CO2 conversion improvement of solid-oxide electrolysis cells by inserting buffer layers between MFe2O4 (M = Ni, Cu, Co, Fe) cathode and electrolyte

Abstract

This study investigated the potential of spinel-structured materials (MFe2O4; M = Ni, Cu, Co, and Fe) as cathodes of solid oxide electrolysis cells (SOECs); at the same time, it revealed that the La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) blocking layers would improve the performance of SOECs by interposing between MFe2O4 and the Sm0.2Ce0.8O2-δ (SDC) electrolytes. The fabricated SOECs were tested under 39% CO2-1% CO-60% He up to 800 °C. Our results showed that the Faradaic efficiency for CO2 reduction was significantly improved and approached the theoretical production rate after the insertion of LSGM blocking layers. In addition, the LSGM barrier layers effectively prevent the short-circuit effect between MFe2O4 and SDC, allowing the open-circuit voltage (OCV) to increase from ∼0.56 V to ∼0.77 V, which dramatically improved the gas generation efficiency of SOECs. According to our optimized SOEC structure, NiFe2O4 and CuFe2O4 exhibited superior electrolytic performance and maintained stable electrolysis after 10 h without degradation. In summary, the inserted LSGM layers would gently modify the interfacial contact and address the mismatch between the spinel-structured materials and SDC to avoid the performance degradation caused by electrode detachment and achieve higher durability than the SOECs without LSGM layers.