The Influence of Spectator Cations on Solvent Reorganization Energy Is a Short-Range Effect

Myint, Kyaw Hpone; Ding, Wendu; Willard, Adam P.

doi:10.1021/acs.jpcb.0c09895

Cited by 3 publications

(1 citation statement)

References 73 publications

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“…An important and long-standing question that applies to all of these fields concerns the distance over which ions perturb water structure and dynamics. − These perturbations principally occur as a result of a balance between favorable electrostatic interactions between the charged ion and the local partial charges present on the water molecule (hydrophilic), as well as the excluded volume and network reshaping as a result of inserting the ion into the water network (hydrophobic) . The nature of these interactions means that small highly charged ions exhibit a more hydrophilic character than larger more weakly charged ions; however, both require substantial water network reorganization, and therefore perturbations to water–water hydrogen bonding, to incorporate the ions.…”

Section: Introductionmentioning

confidence: 99%

Bridging Structure, Dynamics, and Thermodynamics: An Example Study on Aqueous Potassium Halides

et al. 2021

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Aqueous salt systems are ubiquitous in all areas of life. The ions in these solutions impose important structural and dynamic perturbations to water. In this study, we employ a combined neutron scattering, nuclear magnetic resonance, and computational modeling approach to deconstruct ion-specific perturbations to water structure and dynamics and shed light on the molecular origins of bulk thermodynamic properties of the solutions. Our approach uses the atomistic scale resolution offered to us by neutron scattering and computational modeling to investigate how the properties of particular short-ranged microenvironments within aqueous systems can be related to bulk properties of the system. We find that by considering only the water molecules in the first hydration shell of the ions that the enthalpy of hydration can be determined. We also quantify the range over which ions perturb water structure by calculating the average enthalpic interaction between a central halide anion and the surrounding water molecules as a function of distance and find that the favorable anion−water enthalpic interactions only extend to ∼4 Å. We further validate this by showing that ions induce structure in their solvating water molecules by examining the distribution of dipole angles in the first hydration shell of the ions but that this perturbation does not extend into the bulk water. We then use these structural findings to justify mathematical models that allow us to examine perturbations to rotational and diffusive dynamics in the first hydration shell around the potassium halide ions from NMR measurements. This shows that as one moves down the halide series from fluorine to iodine, and ionic charge density is therefore reduced, that the enthalpy of hydration becomes less negative. The first hydration shell also becomes less well structured, and rotational and diffusive motions of the hydrating water molecules are increased. This reduction in structure and increase in dynamics are likely the origin of the previously observed increased entropy of hydration as one moves down the halide series. These results also suggest that simple monovalent potassium halide ions induce mostly local perturbations to water structure and dynamics.

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Section: Introductionmentioning

confidence: 99%

Bridging Structure, Dynamics, and Thermodynamics: An Example Study on Aqueous Potassium Halides

et al. 2021

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Effect of divalent cations on electrochemiluminescence of metal-organic frameworks in bioassay

Feng

Zhu

et al. 2023

Analytica Chimica Acta

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Hydrogen bond network connectivity in the electric double layer dominates the kinetic pH effect in hydrogen electrocatalysis on Pt

et al. 2022

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The hydrogen evolution reaction (HER) on Pt and other noble metals often undergo ~2 orders of magnitude decrease in reaction kinetics when changing the electrolyte pH from acid to alkaline regime. The origin of this kinetic pH effect remains far from a consensus, hindering the rational design of pHspeci c electrocatalysts. Herein, by meticulously comparing the electric double layer (EDL) structures of acid and alkaline interfaces from the ab initio molecular dynamics (AIMD) simulations, and the computational vibration spectra of water molecules in the AIMD-simulated interfaces with the results of in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), we conclude that neither the hydrogen adsorption strength nor the water dissociation barrier is responsible for the greatly reduced HER kinetics on Pt in alkaline media, because the alkaline interface could have more favorite hydrogen adsorption strength and lower barriers for individual Volmer reactions; it is the signi cantly different connectivity of hydrogen bond networks in EDL that cause the huge kinetic pH effect of HER. What's further, using Pt-Ru alloy as model, our results reveal an unprecedented role of OH adsorption in improving the kinetics of alkaline hydrogen electrocatalysis on Pt-based catalysts, namely, by increasing the connectivity of hydrogen bond networks in EDL rather than by directly affecting the energetics of surface steps. These ndings should add signi cant new insights into the key roles of EDL structures in electrocatalysis. Meanwhile, this study offers a referential research paradigm for exploring the atomic structures of electrochemical interfaces by combining AIMD simulations, computational spectroscopy, and experimental spectroscopy.

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The Influence of Spectator Cations on Solvent Reorganization Energy Is a Short-Range Effect

Cited by 3 publications

References 73 publications

Bridging Structure, Dynamics, and Thermodynamics: An Example Study on Aqueous Potassium Halides

Bridging Structure, Dynamics, and Thermodynamics: An Example Study on Aqueous Potassium Halides

Effect of divalent cations on electrochemiluminescence of metal-organic frameworks in bioassay

Hydrogen bond network connectivity in the electric double layer dominates the kinetic pH effect in hydrogen electrocatalysis on Pt

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