Impact of Oxygen Deficiency on the Electrochemical Performance of K2NiF4-Type (La1-xSrx)(2)NiO4-delta Oxygen Electrodes

• Perovskite-related (La1-xSrx)(2)NiO4-delta (x= 0.5-0.8) phases were explored for possible use as oxygen electrodes in solid electrolyte cells with a main focus on the effect of oxygen deficiency on the electrocatalytic activity. (La1-xSrx)(2)NiO4-d solid solutions were demonstrated to preserve the K2NiF4-type tetragonal structure under oxidizing conditions. Acceptor-type substitution by Sr is compensated by the formation of oxygen vacancies and electron holes and progressively increases high-temperature oxygen nonstoichiometry, which reaches as high as d= 0.40 for x= 0.8 at 950 degrees C in air. The electrical conductivity of (La1-xSrx)(2)NiO4-d ceramics at 500-1000 degrees C and p(O-2) >= 10(-3) atm is p-type metallic-like. The highest conductivity, 300 Scm(-1) at 800 degrees C in air, is observed for x= 0.6. The average thermal expansion coefficients, (14.0-15.4) x 10(-6) K-1 at 25900 degrees C in air, are sufficiently low to ensure the thermomechanical compatibility with common solid electrolytes. The polarization resistance of porous (La1-xSrx)(2)NiO4-d electrodes applied on a Ce0.9Gd0.1O2-delta solid electrolyte decreases with increasing Sr concentration in correlation with the concentration of oxygen vacancies in the nickelate lattice and the anticipated level of mixed ionic-electronic conduction. However, this is accompanied by increasing reactivity between the cell components and necessitates the microstructural optimization of the electrode materials to reduce the electrode fabrication temperature.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

ceramics

electrochemistry

fuel cells

layered compounds

nonstoichiometric compounds

Publication and Content Type

ref (subject category)

art (subject category)