1
|
Pikalova EY, Kalinina EG, Pikalova NS, Filonova EA. High-Entropy Materials in SOFC Technology: Theoretical Foundations for Their Creation, Features of Synthesis, and Recent Achievements. MATERIALS (BASEL, SWITZERLAND) 2022; 15:ma15248783. [PMID: 36556589 PMCID: PMC9781791 DOI: 10.3390/ma15248783] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/05/2022] [Accepted: 12/06/2022] [Indexed: 05/31/2023]
Abstract
In this review, recent achievements in the application of high-entropy alloys (HEAs) and high-entropy oxides (HEOs) in the technology of solid oxide fuel cells (SOFC) are discussed for the first time. The mechanisms of the stabilization of a high-entropy state in such materials, as well as the effect of structural and charge factors on the stability of the resulting homogeneous solid solution are performed. An introduction to the synthesis methods for HEAs and HEOs is given. The review highlights such advantages of high-entropy materials as high strength and the sluggish diffusion of components, which are promising for the use at the elevated temperatures, which are characteristic of SOFCs. Application of the medium- and high-entropy materials in the hydrocarbon-fueled SOFCs as protective layers for interconnectors and as anode components, caused by their high stability, are covered. High-entropy solid electrolytes are discussed in comparison with traditional electrolyte materials in terms of conductivity. High-entropy oxides are considered as prospective cathodes for SOFCs due to their superior electrochemical activity and long-term stability compared with the conventional perovskites. The present review also determines the prioritizing directions in the future development of high-entropy materials as electrolytes and electrodes for SOFCs operating in the intermediate and low temperature ranges.
Collapse
Affiliation(s)
- Elena Y. Pikalova
- Laboratory of Solid Oxide Fuel Cells, Institute of High Temperature Electrochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620137, Russia
- Department of Environmental Economics, Graduate School of Economics and Management, Ural Federal University, Yekaterinburg 620002, Russia
| | - Elena G. Kalinina
- Laboratory of Complex Electrophysic Investigations, Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620016, Russia
- Department of Physical and Inorganic Chemistry, Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg 620002, Russia
| | - Nadezhda S. Pikalova
- Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620016, Russia
| | - Elena A. Filonova
- Department of Physical and Inorganic Chemistry, Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg 620002, Russia
| |
Collapse
|
2
|
Zamudio-García J, Porras-Vázquez JM, Losilla ER, Marrero-López D. LaCrO 3-CeO 2-Based Nanocomposite Electrodes for Efficient Symmetrical Solid Oxide Fuel Cells. ACS APPLIED ENERGY MATERIALS 2022; 5:4536-4546. [PMID: 36186956 PMCID: PMC9513820 DOI: 10.1021/acsaem.1c04116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
La0.98Cr0.75Mn0.25O3-δ-Ce0.9Gd0.1O1.95 (LCM-CGO) nanocomposite layers with different LCM contents, between 40 and 60 wt %, are prepared in a single step by a spray-pyrolysis deposition method and evaluated as both air and fuel electrodes for solid oxide fuel cells (SOFCs). The formation of fluorite (CGO) and perovskite (LCM) phases in the nanocomposite electrode is confirmed by different structural and microstructural techniques. The intimate mixture of LCM and CGO phases inhibits the grain growth, retaining the nanoscale microstructure even after annealing at 1000 °C with a grain size lower than 50 nm for LCM-CGO compared to 200 nm for pure LCM. The synergetic effect of nanosized LCM and CGO by combining their high electronic and ionic conductivity, respectively, leads to efficient and durable symmetrical electrodes. The best electrochemical properties are found for 50 wt % LCM-CGO, showing polarization resistance values of 0.29 and 0.09 Ω cm2 at 750 °C in air and H2, respectively, compared to 2.05 and 1.9 Ω cm2 for a screen-printed electrode with the same composition. This outstanding performance is mainly ascribed to the nanoscale electrode microstructure formed directly on the electrolyte at a relatively low temperature. These results reveal that the combination of different immiscible phases with different crystal structures and electrochemical properties could be a promising strategy to design highly efficient and durable air and fuel electrodes for SOFCs.
