Oxygen vacancy concentration, electrochemical oxygen reduction, and performance stability of a LaNiO3- porous electrode

The oxygen vacancy concentration (δ), electrochemical reaction, and durability of LaNiO3-δ, a perovskite-type oxide, were determined as functions of temperature (773–1073 K) and oxygen partial pressure, p(O2). We established the δ value of LaNiO3-δ using high-temperature gravimetry and used the delocalized electron model to analyze by defect equilibrium. LaNiO3-δ has a higher oxygen partial molar enthalpy (△hO0) at δ ≈ 0 than other Ni-based oxides, which indicates that oxygen vacancies are easily formed. The electrochemical properties and durability of LaNiO3-δ were examined to investigate the oxygen reduction reaction and its long-term operational durability. Impedance spectra were analyzed using the distribution of relaxation times method, which separated the electrode reaction into three components: gas conversion/diffusion, reaction at the surface, and reaction at the electrode/electrolyte interface. Further electrochemical experiments demonstrated that the LaNiO3-δ porous electrode performs stably at 1073 K and − 0.2 A.cm−2 for 200 h.