High‐Efficiency CO ₂ Electrolysis Enabled by Interface‐Engineered Composite Electrolytes in Ni‐Based SOEC

Interfacial instability between different electrolyte materials is a critical challenge hindering the commercialization of CO₂ electrolysis via solid oxide electrolysis cells (SOECs). Specifically, the thermal deformation disparity at the yttria-stabilized zirconia (YSZ) and Gd-doped ceria (GDC) electrolyte interface leads to delamination during high-temperature operation, severely degrading cell performance and durability. In this study, this issue is resolved by designing a novel composite intermediate layer, fabricated through a simple dip-coating process using a mixture of YSZ and GDC powders. This composite layer effectively mitigates the thermal deformation disparity, ensuring excellent structural stability without delamination even after high-temperature sintering. Consequently, the cell incorporating the composite interlayer exhibits a significantly reduced interfacial resistance and achieves an exceptional current density of 2.14 A cm^-2 at 800 °C, which is among the highest performance levels reported for Ni-based fuel electrode-supported SOECs. Furthermore, the cell demonstrates excellent long-term stability, maintaining 91% of its initial performance after 80 h of continuous operation under a harsh 1.6 V condition. The electrolyte layer also retains robust and stable interfacial adhesion, confirming the durability of the engineered interface. This study presents an effective electrolyte interface engineering strategy for the development of high-performance and large-area SOECs for CO₂ electrolysis.