Collapse
Affiliation(s)
- Javier Zamudio-García
- Departamento
de Química Inorgánica, Universidad
de Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - José M. Porras-Vázquez
- Departamento
de Química Inorgánica, Universidad
de Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - Enrique R. Losilla
- Departamento
de Química Inorgánica, Universidad
de Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - David Marrero-López
- Departamento
de Física Aplicada I, Universidad
de Málaga, Campus
de Teatinos s/n, 29071 Málaga, Spain
| |
Collapse
|
3
|
Porotnikova N, Khrustov A, Farlenkov A, Khodimchuk A, Partin G, Animitsa I, Kochetova N, Pavlov D, Ananyev M. Promising La 2Mo 2O 9-La 2Mo 3O 12 Composite Oxygen-Ionic Electrolytes: Interphase Phenomena. ACS APPLIED MATERIALS & INTERFACES 2022; 14:6180-6193. [PMID: 35045251 DOI: 10.1021/acsami.1c20839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The La2Mo2O9-La2Mo3O12 composite materials represent a novel class of highly conductive materials demonstrating increased oxygen-ion conductivity. Extensive research of (100 - x)La2Mo2O9-xLa2Mo3O12 composites over a wide range of concentrations (x = 5, 10, 15, 20, 30, and 100) was carried out for the first time. An increase in conductivity, oxygen surface exchange coefficient, and oxygen diffusivity is observed for composites compared to individual oxides, which is associated with the segregation of different ions on the surface of the grains and the formation of a La5Mo3O16 new phase at the contact boundary of La2Mo2O9 and La2Mo3O12. 3D-modeling of the composite microstructure was performed on the basis of SEM-image analysis data in order to estimate the conductivity of the interphase layer between the La2Mo2O9 and La2Mo3O12 grains containing La5Mo3O16. The electrical conductivity values of the composite materials calculated from a 3D-simulated microstructure and the experimentally measured conductivity correlate and demonstrate a composite effect.
Collapse
Affiliation(s)
- N Porotnikova
- Institute of High Temperature Electrochemistry, Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg, Russia
| | - A Khrustov
- Institute of High Temperature Electrochemistry, Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg, Russia
| | - A Farlenkov
- Ural Federal University Named After the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia
| | - A Khodimchuk
- Institute of High Temperature Electrochemistry, Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg, Russia
| | - G Partin
- Ural Federal University Named After the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia
| | - I Animitsa
- Ural Federal University Named After the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia
| | - N Kochetova
- Ural Federal University Named After the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia
| | - D Pavlov
- Institute of High Temperature Electrochemistry, Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg, Russia
| | - M Ananyev
- Ural Federal University Named After the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia
- Federal State Research and Design Institute of Rare Metal Industry (Giredmet JSC), 2 Elektrodnaya ul., 111524 Moscow, Russia
| |
Collapse
|
4
|
Nikitin SS, Markov AA, Merkulov OV, Chukin AV, Patrakeev MV. Impact of oxygen content on preferred localization of p- and n-type carriers in La 0.5Sr 0.5Fe 1-xMn xO 3-δ. Dalton Trans 2021; 50:17967-17980. [PMID: 34854863 DOI: 10.1039/d1dt03628a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxygen content in La0.5Sr0.5Fe1-xMnxO3-δ, measured by coulometric titration in a wide range of oxygen partial pressure at various temperatures, was used for defect chemistry analysis. The obtained data were well approximated by a model assuming defect formation in La0.5Sr0.5Fe1-xMnxO3-δvia Fe3+ and Mn3+ oxidation reactions and charge disproportionation on Fe3+ and Mn3+ ions. The partial molar enthalpy and entropy of oxygen in La0.5Sr0.5Fe1-xMnxO3-δ obtained by statistical thermodynamic calculations were found to be in satisfactory agreement with those obtained using the Gibbs-Helmholtz equations, thus further confirming the adequacy of the model. The impact of manganese substitution on defect equilibrium in La0.5Sr0.5Fe1-xMnxO3-δ was shown to be attributed to a lower enthalpy of Mn3+ oxidation reaction (vs. for the oxidation of Fe3+) and the charge disproportionation reaction on Mn3+ (vs. for that on Fe3+). The former makes Mn4+ ions more resistant to reduction than Fe4+. The latter favors the presence of Mn2+, Mn3+, and Mn4+ ions in oxides in comparable concentrations. The distribution of charge carriers over iron and manganese ions was determined as a function of oxygen content in La0.5Sr0.5Fe1-xMnxO3-δ.
Collapse
Affiliation(s)
- Sergey S Nikitin
- Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg, Russia. .,Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 630128 Novosibirsk, Russia
| | - Alexey A Markov
- Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg, Russia.
| | - Oleg V Merkulov
- Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg, Russia.
| | | | | |
Collapse
|
5
|
Osinkin D. Hydrogen oxidation kinetics on a redox stable electrode for reversible solid-state electrochemical devices: The critical influence of hydrogen dissociation on the electrode surface. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138792] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
6
|
Zhai R, Chen H, Shan Z. Exploration of collagen cavitation based on peptide electrolysis. Sci Rep 2021; 11:17080. [PMID: 34429475 PMCID: PMC8384864 DOI: 10.1038/s41598-021-96533-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 08/11/2021] [Indexed: 12/03/2022] Open
Abstract
Electrochemical modification of animal skin is a new material preparation method and new direction of research exploration. In this study, under the action of the electric field using NaCl as the supporting electrolyte, the effect of electrolysis on Glycyl-glycine(GlyGl), gelatin(Gel) and Three-dimensional rawhide collagen(3DC) were determined. The amino group of GlyGl is quickly eliminated within the anode region by electrolysis isolated by an anion exchange membrane. Using the same method, it was found that the molecular weight of Gel and the isoelectric point of the Gel decreased, and the viscosity and transparency of the Gel solution obviously changed. The electrolytic dissolution and structural changes of 3DC were further investigated. The results of TOC and TN showed that the organic matter in 3DC was dissolved by electrolysis, and the tissue cavitation was obvious. A new approach for the preparation of collagen-based multi-pore biomaterials by electrochemical method was explored.
Collapse
Affiliation(s)
- Rui Zhai
- The Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu, 610065, China
| | - Hui Chen
- The Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu, 610065, China.
| | - Zhihua Shan
- The Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu, 610065, China.
| |
Collapse
|
7
|
Porotnikova NM, Vlasov MI, Zhukov Y, Kirschfeld C, Khodimchuk AV, Kurumchin EK, Farlenkov AS, Khrustov AV, Ananyev MV. Correlation between structure, surface defect chemistry and 18O/ 16O exchange for La 2Mo 2O 9 and La 2(MoO 4) 3. Phys Chem Chem Phys 2021; 23:12739-12748. [PMID: 34041516 DOI: 10.1039/d1cp00401h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The La2Mo2O9 and La2(MoO4)3 powders were synthesized using a solid-state reaction method and used to prepare dense ceramics. X-ray photoelectron spectroscopy was used to study the chemical composition and charge numbers of the elements in the subsurface area of dense ceramics of lanthanum molybdates. The spectra were measured under an ultra-high vacuum of 7 × 10-11 atm at 30 °C and 600 °C, and under an oxygen atmosphere at 2 × 10-3 atm at 600 °C and 825 °C. High resolution spectra for La 3d, Mo 3d and O 1s states were obtained and analyzed. The kinetics of oxygen exchange were considered in the framework of a two-step model including the consecutive steps of dissociative adsorption and the incorporation of oxygen. The oxygen adsorption (ra) and incorporation (ri) rates were calculated. Correlations between the oxide surface defect chemistry and the rates of individual oxygen-exchange steps were discussed.
Collapse
Affiliation(s)
- Natalia M Porotnikova
- Institute of High Temperature Electrochemistry, Ural Branch of Russian Academy of Sciences, 620990 Ekaterinburg, Russia.
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Porotnikova N, Farlenkov A, Naumov S, Vlasov M, Khodimchuk A, Fetisov A, Ananyev M. Effect of grain boundaries in La 0.84Sr 0.16CoO 3-δ on oxygen diffusivity and surface exchange kinetics. Phys Chem Chem Phys 2021; 23:11272-11286. [PMID: 33972961 DOI: 10.1039/d1cp01099a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The single crystal and polycrystalline specimens of La0.84Sr0.16CoO3-δ oxide were synthesized and characterized by X-ray powder diffraction analysis, energy dispersive X-ray microanalysis, the electron backscatter diffraction technique, and X-ray photoelectron spectroscopy. A thin slab was prepared from the grown single crystal with its surface corresponding to the (110) plane. The kinetics of the oxygen exchange between the gas phase and a single crystal and a polycrystalline specimen was studied by means of 16O/18O oxygen isotope exchange at T = 750-850 °C and PO2 = 5.3 × 10-3-2.2 × 10-2 atm. Temperature dependencies of the oxygen heterogeneous exchange rate, the oxygen dissociative adsorption and incorporation rates, and oxygen diffusion coefficients were obtained. The relationship between the crystallographic orientation of oxides and the kinetic parameters of oxides has been established. Correlations between the surface state and the rates of individual stages of oxygen exchange as well as oxygen diffusion pathways in the single crystal compared with those in the polycrystalline specimen are considered.
Collapse
Affiliation(s)
- Natalia Porotnikova
- Institute of High Temperature Electrochemistry, UB RAS, Ekaterinburg, Russia.
| | - Andrei Farlenkov
- Ural Federal University named after the First President of Russia B.N. Yeltsin, Ekaterinburg, Russia
| | - Sergey Naumov
- Institute of Metal Physics, UB RAS, Ekaterinburg, Russia
| | - Maxim Vlasov
- Institute of High Temperature Electrochemistry, UB RAS, Ekaterinburg, Russia.
| | - Anna Khodimchuk
- Institute of High Temperature Electrochemistry, UB RAS, Ekaterinburg, Russia.
