In the context of carbon neutrality, conversion of CO₂ into CO is an effective way for negative carbon emission. Electrochemical reduction is a novel developed pathway, among which, solid oxide co-electrolysis technology is promising for its high efficiency and low electricity demand. Researches concerning the large-size cell and stack of application level are important. This review, targeting at the not yet fully understood reaction mechanism and the most concerning issue of durability, details the reported factors playing important roles in the reaction mechanism and durability of co-electrolysis. It is found that the operating conditions such as inlet mixtures and applied current significantly affect the reaction mechanism of co-electrolysis and the experiments on button cells can not reflect the real reaction mechanism on industrial-size cells. Besides, the durability test of large-size single cells and stacks at high current with high conversion rate and the potential of solid oxide co-electrolysis combing with intermittent renewable energy are also reviewed and demonstrated. Finally, an outlook for future exploration is also offered.

Gadolinium-doped ceria (GDC) interlayers are required to prevent the interfacial reaction between La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode and Y₂O₃-stabilized ZrO₂ (YSZ) electrolyte in solid oxide fuel cells (SOFCs). However, it's difficult to prepare a thin and dense GDC interlayer on the sintered half-cell at a low temperature. In this study, the physical vapor deposition (PVD) method was employed to successfully manufacture dense GDC interlayers with the thickness of 1 μm. The influences of GDC sintering temperature (900 °C, 1000 °C and 1100 °C) on cell performance characteristics and degradation behavior were investigated. The cell with GDC interlayer sintered at 1100 °C showed the lowest degradation rate during the 216-h operation. The best stability was attributed to the most effective inhibition of Sr diffusion by the GDC interlayer, which was demonstrated by the almost unchanged Ohmic and polarization resistances during the aging stage and the negligible Sr enrichment at YSZ/GDC interface. Compared to the conventional screen-printed GDC interlayers (sintered above 1250 °C), the GDC interlayer prepared by the PVD method and sintered at 1100 °C was significantly denser and thinner, showing a promising application prospect due to its benefits for cell stability.