Comparative investigation of composition, microstructure and property influences on electrocatalysis of two representative cathodes: BaCo0.4Fe0.4Zr0.1Y0.1O3-δ versus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

Abstract

BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ (BCFZY) and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) perovskites are two representative high-performance cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here, symmetric cell tests demonstrate that polarization resistance values of BCFZY cathode are only 0.21–0.29 times those of BSCF cathode at 740–660 °C, and 0.21–0.26 times those of BSCF cathode at the oxygen partial pressures of 1.00–0.10 atm. Distribution of relaxation times (DRT) is applied to detect individual electrode processes overlapped in impedance spectra, which finds that the dominant processes of oxygen dissociation, subsequent species transfer and reduction on BCFZY cathode are superior to those of BSCF cathode. By temperature-programmed desorption of oxygen (O₂-TPD), thermal expansion coefficient (TEC) measurements, scanning electron micrograph (SEM) and energy dispersive spectra measurements, the strong oxygen combination ability with higher activation energy of oxygen desorption (E_d = 84 kJ mol^-1), peculiar surface state with evident nano-particle structure, more matchable TEC (19.0 × 10^-6 K⁻¹) and excellent interfacial connection with the electrolyte are observed on BCFZY cathode to account for its distinctive catalysis, as compared to BSCF cathode (E_d = 68 kJ mol^-1, TEC = 24.2 × 10^-6 K⁻¹).