Preparation and electrical properties of cathode material based on zinc-doped Sr₂Fe_1.5Mo_0.5O₆ for solid oxide fuel cells

A novel solid oxide fuel cell cathode material based on Zn-doped Sr₂Fe_1.5Mo_0.5O₆ is synthesized by combustion method. The structural, chemical compatibility, and electrochemical properties are investigated. Results show that Sr₂Fe_1.5−xZn_xMo_0.5O_6-δ (SFZn_xM) retains the perovskite structure when Fe element in Sr₂Fe_1.5Mo_0.5O₆ is partially replaced by Zn. The thermal expansion coefficient of Sr₂Fe_1.5Mo_0.5O₆ increases with Zn doping remarkably, so doping with excessive Zn is detrimental to the chemical compatibility of SFZn_xM cathode with gadolinium-doped ceria (GDC) electrolyte. The conductivity of Sr₂Fe_1.5Mo_0.5O₆ is improved by doping with appropriate content of Zn, and the maximal electrical conductivity of 27.3 S cm⁻¹ at 450 °C is measured for the Sr₂Fe_1.45Zn_0.05Mo_0.5O_6-δ cathode. Electrochemical performance of symmetrical cell with configuration of SFZnxM/SDC/SFZnxM are evaluated using wet H₂. The symmetrical cell with the structure of SFZn_0.05M/SDC/SFZn_0.05M shows the maximum power density of 636 mW cm⁻² at 800 °C. As a result, Sr₂Fe_1.5−xZn_xMo_0.5O_6-δ is a potentially cathode material for solid oxide fuel cells.