Nanoscaled (La[sub 0.5]Sr[sub 0.5])CoO[sub 3−δ] Thin Film Cathodes for SOFC Application at 500°C<T<700°C

Abstract

Nanoscaled and nanoporous ͑La 0.5 Sr 0.5 ͒CoO 3−␦ ͑LSC͒ thin film cathodes ͑film thickness ranging from 200 to 300 nm, grain and pore size in the range of 50 nm͒ were electrochemically characterized to determine their potential for intermediate and lowtemperature solid oxide fuel cells ͑SOFCs͒. Chemically homogeneous, large area ͑25 cm 2 ͒, and nanoporous LSC thin films were derived from metallorganic precursors ͑metallorganic deposition͒ and deposited on yttria-doped zirconia ͓͑YSZ͒ "design 1"͔ and gadolinia-doped ceria ͓͑GCO͒ "design 2"͔. The area-specific polarization resistance ͑ASR pol ͒ of both designs was evaluated on symmetrical cells with special emphasis on constancy, depending on temperature ͑500-850°C͒ and time by means of electrochemical impedance spectroscopy. For both designs, we report the capability of low polarization resistances, e.g., at 600°C, 146 m⍀ cm 2 ͑LSC/YSZ͒, respectively, 130 m⍀ cm 2 ͑LSC/GCO͒. Oxygen reduction reaction was facilitated by a substantial inner surface area of the porous thin-film cathode, as suggested by the application of Adler's model. Nanoporous LSC thin-film cathodes from this study were compared to alternative design concepts for high-performance porous cathodes and with dense ͑La 0.52 Sr 0.48 ͒͑Co 0.18 Fe 0.82 ͒O 3−␦ thin-film cathodes. Furthermore, the aim of our study was ͑i͒ to find a temperature regime with a perspective for chemical durability of an LSC/YSZ interface. We could prove that at a temperature of 500°C and for 100 h, polarization resistance of the LSC/YSZ interface remains constant, and at unreported low values, which reopens LSC/YSZ for micro-SOFC application; ͑ii͒ to estimate the structural durability of nanoscaled and nanoporous LSC thin-film cathodes. We have been able to demonstrate stable and unreported low polarization resistance for LSC/GCO in the temperature range between 500 and 700°C, which is of technical interest for auxiliary-power-unit application.

Porous La0.6Sr0.4CoO3−δ thin film cathodes for large area micro solid oxide fuel cell power generators

“…Indeed, some attempts have been already reported on the development of pure oxide-based electrodes for fabricating fully-ceramic µSOFC, based on state-of-the-art materials on bulk SOFC systems working as cathodes [19][20][21][22][23][24][25][26][27] or anodes [28]. However, only few results have been reported on µSOFC performance using ceramic electrodes [29][30][31][32].…”

Micro-solid oxide fuel cells: status, challenges, and chances

“…Other common cathode materials in micro-SOFCs with operating temperatures of below 600°C are ABO 3 perovskites, such as mixed conducting lanthanum strontium cobalt (LSC) oxide [59][60][61], lanthanum strontium cobalt iron oxide (LSCF) [62][63][64][65][66] and barium strontium cobalt iron oxide (BSCF) [67][68][69]. Most of the studies reported so far in the literature on cathodes for micro-SOFCs essentially focus on the investigation of oxygen reduction mechanisms with geometrically well- Fig.…”

An Isothermal Study of the Electrochemical Performance of Intermediate Temperature Solid Oxide Fuel Cells

“…(IT-SOFCs) [9] [10]; these may be achieved by either reducing the thickness of the electrolyte which reduces its ohmic resistance [11] [12] [13], developing new electrodes with improved catalytic activities which reduce overpotential [14] [15] [16] [17] or improving the electrode microstructure which increases the electrochemical reaction area [3] [18] [19].…”