Cathode Materials for Reduced-Temperature SOFCs

Abstract

The progress toward a commercial solid oxide fuel cell ͑SOFC͒ continues to be a slow struggle due to materials, stacking, and system challenges. One long-term challenge has been the search for suitable cathode materials for use on intermediate ͑650-800°C͒ yttria-stabilized zirconia ͑YSZ͒ electrolytes and low-temperature ͑500-650°C͒ gadolinia-doped ceria ͑CGO͒ electrolytes. The present study has identified La͑Sr͒FeO 3 and possibly Pr͑Sr͒FeO 3 as potential cathode materials for YSZ. A La-deficient La͑Sr͒FeO 3 cathode has achieved an area-specific resistance of 0.1 ⍀ cm 2 at 800°C, with stable long-term performance. On CGO, Pr͑Sr͒CoO 3 , Gd͑Sr͒CoO 3 , and Sr͑Co/Fe) 1.5 O 3.25 have all achieved an area-specific resistance close to 0.1 ⍀ cm 2 at 650°C, with relatively stable long-term performance, but further reduction in temperature to 600°C is necessary for efficient CGO operation.

Materiais cerâmicos para células a combustível

“…Analogamente, sabe-se que nas perovskitas de (LaSr)FeO 3-x a substituição do Fe dos sítios B por Mn, Cr, Co e Ni aumenta a reatividade da fase perovskita com a zircônia [49]. Deve ser mencionado que a formação da(s) fase(s) pirocloro não ocorre se o La for substituído por cátions de terras raras com raios iônicos menores, como por exemplo Pr, ou se outros materiais, como por exemplo soluções sólidas à base de céria, são usados como eletrólito (Tabela II) [50]. Isso pode ser explicado pelo fato de que os compostos Pr 2 Zr 2 O 7 ou La 2 Ce 2 O 7 são termodinamicamente instáveis na temperatura de operação de células a combustível de óxido sólido.…”

NO x conversion on porous LSF15–CGO10 cell stacks with KNO3 or K2O impregnation

“…The stacks were subjected to electrochemical impedance spectroscopy and conversion/polarisation experiments while the gas composition was monitored by a mass spectrometer (MS) and a chemiluminiscense detector (CLD). The cell stacks differed from each other in the way they were impregnated: one stack had no impregnation, one stack was impregnated with KNO 3 and one stack was impregnated with K 2 O. LSF was chosen as electrode material, since LSF as a mixed conductor [18] [19] has been evaluated to be a promising material for intermediate temperate solid oxide electrodes [20] while CGO was chosen as an electrolyte, as CGO has superior oxygen ion-conductivity below 600 °C when compared to yttria stabilized zirconia [21]. KNO 3 /K 2 O was chosen for impregnation, as potassium is known to act both as a NO x -storage compound [22] and also to improve simultaneous NO x and soot removal [23,24], the latter being of interest for future development of the electrochemical deNO x technique.…”

An EIS study of La2 − x Sr x NiO4 + δ SOFC cathodes

“…On the cathode side several alternatives exist to * e-mail: kent.kammer.hansen@risoe.dk the classical LSM/YSZ (LSM = Strontium substituted Lanthanum Manganite, YSZ = Yttria Stabilised Zirconia) SOFC cathode. Among the alternative cathodes Co and FeCo based perovskites reveal the highest activity towards the reduction of oxygen [3].…”

“…The resulting powders were then transferred to alumina crucibles and the powders were calcined at 1100 o C/12 h in air in a box furnace. The metal nitrates used were the following: La(NO 3 ) 3 •6H 2 O (Alfa Aesar, 99.9 %), Sr(NO 3 ) 2 (Alfa Aesar, 99 %) and Ni(NO 3 ) 2 •6H 2 O (Fluka, 97 %). After calcination the powders were investigated with powder X-ray diffraction (XRD) using a Stoe theta-theta diffractometer equipped with Cu kα radiation.…”