Determining oxidation states of transition metals in molten salt corrosion using electron energy loss spectroscopy

Bawane, Kaustubh; Manganaris, Panayotis; Wang, Yachun; Sure, Jagadeesh; Ronne, Arthur; Halstenberg, Phillip; Dai, Sheng; Gill, Simerjeet K.; Sasaki, Kotaro; Chen‐Wiegart, Yu‐chen Karen; Gakhar, Ruchi; Mahurin, Shannon M.; Pimblott, Simon M.; Wishart, James F.; He, Lingfeng

doi:10.1016/j.scriptamat.2021.113790

Cited by 22 publications

(11 citation statements)

References 26 publications

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“…One of the isolated red pixels surrounded by the white dash square is enlarged in Figure 1i, where the serial numbers match with that of extracted EELS spectra in Figure 1j. Thereinto, the signal peak ≈578 eV, corresponding to the Cr L 3 edge, [ 12 ] is only detected in the central red pixel, implying that the Cr atoms are atomically dispersed at the CoSe 2 support.…”

Section: Resultsmentioning

confidence: 99%

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst

et al. 2022

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However, in most cases, stoichiometricamounts peroxides like H 2 O 2 and tertbutyl hydroperoxide (TBHP) were used as exogenous oxidizing reagents and oxygen sources, [2] resulting in massive waste and an increase in costs. [3] The strategy that water serves as the oxygen source to produce high-value organic chemicals has drawn more attention due to its low price and cleanliness, [4] yet its inertia under ambient temperatures leads to more energy consumption in practical working conditions. Electrochemical methods with waste-free electrons as redox agents provide a green and mild pathway to watermediated oxidation of organics, [5] where the balance between the oxidation of organics and the competitive oxygen evolution reaction (OER) is deemed as the main problem. [6] Inspired by the tandem catalysis tactic, turning this competition between the OER and the selective oxidation of styrene to benzaldehyde into cooperation should be feasible, but it has rarely been achieved.Single-atom catalysts (SACs) meet with great favor in electro catalysis for their superior activity, higher metal-utilization efficiency, and enhanced selectivity. [7] In the past decade, enormous encouraging SACs have been created and utilized to catalyze the oxygen reduction reaction, the OER, and other heterogeneous reactions. [8] However, the activity of SACs often suffers the limit for complex reactions with multiple intermediates, because the single site is not able to catalyze efficiently all the reactions in the whole system. [9] Although introducing extra active centers into SACs has the potential to break this limit, [10] spatiotemporal transfer of intermediates over catalytic sites and inherent synergetic mechanisms remain unexplored, thus leading to a low product yield and undesirable side reactions. Besides, insufficient cognition on the reconstruction of the catalytic sites in working conditions also increases the difficulty of their design. Therefore, constructing active sites with a specific function to catalyze complex reactions in a tandem system still confronts a great challenge.Herein, we fabricate a single-atom catalyst with Cr atoms atomically dispersed at CoSe 2 support (Cr 1 /CoSe 2 ), in which Co and Cr sites are endowed with a specific function to oxidize water and styrene respectively. Especially, the anchored Cr single atoms could not only serve as the active sites for the Electrocatalytic oxidation of organics using water as the oxygen source is a prospective but challenging method to produce high-value-added chemicals; especially, the competitive oxygen evolution reaction (OER) limits its efficiency. Herein, a tandem catalysis strategy based on a single-atom catalyst with Cr atoms atomically dispersed at a CoSe 2 support (Cr 1 /CoSe 2 ) is presented. Thereinto, Co and Cr sites are endowed with a specific function to activate water and styrene respectively, and the competition between the OER and styrene oxidation is turned into mutual benefits via cooperated active sites. Under a potential of 1.6 V Ag/AgCl , exce...

