Exploiting Zn and Zr synergy in co-doped Sr(Fe1-xMox)O3-δ – versatile Co-free electrode materials for Solid Oxide Fuel Cells

Abstract

Possessing high versatility, excellent stability under a wide range of oxygen partial pressures, and high catalytic activity, the perovskites from the Sr(Fe_1-xMo_x)O_3-δ (SFM) group have attracted a lot of attention, particularly with respect to the technology of conventional (SOFC) and symmetrical solid oxide fuel cells (S-SOFCs). However, their performance, especially as air electrodes, is still lacking compared to those of more specialized, dedicated cathodes. In this work, the co-doping of the conventional SrFe_0.75Mo_0.25O_3-δ material with Zn and Zr is proposed to improve its catalytic capabilities, through increased lattice basicity and oxygen nonstoichiometry. The impact of dopants is studied for the Sr(Fe_0.75Mo_0.25)_1-2xZn_xZr_xO_3-δ (x ≤ 0.2) series under both oxidizing and reducing atmospheres, including the evolution of the structure, oxygen non-stoichiometry, and transport properties. Evaluation of cathodic polarization resistance R p shows that the selected SrFe_0.6Mo_0.2Zn_0.1Zr_0.1O_3-δ material is characterized by superior cathodic performance compared to SFM, with an R_p value of 0.15 Ω•cm² at ca. 740 °C and a power density of a full cell equal to 978 mW•cm^-2 at 900 °C. This performance, excellent for a Co-free material, makes Sr(Fe_0.75Mo_0.25)_1-2xZn_xZr_xO_3-δ extremely promising candidate materials for SOFC/S-SOFC technology.