Alkali free perovskites – Exploiting B-site synergies in Sr-free, high-entropy cathodes for intermediate-temperature Solid-Oxide fuel cells

• La(Co,Fe,Ga,X 1 ,X 2 )O 3 (X 1 , X 2 = Cu, Mg, Mn, Ni) high-entropy perovskites are obtained for the first time. • Cathodic polarization resistance is as low as 0.105 Ω·cm 2 at 700 °C for La(Co,Fe,Ga,Cu,Mn)O 3-δ. • The materials display an excellent combination of catalytic and functional features. • The IT-SOFC level of performance is achieved without alkali ion content. The degradation of cathode materials in Solid-Oxide Fuel Cells (SOFCs) remains one of the main issues of this technology. In most cases, the main reason behind these deleterious processes are the alkali dopants, which simultaneously are considered indispensable to achieve the sufficient level of the electrochemical performance. Here, by exploiting the synergies between selection of different B-site elements, we propose a new group of alkali-free, high-entropy La(Co,Fe,Ga,X 1 ,X 2 )O 3 (X 1 , X 2 = Cu, Mg, Mn, Ni) perovskites as potential air-electrode materials for intermediate-temperature SOFCs (IT-SOFCs). Four out of six materials studied are single-phase, exhibiting similar oxygen non-stoichiometry behavior, with its little to no temperature dependence. Electrical properties vary significantly in the series, showing behavior outside of the typical predictions of the rule-of-mixtures. All materials exhibit favorable thermomechanical behavior, combined with good thermal and chemical stability, in the latter case toward typical GDC and LSGM electrolytes. Electrochemical performance appears to be especially promising in the case of La(Co,Fe,Ga,Cu,Mn)O 3-δ and La(Co,Fe,Ga,Cu,Ni)O 3-δ , for which the cathodic polarization resistance reaches the typical 0.15 Ω·cm 2 threshold at 684 and 754 °C, respectively. Such qualities are achieved despite the lack of alkali A-site dopants, potentially providing additional benefits in terms of longevity and decreased susceptibility to Cr and CO 2 -poisoning effects, making both materials an attractive alternative to state-of-the-art electrocatalysts.