La2NiO4+δ as oxygen electrode in reversible solid oxide cells

Abstract

The delamination of oxygen electrode during the electrolysis mode operation, which is mainly attributed to interfacial stress arising from the inability of oxygen electrode to accommodate oxygen species transported by oxide ion conducting electrolyte at the three phase boundary (TPB), has been major concern in the development of reversible solid oxide cell (RSOC) systems. The use of lanthanum nickelate, La2NiO4+δ (LNO) as a RSOC oxygen electrode, because of its ability to accommodate excess oxygen species in interstitial positions, can be helpful in reliving such interfacial stresses and thus mitigating the problem of delamination. In this work, the possibility of using LNO as an oxygen electrode in RSOCs is examined. The button cells with 10% gadolinium doped ceria (GDC10) electrolyte, Ni-GDC10 fuel electrode and LNO oxygen electrode are fabricated and their current–voltage–power (I–V–P) performance is analyzed in different gas conditions while operating in fuel cell mode in 500–650°C range. The button cell shows a maximum power density of ~0.19Wcm−2 at a current density of ~0.5Acm−2 at 650°C. Electrochemical impedance spectroscopy was performed in open circuit voltage (OCV) condition to analyze the various factors affecting the fuel cell performance. The long term operation of the fuel cell at a fixed input current of 0.1Acm−2 for 100h at 600°C indicates that the fuel cell is capable of stable performance. The microstructural analysis of the fuel cell after the long term operations indicates no structural degradation.