A high power metal-supported protonic ceramic fuel cell using increased proton conductivity in the cathode functional layer of La1−xSrxScO3 (LSSc, x = 0.1–0.25)

Abstract

Metal-supported protonic ceramic fuel cells (PCFCs) are highly attractive due to their high efficiency, reliability, and low cost. However, until now, there are limited reports on metal-supported PCFCs. In this study, a selective reduction method was used for preparing the metal-supported BaZr_0.44Ce_0.36Y_0.2O₃ (BZCY) cell. It was found that insertion of an La_1−xSr_xScO₃ (LSSc, x = 0.1–0.25) cathode functional film (CFL) was highly effective for decreasing cathodic overvoltage and ohmic loss, leading to significant increase in power density. Among the examined compositions, La_0.85Sr_0.15ScO₃ was identified as the optimal composition of the CFL. With this configuration, an open circuit voltage (OCV) of 1.15 V and a maximum power density (MPD) of 233 mW cm⁻² were achieved at 773 K. Impedance analysis suggests that the increased power density can be attributed to the decreased overvoltage and ohmic loss in the cathode side, due to significantly increased proton conductivity in the LSSc film. This improvement is likely the result of the high concentration of H⁺ in the LSSc film, as indicated by thermogravimetric (TG) and Hall effect measurement. Another challenge in PCFCs is the leakage current at higher oxygen partial pressure. However, the LSSc CFL also effectively prevented H⁺ crossover, resulting in the OCV being almost the same as the theoretical value. Achieving near-theoretical OCV is crucial for the high energy conversion efficiency of PCFCs.