AUTHOR=Dąbrowa Juliusz , Stępień Anna , Szymczak Maria , Zajusz Marek , Czaja Paweł , Świerczek Konrad 

TITLE=High-entropy approach to double perovskite cathode materials for solid oxide fuel cells: Is multicomponent occupancy in (La,Pr,Nd,Sm,Gd)BaCo2O5+δ affecting physicochemical and electrocatalytic properties?

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2022.899308

DOI=10.3389/fenrg.2022.899308

ISSN=2296-598X

ABSTRACT=High-entropy (La,Pr,Nd,Sm,Gd)BaCo2O5+δ double perovskite-type oxide having an equimolar, high-entropy, A-site layered arrangement of cations is synthesized for the first time. A modified Pechini method, followed by calcination and sintering at 1100 °C enables obtaining a single-phase, homogenous material with tetragonal I4/mmm symmetry. In-situ X-ray diffraction and dilatometric studies show excellent phase stability up to 1100 °C in air, with the average thermal expansion coefficient of 23.7∙10-6 K-1 within the 25 to 1100 °C range. Total electrical conductivity of metallic character exceeds 1600 S cm-1 at room temperature. Equilibrated oxygen content at room temperature is determined as 5.69. The cathodic polarization resistance of (La,Pr,Nd,Sm,Gd)BaCo2O5+δ layers manufactured on the La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM) solid electrolyte of proved inertness, is as low as 0.037 Ω cm2 at 900 °C, and 0.175 Ω cm2 at 750 °C. The determined value of the power density in fuel cell reaches 857 mW cm-2. These results indicate possible applicability of the developed cathode material for Solid Oxide Fuel Cells, making it also one of the best-performing high-entropy air electrodes reporet until now. However, the determined physiochemical characteristics of the material indicate a relatively limited influence of the high-entropy A-site arrangement in comparison to the conventional analogs, including the synthesized Nd0.88Sm0.12Co2O5+δ composition, characterized by the same effective radius of the lanthanide cations