Dual-Phase Cathodes for Metal-Supported Solid Oxide Fuel Cells: Processing, Performance, Durability

Abstract

Cathode processing is one of the main challenges in the manufacturing of metal-supported solid oxide fuel cells (MSCs). Cathode sintering in ambient air is not applicable to MSCs, as oxidation of the metal substrate and the metallic Ni of the anode damages the cell. A recently developed ex situ sintering procedure for the LSCF cathode in an argon atmosphere was shown to significantly improve cathode adherence. However, the stability of the sintered cathode layer posed a challenge during storage in ambient air. In the present work, adapting the ex situ sintering approach to LSC/GDC dual-phase cathodes not only enabled the ex situ sintering process to be applied to LSC-based cathodes, but also resulted in the superior stability of the cathode after sintering. Despite the hygroscopic properties of the partially decomposed perovskite, LSC/GDC dual-phase cathodes were shown to withstand more than 1 year of storage in ambient air without failure. Electrochemical single-cell measurements and post-test analysis confirmed the reversibility of phase transformations and the electrochemical activity of such dual-phase cathodes. Current densities of 1.30 A cm −2 at 750°C, 0.85 A cm −2 at 700°C, and 0.54 A cm −2 at 650°C were obtained at a cell voltage of 0.7 V.

Field-Assisted Sintering/Spark Plasma Sintering of Gadolinium-Doped Ceria with Controlled Re-Oxidation for Crack Prevention

“…Furthermore, it has potential as electrochemically active membrane material for oxygen transport membranes [ 4 ]. Recently, our group demonstrated that GDC increases electrochemical activity of Ni-based cermet anodes [ 5 , 6 ] as well as mechanical stability of perovskite cathodes in SOFC [ 7 ], making this material a bright future prospect for manifold applications in the chemistry and energy sector. However, processing of GDC as bulk or membrane material is a challenging task, which usually requires either high temperatures or careful atmosphere control as discussed in more detail below.…”

“…However, processing of GDC as bulk or membrane material is a challenging task, which usually requires either high temperatures or careful atmosphere control as discussed in more detail below. The complexity of processing GDC becomes even higher, when it is in contact with other functional materials, which is the usual case in electrochemical devices, e.g., in cermet electrodes [ 5 , 6 , 7 ] or dual phase membranes [ 4 ]. In this work, the focus will lie on problems and solutions in processing of pure GDC by Field-Assisted Sintering Technique, also known as Spark Plasma Sintering (FAST/SPS).…”

Degradation Mechanisms of Metal-Supported Solid Oxide Cells and Countermeasures: A Review

“…The solution to this problem is to design stable cathode nanometer catalytic materials. Compared with the infiltration method, ex situ sintering is another method that has been used to suppress the cathode’s degradation in recent years [ 119 , 120 , 121 , 122 , 123 ]. The sintering of the cathode on the whole cell is typically performed in argon at 950 °C.…”

“…However, La 2 O 3 was found during the sintering when LSC-based cathode was used, which led to the formation of La(OH) 3 and potentially decreased the performance and durability of cells [ 121 ]. LSC/GDC dual-phase cathode was used to suppress the degradation caused by La(OH) 3 because the rigid GDC network can additional mechanical stability for the cathode, according to Udomsilp et al (2019) [ 120 ].…”

Development of a processing map for safe flash sintering of gadolinium‐doped ceria

“…Thus, it is used as a catalyst, or as a catalyst support for chemical processing [3][4][5] . It also possesses high ionic conductivity between 500 to 600 °C 6,7 , which makes it a strong candidate for electrochemical devices like oxygen sensors 8,9 , oxygen transport membranes 10,11 , cermet electrodes [12][13][14] and electrolytes for solid oxide fuel and electrolysis cells (SOFC/SOECs) 6,7,15,16 .…”