Study on the effects of configuration entropy to electrochemical properties of A2BO4-type cathode materials for SOFCs

High entropy oxides are one of the research topicalities in the field of SOFC. However, the relationship between configuration entropy and the electrochemical properties of these materials is not well understood. Here, a medium entropy material (La 0.2 Pr 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 CuO 4 ((Ln 0.2 ) 2 CuO 4 ) derived from Nd 2 CuO 4 material is designed. It was found that increasing the configuration entropy of the A-site promotes the production of highly reactive/concentrated non-stoichiometric oxygen and increases the covalency of the Cu3d-O2p orbital. The polarization impedance of (Ln 0.2 ) 2 CuO 4 is 0.92 Ω cm 2 at 700 °C, which is smaller than that of Nd 2 CuO 4 (1.8 Ω cm 2 at 700 °C). The peak power density of single cells NiO-YSZ|YSZ|GDC|cathode is 526 mW cm −2  at 700 °C within 60 h of stable operation at 0.5 V. First-principles calculations demonstrate that (Ln 0.2 ) 2 CuO 4 has lower charge transfer energy, which promotes the electronic conduction. Furthermore, the dissociation energy of adsorbed oxygen (O ad ) on the surface of (Ln 0.2 ) 2 CuO 4 is 2.24 eV, which is smaller than that of Nd 2 CuO 4 (2.26 eV). These results suggest that the entropy-increasing strategy can enhance the electrocatalytic performance.