Gd and cu co-doped BaFeO3-δ as a cobalt-free air electrode for solid oxide electrolysis cell

Solid oxide electrolysis cell (SOEC) is an efficient and environmentally friendly energy conversion device. The commercialization of SOEC is limited by the oxygen electrodes, whose problems include high costs and unexpected degradation of cobalt/strontium. In this study, we proposed a co-doping strategy and synthesized cobalt-free and strontium-free perovskite materials, specifically Ba 0.95 Gd 0.05 Fe 1-x Cu x O 3-δ (BGFCu x ), via the sol-gel method. These materials were evaluated as potential air electrodes for SOEC. The BGFCu x samples were systematically characterized by crystal structure, oxygen content, thermal properties, electrical conductivity, and electrochemical performance. X-ray diffraction results show that the solid-solution concentration of Cu in BGFCu x cannot exceed 0.1. X-ray photoelectron spectroscopy results suggest that Cu doping increases oxygen vacancy concentration. Among all BGFCu x perovskites, BGFCu0.1 exhibited a low polarization resistance of 0.069 Ω·cm 2 at 800 °C (0.2 V) and a high current density of 216 mA·cm −2 at an anodic bias of 40 mV. Hence, the Gd and Cu co-doped BGFCu0.1 perovskite material is a promising air electrode for SOEC. • Gd and Cu co-doping effectively stabilized the cubic structure of BFO at a sintering temperature of 900 °C. • Gd and Cu co-doped reduce the thermal expansion coefficient of Co-free perovskites. • Ba 0.95 Gd 0.05 Fe 0.9 Cu 0.1 O 3-δ exhibited superior electrochemical performance than other samples.