Coupled Surface–Bulk Engineering of Ceria-Based Cathodes Enables High-Temperature CO ₂ Electrolysis

Solid oxide electrolysis cells (SOECs) enable efficient high-temperature electrochemical CO 2 conversion, yet cathode performance is limited by insufficient surface reactivity and bulk transport. Herein, we report a coupled engineering strategy to enhance surface reactivity and bulk transport of Ce-based cathodes via rational dual-metal (Co, Fe) incorporation. The resulting Co 0.05 Fe 0.05 -incorporated Gd-doped ceria (Co 0.05 Fe 0.05 -GDC) exhibits enriched surface Ce 3+ –oxygen vacancy (Ce surf. 3+ – V O ) motifs and improved bulk transport. A single cell with the Co 0.05 Fe 0.05 -GDC cathode achieves a current density of 1.88 A cm –2 (2.20 A cm –2 with a thinner 250 μm electrolyte) at 800 °C under 1.6 V and demonstrates stable operation for 580 h. Mechanistic studies reveal that Fe promotes CO 2 adsorption, activation, and dissociation via enriched Ce surf. 3+ – V O motifs and active Fe sites, whereas Co lowers the oxygen migration barrier and narrows the bandgap, overcoming bulk transport limitations. This work provides a cost-effective design for high-performance ceria-based cathodes by coupling surface reactivity with bulk transport.