A New Family of Mo-Doped SrCoO3−δ Perovskites for Application in Reversible Solid State Electrochemical Cells

The effect of Mo doping on the crystal structure and thermal, electrical, and electrochemical properties of the SrCo1–x Mo x O3−δ (x = 0.05, 0.1) system has been studied. The introduction of Mo as a substitution for Co in SrCoO3−δ leads to a change from a hexagonal to a tetragonal perovskite structure at room temperature. The electrical conductivity is largely enhanced by the introduction of Mo at intermediate temperature due to the stabilization of the 3D-perovskite structure. However, the increase in Mo content decreases the total conductivity probably due to partial disruption of the electronic pathway. The use of these materials as cathodes in a solid-oxide fuel cell (SOFC) and as anodes in a solid oxide electrolyzer (SOE) has been evaluated, showing low values of electrode polarization resistances in both configurations over the intermediate temperature range. Interestingly, better performance was obtained under anodic polarization conditions reaching overpotential values as low as 28 mV for a current density of 210 mA·cm–2 at 700 °C. The good performance of the SrCo1–x Mo x O3−δ compounds in both cathodic and anodic conditions makes this system a promising candidate for reversible oxygen electrodes in cells that could operate as both SOFC and SOE.