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Section: Resultsmentioning

confidence: 99%

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst

et al. 2022

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“…Apart from the elemental distribution, the chemical (oxidation) state of the Cr in the salt after corrosion was characterized by STEM-EELS. The Cr chemical state was determined based on a comparison of the integrated intensity ratios of the Cr L 3 and L 2 peaks in the EELS spectra from the sample with known references (Cr, CrCl 2 , and CrCl 3 ), as demonstrated in our prior work . Several regions of interest (ROIs) were selected in the STEM–BF images in Figure A–B, including ROIs (a–d) from the salt and ROI (e) in the corroded alloy.…”

Section: Resultsmentioning

confidence: 99%

“…The Cr chemical state was determined based on a comparison of the integrated intensity ratios of the Cr L 3 and L 2 peaks in the EELS spectra from the sample with known references (Cr, CrCl 2 , and CrCl 3 ), as demonstrated in our prior work. 41 Several regions of interest (ROIs) were selected in the STEM−BF images in Figure 5A− B, including ROIs (a−d) from the salt and ROI (e) in the corroded alloy. The Cr-L 2,3 peaks (Figure 5C) occurred in ROIs (a−d), while no Cr-L 2,3 peaks (Figure S9A) were observed at the surface of a grain (ROI (e)).…”

Section: In Situ 3d Morphologicalmentioning

confidence: 99%

Temperature-Dependent Morphological Evolution during Corrosion of the Ni-20Cr Alloy in Molten Salt Revealed by Multiscale Imaging

Liu

Bawane

Zheng

et al. 2023

ACS Appl. Mater. Interfaces

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Understanding the mechanisms leading to the degradation of alloys in molten salts at elevated temperatures is significant for developing several key energy generation and storage technologies, including concentrated solar and next-generation nuclear power plants. Specifically, the fundamental mechanisms of different types of corrosion leading to various morphological evolution characteristics for changing reaction conditions between the molten salt and alloy remain unclear. In this work, the three-dimensional (3D) morphological evolution of Ni–20Cr in KCl–MgCl2 is studied at 600 °C by combining in situ synchrotron X-ray and electron microscopy techniques. By further comparing different morphology evolution characteristics in the temperature range of 500–800 °C, the relative rates between diffusion and reaction at the salt–metal interface lead to different morphological evolution pathways, including intergranular corrosion and percolation dealloying. In this work, the temperature-dependent mechanisms of the interactions between metals and molten salts are discussed, providing insights for predicting molten salt corrosion in real-world applications.

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“…Rapid dealloying (corrosion) initiated at the interface of the microwire and molten salt and propagated to the center of the sample, forming an open porous structure. Here, primarily Cr was removed ( ) from the parent alloy Ni–20Cr because the Cr/CrCl 2 redox couple has a more negative redox potential than Cr/CrCl 3 and Ni/NiCl 2 in chloride salts at 800 °C, while studies have shown that CrCl 3 may form as well depending on the reaction conditions 37 , 50 . The cathodic reaction and the overall reactions following the Cr dissolution are much more complex as shown by S. Bell et al 51 .…”

Section: Resultsmentioning

confidence: 99%

Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography

Liu

Ronne

et al. 2021

Nat Commun

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Three-dimensional bicontinuous porous materials formed by dealloying contribute significantly to various applications including catalysis, sensor development and energy storage. This work studies a method of molten salt dealloying via real-time in situ synchrotron three-dimensional X-ray nano-tomography. Quantification of morphological parameters determined that long-range diffusion is the rate-determining step for the dealloying process. The subsequent coarsening rate was primarily surface diffusion controlled, with Rayleigh instability leading to ligament pinch-off and creating isolated bubbles in ligaments, while bulk diffusion leads to a slight densification. Chemical environments characterized by X-ray absorption near edge structure spectroscopic imaging show that molten salt dealloying prevents surface oxidation of the metal. In this work, gaining a fundamental mechanistic understanding of the molten salt dealloying process in forming porous structures provides a nontoxic, tunable dealloying technique and has important implications for molten salt corrosion processes, which is one of the major challenges in molten salt reactors and concentrated solar power plants.

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Determining oxidation states of transition metals in molten salt corrosion using electron energy loss spectroscopy

Cited by 22 publications

References 26 publications

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst

Temperature-Dependent Morphological Evolution during Corrosion of the Ni-20Cr Alloy in Molten Salt Revealed by Multiscale Imaging

Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography

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Determining oxidation states of transition metals in molten salt corrosion using electron energy loss spectroscopy

Cited by 22 publications

References 26 publications

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr1/CoSe2 Catalyst

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr1/CoSe2 Catalyst

Temperature-Dependent Morphological Evolution during Corrosion of the Ni-20Cr Alloy in Molten Salt Revealed by Multiscale Imaging

Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography

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Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single‐Atom Cr₁/CoSe₂ Catalyst