Improved Durability of High-Performance Intermediate-Temperature Solid Oxide Fuel Cells with a Ba-Doped La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ Cathode

Abstract

As a device for direct conversion of chemical energy into electrical energy, the solid oxide fuel cell (SOFC) contributes positively to the sustainable development strategy. However, the commercialization of fuel cells is still impeded by severe cathode degradation caused by its limited stability at operating temperatures and being prone to Cr-poisoning from Cr-containing alloy interconnectors commonly used in these cells. This paper reports the development of a high-durability Ba-doped LSCF(La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ ) cathode material under realistic fuel cell operating conditions in the presence of the Cr alloy. In particular, when tested in a symmetrical cell constructed of Ba-doped LSCF, the polarization resistance of the cell remains very low at 0.06 Ω cm 2 after being tested at 800 °C for 120 h exposed to Cr in 3% humidified air. In contrast, for the undoped LSCF under the same testing conditions, the polarization resistance of the cell increases ∼10 times from 0.22 Ω cm 2 of the pristine cell to 2.18 Ω cm 2 after Cr-exposure testing. Furthermore, when tested in an anode-supported complete cell as a cathode under typical SOFC operation conditions at 750 °C, the cell with the Ba-doped LSCF cathode displays significantly low degradation rates of 0.00056% h −1 (without Cr) and 0.00310% h −1 (with Cr); both are much lower than that of the cell using the undoped LSCF cathode (0.00124% h −1 without Cr and 0.01082% h −1 with Cr). This enhanced durability and Cr-tolerance exhibited by the Ba-doped LSCF cathode stem from its higher crystal structure stability and improved chemical resistance compared to undoped LSCF.

Heterogeneous Catalyst Coating for Boosting the Activity and Chromium Tolerance of Cathodes for Solid Oxide Fuel Cells

“…The significant Cr tolerance of Ba-containing cathodes or promoters has also been observed by many research groups. [17][18][19][20][21][22][23][24][25][26]31,34,69] The Cr tolerance mechanism of the CC-LSCF cathode is schematically illustrated in Figure 8.…”

“…[ 8–10 ] Volatile Cr species can also be captured by inserting a layer of catcher material on the cathode, [ 11,12 ] although maintaining the adsorption capability and structural stability of the catcher is challenging in the harsh environment. Researchers have also developed Cr‐resistant cathode materials, such as La(Ni, Fe)O 3–δ [ 13,14 ] and Re 2 NiO 4–δ (Re = Nd, La, Pr), [ 15,16 ] as well as Ba‐containing [ 17–24 ] and high‐entropy perovskite electrodes. [ 25–27 ] However, relying on a single phase to simultaneously meet the stringent requirements of an ideal cathode, such as high electrocatalytic activity and excellent Cr durability, is almost impossible, whereas the design and development of a multiphase cathode provides new opportunities.…”

Review on Fe-based double perovskite cathode materials for solid oxide fuel cells

“…The attention was quickly shifted to perovskite oxides (see Note below), such as La 1-x Sr x MnO 3 , when it was discovered to have excellent oxygen catalytic activity at 800-1,000 °C [12] . However, as a pure electronic conductor, the ORR could only occur at the interface of the cathode and electrolyte [13] . This results in very limited catalytic efficiency of the cathode.…”

A Low-Lewis-Acid-Strength Cation Cs+-Doped Double Perovskite for Fast and Durable Oxygen Reduction/Evolutions on Protonic Ceramic Cells

“…While several air electrode materials have been presented, most of them only exhibit insufficiently high electrochemical performance in R-PCECs, even though considerable attempts have been made in the past few decades. − Considerable studies have concluded that Co-containing air electrode materials exhibit high catalytic activity in both ORR ,, and OER. ,, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3‑δ (LSCF6428), as one of the traditional mixed ionic and electronic air electrode materials, has been widely used in oxygen-ion conducting solid oxide fuel cells (O-SOFCs) − and protonic ceramic fuel cells (PCFCs) , due to its excellent catalytic activity. However, the performance of cells with LSCF6428-based air electrodes shows a fast degradation since Sr segregation on the air electrode surface is prone to forming another destructive secondary phase (such as SrCO 3 , SrO or Sr­(OH) 2 ), limiting the catalytic activity of electrode materials. , Designing a Sr-free Co-based air electrode with high activity has recently attracted great attention. ,, Due to its excellent electronic conductivity and oxygen ionic conductivity, rapid oxygen surface exchange, and oxygen ion bulk diffusion kinetics, a double-perovskite material PrBaCo 2 O 5+δ (PBC) has demonstrated desirable electrochemical performance as the air electrode for SOFCs. , For instance, Ca-doped PBC (PrBa 0.8 Ca 0.2 Co 2 O 5+δ ) double-perovskite oxide exhibited an outstanding ORR electrocatalytic activity as a highly promising electrode material for SOFCs .…”