resumo
The submicron powder of La(2)Ni(0.8)Cu(0.2)O(4+delta) with K(2)NiF(4)-type structure, having grain size of 30-60 nm, was synthesized via glycine-nitrate process (GNP) and used for the preparation of porous cathode layers applied onto (La(0.9)Sr(0.1))(0.98)Ga(0.8)Mg(0.2)O(3-delta) (LSGM) solid electrolyte. In air, dense ceramics of LaNi(0.8)Cu(0.2)O(4+delta) possess thermal expansion coefficient of 13.3 x 10(-6) K(-1) at 400-1240 K, p-type electronic conductivity of 50-85 S/cm at 800-1300 K and relatively high oxygen permeability limited by the surface exchange. These properties provide a substantially high performance of porous electrodes, exhibiting cathodic overpotential lower than 50 mV at 1073 K and current density of 200 mA/cm(2). As for the oxygen transport through dense membranes, the results on electrode behavior, including the overpotential-microstructure relationships and the p(O(2)) dependence of polarization resistance, suggest that the cathodic reaction rate is affected by surface-related processes. Due to this, electrode performance can be considerably enhanced by surface activation, particularly via impregnation with Pr-containing solutions, and also by decreasing fabrication temperature. At 873 K, the surface modification with praseodymium oxide decreases overpotential of La(2)Ni(0.8)Cu(0.2)O(4+delta) cathode, screen-printed onto LSGM and annealed at 1473 K, from 330 down to approximately 175 mV at 50 mA/cm(2). (C) 2003 Elsevier B.V. All rights reserved.
palavras-chave
OXIDE FUEL-CELLS; MG-DOPED LAGAO3; ELECTROCHEMICAL PROPERTIES; STABILIZED ZIRCONIA; ION TRANSPORT; PERMEABILITY; CERAMICS; KINETICS; CATHODE; CONDUCTIVITY
categoria
Chemistry; Physics
autores
Kharton, VV; Tsipis, EV; Yaremchenko, AA; Frade, JR
nossos autores
Aleksey Yaremchenko
Investigador Principal
Jorge Ribeiro Frade
Professor(a) Jubilado(a)