Early interaction between Fe–Cr alloy metallic interconnect and Sr-doped LaMnO₃ cathodes of solid oxide fuel cells

Abstract

The initial stages of the interaction between the Fe-Cr alloy metallic interconnect and Sr-doped LaMnO 3 (LSM) electrode of solid oxide fuel cells (SOFC) were investigated under cathodic polarization at the temperature range of 700-900°C. Cr deposits on the Y 2 O 3 -ZrO 2 (YSZ) electrolyte surface increased with the polarization time. However, it was observed that at the early stages of the reaction, there is no preferential Cr deposition at the three-phase boundary areas at the LSM electrode/YSZ electrolyte interface region. With the decrease of the temperature the Cr deposition reduced significantly, probably due to the significant reduction in the partial pressure of the gaseous Cr species and the cationic diffusivities in the LSM electrode. The results clearly demonstrated that the deposition of Cr species at the LSM electrode/YSZ electrolyte is basically a chemical reaction and kinetically controlled by the nucleation reaction between the gaseous Cr species and the Mn 2+ species generated under cathodic polarization.

Effect of cathode and electrolyte transport properties on chromium poisoning in solid oxide fuel cells

“…This preferential Cr 2 O 3 deposition at the three-phase boundary (electrolyte-electrode-gas), where the chromium-containing gas, oxygen vacancies and electron holes are available, as shown schematically in Fig. 2, supports the electrochemical mechanism [18,20,23,26,27,31,32,36]. The deposition reaction shown in Fig.…”

“…Although such an increase in the amount of degradation with increasing temperature has been observed [31], this is not always the case. For example, Kaun et al [30] and Kim et al [39] reported that the amount of degradation increased as the temperature was decreased from 800 to 700 • C and 850 to 750 • C, respectively.…”

“…The chromium transport occurs primarily through the formation of Cr 6+ -containing species, such as CrO 3 or CrO 2 (OH) 2 , from oxidation of chromium oxide in the interconnect [9][10][11][12][13][14][15][16][17]. Chromium poisoning has been observed in chromium-based [18,19], nickel-based [20][21][22][23] and iron-based [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] interconnect alloys, so that one of the objectives in the design of new alloys for SOFC interconnects is to reduce scale volatilization. One alloying addition used to reduce volatilization is manganese, which is incorporated in the oxide scale and leads to the formation of a (Mn,Cr) 3 O 4 spinel layer on the scale surface.…”

Novel Composite Materials for SOFC Cathode-Interconnect Contact

“…However, it has been widely observed that volatilized chromium vapor species readily react with LSM to form both (Mn,Cr) 3 O 4 and (La,Sr)(Cr,Mn)O 3 in SOFC environments [28][29][30]. The work by Jiang et al [31] demonstrated that Cr deposition at the LSM/YSZ interface was primarily due to the generation of Mn 2+ ions during cathodic polarization, which readily reacted with the CrO 3 vapor species to form (Mn,Cr) 3 O 4 on the YSZ surface. This not only confirmed the reactivity of LSM with Cr vapor species but also indicated that the Mn-Cr spinel was not captured by or attached to the LSM surface; rather, the spinel deposited preferentially on the yttria-stabilized zirconia (YSZ).…”

Electrically Conductive, Corrosion-Resistant Coatings Through Defect Chemistry for Metallic Interconnects

“…However, rapid oxidation kinetics, easy spalling tendency of the oxide scale and the formation of chromia as an oxide (which has a high electrical resistivity and a high volatility as hexavalent Cr [5][6][7]) restrict the use of many of the commercially available iron-based and nickel-based alloys as SOFC interconnect to short term applications. Currently, FeCr alloys are being explored for application as SOFC interconnect [8][9][10][11][12]. The Fe-Cr alloys, typically ferritic stainless steels, are generally better matched in thermal expansion coefficient (around 11-13 x 10 -6 K -1 ) with that of other cell components than Ni-Cr alloys, and are relatively inexpensive.…”