B-Site Metal (Pd, Pt, Ag, Cu, Zn, Ni) Promoted La1−xSrxCo1−yFeyO3–δ Perovskite Oxides as Cathodes for IT-SOFCs

Abstract

Perovskite oxides La1−xSrxCo1−yFeyO3-δ (LSCF) have been extensively investigated and developed as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to mixed ionic-electronic conductivity and high electrooxygen reduction activity for oxygen reduction. Recent literature investigations show that cathode performances can be improved by metal surface modification or B-site substitution on LSCF. Although the specific reaction mechanism needs to be further investigated, the promoting effect of metal species in enhancing oxygen surface exchange and oxygen bulk diffusion is well recognized. To our knowledge, no previous reviews dealing with the effect of metal promotion on the cathodic performances of LSCF materials have been reported. In the present review, recent progresses on metal (Pd, Pt, Ag, Cu, Zn, Ni) promotion of LSCF are discussed focusing on two main aspects, the different synthesis approaches used (infiltration, deposition, solid state reaction, one pot citrate method) and the effects of metal promotion on structural properties, oxygen vacancies content and cathodic performances. The novelty of the work lies in the fact that the metal promotion at the B-site is discussed in detail, pointing at the effects produced by two different approaches, the LSCF surface modification by the metal or the metal ion substitution at the B-site of the perovskite. Moreover, for the first time in a review article, the importance of the combined effects of oxygen dissociation rate and interfacial oxygen transfer rate between the metal phase and the cathode phase is addressed for OPEN ACCESSCatalysts 2015, 5 367 metal-promoted LSCF and compared with the un-promoted oxides. Perspectives on new research directions are shortly given in the conclusion.

Tailoring SOFC Electrode Microstructures for Improved Performance

“…[174,175] Improvements were generally more pronounced at lower operational temperatures (500-650 °C) indicating the potential benefit of cathode infiltration with metal promoters for reduced temperature SOFCs. Guo et al [175] pointed out that the effect of metal promoter interaction with the lattice of the oxygen-ion conducting LSCF perovskite could be associated with the size of the metal cation in comparison with that of the A-site or B-site cation in the ABO 3 perovskite. Serra et al [165] experimented with Pd impregnation in LSCF and found by XPS that ≈20% of the Pd is present as metal and the rest exists in oxidized form, presumably incorporated into LSCF B-site.…”

“…Serra et al [165] experimented with Pd impregnation in LSCF and found by XPS that ≈20% of the Pd is present as metal and the rest exists in oxidized form, presumably incorporated into LSCF B-site. As illustrated by Guo et al [175] the loading level of transitional metal oxides and noble metals has an optimum above which the interfacial oxygen transfer can be negatively influenced as the promoting nanoparticles start to obstruct the interaction sites of interfacial O with the cathode surface oxygen vacancies (see Figure 10). Sakito et al [168] reported enhancement of maximum output power density by 1.5 times by infiltration of AgNO 3 solutions into porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 electrodes.…”

Powering Solid Oxide Fuel Cells with Syngas Using La0.4Sr0.5Ba0.1TiO3 Anode Infitrated with Nano‐composite

“…Herein, we introduce three types of infiltrates (Co, Cu and CeO 2 ). It is expected that the addition of Co and Cu can enhance the catalytic activity and carbon resistance, respectively . CeO 2 not only can increase the redox and thermal stabilities of the infiltrated Co or Cu, but also behave as an oxygen reservoir to enhance the carbon resistance of the anode.…”

Inkjet printing infiltration of Ni-Gd:CeO2 anodes for low temperature solid oxide fuel cells

“…Several detailed review papers have been published summarising some exceptionally encouraging results [6,8,[12][13][14][15][16][17][18]. The infiltrated inks were usually calcined at relatively low temperature, typically below 800°C, resulting in formation of distributed nanoparticles without detrimental chemical reaction between the scaffold and the infiltrate material.…”