The redox potentials for U, Np, Pu, and Am for oxidation states +III up to +VIII in alkaline aqueous solutions were predicted using density functional theory (DFT) and small-core pseudopotentials and their basis sets, with a hybrid explicit/implicit solvent model using SHE = 4.28 V. For each oxidation state, various oxo/hydroxo complexes were evaluated resulting in a variety of one-electron redox pathways. For An(VIII/VII) couples, the predicted redox potentials for the [An(VIII)O5(OH)]-3/[An(VII)O4(OH)2]-3, or [An(VIII)O4(OH)2]-2/[An(VII)O4(OH)2]-3 couples are in good agreement with existing estimates. For An(VII/VI) redox couples, all couples, particularly [An(VII)O4(OH)2]-3/[An(VI)O2(OH)4]-2, were in agreement with experimental values for U, Np, and Pu, but the results for Am showed larger differences from the estimated potentials. The An(VI/V) couples were consistent with experiment for dioxo/tetrahydroxo couples, and the An(V/IV) couples showed acceptable agreement based on actinide-specific couples, with neutral hydroxides often favored in the +IV state. The An(IV/III) couples were consistent with literature values when modeled as soluble neutral hydroxides. The use of our approach yielded calculated redox potentials that were within ±0.2 V from experimental or estimated values consistent with our prior calculations on redox potentials of actinides from Ac to Am in acidic aqueous solutions. As a result, this supports the robustness of our DFT-based methodology for predicting actinide redox potentials, offering valuable insights for actinide chemistry in aqueous solutions.
Dutra, Felipe R. and Dixon, David A.. "Prediction of Redox Potentials for Different Oxidation States of U, Np, Pu, and Am in Alkaline Aqueous Solution." Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, vol. 129, no. 10, Feb. 2025. https://doi.org/10.1021/acs.jpca.4c08794
Dutra, Felipe R., & Dixon, David A. (2025). Prediction of Redox Potentials for Different Oxidation States of U, Np, Pu, and Am in Alkaline Aqueous Solution. Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, 129(10). https://doi.org/10.1021/acs.jpca.4c08794
Dutra, Felipe R., and Dixon, David A., "Prediction of Redox Potentials for Different Oxidation States of U, Np, Pu, and Am in Alkaline Aqueous Solution," Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory 129, no. 10 (2025), https://doi.org/10.1021/acs.jpca.4c08794
@article{osti_3004795,
author = {Dutra, Felipe R. and Dixon, David A.},
title = {Prediction of Redox Potentials for Different Oxidation States of U, Np, Pu, and Am in Alkaline Aqueous Solution},
annote = {The redox potentials for U, Np, Pu, and Am for oxidation states +III up to +VIII in alkaline aqueous solutions were predicted using density functional theory (DFT) and small-core pseudopotentials and their basis sets, with a hybrid explicit/implicit solvent model using SHE = 4.28 V. For each oxidation state, various oxo/hydroxo complexes were evaluated resulting in a variety of one-electron redox pathways. For An(VIII/VII) couples, the predicted redox potentials for the [An(VIII)O5(OH)]-3/[An(VII)O4(OH)2]-3, or [An(VIII)O4(OH)2]-2/[An(VII)O4(OH)2]-3 couples are in good agreement with existing estimates. For An(VII/VI) redox couples, all couples, particularly [An(VII)O4(OH)2]-3/[An(VI)O2(OH)4]-2, were in agreement with experimental values for U, Np, and Pu, but the results for Am showed larger differences from the estimated potentials. The An(VI/V) couples were consistent with experiment for dioxo/tetrahydroxo couples, and the An(V/IV) couples showed acceptable agreement based on actinide-specific couples, with neutral hydroxides often favored in the +IV state. The An(IV/III) couples were consistent with literature values when modeled as soluble neutral hydroxides. The use of our approach yielded calculated redox potentials that were within ±0.2 V from experimental or estimated values consistent with our prior calculations on redox potentials of actinides from Ac to Am in acidic aqueous solutions. As a result, this supports the robustness of our DFT-based methodology for predicting actinide redox potentials, offering valuable insights for actinide chemistry in aqueous solutions.},
doi = {10.1021/acs.jpca.4c08794},
url = {https://www.osti.gov/biblio/3004795},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
issn = {ISSN 1520-5215},
number = {10},
volume = {129},
place = {United States},
publisher = {American Chemical Society},
year = {2025},
month = {02}}
University of Alabama, Tuscaloosa, AL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); São Paulo Research Foundation (FAPESP)
Grant/Contract Number:
SC0018921
OSTI ID:
3004795
Journal Information:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 10 Vol. 129; ISSN 1089-5639; ISSN 1520-5215
Journal Article
·
Wed Jul 03 00:00:00 EDT 2024
· Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
·OSTI ID:3004800