High oxide-ion conductivity through the interstitial oxygen site in Ba7Nb4MoO20-based hexagonal perovskite related oxides

Yashima, Masatomo; Tsujiguchi, Takafumi; Sakuda, Yuichi; Yasui, Yuta; Zhou, Yu; Fujii, Kotaro; Torii, Shuki; Kamiyama, Takashi; Skinner, Stephen J.

doi:10.1038/s41467-020-20859-w

Cited by 101 publications

(178 citation statements)

References 48 publications

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“…However, WO 3 to be a direct bandgap semiconductor with less disseminative valence and conduction bands has shown considerable interest for multiple applications in energy devices. WO 4 /WO 3− type oxides exhibit a high oxide ion conduction, e.g., Pb 0.9 Sm 0.1 WO 4+δ shows a conductivity of ∼2 × 10 −2 S cm −1 at 800 • C, which is comparable to that of YSZ (3.6 × 10 −2 S cm −1 at 800 • C) [18].…”

Section: Introductionmentioning

confidence: 95%

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

Song

Guo

et al. 2021

Crystals

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High ionic conductivity in low-cost semiconductor oxides is essential to develop electrochemical energy devices for practical applications. These materials exhibit fast protonic or oxygen-ion transport in oxide materials by structural doping, but their application to solid oxide fuel cells (SOFCs) has remained a significant challenge. In this work, we have successfully synthesized nanostructured monoclinic WO3 through three steps: co-precipitation, hydrothermal, and dry freezing methods. The resulting WO3 exhibited good ionic conductivity of 6.12 × 10−2 S cm−1 and reached an excellent power density of 418 mW cm−2 at 550 °C using as an electrolyte in SOFC. To achieve such a high ionic conductivity and fuel cell performance without any doping contents was surprising, as there should not be any possibility of oxygen vacancies through the bulk structure for the ionic transport. Therefore, laterally we found that the surface layer of WO3 is reduced to oxygen-deficient when exposed to a reducing atmosphere and form WO3−δ/WO3 heterostructure, which reveals a unique ionic transport mechanism. Different microscopic and spectroscopic methods such as HR-TEM, SEM, EIS, Raman, UV-visible, XPS, and ESR spectroscopy were applied to investigate the structural, morphological, and electrochemical properties of WO3 electrolyte. The structural stability of the WO3 is explained by less dispersion between the valence and conduction bands of WO3−δ/WO3, which in turn could prevent current leakage in the fuel cell that is essential to reach high performance. This work provides some new insights for designing high-ion conducting electrolyte materials for energy storage and conversion devices.

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Section: Introductionmentioning

confidence: 95%

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

Song

Guo

et al. 2021

Crystals

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“…[41][42][43] More recently, high oxide-ion and proton conductivities were reported in Ba 7 Nb 4 MoO 20 , a 7H hexagonal perovskite derivative. [44][45][46] The oxide-ion conductivity of this material was further enhanced in Ba 7 Nb 3.9 Mo 1.1 O 20.05 by introducing interstitial oxygens. [46] Maximum entropy structure analyses of Ba 7 Nb 3.9 Mo 1.1 O 20.05 revealed 2D oxide-ion migration pathways through tetrahedral and octahedral oxygen sites in the intrinsically oxygen-deficient c′ layers.…”

Section: Introductionmentioning

confidence: 99%

High Oxide‐Ion Conductivity in a Hexagonal Perovskite‐Related Oxide Ba₇Ta_3.7Mo_1.3O_20.15 with Cation Site Preference and Interstitial Oxide Ions

