Growth Kinetics of Individual Co Particles Ex-solved on SrTi0.75Co0.25O3-δ Polycrystalline Perovskite Thin Films

Jo, Yong Ryun; Koo, Bonjae; Seo, Min Ji; Kim, Jun Kyu; Lee, Siwon; Kim, Kyeounghak; Han, Jeong Woo; Jung, WooChul; Kim, Bong Joong

doi:10.1021/jacs.9b01882

Cited by 86 publications

(108 citation statements)

References 43 publications

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“…6 and suggests that the growth rate of the particles is limited by the rate of iron reduction at the surface of LSF. This result is also in line with studies in literature, which also found a reactioncontrolled growth of metallic particles exsolved from perovskite-type oxides 21,34 . However, for the exsolution of Fe 0 from LSF a distinction between strain-and reactant-controlled is not possible, but since Fe is the only element on the B-site of LSF and its high concentration does not change drastically upon exsolution, a minor (if any) role of the reactant concentration for the particle growth rate can be assumed.…”

Section: Resultssupporting

confidence: 93%

“…6a and the entire data set of particle growth-in-situ and ex-situ-was analysed by employing kinetic models described in literature (for details please refer to the Methods section) 33 . As a result, we suggest a reaction-controlled growth with a significant effect of the strain of the particles, in line with studies focussing on the kinetics of the exsolution process 21,34 . Interestingly, this increase of the exsolution particle size is not reflected in the current-voltage curve, since differences of reaction rates (i.e., currents) for different times (e.g., at 9 and 92 min in Fig.…”

Section: Resultssupporting

confidence: 88%

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Understanding electrochemical switchability of perovskite-type exsolution catalysts

et al. 2020

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Exsolution of metal nanoparticles from perovskite-type oxides is a very promising approach to obtain catalysts with superior properties. One particularly interesting property of exsolution catalysts is the possibility of electrochemical switching between different activity states. In this work, synchrotron-based in-situ X-ray diffraction experiments on electrochemically polarized La0.6Sr0.4FeO3-δ thin film electrodes are performed, in order to simultaneously obtain insights into the phase composition and the catalytic activity of the electrode surface. This shows that reversible electrochemical switching between a high and low activity state is accompanied by a phase change of exsolved particles between metallic α-Fe and Fe-oxides. Reintegration of iron into the perovskite lattice is thus not required for obtaining a switchable catalyst, making this process especially interesting for intermediate temperature applications. These measurements also reveal how metallic particles on La0.6Sr0.4FeO3-δ electrodes affect the H2 oxidation and H2O splitting mechanism and why the particle size plays a minor role.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 88%

Understanding electrochemical switchability of perovskite-type exsolution catalysts

et al. 2020

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“…In situ TEM has been employed to provide insights at nanoscale into the exsolution of metallic nanoparticles in perovskites under reducing atmosphere . Herein, we use in situ STEM and ESEM to provide direct insight into the exsolution/reincorporation of CoFe alloy nanoparticles under both reducing and oxidizing atmospheres ( Figure and Figure S3, Supporting Information).…”

Section: Figurementioning

confidence: 99%

In Situ Investigation of Reversible Exsolution/Dissolution of CoFe Alloy Nanoparticles in a Co‐Doped Sr₂Fe_1.5Mo_0.5O₆₋_δ Cathode for CO₂ Electrolysis

et al. 2020

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CO 2 electrolysis via solid oxide electrolysis cell (SOEC) has shown promising practical applications in CO 2 conversion and renewable electricity storage due to low overpotential, large current density, high Faradaic efficiency, and energy efficiency facilitated by high-temperature operation. [1] Perovskites have been extensively investigated as cathode materials for direct CO 2 electrolysis in SOEC in the absence of protective gas [2] ; however, the perovskites still suffer from insufficient CO 2 electrolysis performance. [3] In situ exsolving metal nanoparticles on the perovskite surface have been explored as an efficient strategy to improve CO 2 electrolysis performance due to the exsolution of highly active metal nanoparticles and the simultaneous generation of oxygen vacancies within perovskite, where abundant metal-oxide interfaces are generated for highly efficient CO 2 electrolysis. [4] In addition, reversible exsolution and dissolution of metal nanoparticles in perovskite have been proposed as vital properties for resolving the possible particle agglomeration and coke formation during a long-term operation of SOECs. [2b,5] To date, although some perovskites have demonstrated redox reversibility with exsolution and dissolution of metal nanoparticles in reducing and oxidizing atmosphere, [6] fundamental understanding of these phenomena is still scarce. [7] Ex situ scanning/transmission electron microscopy (SEM/ TEM) and X-ray diffraction (XRD) techniques have been employed to investigate the morphology and crystalline evolution after reducing and oxidizing treatments. [8] Irvine et al. found that a decrease in the stoichiometry of perovskite from A/B = 1 to A/B<1 could break the bottleneck of exsolution level and facilitate high-population exsolution of metal nanoparticles. [7,9] Kim et al. investigated the reducibility of different cations in perovskite using co-segregation energy as a descriptor. The co-segregation energy of B-site dopant and oxygen vacancies plays a critical role in the exsolution. [10] Furthermore, Luo et al. used in situ TEM to investigate the exsolution of Co nano particles in Pr 0.5 Ba 0.5 Mn 0.9 Co 0.1 O x (PBMCo) perovskite, excluding the possibility of metal nanoparticles Reversible exsolution and dissolution of metal nanoparticles in perovskite has been investigated as an efficient strategy to improve CO 2 electrolysis performance. However, fundamental understanding with regard to the reversible exsolution and dissolution of metal nanoparticles in perovskite is still scarce. Herein, in situ exsolution and dissolution of CoFe alloy nanoparticles in Co-doped Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFMC) revealed by in situ X-ray diffraction, scanning transmission electron microscopy, environmental scanning electron microscopy, and density functional theory calculations are reported. Under a reducing atmosphere, facile exsolution of Co promotes reduction of the Fe cation to generate CoFe alloy nanoparticles in SFMC, accompanied by structure transformation from double perovskite to layer...

