Enhanced Anode Performance and Coking Resistance by In Situ Exsolved Multiple-Twinned Co–Fe Nanoparticles for Solid Oxide Fuel Cells

Abstract

The broad and large-scale application of solid oxide fuel cells (SOFCs) technology hinges significantly on the development of highly active and robust electrode materials. Here, Ni-free anode materials decorated with metal nanoparticles are synthesized by in situ reduction of Fe-doping Sr 2 CoMo 1−x Fe x O 6−δ (x = 0, 0.05, 0.1) double perovskite oxides under a reducing condition at 850 °C. The exsolved nanoparticles from the Sr 2 CoMo 0.95 Fe 0.05 O 6−δ (SCMF0.05) lattice are Co−Fe alloys with rich multipletwinned defects, significantly enhancing the catalytic activity of the SCMF0.05 anode toward the oxidation of H 2 and CH 4 . The electrolyte-supported single cell with the reuduced SCMF0.05 anode reaches peak power densities as high as 992.9 and 652.3 mW cm −2 in H 2 and CH 4 at 850 °C, respectively, while maintaining superior stability (∼50 h at 700 °C). The reduced SCMF0.05 anode also demonstrates excellent coking resistance in CH 4 , which can be attributed to the increased oxygen vacancies due to Fe doping and the effective catalysis of multiple-twinned Co−Fe alloy nanoparticles for reforming of CH 4 to H 2 and CO. The findings in this work may provide a new insight for the design of highly active and durable anode catalysts in SOFCs.

Trends and Prospects of Bimetallic Exsolution

“…Exsolution of Fe−Co nanoparticles has also been studied extensively usually as anode materials for SOFCs and similar to their Fe−Ni counterparts, they demonstrate a plethora of promising properties such as high activity, stability, coking resistance and sulfur tolerance [6b, c, 7e–g] . A Co‐doped La 0.6 Sr 0.4 FeO 3‐δ (LSF) anode was found to achieve high power density and lower polarization resistance in a SOFC cell as compared to its Mn‐doped counterpart due to the high catalytic activity of the exsolved Fe−Co particles towards hydrogen oxidation and the higher oxygen‐ion conductivity of the newly formed LaSrFeO 4 –La(Sr)Fe(Co)O 3 (the perovskite phase of the Mn‐doped LSF was retained without formation of other phases after reduction) [22] .…”

“…The use of bimetallic exsolved systems spans over all kinds of applications including but not limited to electrochemistry (71 %), catalysis (19 %) and membranes (3 %) (Figure 1 b). Among these, electrochemistry [6a–c, 7] is the most common application but there are also a few studies focusing on catalytic applications such as methane conversion, [8] CO oxidation [9] or the water‐gas‐shift reaction [10] . In spite of these exciting developments, to the best of our knowledge, there is no review that summarizes the advances on bimetallic exsolution.…”

Progress and Opportunities for Exsolution in Electrochemistry

“…Recently, Barnett has shown that exsolution electrodes on the basis of A-site-deficient and B-site-doped strontium titanates have comparable current densities to NiO/YSZ, and are therefore becoming industrially relevant materials [33]. These results show great promise that cleverly engineered stoichiometry can be synthesized in order to form mixed ionic-electric conductors (MIECs), tailor the electronic properties of the exsolved catalytic nanoparticles through alloying, [33,[35][36][37][38][39] and utilize strain engineering or twinning to enhance catalytic properties [40]. One of the major advantages of SOFCs over room temperature (e.g., PEM) fuel cells is their fuel flexibility and ability to operate using non-precious-metal catalysts.…”

Enhancing Stability and Catalytic Activity by In Situ Exsolution for High-Performance Direct Hydrocarbon Solid Oxide Fuel Cell Anodes

“…In a SOFC system fueled by hydrocarbon, the anode plays an important role in determining the electrochemical performance and durability of the cell. 7 The anode materials should have a suitable thermal expansion coefficient, high ionic conductivity, high catalytic activity, and strong tolerance to carbon deposition. Conventionally, Ni-based composites, such as Ni-YSZ, which exhibit high catalytic activity and effective current collection, are most commonly used as the anode materials of SOFCs.…”

“…A typical SOFC is composed of a dense electrolyte sandwiched between the porous anode and cathode. In a SOFC system fueled by hydrocarbon, the anode plays an important role in determining the electrochemical performance and durability of the cell . The anode materials should have a suitable thermal expansion coefficient, high ionic conductivity, high catalytic activity, and strong tolerance to carbon deposition.…”