Effect of Ni-based cathodic layer on intermediate temperature tubular electrolysis cell using LaGaO₃-based electrolyte thin film

NiO-YSZ tubular-type supported solid oxide electrolysis cell (SOEC) was prepared by dip-coating and co-sintering process for intermediate temperature steam electrolysis. To achieve a small overpotential, infiltration of Sm_0.5Sr_0.5CoO_3−δ (SSC) powder into porous La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) layer on dense LSGM electrolyte film was performed for the air electrode. In this study, the effect of the Ni-Sm_0.2Ce_0.8O_2−δ (Ni-SDC) and Ni-Fe₂O₃ (Ni-Fe) cathodic layer on steam electrolysis was further investigated. It was found that the Ni-based layer was effective for increasing electrolysis performance of the cell at low temperature in particular, but Ni-Fe layer was more effective. Impedance analysis suggests that this increased electrolysis performance of the cell using Ni-Fe layer was attributed to the decrease both in cathodic IR loss and overpotential. Electrolysis current density at 1.5 V was achieved to current density of 0.69, 0.47 and 0.28 A cm⁻² at 873, 823 and 773 K, respectively. In addition, the overpotential was also decreased by the insertion of Ni-SDC layer, which shows the mixed conductivity. The long-term stability of the cell when using Ni-SDC layer was also measured up to 150 h and stable electrolysis performance was demonstrated (degradation rate: around 1.9%/100 h).