Vertically aligned nanocomposite La0.8Sr0.2CoO3/(La0.5Sr0.5)2CoO4 cathodes – electronic structure, surface chemistry and oxygen reduction kinetics

Ma, Wubin; Kim, Jae Jin; Цветков, Н. А.; Daio, Takeshi; Kuru, Yener; Cai, Zhuhua; Chen, Yan; Sasaki, Kazunari; Tuller, Harry L.; Yildiz, Bilge

doi:10.1039/c4ta04993d

Cited by 85 publications

(89 citation statements)

References 56 publications

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“…As shown in Figure 5, Ma et al 48 showed, in the temperature range of 320-400 • C, CoO 4 films. Therefore, the higher reactivity of the VAN surface to the oxygen reduction reaction is attributed to enhanced electron availability for charge transfer as well as the suppression of detrimental cation segregation.…”

Section: B Solid Oxide Fuel Cellsmentioning

confidence: 99%

“…Very recently, as shown in Figure 1(d), new and novel device architectures, vertically aligned nanostructured (VAN) films, [43][44][45][46][47][48][49][50][51][52][53] were developed to overcome several issues in conventional ionic devices as mentioned above. Basically, the development of ionic devices by using VAN films started from a similar motivation of laterally aligned heteroepitaxy films.…”

Section: New Device Architectures For Ionic Devicesmentioning

confidence: 99%

“…In this section, we will introduce several interesting examples, such as memories using RS phenomena, 46 oxide fuel cells, 43,[47][48][49][50] and water splitting. 53 Further applications, as yet unexplored, would be entirely possible by tailoring the various properties of VAN films.…”

Section: Emerging Nanoionics In Van Filmsmentioning

confidence: 99%

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Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Lee

MacManus‐Driscoll

2017

APL Materials

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This review provides the design principles to develop new nanoionic applications using vertically aligned nanostructured (VAN) thin films, incorporating two phases which self-assemble in one film. Tunable nanoionics has attracted great attention for energy and device applications, such as ion batteries, solid oxide fuel cells, catalysts, memories, and neuromorphic devices. Among many proposed device architectures, VAN films have strong potential for nanoionic applications since they show enhanced ionic conductivity and tunability. Here, we will review the recent progress on state-of-the-art nanoionic applications, which have been realized by using VAN films. In many VAN systems made by the inclusion of an oxygen ionic insulator, it is found that ions flow through the vertical heterointerfaces. The observation is consistent with structural incompatibility at the vertical heteroepitaxial interfaces resulting in oxygen deficiency in one of the phases and hence to oxygen ion conducting pathways. In other VAN systems where one of the phases is an ionic conductor, ions flow much faster within the ionic conducting phase than within the corresponding plain film. The improved ionic conduction coincides with much improved crystallinity in the ionically conducting nanocolumnar phase, induced by use of the VAN structure. Furthermore, for both cases Joule heating effects induced by localized ionic current flow also play a role for enhanced ionic conductivity. Nanocolumn stoichiometry and strain are other important parameters for tuning ionic conductivity in VAN films. Finally, double-layered VAN film architectures are discussed from the perspective of stabilizing VAN structures which would be less stable and hence less perfect when grown on standard substrates.

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Section: B Solid Oxide Fuel Cellsmentioning

confidence: 99%

Section: New Device Architectures For Ionic Devicesmentioning

confidence: 99%

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Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Lee

MacManus‐Driscoll

2017

APL Materials

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“…Pore-free film samples with a high TPB density were prepared either by surface decoration of a dense P film with small amounts of R 5-7 (see Fig. 1b), or by phase separation during PLD 8,12 (Fig. 1c).…”

Section: -11mentioning

confidence: 99%

“…(La,Sr)CoO 3-δ /(La,Sr) 2 CoO 4±δ (perovskite phase, P/RuddlesdenPopper phase, R) two-phase materials were reported in literature to show enhanced activity for the oxygen reduction reaction (ORR) compared to reference single-phase samples [1][2][3][4][5][6][7][8][9][10][11] making them a promising new material for highly active cathodes in intermediate temperature solid oxide fuel cells. This enhancement was attributed to effects at the P/R/O 2 triple phase boundary (TPB).…”

