Assessment of the Cathode Contribution to the Degradation of Anode-Supported Solid Oxide Fuel Cells

Abstract

The degradation of anode-supported cells was studied over 1500 h as a function of cell polarization either in air or oxygen on the cathode side. Based on impedance analysis, contributions of the anode and cathode to the increase of total resistance were assigned. Accordingly, the degradation rates of the cathode were strongly dependent on the pO 2 . Microstructural analysis of the cathode/electrolyte interface carried out after removal of the cathode showed craters on the electrolyte surface where the lanthanum strontium manganite ͑LSM͒ particles had been located. The changes of shape and size of these craters observed after testing correlated with the cell voltage degradation rates. The results can be interpreted in terms of element redistribution at the cathode/ electrolyte interface and formation of foreign phases giving rise to a weakening of local contact points of the LSM cathode and yttria-stabilized zirconia electrolyte and consequently a reduced three-phase boundary length.

Progressive activation of degradation processes in solid oxide fuel cells stacks: Part I: Lifetime extension by optimisation of the operating conditions

“…This is not included in the present study, because a consistent set of data on the temperature dependence of the evolution of the area specific resistance (ASR) of coated MIC could not be found. The relation by Liu et al [35] [40]. It should be emphasised that depending on the humidity, other phenomena, not necessarily related to chromium contamination, may predominantly cause the degradation of the LSMeYSZ cathode [41].…”

Evaluation of Metal Supported Ceria Based Solid Oxide Fuel Cell Fabricated by Wet Powder Spray and Sintering

“…After 1375 h, the arc at the high frequency seems to grow, with its peak frequency shifting toward the low frequency from 5.0 ϫ 10 2 Hz at 1375 h to 1.6 ϫ 10 2 Hz at 2700 h, and the overall resistance increases by 0.19 ⍀ cm 2 .I nt h e nickel-cermet anode supported zirconia cells tested for 1500 h at 750°C at various current densities, the high frequency arc is reported to increase with increasing current densities. 31 Compared to the change in the overall resistance, the ohmic resistance change is only 0.05 ⍀ cm 2 , and high current density operation is found to deteriorate polarization resistance. Because the range of the high frequency arc observed on a cell under open potential is closer to that of an arc observed on the cathode symmetrical cell, the high frequency arc is thought to reflect polarization in the cathode rather than polarization in the anode.…”

The Effects of Dynamic Dispatch on the Degradation and Lifetime of Solid Oxide Fuel Cell Systems

“…A typical compressed air steam content of 0.1% is assumed. 5 The gaseous CrO 2 (OH) 2 content is governed by mass transport limitations, as suggested by Opila et al 42,43 The equilibrium partial pressures for all chromium species are computed from thermodynamic data produced by Ebbinghaus et al 44 for a Cr 2 O 3 oxide. The modeling here of a Cr 2 O 3 MIC oxide scale yields excessive predictions for chromium contamination since coatings reduce the release of chromium volatile species.…”

“…45,46 (v) Electrically-insulating LZO/SZO phases cause severe detrimental effects on LSM-YSZ cathode performance. 5 A lack of quantitative data inhibits detailed modeling, but sufficient data exist to enable prediction of the onset of formation. The thermodynamic data on the critical oxygen partial pressure from Liu et al 6 is interpolated and compared with the local one, computed from the local overpotential in the LSM-YSZ cathode and oxygen gas phase concentration.…”

“…Cathodes made of lanthanum strontium manganite and yttria-stabilized zirconia (LSM-YSZ) composite or of single-component lanthanum strontium cobaltite ferrite (LSCF) are subjected to chromium contamination and formation of lanthanum (LZO) or strontium zirconate (SZO) phases with low electrical conductivity. [1][2][3][4][5][6] Nickel-based (Ni-YSZ) anodes suffer from sulfur poisoning, nickel particle coarsening and re-oxidation. 7,8 The ohmic losses increase in a SOFC stack due to the oxidation of the metallic interconnects (MIC) and decrease of the ionic conductivity of YSZ.…”