Unraveling the Temperature-Dependent Redox Cycle of Chromium Species in Molten Chloride Salt via In-Situ X-ray Absorption Spectroscopy
10 affiliations
- 1Department of Materials Science and Chemical Engineering
- 2Stony Brook University
- 3The Department of Chemistry
- 4Hunter College
- 5Brookhaven National Laboratory
- 6Chemistry Division
- 7Department of Chemistry
- 8University of Tennessee Knoxville
- 9Chemical Sciences Division
- 10Oak Ridge National Laboratory
Abstract
Molten chloride salt is a widely studied high-temperature electrolyte, with established use in pyrochemical reprocessing and electrorefining, and frequent use as a model system for concentrated solar power and molten salt reactor applications. Chromium (Cr) is a key element in high-temperature structural alloys. However, the temperature-dependent evolution and stability of Cr species in this environment remain insufficiently understood. Cr-redox chemistry in molten chloride salts governs the dissolution, oxidation and transformation of Cr-containing species, with direct implications for corrosion and dealloying of structural alloys as well as broader molten-salt processing applications. In the present study, the chemical stability of CrCl 2 , CrCl 3 , and Cr 2 O 3 in LiCl-KCl eutectic molten salt during heating and cooling was systematically investigated using in-situ X-ray absorption spectroscopy. The results revealed that CrCl 3 and Cr 2 O 3 remained chemically stable under the tested conditions, whereas CrCl 2 underwent oxidation by impurities to form Cr 2 O 3 at 500 °C, but partially converted back to Cr 2+ species upon cooling to room temperature. Additional gas chromatography measurements detected H 2 evolution during heating of CrCl 2 in LiCl–KCl, supporting the involvement of residual moisture in the oxidation process. Additionally, the interaction between chromium and NiCl 2 in molten salt was examined, indicating that chromium likely reduced Ni 2+ to metallic Ni 0 , while being oxidized to Cr 2+ , which subsequently underwent a similar chemical evolution as CrCl 2 in the molten salt. These findings unravel a temperature-dependent, impurity-mediated redox cycle of Cr species between the initial room-temperature, molten, and post-cooling states in molten chloride salt, providing a foundation for understanding and controlling Cr the dissolution, oxidation and transformation, and for developing effective corrosion-mitigation strategies to enhance the stability of high-temperature structural alloys in molten-salt systems.
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BibTeX
@misc{peng2026unraveling,
title = {{Unraveling the Temperature-Dependent Redox Cycle of Chromium Species in Molten Chloride Salt via In-Situ X-ray Absorption Spectroscopy}},
author = {Yuxiang Peng and Kaifeng Zheng and Kazuhiro Iwamatsu and Ankita Mohanty and Denis Leshchev and Akhil Tayal and Jorge Moncada Vivas and Bobby Layne and Xiaoyin Zheng and Ellie Kim and Phillip Halstenberg and Sheng Dai and James F. Wishart and Anatoly I. Frenkel and Yu-chen Karen Chen-Wiegart},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15005212/v3},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15005212/v3},
note = {CC BY},
}
RIS
TY - UNPB
TI - Unraveling the Temperature-Dependent Redox Cycle of Chromium Species in Molten Chloride Salt via In-Situ X-ray Absorption Spectroscopy
AU - Yuxiang Peng
AU - Kaifeng Zheng
AU - Kazuhiro Iwamatsu
AU - Ankita Mohanty
AU - Denis Leshchev
AU - Akhil Tayal
AU - Jorge Moncada Vivas
AU - Bobby Layne
AU - Xiaoyin Zheng
AU - Ellie Kim
AU - Phillip Halstenberg
AU - Sheng Dai
AU - James F. Wishart
AU - Anatoly I. Frenkel
AU - Yu-chen Karen Chen-Wiegart
PY - 2026
DA - 2026/10/13
PB - ChemRxiv
DO - 10.26434/chemrxiv.15005212/v3
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15005212/v3
AB - Molten chloride salt is a widely studied high-temperature electrolyte, with established use in pyrochemical reprocessing and electrorefining, and frequent use as a model system for concentrated solar power and molten salt reactor applications. Chromium (Cr) is a key element in high-temperature structural alloys. However, the temperature-dependent evolution and stability of Cr species in this environment remain insufficiently understood. Cr-redox chemistry in molten chloride salts governs the dissolution, oxidation and transformation of Cr-containing species, with direct implications for corrosion and dealloying of structural alloys as well as broader molten-salt processing applications. In the present study, the chemical stability of CrCl 2 , CrCl 3 , and Cr 2 O 3 in LiCl-KCl eutectic molten salt during heating and cooling was systematically investigated using in-situ X-ray absorption spectroscopy. The results revealed that CrCl 3 and Cr 2 O 3 remained chemically stable under the tested conditions, whereas CrCl 2 underwent oxidation by impurities to form Cr 2 O 3 at 500 °C, but partially converted back to Cr 2+ species upon cooling to room temperature. Additional gas chromatography measurements detected H 2 evolution during heating of CrCl 2 in LiCl–KCl, supporting the involvement of residual moisture in the oxidation process. Additionally, the interaction between chromium and NiCl 2 in molten salt was examined, indicating that chromium likely reduced Ni 2+ to metallic Ni 0 , while being oxidized to Cr 2+ , which subsequently underwent a similar chemical evolution as CrCl 2 in the molten salt. These findings unravel a temperature-dependent, impurity-mediated redox cycle of Cr species between the initial room-temperature, molten, and post-cooling states in molten chloride salt, providing a foundation for understanding and controlling Cr the dissolution, oxidation and transformation, and for developing effective corrosion-mitigation strategies to enhance the stability of high-temperature structural alloys in molten-salt systems.
ER -