Electrochemical performance of novel NGCO-LSCF composite cathode for intermediate temperature solid oxide fuel cells

In this study, a co-dopant CGO was synthesized to produce more efficient cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC) applications. Neodymium (Nd) was doped into CGO in four different weight ratios in the formula NdxGd0.15Ce0.85-xO2-delta (NGCO); the selected percentages for x were 1%, 3%, 5% and 7%. XRD patterns showed pure phase for all synthesized compositions and good compatibility at high temperature under static air with the most common ceramic cathode material in IT-SOFC (La0.60Sr0.40Co0.20Fe0.80O2-a, LSCF). Impedance spectroscopic characterization of symmetrical cells of the composite NGCO-LSCF at different temperatures (650-800 degrees C in steps of 50 degrees C) and a frequency range of 0.1-1 MHz in synthetic air revealed interesting results. The lowest polarization resistance (R-p) was achieved for NdxGd0.15Ce0.85-xO2-delta (0.06 Omega cm(2) at 800 degrees C, 0.17 Omega cm(2) at 750 degrees C, 0.31 Omega cm(2) at 700 degrees C, and 0.59 Omega cm(2) at 650 degrees C). The expected decrease in R-p was not observed for the sample with higher Nd content (7% Nd). Thus, it can be said that there is a distinction between the compositions NdxGd0.15Ce0.85-xO2-delta and Nd0.07Gd0.15Ce0.78O2-delta; the co-doping of Nd in NGCO incremented the oxygen ion diffusion path, thereby optimization in the triple phase boundary (TPB) sites was obtained. Furthermore, SEM and TGA measurements were conducted to clarify the reasons of such improvements. This work showed that an NGCO-LSCF composite can be considered as a potential candidate for cathode material for future IT-SOFC applications. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.