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Accounting for species’ thermodynamic activities changes mechanistic interpretations of electrochemical kinetic data

Williams, Kindle and Limaye, Aditya and Weiss, Trent and Chung, Minju and Manthiram, Karthish (2022) Accounting for species’ thermodynamic activities changes mechanistic interpretations of electrochemical kinetic data. . (Unpublished)

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The thermodynamic activity of a reacting species, rather than the concentration of that species, generally determines the rate of a kinetically-limited reaction. In this work we demonstrate the need for the explicit accounting of reacting species’ thermodynamic activities in solution, especially when conducting electrochemical kinetic tests. In hydrogen evolution in an alkaline acetonitrile-water blended electrolyte as well as previously-reported oxygen-atom transfer reactions (cyclooctene epoxidation and cyclohexanone lactonization), we demonstrate that accounting for species thermodynamic activity causes water-dependence measurements to yield different mechanistic interpretations than data which treats concentration as a proxy for activity. We hypothesize many ways in which water contributes to the reaction rate beyond direct participation in the reaction, offer initial molecular interpretations of the water activity-concentration relationship in the blended electrolyte, and discuss implications of these findings for better understanding solvent effects.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper Information
Williams, Kindle0000-0001-9640-7849
Limaye, Aditya0000-0003-0639-4154
Chung, Minju0000-0003-4359-7508
Manthiram, Karthish0000-0001-9260-3391
Additional Information:The content is available under CC BY NC ND 4.0 License. The authors would like to thank Thejas Wesley for insightful contributions on nonideal rate laws in the transition state theory framework. We also appreciate feedback from James Mayer, Morris Bullock, Catherine Wise, and Rishi Agarwal on the measurement of RHE in nonaqueous electrolytes. In addition, we are grateful to Zachary Schiffer, Nikifar Lazouski, Nathan Corbin, Joy Zeng, Joseph Maalouf, Katherine Steinberg, Simar Mattewal, Fang-Yu Kuo, Sayandeep Biswas, Kyoungsuk Jin, Deng-Tao Yang, and Hee Jo Song for ongoing discussions and feedback on this work. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Author Contributions: Conceptualization: K.S.W. and K.M.; experiments: K.S.W.; MD simulations: A.M.L.; reproduction: M.C. and K.S.W.; writing (original draft, all except simulation portion): K.S.W.; writing (original draft, simulation portion): A.M.L. and K.S.W.; writing (review and editing): K.S.W., T.A.W., M.C., A.M.L., and K.M.; supervision: K.M.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:electrochemistry; electrocatalysis; hydrogen evolution; HER; nonideal thermodynamics; thermodynamic activity; blended electrolytes; electrochemical kinetics; mechanistic analysis; solvent effects; oxygen-atom transfer
Record Number:CaltechAUTHORS:20220505-565017000
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Official Citation:Williams K, Limaye A, Weiss T, Chung M, Manthiram K. Accounting for species’ thermodynamic activities changes mechanistic interpretations of electrochemical kinetic data. ChemRxiv. 2022. doi:10.26434/chemrxiv-2022-vk5z9
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114605
Deposited By: George Porter
Deposited On:06 May 2022 16:10
Last Modified:06 May 2022 16:10

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