Murakami

Shibata

Yasui

et al. 2021

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The high efficiency and fuel flexibility of SOFCs make them a promising technology for clean energy conversion. The development of SOFC devices requires materials with high oxide-ion conductivity and chemical and electrical stability. [2,3,8,9] However, commercially available oxide-ion electrolytes such as yttria-stabilized zirconia show sufficient conductivity only at temperatures above 700 °C, limiting the practical application of SOFCs in a wide range of fields. Therefore, there is a strong need for alternative materials with high ion conductivity at intermediate temperatures (300-600 °C).Discovery of oxide-ion conductors with new structures has been a challenging task. Since ion conduction in solid oxides is fundamentally related to their underlying crystal structures, high oxide-ion conductivity has been reported in a limited number of structure families. Examples include perovskites, [10][11][12][13][14] apatites, [15,16] fluorites, [17,18] and melilites, [19,20] among which perovskite-type oxides are one of the most well-studied structural families to date. The perovskite-type and related oxides can be broadly classified into four structural groups: a) AMO 3 perovskite-type, b) AMO 3 -related, c) hexagonal perovskite-related, and d) modular structures. [21] Here, A and M represent, respectively, large and small cations. Many AMO 3 perovskites have been reported to be excellent oxide-ion conductors, such as LaGaO 3 -based and Na 0.5 Bi 0.5 TiO 3 -based materials. [11,12] Several compounds crystallizing in the AMX 3 -related (e.g., a double perovskite PrBaCo 2 O 6−δ ; δ is the amount of oxygen deficiency) and modular structures (e.g., Dion-Jacobson phase CsBi 2 Ti 2 NbO 10−δ ) have also been reported as promising oxide-ion conductors. [22][23][24][25][26][27][28][29] Hexagonal perovskite-related oxides are composed of hexagonal close-packed AO 3 (h) layers or sequences of hexagonal and cubic close-packed AO 3 (c) layers. [21,[30][31][32] Oxygendeficient AO 3−δ layers can be formed for both hexagonal and cubic layers (labeled h′ and c′, respectively). Despite the variety of crystal structures, pure oxide-ion conduction in hexagonal perovskite-related oxides has been limited so far, although electronic, proton, and mixed (oxide-ion and electronic) conductors have been reported in several compounds. [33][34][35][36] In 2016, significant oxide-ion conductivity was reported in Ba 3 NbMoO 8.5 , Solid oxide-ion conductors are crucial for enabling clean and efficient energy devices such as solid oxide fuel cells. Hexagonal perovskite-related oxides have been placed at the forefront of high-performance oxide-ion conductors, with Ba 7 Nb 4−x Mo 1+x O 20+x/2 (x = 0−0.1) being an archetypal example. Herein, high oxide-ion conductivity and stability under reducing conditions in Ba 7 Ta 3.7 Mo 1.3 O 20.15 are reported by investigating the solid solutions Ba 7 Ta 4-x Mo 1+x O 20+x/2 (x = 0.2−0.7). Neutron diffraction indicates a large number of interstitial oxide ions in Ba 7 Ta 3.7 Mo 1.3 O 20.15 , leading to a high level...

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“…With the progress of science and technology as well as the development of social economy, people are very active in the research on the development and utilization of various energy resources [1][2][3][4][5][6]. In recent years, ABO 3 perovskite composite oxides have attracted great interest [3,4,[7][8][9][10][11][12][13][14][15]. Research has focused on the development of new perovskite materials to improve activity, selectivity, and stability, as well as the development of advanced manufacturing techniques to reduce their cost while ensuring their reliability, safety, and reproducibility [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, ABO 3 perovskite composite oxides have attracted great interest [3,4,[7][8][9][10][11][12][13][14][15]. Research has focused on the development of new perovskite materials to improve activity, selectivity, and stability, as well as the development of advanced manufacturing techniques to reduce their cost while ensuring their reliability, safety, and reproducibility [14][15][16]. In ABO 3 perovskite oxides, the A site is the rare earth or alkaline earth metal ions, which usually stabilize the structure, while the B site is occupied by the smaller transition metal ions [17].…”

Section: Introductionmentioning

confidence: 99%

Predicting Perovskite Performance with Multiple Machine-Learning Algorithms

Qin

Tian

et al. 2021

Crystals

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Perovskites have attracted increasing attention because of their excellent physical and chemical properties in various fields, exhibiting a universal formula of ABO3 with matching compatible sizes of A-site and B-site cations. In this work, four different prediction models of machine learning algorithms, including support vector regression based on radial basis kernel function (SVM-RBF), ridge regression (RR), random forest (RF), and back propagation neural network (BPNN), are established to predict the formation energy, thermodynamic stability, crystal volume, and oxygen vacancy formation energy of perovskite materials. Combined with the fitting diagrams of the predicted values and DFT calculated values, the results show that SVM-RBF has a smaller bias in predicting the crystal volume. RR has a smaller bias in predicting the thermodynamic stability. RF has a smaller bias in predicting the formation energy, crystal volume, and thermodynamic stability. BPNN has a smaller bias in predicting the formation energy, thermodynamic stability, crystal volume, and oxygen vacancy formation energy. Obviously, different machine learning algorithms exhibit different sensitivity to data sample distribution, indicating that we should select different algorithms to predict different performance parameters of perovskite materials.

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High oxide-ion conductivity through the interstitial oxygen site in Ba7Nb4MoO20-based hexagonal perovskite related oxides

Cited by 101 publications

References 48 publications

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

High Oxide‐Ion Conductivity in a Hexagonal Perovskite‐Related Oxide Ba₇Ta_3.7Mo_1.3O_20.15 with Cation Site Preference and Interstitial Oxide Ions

Predicting Perovskite Performance with Multiple Machine-Learning Algorithms

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High oxide-ion conductivity through the interstitial oxygen site in Ba7Nb4MoO20-based hexagonal perovskite related oxides

Cited by 101 publications

References 48 publications

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

High Oxide‐Ion Conductivity in a Hexagonal Perovskite‐Related Oxide Ba7Ta3.7Mo1.3O20.15 with Cation Site Preference and Interstitial Oxide Ions

Predicting Perovskite Performance with Multiple Machine-Learning Algorithms

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High Oxide‐Ion Conductivity in a Hexagonal Perovskite‐Related Oxide Ba₇Ta_3.7Mo_1.3O_20.15 with Cation Site Preference and Interstitial Oxide Ions