The H•/H-Redox Couple and Absolute Hydration Energy of H-

Ashley S. McNeill; Chang Guo Zhan; Aaron M. Appel; David M. Stanbury; David A. Dixon

doi:10.1021/acs.jpca.0c03833

The H•/H^-Redox Couple and Absolute Hydration Energy of H^-

Ashley S. McNeill, Chang Guo Zhan, Aaron M. Appel, David M. Stanbury, David A. Dixon

Pacific Northwest National Laboratory

Research output: Contribution to journal › Article › peer-review

Abstract

A supermolecule-continuum approach with water clusters up to n = 16 H2O molecules has been used to predict the absolute hydration free energies at 298 K (ΔGhyd) of both hydrogen (H•) and hydride (H-) to be 4.6 ± 1 and -78 ± 3 kcal/mol, respectively. These values are combined with a high accuracy prediction of the gas-phase electron affinity (ΔGgas,298K = -16.9 kcal/mol) to determine the aqueous electron affinity of H•of 99.5 ± 3 kcal/mol, which yields a reduction potential for H•vs SHE of -0.03 ± 0.15 V. This value is in agreement within 0.2 V with most estimates obtained using a wide variety of approaches. These results can be used to improve the absolute hydricity scale in water which provides additional insights into how a putative hydride interacts with solvent but do not change the ability to predict the relative reactivity of two species using relative hydricity scales.

Original language	English
Pages (from-to)	6084-6095
Number of pages	12
Journal	Journal of Physical Chemistry A
Volume	124
Issue number	29
DOIs	https://doi.org/10.1021/acs.jpca.0c03833
Publication status	Published - Jul 23 2020

ASJC Scopus subject areas

Physical and Theoretical Chemistry

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@article{a596c3bd3c2f4338ab2178dc8582542c,

title = "The H•/H-Redox Couple and Absolute Hydration Energy of H-",

abstract = "A supermolecule-continuum approach with water clusters up to n = 16 H2O molecules has been used to predict the absolute hydration free energies at 298 K (ΔGhyd) of both hydrogen (H•) and hydride (H-) to be 4.6 ± 1 and -78 ± 3 kcal/mol, respectively. These values are combined with a high accuracy prediction of the gas-phase electron affinity (ΔGgas,298K = -16.9 kcal/mol) to determine the aqueous electron affinity of H•of 99.5 ± 3 kcal/mol, which yields a reduction potential for H•vs SHE of -0.03 ± 0.15 V. This value is in agreement within 0.2 V with most estimates obtained using a wide variety of approaches. These results can be used to improve the absolute hydricity scale in water which provides additional insights into how a putative hydride interacts with solvent but do not change the ability to predict the relative reactivity of two species using relative hydricity scales.",

author = "McNeill, {Ashley S.} and Zhan, {Chang Guo} and Appel, {Aaron M.} and Stanbury, {David M.} and Dixon, {David A.}",

note = "Funding Information: Research by A.S.M., A.M.A., and D.A.D. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under the DOE BES Catalysis Center Program. A portion of the computational work was performed using the resources in the Molecular Sciences Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research, DE-AC06-76RLO 1830. D.A.D. also thanks the Robert Ramsay Chair Fund of The University of Alabama for support. Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

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doi = "10.1021/acs.jpca.0c03833",

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AU - Stanbury, David M.

AU - Dixon, David A.

N1 - Funding Information: Research by A.S.M., A.M.A., and D.A.D. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under the DOE BES Catalysis Center Program. A portion of the computational work was performed using the resources in the Molecular Sciences Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research, DE-AC06-76RLO 1830. D.A.D. also thanks the Robert Ramsay Chair Fund of The University of Alabama for support. Publisher Copyright: Copyright © 2020 American Chemical Society.

PY - 2020/7/23

Y1 - 2020/7/23

N2 - A supermolecule-continuum approach with water clusters up to n = 16 H2O molecules has been used to predict the absolute hydration free energies at 298 K (ΔGhyd) of both hydrogen (H•) and hydride (H-) to be 4.6 ± 1 and -78 ± 3 kcal/mol, respectively. These values are combined with a high accuracy prediction of the gas-phase electron affinity (ΔGgas,298K = -16.9 kcal/mol) to determine the aqueous electron affinity of H•of 99.5 ± 3 kcal/mol, which yields a reduction potential for H•vs SHE of -0.03 ± 0.15 V. This value is in agreement within 0.2 V with most estimates obtained using a wide variety of approaches. These results can be used to improve the absolute hydricity scale in water which provides additional insights into how a putative hydride interacts with solvent but do not change the ability to predict the relative reactivity of two species using relative hydricity scales.

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