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=10

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=<p>High-entropy (La,Pr,Nd,Sm,Gd)BaCo<sub>2</sub>O<sub>5+<italic>δ</italic></sub> 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 1,100°C helps in obtaining a single-phase, homogenous material with tetragonal <italic>I</italic>4<italic>/mmm</italic> symmetry. <italic>In situ</italic> X-ray diffraction and dilatometric studies show excellent phase stability up to 1,100°C in air, with the average thermal expansion coefficient of 23.7∙10<sup>–6</sup> K<sup>−1</sup> within the 25–1,100°C range. Total electrical conductivity of the metallic character exceeds 1,600 S cm<sup>−1</sup> at room temperature. Equilibrated oxygen content at room temperature is determined as 5.69. The cathodic polarization resistance of the (La,Pr,Nd,Sm,Gd)BaCo<sub>2</sub>O<sub>5+<italic>δ</italic></sub> layers, manufactured on the La<sub>0.8</sub>Sr<sub>0.2</sub>Ga<sub>0.8</sub>Mg<sub>0.2</sub>O<sub>2.8</sub> (LSGM) solid electrolyte of proved inertness, is as low as 0.037 Ω cm<sup>2</sup> at 900°C, and 0.175 Ω cm<sup>2</sup> at 750°C. The determined value of the power density in the LSGM-based, electrolyte-supported (thickness ca. 200 μm) fuel cell reaches 857 mW cm<sup>−2</sup>. 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 reported 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 Nd<sub>0.88</sub>Sm<sub>0.12</sub>Co<sub>2</sub>O<sub>5+δ</sub> composition, characterized by the same effective radius of the lanthanide cations.</p>