Constructing a Robust Composite Cathode to Revitalize Efficient CO ₂ /H ₂ O Coelectrolysis and Controllable Syngas Production

The practical application of high-temperature CO2/H2O coelectrolysis in solid oxide electrolysis cells (SOECs) is critically limited by the inadequate activity and durability of cathode materials under demanding operational environments. Herein, a robust composite cathode was constructed via incorporating high-oxygen transport gadolinium-doped ceria (GDC) into a (PrBa)0.95Fe1.6Ni0.4O6−δ matrix to improve electrolysis performance in SOECs. The current density over the composite cathode with a GDC loading of 40 wt % reaches 1.029 A cm–2 at 1.5 V and 800 °C under a pure CO2 atmosphere, significantly outperforming the PB95FN cathode (0.876 A cm–2). This enhancement can be attributed to facilitated oxygen transport and extended triple-phase boundaries (TPBs) with addition of GDC, which promote the CO2 adsorption and dissociation process. Furthermore, this composite exhibits considerable H2O/CO2 coelectrolysis performance, achieving a current density of 1.306 A cm–2. Adjusting the steam concentration enables control over the H2/CO ratio in the syngas product, enabling its direct use in the production of methanol, gasoline, and various industrial fuels. More importantly, the inclusion of GDC effectively mitigates cathode delamination under high humidity, thereby ensuring exceptional mechanical integrity. The SOEC with the PBFN-40GDC cathode demonstrates remarkable operational stability over 100 h under a 20 vol % humidified gas feed at 800 °C. This work provides an effective material design strategy and fundamental insights into developing highly durable and active cathodes for efficient syngas production via SOEC-based coelectrolysis.