Enhanced performance of reversible solid oxide fuel cells by densification of Gd0.1Ce0.9O2−δ (GDC) barrier layer/La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428)-GDC oxygen-electrode interface

Abstract

In reversible solid oxide cells (RSOCs) with yttria-stabilized zirconia (YSZ) electrolyte and LSCF6428-based oxygen electrode, a GDC barrier layer is used to prevent inter-diffusion of constituents. However, the performance of such RSOC is limited to the achievable density of GDC at prevailing temperatures of traditional fabrication methods. In this work, the GDC barrier layer was densified via infiltration with polyvinylpyrrolidone (PVP) chelated metal precursors sol and subsequent sintering at 1200 °C. The NiO-YSZ fuel electrode-supported RSOCs with YSZ electrolyte, porous or infiltrated GDC barrier layer and LSCF6428-GDC composite oxygen electrode were fabricated. The RSOCs were analyzed with respect to operating temperature (650–800 °C), water partial pressure at fuel electrode (pH2OFE=0.03–0.5 atm), oxygen partial pressure at oxygen electrode (pO2AE=0.02–0.21 atm) and current loading. The performance evaluation, using current-voltage curve and electrochemical impedance spectroscopy (EIS), showed that the RSOC with an infiltrated GDC barrier layer exhibited a 32–48% increase in performance in fuel cell (FC) mode in the 650–800 °C range, compared to that of the RSOC with a porous GDC layer. Similarly, in electrolysis cell (EC) mode, comparing current density at 1.3 V, chosen as the reference voltage for ease of comparison, based on a thermoneutral voltage of 1.285 V in electrolysis cell (EC) operation at 750 °C[1], the RSOC with an infiltrated GDC barrier layer exhibited values of over 1.2 A∙cm−2, in contrast to the RSOC with a porous GDC barrier layer, which showed 0.8 A∙cm−2. In the case of the RSOC with infiltrated GDC, a durability test was conducted at 750 °C under an EC current density of 1A∙cm−2for 100 h. Our experimental results demonstrate that the RSOC with an infiltrated GDC barrier layer not only exhibits enhanced performance but also maintains stability. Comparative analysis was conducted using Distribution of Relaxation Time (DRT) analysis of Electrochemical Impedance Spectroscopy (EIS) data, to further understand the differences between the cells.