Fe-based double perovskite with Zn doping for enhanced electrochemical performance as intermediate-temperature solid oxide fuel cell cathode material

This study aims to investigate the implications of transition-metal Zn doping at the B-site on the crystal structure, average thermal expansion coefficient (TEC), electrocatalytic activity, and electrochemical performance of LaBaFe(2)O(5+δ) by preparing LaBaFe(2−x)Zn(x)O(5+δ) (x = 0, 0.05, 0.1, 0.15, 0.2, LBFZ(x)). The X-ray diffraction (XRD) results show that Zn(2+) doping does not change the crystal structure, the unit cell volume increases, and the lattice expands. The X-ray photoelectron spectroscopy (XPS) and mineral titration results show that the oxygen vacancy concentration and Fe(4+) content gradually increase with the increase in doping amount. TEC decreases with the increase in Zn(2+) doping amount, and the TEC of LBFZ(0.2) is 11.4 × 10(−6) K(−1) at 30–750 °C. The conductivity has the best value of 103 S cm(−1) at the doping amount of x = 0.1. The scanning electron microscopy (SEM) images demonstrate that the electrolyte CGO(Gd(0.1)Ce(0.9)O(1.95)) becomes denser after high-temperature calcination, and the cathode material is well attached to the electrolyte. The electrochemical impedance analysis shows that Zn(2+) doping at the B-site can reduce the (R(p)) polarization resistance, and the R(p) value of the symmetric cell with LaBaFe(1.8)Zn(0.2)O(5+δ) as cathode at 800 °C is 0.014 Ω cm(2). The peak power density (PPD) value of the anode-supported single cell is 453 mW cm(−2), which shows excellent electrochemical performance.