mentioning

confidence: 99%

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity

Stämmler

Merkle

Maier

2017

J. Electrochem. Soc.

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Thin compact La-Sr-Co-O composite films consisting of (La,Sr)CoO 3-δ and (La,Sr) 2 CoO 4+δ crystallites were prepared by compositional phase separation during pulsed laser deposition. While the total La:Sr ratio is kept constant at 70:30, different phase ratios and crystallite sizes are investigated. The effect of hetero-interfaces on the oxygen reduction reaction (ORR) kinetics was investigated by impedance spectroscopy. The enhancement relative to the appropriate reference activity is quantified in terms of the triple phase boundary (TPB) length specific activity k TPB , resulting in k TPB = 2-9 · 10 −13 cm 2 /s at 600 • C. A metastable Co-deficient perovskite phase La 0.7 Sr 0.3 Co 0.9 O 3-δ formed in La-Sr-Co-O films under certain conditions was found to be highly active with an effective rate constant k q = 3 · 10 −6 cm/s at 600 • C, representing one possible source for the activity enhancement in these composite films. (La,Sr)CoO 3-δ /(La,Sr) 2 CoO 4±δ (perovskite phase, P/RuddlesdenPopper phase, R) two-phase materials were reported in literature to show enhanced activity for the oxygen reduction reaction (ORR) compared to reference single-phase samples 1-11 making them a promising new material for highly active cathodes in intermediate temperature solid oxide fuel cells. This enhancement was attributed to effects at the P/R/O 2 triple phase boundary (TPB). It is important to note that -in contrast to the traditional use -here TPB does not refer to the contact of gas phase, electrode and electrolyte material, but to locations where hetero-grain boundaries of two components of the cathode material are exposed to the atmosphere. The literature approaches to investigate this ORR enhancement at P/R hetero-interfaces (additional ORR activity related to TPBs, which in this work is simply denoted as "TPB effect") can be roughly divided into local ORR activity measurements by 18 O exchange and SIMS experiments, 1-4 and integral activity measurements of macroscopic two-phase electrodes with high TPB density by impedance spectroscopy. 5-11With a local measurement, the activity of the surface at a single TPB as well as that at neighboring P and R phases (reference activities) can be determined. If sufficiently high lateral resolution and vertical sampling depth is available, the strength of the TPB effect can be quantified in terms of a TPB length specific contribution to the activity. With an integral measurement of a whole electrode which contains a large amount of P and R grains and TPBs, an average activity is measured with contributions from the grains (surfaces with effective rate constants k P (x) in P La 1-x Sr x CoO 3-δ with Sr fraction x and k R (y) in R (La 1-y Sr y ) 2 CoO 4±δ with Sr fraction y) and from TPBs, which has to be compared to an appropriate reference activity and related to the TPB density for quantification.In literature, local activity measurements were performed either on ceramic samples where P/R hetero-interfaces formed sporadically by spontaneous phase separation, 1,3 or as illustrated ...

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Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

Wang

Syed

Ning

et al. 2021

Adv Funct Materials

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Nanostructured functional oxides play an important role in enabling clean energy technologies and novel memory and processor devices. Using thin‐film La0.6Sr0.4FeO3 (LSF) as a model system, the novel utility of exsolution in fabricating self‐assembled metal oxide nanocomposites with tunable functionalities is shown. Exsolution triggers the formation of metallic iron (Fe0) nanoparticles, Ruddlesden–Popper domains, and nm‐scale percolated Fe‐deficient channels in LSF. Combining multimodal characterization with numerical modeling, the chemical, magnetic, and electrical properties of the exsolution‐synthesized nanocomposite at different stages of Fe0 exsolution as well as during redox cycling are assessed. After exsolution, the electronic conductivity of the nanocomposite LSF increased by more than two orders of magnitude. Based on numerical analysis representing all the constituents, it is expected that this increase in conductivity originates mainly from the Fe‐deficient percolating channels formed during exsolution. Moreover, the exsolved nanocomposite is redox‐active even at moderate temperatures. Such redox capabilities can enable dynamic control of the nanocomposite functionality by tailoring the oxygen non‐stoichiometry. This concept is demonstrated with a continuous modulation of magnetization between 0 and 110 emu cm−3. These findings point out that exsolution may serve as a platform for scalable fabrication of complex metal oxide nanocomposites for electrochemical and electronic applications.

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Vertically aligned nanocomposite La_0.8Sr_0.2CoO₃/(La_0.5Sr_0.5)₂CoO₄ cathodes – electronic structure, surface chemistry and oxygen reduction kinetics

Cited by 85 publications

References 56 publications

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity

Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

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Vertically aligned nanocomposite La0.8Sr0.2CoO3/(La0.5Sr0.5)2CoO4 cathodes – electronic structure, surface chemistry and oxygen reduction kinetics

Cited by 85 publications

References 56 publications

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO3-δ/(La,Sr)2CoO4+δ/O2Triple Phase Boundary Activity

Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

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Product

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Vertically aligned nanocomposite La_0.8Sr_0.2CoO₃/(La_0.5Sr_0.5)₂CoO₄ cathodes – electronic structure, surface chemistry and oxygen reduction kinetics

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity