A composite cathode based on scandium-doped chromate for direct high-temperature steam electrolysis in a symmetric solid oxide electrolyzer

Composite cathodes based on La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) are promising candidates for direct steam electrolysis while their insufficient electro-catalytic activity still restricts Faradic efficiency and electrode performance. In this work, scandium is doped into LSCM (LSCMS) to enhance the performance of the composite cathode. The combined characterization of XRD, TEM, TGA and XPS indicates successful partial replacement of Cr/Mn by scandium in the B site of chromate. The doping of scandium remarkably improves ionic conductivity while accordingly decreases the mixed conductivity. Electrochemical measurements demonstrate the decreased electrode polarizations of LSCMS cathodes. The Faradic efficiencies are accordingly enhanced by 20% and 50% compared with the electrolyzer with LSCM cathode for high temperature steam electrolysis by exposing cathode to 5%H₂O/5%H₂/Ar and 5%H₂O/Ar, respectively.