Ruddlesden–Popper type La$_{1.5-x}$Eu$_x$Pr$_{0.5}$Ni$_{0.9}$Cu$_{0.1}$O$_{4+\delta}$ as a potential cathode material for H-SOFC

As a potential cathode material, the La$_{1.5-x}$Eu$_x$Pr$_{0.5}$Ni$_{0.9}$Cu$_{0.1}$O$_{4+\delta}$ (LEPNC-$x$, $x$ = 0, 0.1, 0.2, 0.3, 0.4, 0.6, and 0.8) oxide is synthesized and studied. A pure Ruddlesden–Popper (R–P) type K$_2$NiF$_4$ structure can only be obtained for $x$ = 0.4 and lower. The thermal expansion coefficient (TEC) of Eu-doped LEPNC-$x$ stays almost constant with temperature, and decreases with increasing $x$. The optimal electrochemical performance of NiO-BZCY|BZCY|LEPNC-$x$ single cells can be achieved for $x$ = 0.2, although the corresponding electrical conductivity is the lowest. The result ofelectrochemical impedance spectra (EIS) also confirms this conclusion. EIS analysis suggests that the pre-exponential factor and activation energy of polarization resistance should be mainly determined by the electrical conductivity and oxygen ion diffusion of cathode material, respectively.