Mn Valence Determination for Lanthanum Strontium Manganite Solid Oxide Fuel Cell Cathodes

Shih, Shao‐Ju; Sharghi-Moshtaghin, Reza; Guire, Mark R. De; Goettler, Richard; Xing, Zhengliang; Liu, Zhien; Heuer, A. H.

doi:10.1149/1.3625279

Cited by 18 publications

(9 citation statements)

References 29 publications

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“…TPX of LSM in 25 000 ppm 18 O 2 with and without the presence of 2500 ppm CO 2 is shown in Figure . Without the presence of CO 2 (open symbols), the 18 O 2 signal does not exchange with the LSM surface until 650–700 °C (eqs and ), and this temperature range is consistent with the reported temperature for LSM to form surface vacancies, that is, the reduction of Mn. ,,− …”

Section: Results and Discussionsupporting

confidence: 79%

CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

2019

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Understanding the multigas reaction mechanism on metal oxides is vital to advance the design principle for electrodes of energy conversion devices exposed to air. Here, CO2 and O2 co-exchange on two perovskite oxides La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and (La0.8Sr0.2)0.95MnO3±δ (LSM) has been investigated via in situ gas-phase isotopic oxygen exchange. LSCF shows high catalytic activity for heteroexchange of lattice oxygen with oxygen in gaseous CO2, possibly because of a high concentration of oxygen vacancies. The exchange between CO2 and lattice oxygen of LSCF is observed to be as low as 50 °C. Conversely, LSM appears to be relatively inert toward CO2 exchange, and the CO2 exchange reaction occurs over the specific temperature region where surface oxygen vacancies are formed. The isotope exchange results provide insights into the study of multigas reaction mechanism on oxide catalysts.

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Section: Results and Discussionsupporting

confidence: 79%

CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

2019

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“…The two temperature ranges for the water exchange with LSM are consistent with the change of stability of valance states of manganese, [49][50][51][52][53][54] and at these temperature ranges, Mn in the B site of ABO 3 shows the ability to actively change valence states. The contour plot of water exchange with LSCF as a function of PO 2 and temperature are shown in Figure 10.…”

Section: Resultssupporting

confidence: 53%

Fundamental Impact of Humidity on SOFC Cathode ORR

Huang

Pellegrinelli

Wachsman

2015

J. Electrochem. Soc.

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Although solid oxide fuel cells (SOFC) have demonstrated excellent performance, the durability of SOFCs under real working conditions is still an issue for commercial deployment. In particular cathode exposure to atmospheric air contaminants, such as humidity, can result in long-term performance degradation issues. Therefore, a fundamental understanding of the interaction between water molecules and cathodes is essential to resolve this issue and further enhance cathode durability. To study the effects of humidity on the oxygen reduction reaction (ORR), we used in-situ 18 O isotope exchange techniques to probe the exchange of water with two of the most common SOFC cathode materials, (La 0.8 Sr 0.2 ) 0.95 MnO 3±δ (LSM) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF). In this experiment, heavy water, D 2 O (with a mass/charge ratio of m/z = 20), is used to avoid the overlapping of H 2 O and the 18 O 2 cracking fraction, which both provide a peak at m/z = 18. A series of temperature programmed isotope exchange measurements were performed to comprehensively study the interaction of water with the cathode surface as a function of temperature, oxygen partial pressure, and water vapor concentration. The results suggest that water and O 2 share the same surface exchange sites, leading to competitive adsorption. Our findings show that water prefers to exchange with LSCF at lower temperatures, around 300-450 • C. For LSM, O 2 is more favorable than water to be adsorbed on the surface and the presence of O 2 limits water exchange. The experimental data are summarized in a Temperature-PO 2 diagram to help visualize how the exchange of water on each material depends on the operating conditions. © The Author Solid oxide fuel cells (SOFC) electrochemically oxidize fuels for the generation of electricity. Two key advantages of SOFCs are their high efficiency and ability to utilize conventional fuels. This fuel flexibility stems from the dissociation and transport of oxygen from the cathode through the electrolyte to the anode, where the fuels are oxidized. Unfortunately, cathode degradation under real working conditions is a factor that limits SOFC performance. 1-6The long term durability of these materials is a major challenge, due to the high temperature required for the thermally activated oxygen reduction reaction (ORR), 7 as well as the variety of gases present during operation. 8,9 The impurities present in air on the cathode side of the cell can induce undesirable reactions. Some of these impurities, such as Cr or silica, 10-15 arise due to the interconnect and seal materials while some are intrinsic to ambient air, such as humidity and CO 2 . 16 Humidity has been found to degrade the performance of (La 0.8 Sr 0.2 ) 0.95 MnO 3±δ (LSM) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) based cells. 11,[17][18][19][20][21][22][23][24] This degradation can be either reversible or irreversible. 21 However, there is no conclusive evidence showing, fundamentally, how water participates in the degradation process, and it is hard to quan...

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“…For the present work, Mn ions in the composite are totally in an oxidation state of +4, since core level of Mn2p is constructed by two peaks of 2p 3/2 at 642.7 eV and 2p 1/2 at 654.3 eV (Fig. 4b), and since the binding energy of Mn2p 3/2 is higher than that of MnO and Mn 2 O 3 [31]. Concerning the Ni ions, as indicated in Fig.…”

Section: Resultsmentioning

confidence: 79%

Composite Li[Li0.11Mn0.57Ni0.32]O2: Two-step molten-salt synthesis, oxidation state stabilization, and uses as high-voltage cathode for lithium-ion batteries

Yu¹,

Li²,

Guan³

et al. 2012

Journal of Alloys and Compounds

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Mn Valence Determination for Lanthanum Strontium Manganite Solid Oxide Fuel Cell Cathodes

Cited by 18 publications

References 29 publications

CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

Fundamental Impact of Humidity on SOFC Cathode ORR

Composite Li[Li0.11Mn0.57Ni0.32]O2: Two-step molten-salt synthesis, oxidation state stabilization, and uses as high-voltage cathode for lithium-ion batteries

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Mn Valence Determination for Lanthanum Strontium Manganite Solid Oxide Fuel Cell Cathodes

Cited by 18 publications

References 29 publications

CO2 and O2 Co-Exchange on Multivalent Metal Oxides

CO2 and O2 Co-Exchange on Multivalent Metal Oxides

Fundamental Impact of Humidity on SOFC Cathode ORR

Composite Li[Li0.11Mn0.57Ni0.32]O2: Two-step molten-salt synthesis, oxidation state stabilization, and uses as high-voltage cathode for lithium-ion batteries

Contact Info

Product

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CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides