Ag Thin Film Cathode for LSGM Electrolyte LT-SOFCs

Abstract

A composite Ag-La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 (LSGM) thin film cathode was synthesized on the LSGM electrolyte successfully by a simultaneous RF sputtering of Ag and LSGM. Microstructure of the thin composite film cathode was examined by FE-SEM and EDX. Nano-size LSGM particles existed in the grain boundary of the Ag thin film, and prevented the agglomeration of Ag. As a result, crystal grains of the Ag thin film cathode became small, and although it was a thin film, it had high thermal stability. The coexistence of Ag and LSGM was investigated by FE-SEM, and EDX. There was no elemental migration between Ag and LSGM. The initial performance and durability of the composite Ag-LSGM thin film as reduced-temperature SOFCs (LT-SOFCs) cathode operated at 500 to 600 o C were studied by the three-probe ACimpedance method. The composite Ag-LSGM thin film cathode has a larger cathodic interfacial conductivity , σ E , than that of the pure Ag thin film cathode.

Determination of Oxygen Pathway in Silver Cathodes by Secondary-Ion Mass Spectroscopy Using Oxygen Isotope Exchange

“…However, as the operating temperature decreases, the performance of SOFCs decreases drastically as a result of an increase in cathode resistance. In order to reduce this effect, silver has been investigated as a cathode material [2][3][4][5][6][7][8][9][10][11][12][13][14] because of its high catalytic-activity for oxygen reduction in low-operating-temperature SOFCs (around 500 • C). 2,7 The evaporation rate of silver during SOFC operation was reported by Lu et al 15 to be negligible (e.g., 3 × 10 −15 g cm −2 s −1 ).…”

Influence of Dispersed Ceramic Nanoparticles on Microstructure and Performance of the Ag Thin-Film Cathode in Solid Oxide Fuel Cells

“…[4][5][6][7][8][9][10][11][12][13][14] Sasaki et al and Muranaka et al noted the high permeability of oxygen through Ag, the high conductivity of Ag, and its high catalytic activity and investigated the use of a Ag thin film as the cathode to realize low temperature operating SOFCs. [7][8][9][10][11][12][13] In the Ag thin-film cathode, the oxide ions from the cathode can be transferred into the electrolyte through the entire Ag/electrolyte interface. 4,9 Sasaki et al fabricated a pure Ag thin-film cathode using the radio-frequency ͑rf͒ magnetron sputtering method.…”

“…[7][8][9][10][11][12][13] In the Ag thin-film cathode, the oxide ions from the cathode can be transferred into the electrolyte through the entire Ag/electrolyte interface. 4,9 Sasaki et al fabricated a pure Ag thin-film cathode using the radio-frequency ͑rf͒ magnetron sputtering method. 9 Due to the low melting point of Ag ͑962°C͒, the grains of the pure Ag thin-film cathode grew to 5 m in diameter and holes were formed during annealing in air at 600°C for 100 h. This hole formation results in a decrease in the area of the Ag/electrolyte interface.…”

“…4,9 Sasaki et al fabricated a pure Ag thin-film cathode using the radio-frequency ͑rf͒ magnetron sputtering method. 9 Due to the low melting point of Ag ͑962°C͒, the grains of the pure Ag thin-film cathode grew to 5 m in diameter and holes were formed during annealing in air at 600°C for 100 h. This hole formation results in a decrease in the area of the Ag/electrolyte interface. A film thickness of about 5 m is required to prevent hole formation; however, the cathode resistance of pure Ag increases with increasing film thickness.…”

“…A film thickness of about 5 m is required to prevent hole formation; however, the cathode resistance of pure Ag increases with increasing film thickness. 9 Muranaka et al demonstrated the high performance of the Ag-La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.9 ͑LSGM͒ composite thin-film cathode, in which the dispersed LSGM nanoparticles inhibit the grain growth of Ag. 10,11 As the concentration of the dispersed LSGM nanoparticles increased, the size of the Ag grains in the cathode decreased, and the area specific resistance ͑ASR͒ of the cathode also decreased.…”