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“…[ 7 ] Furthermore, the metal NPs produced by ex‐solution are strongly bound to the host oxide and thus have excellent thermal and chemical stability. [ 8,9 ] Accordingly, thanks to these advantages, the ex‐solution process is now being applied in high‐temperature chemical and electrochemical applications, such as solid oxide fuel cells, [ 10 ] electrolyzers, [ 11 ] and oxidation catalysts. [ 12 ]…”

Section: Figurementioning

confidence: 99%

Dopant‐Driven Positive Reinforcement in Ex‐Solution Process: New Strategy to Develop Highly Capable and Durable Catalytic Materials

Jang

Kim

et al. 2020

Advanced Materials

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Supported catalysts, in which metal nanoparticles (NPs) are distributed on oxide supports, are widely used in a variety of industrial processes, including in catalysis, [1] sensing, [2] and renewable energy. [3] To improve the reactivity, costeffectiveness, and durability of catalysts, decreasing their particle size to ensure uniform dispersion on the support and to suppress their aggregation during operation, particularly at high temperatures (>500 °C) is of utmost importance. Thus far, not only conventional impregnation and coprecipitation approaches but also numerous new synthesis and dispersion techniques have been actively studied. [4] Recently, the spontaneous growth of metal NPs on the surface of a host oxide, called "ex-solution," has attracted much attention as a new route to obtain supported catalysts. [5] It is based on the phenomenon that certain cations in a complex oxide lattice selectively precipitate on the surface when the oxide is partially reduced at high temperatures. [6] In particular, when catalytically active and highly reducible transition metals are used as dopants, metal NPs can be uniformly dispersed on the oxide surface with only a single heat treatment. [7] Furthermore, the metal NPs produced by ex-solution are strongly bound to the host oxide and thus have excellent thermal and chemical stability. [8,9] Accordingly, thanks to these advantages, the ex-solution process is now being applied in high-temperature chemical and electrochemical applications, such as solid oxide fuel cells, [10] electrolyzers, [11] and oxidation catalysts. [12] However, the high-temperature heat treatment required to obtain ex-solved particles is a substantial barrier that significantly limits the use of this process in a wider range of applications. To achieve high catalytic reactivity, not only the metal particles but also the oxide support should have a large specific surface area, whereas at high temperatures, sintering between the oxide supports often occurs, deactivating the catalysts. Therefore, it is necessary to develop a strategy for activating the ex-solution process at a temperature low enough that the nanoscale oxide supports do not aggregate. In this regard, Irvine et al. proposed facilitating the extrusion of B-site cations The ex-solution phenomenon, a central platform for growing metal nanoparticles on the surface of host oxides in real time with high durability and a fine distribution, has recently been applied to various scientific and industrial fields, such as catalysis, sensing, and renewable energy. However, the high-temperature processing required for ex-solutions (>700 °C) limits the applicable material compositions and has hindered advances in this technique. Here, an unprecedented approach is reported for lowtemperature particle ex-solution on important nanoscale binary oxides. WO 3 with a nanosheet structure is selected as the parent oxide, and Ir serves as the active metal species that produces the ex-solved metallic particles. Importantly, Ir doping facilitates a phase transition ...

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Growth Kinetics of Individual Co Particles Ex-solved on SrTi_0.75Co_0.25O_3-δ Polycrystalline Perovskite Thin Films

Cited by 86 publications

References 43 publications

Understanding electrochemical switchability of perovskite-type exsolution catalysts

Understanding electrochemical switchability of perovskite-type exsolution catalysts

In Situ Investigation of Reversible Exsolution/Dissolution of CoFe Alloy Nanoparticles in a Co‐Doped Sr₂Fe_1.5Mo_0.5O₆₋_δ Cathode for CO₂ Electrolysis

Dopant‐Driven Positive Reinforcement in Ex‐Solution Process: New Strategy to Develop Highly Capable and Durable Catalytic Materials

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Growth Kinetics of Individual Co Particles Ex-solved on SrTi0.75Co0.25O3-δ Polycrystalline Perovskite Thin Films

Cited by 86 publications

References 43 publications

Understanding electrochemical switchability of perovskite-type exsolution catalysts

Understanding electrochemical switchability of perovskite-type exsolution catalysts

In Situ Investigation of Reversible Exsolution/Dissolution of CoFe Alloy Nanoparticles in a Co‐Doped Sr2Fe1.5Mo0.5O6−δ Cathode for CO2 Electrolysis

Dopant‐Driven Positive Reinforcement in Ex‐Solution Process: New Strategy to Develop Highly Capable and Durable Catalytic Materials

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Growth Kinetics of Individual Co Particles Ex-solved on SrTi_0.75Co_0.25O_3-δ Polycrystalline Perovskite Thin Films

In Situ Investigation of Reversible Exsolution/Dissolution of CoFe Alloy Nanoparticles in a Co‐Doped Sr₂Fe_1.5Mo_0.5O₆₋_δ Cathode for CO₂ Electrolysis