| | | | - Maxim Ananyev
- Ural Federal University named after the First President of Russia B.N. Yeltsin, Ekaterinburg, Russia
| |
Collapse
|
9
|
Gou Y, Li G, Ren R, Xu C, Qiao J, Sun W, Sun K, Wang Z. Pr-Doping Motivating the Phase Transformation of the BaFeO 3- δ Perovskite as a High-Performance Solid Oxide Fuel Cell Cathode. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20174-20184. [PMID: 33886261 DOI: 10.1021/acsami.1c03514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Intermediate temperature solid oxide fuel cells (IT-SOFCs) have been extensively studied due to high efficiency, cleanliness, and fuel flexibility. To develop highly active and stable IT-SOFCs for the practical application, preparing an efficient cathode is necessary to address the challenges such as poor catalytic activity and CO2 poisoning. Herein, an efficient optimized strategy for designing a high-performance cathode is demonstrated. By motivating the phase transformation of BaFeO3-δ perovskites, achieved by doping Pr at the B site, remarkably enhanced electrochemical activity and CO2 resistance are thus achieved. The appropriate content of Pr substitution at Fe sites increases the oxygen vacancy concentration of the material, promotes the reaction on the oxygen electrode, and shows excellent electrochemical performance and efficient catalytic activity. The improved reaction kinetics of the BaFe0.95Pr0.05O3-δ (BFP05) cathode is also reflected by a lower electrochemical impedance value (0.061 Ω·cm2 at 750 °C) and activation energy, which is attributed to high surface oxygen exchange and chemical bulk diffusion. The single cells with the BFP05 cathode achieve a peak power density of 798.7 mW·cm-2 at 750 °C and a stability over 50 h with no observed performance degradation in CO2-containing gas. In conclusion, these results represent a promising optimized strategy in developing electrode materials of IT-SOFCs.
Collapse
Affiliation(s)
- Yunjie Gou
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Guangdong Li
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Rongzheng Ren
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Chunming Xu
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Jinshuo Qiao
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Wang Sun
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Kening Sun
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Zhenhua Wang
- Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| |
Collapse
|
10
|
Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ Composite Cathodes for Proton Ceramic Fuel Cells. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11083407] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Layered Ruddlesden-Popper (RP) lanthanide nickelates, Lnn+1NinO3n+1 (Ln = La, Pr, and Nd; n = 1, 2, and 3) have generated great interest as potential cathodes for proton conducting fuel cells (PCFCs). The high-order phase (n = 3) is especially intriguing, as it possesses the property of a high and metallic-type electronic conductivity that persists to low temperatures. To provide the additional requirement of high ionic conductivity, a composite electrode is here suggested, formed by a combination of La4Ni3O10±δ with the proton conducting phase BaCe0.9Y0.1O3-δ (40 vol%). Electrochemical impedance spectroscopy (EIS) is used to analyse this composite electrode in both wet (pH2O ~ 10−2 atm) and low humidity (pH2O ~ 10−5 atm) conditions in an O2 atmosphere (400–550 °C). An extended analysis that first tests the stability of the impedance data through Kramers-Kronig and Bayesian Hilbert transform relations is outlined, that is subsequently complemented with the distribution function of relaxation times (DFRTs) methodology. In a final step, correction of the impedance data against the short-circuiting contribution from the electrolyte substrate is also performed. This work offers a detailed assessment of the La4Ni3O10±δ-BaCe0.9Y0.1O3-δ composite cathode, while providing a robust analysis methodology for other researchers working on the development of electrodes for PCFCs.
Collapse
|
11
|
Undoped Sr 2MMoO 6 Double Perovskite Molybdates (M = Ni, Mg, Fe) as Promising Anode Materials for Solid Oxide Fuel Cells. MATERIALS 2021; 14:ma14071715. [PMID: 33807360 PMCID: PMC8036809 DOI: 10.3390/ma14071715] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 03/28/2021] [Accepted: 03/29/2021] [Indexed: 11/29/2022]
Abstract
The chemical design of new functional materials for solid oxide fuel cells (SOFCs) is of great interest as a means for overcoming the disadvantages of traditional materials. Redox stability, carbon deposition and sulfur poisoning of the anodes are positioned as the main processes that result in the degradation of SOFC performance. In this regard, double perovskite molybdates are possible alternatives to conventional Ni-based cermets. The present review provides the fundamental properties of four members: Sr2NiMoO6-δ, Sr2MgMoO6-δ, Sr2FeMoO6-δ and Sr2Fe1.5Mo0.5O6-δ. These properties vary greatly depending on the type and concentration of the 3d-element occupying the B-position of A2BB’O6. The main emphasis is devoted to: (i) the synthesis features of undoped double molybdates, (ii) their electrical conductivity and thermal behaviors in both oxidizing and reducing atmospheres, as well as (iii) their chemical compatibility with respect to other functional SOFC materials and components of gas atmospheres. The information provided can serve as the basis for the design of efficient fuel electrodes prepared from complex oxides with layered structures.
Collapse
|