resumo
The cathodic performance of selected mixed-conducting electrodes, including perovskite-type SrMn(0.6)Nb(0.4)O(3 - delta), Sr(0.7)CeO(3)Mn(0.9)Cr(0.1)O(3) (- delta) and Gd(0.6)Ca(0.4)Mn(0.9)Ni(0.1)O(3 - delta), and Ruddlesden-Popper La(2)Ni(0.5)Cu(0.5)O(4) (+) (delta), LaSr(2)Mn(1.6)Ni(0.4)O(7 - delta) La(4)Ni(3 - x)Cu(x)O(10 - delta) (x=0-0.1) and La(3.95)Sr(0.05)Ni(2)CoO(10 - delta) was evaluated in contact with apatite-type La(10)Si(5)AlO(26.5) solid electrolyte at 873-1073 K and atmospheric oxygen pressure. The electrochemical activity of porous nickelate-based layers was found to correlate with the concentration of mobile ionic charge carriers and bulk oxygen transport, thus lowering in the series La(4)Ni(2.9)Cu(0.1)O(10 - delta) > La(4)Ni(3)O(10 - delta) > La(3.95)Sr(0.05)Ni(2)CoO(10 - delta) and decreasing on copper doping in K(2)NiF(4)-type La(2)Ni(1 - x)Cu(x)O(4 - delta). The relatively high overpotentials of nickelate-based cathodes, varying in the range - 240 to - 370 mV at 1073 K and current density of - 200 mA/cm(2), are primarily associated with surface diffusion of silica from La(10)Si(5)AlO(26.5), which partially blocks the electrochemical reaction zone. As compared to the intergrowth nickelate materials, the manganite-based electrodes exhibit substantially worse electrochemical properties, in correlation with the level of oxygen-ionic and electronic conduction in Mn-containing phases. The effects of cation interdiffusion between the cell components as a performance-deteriorating factor are briefly discussed. (C) 2009 Elsevier B.V. All rights reserved.
palavras-chave
FUEL-CELLS; ELECTRICAL-PROPERTIES; TRANSPORT-PROPERTIES; OXYGEN PERMEABILITY; REACTION-MECHANISMS; IONIC-CONDUCTIVITY; EXPANSION; SYSTEM; GD; ND
categoria
Chemistry; Physics
autores
Yaremchenko, AA; Kharton, VV; Bannikov, DO; Znosak, DV; Frade, JR; Cherepanov, VA
nossos autores
Aleksey Yaremchenko
Investigador Principal
Jorge Ribeiro Frade
Professor(a) Jubilado(a)