Oxygen pumping based on c-axis-oriented lanthanum silicate ceramics: challenge toward low operating temperature

Abstract

A new electrochemical oxygen separation pump was developed by using c-axis-oriented La_9.66Si_5.3B_0.7O_26.14 (c-LSBO), which has high oxide-ionic conductivity (>10⁻³ S cm⁻¹) up to 300°C. Interfacial resistance between the electrode and c-LSBO was investigated to realize the full potential of LSBO as an oxygen separation material. The formation of a Sm-doped CeO₂ (SDC) thin film (thickness: 300 nm) between the electrode and c-LSBO was effective for suppressing the interfacial resistance. Furthermore, a mixed conductive La_0.6Sr_0.4Co_0.78Ni_0.02Fe_0.2O_3−δ (LSCFN) was applied to the electrode for enhancing the oxygen reduction/evolution activity on the electrode. The LSCFN/SDC/c-LSBO symmetric cell showed an oxygen permeation flux of 3.5 mL cm⁻² min⁻¹ (1.0 A cm⁻²) at 600°C under an applied DC voltage of 1.5 V; this value was 67 times that of Pt/c-LSBO. This oxygen pump based on the LSCFN/SDC/c-LSBO symmetric cell would find promising application in oxygen separation at intermediate temperatures. Further reduction of the interfacial resistance and polarization resistance of the electrode may decrease the operating temperatures to below 400°C.