Multicomponent Gd1-xSmxBa0.5Sr0.5CoCuO5+δ double perovskites as oxygen electrodes for Solid Oxide Cells: Effect of chemical composition and electrospun morphology

Multicomponent Gd1-xSmxBa0.5Sr0.5CoCuO5+δ double perovskites are optimized for application in terms of chemical composition and morphology for the use as oxygen electrodes in Solid Oxide Cells. Structural and studies of other physicochemical properties are conducted on a series of materials obtained by a sol-gel method having a different ratio of Gd and Sm cations. It is documented that changing of the x value, and the resulting adjustment of the average ionic radius, has a significant impact on the crystal structure, stability, as well as on the total conductivity and thermomechanical properties of the materials, with the best results obtained for the Gd0.75Sm0.25Ba0.5Sr0.5CoCuO5+δ composition. Oxygen electrodes are prepared using the selected compound, allowing to obtain low polarization resistance values, e.g. 0.087 Ω cm2 at 800 °C. Systematic studies of electrocatalytic activity were conducted using La0.8Sr0.2Ga0.8Mg0.2O3-δ as the electrolyte for all electrodes, and Ce0.8Gd0.2O2-δ electrolyte for the best performing Gd0.75Sm0.25Ba0.5Sr0.5CoCuO5+δ electrodes. The electrochemical data were analyzed using the Distribution of Relaxation Times (DRT) method. Also, the influence of the preparation method of the electrode material is investigated, with using the electrospinning technique. Finally, the performance of the Gd0.75Sm0.25Ba0.5Sr0.5CoCuO5+δ electrodes is tested in a Ni-YSZ anode-supported cell with a Ce0.8Gd0.2O2-δ buffer layer, in the fuel cell and electrolyzer operating modes. With the electrospun electrode, a power density of 0.46 W cm-2 is obtained at 700 °C, with a current density of ca. 0.2 A cm-2 at 1.3 V for the electrolysis at the same temperature, indicating better performance compared to the sol-gel-based electrode.