant potential for CO₂ conversion. However, the degradation of cathode materials (such as coking and oxidation of Ni-YSZ) during electrolysis severely restricts their long-term stability and efficiency. This review systematically summarizes recent advances in CO₂ electrolysis using SOECs, with a particular focus on the mechanisms of carbon deposition and strategies for its suppression. Studies indicate that carbon deposition is primarily driven by the Boudouard reaction and catalytic activity of nickel, leading to pore blockage and loss of active sites. Significant improvement in carbon tolerance can be achieved through material modification, replacement of Ni-based cathodes with perovskite oxides, and optimization of operating conditions. Furthermore, the structural design of electrodes and flow-field optimization contribute to enhanced mass transfer efficiency and uniform temperature distribution. Although progress has been made in oxygen production on Mars and industrial demonstrations, large-scale application of SOECs still faces challenges related to material stability, system integration, and economic feasibility. Future efforts should focus on gaining deeper insight into the kinetics of CO₂ reduction, developing novel carbon-resistant materials, and promoting modular system design to facilitate commercial adoption. Finally, this review discusses ongoing challenges and suggests promising directions for future study.