U.S. Department of Energy Office of Scientific and Technical Information
Characterization of Structural and Electronic Transitions During Reduction and Oxidation of Ru(acac) 3 Flow Battery Electrolytes by using X‐ray Absorption Spectroscopy
Metal acetylacetonates possess several very attractive electrochemical properties; however, their cyclabilities fall short of targets for use in nonaqueous redox flow batteries. This paper describes structural and compositional changes during the reduction and oxidation of ruthenium(III) acetylacetonate [Ru(acac) 3 ], a representative acetylacetonate. Voltammetry, bulk electrolysis, and in situ X‐ray absorption spectroscopy (XAS) results are complemented by those from density functional theory (DFT) calculations. The reduction of Ru(acac) 3 in acetonitrile is highly reversible, producing a couple at −1.1 V versus Ag/Ag + . In situ XAS and DFT indicate the formation of [Ru(acac) 3 ] − with Ru−O bonds lengthened relative to Ru(acac) 3 , nearly all of the charge localized on Ru, and no ligand shedding. The oxidation of Ru(acac) 3 is quasireversible, with a couple at 0.7 V. The initial product is likely [Ru(acac) 3 ] + ; however, this species is short‐lived, converting to a product with a couple at −0.2 V, a structure that is nearly identical to that of Ru(acac) 3 within 3 Å of Ru, and approximately 70 % of the charge extracted from Ru (balance from acetylacetone). This non‐innocence likely contributes to the instability of [Ru(acac) 3 ] + . Taken together, the results suggest that the stabilities and cyclabilities of acetylacetonates are determined by the degree of charge transfer to/from the metal.
Kucharyson, Jonathan F., et al. "Characterization of Structural and Electronic Transitions During Reduction and Oxidation of Ru(acac) <sub>3</sub> Flow Battery Electrolytes by using X‐ray Absorption Spectroscopy." ChemElectroChem, vol. 3, no. 11, Aug. 2016. https://doi.org/10.1002/celc.201600360
Kucharyson, Jonathan F., Gaudet, Jason R., Wyvratt, Brian M., & Thompson, Levi T. (2016). Characterization of Structural and Electronic Transitions During Reduction and Oxidation of Ru(acac) <sub>3</sub> Flow Battery Electrolytes by using X‐ray Absorption Spectroscopy. ChemElectroChem, 3(11). https://doi.org/10.1002/celc.201600360
Kucharyson, Jonathan F., Gaudet, Jason R., Wyvratt, Brian M., et al., "Characterization of Structural and Electronic Transitions During Reduction and Oxidation of Ru(acac) <sub>3</sub> Flow Battery Electrolytes by using X‐ray Absorption Spectroscopy," ChemElectroChem 3, no. 11 (2016), https://doi.org/10.1002/celc.201600360
@article{osti_1401216,
author = {Kucharyson, Jonathan F. and Gaudet, Jason R. and Wyvratt, Brian M. and Thompson, Levi T.},
title = {Characterization of Structural and Electronic Transitions During Reduction and Oxidation of Ru(acac) <sub>3</sub> Flow Battery Electrolytes by using X‐ray Absorption Spectroscopy},
annote = {Abstract Metal acetylacetonates possess several very attractive electrochemical properties; however, their cyclabilities fall short of targets for use in nonaqueous redox flow batteries. This paper describes structural and compositional changes during the reduction and oxidation of ruthenium(III) acetylacetonate [Ru(acac) 3 ], a representative acetylacetonate. Voltammetry, bulk electrolysis, and in situ X‐ray absorption spectroscopy (XAS) results are complemented by those from density functional theory (DFT) calculations. The reduction of Ru(acac) 3 in acetonitrile is highly reversible, producing a couple at −1.1 V versus Ag/Ag + . In situ XAS and DFT indicate the formation of [Ru(acac) 3 ] − with Ru−O bonds lengthened relative to Ru(acac) 3 , nearly all of the charge localized on Ru, and no ligand shedding. The oxidation of Ru(acac) 3 is quasireversible, with a couple at 0.7 V. The initial product is likely [Ru(acac) 3 ] + ; however, this species is short‐lived, converting to a product with a couple at −0.2 V, a structure that is nearly identical to that of Ru(acac) 3 within 3 Å of Ru, and approximately 70 % of the charge extracted from Ru (balance from acetylacetone). This non‐innocence likely contributes to the instability of [Ru(acac) 3 ] + . Taken together, the results suggest that the stabilities and cyclabilities of acetylacetonates are determined by the degree of charge transfer to/from the metal. },
doi = {10.1002/celc.201600360},
url = {https://www.osti.gov/biblio/1401216},
journal = {ChemElectroChem},
issn = {ISSN 2196-0216},
number = {11},
volume = {3},
place = {Germany},
publisher = {Wiley Blackwell (John Wiley & Sons)},
year = {2016},
month = {08}}