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Title: Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

Abstract

Using ab initio molecular dynamics (as implemented in periodic, self-consistent (GGA-PBE) density functional theory (DFT) we investigated the mechanism of methanol electro-oxidation on Pt(111). We investigated the role of solvation and electrode potential on the energetics of the first proton transfer step, methanol electro-oxidation to methoxy (CH 3O) or hydroxymethyl (CH 2OH). The results show that solvation weakens the adsorption of methoxy to uncharged Pt(111), while the binding energy of methanol and hydroxymethyl are not significantly affected. The free energies of activation for breaking the C-H and O-H bonds in methanol were calculated through a Blue Moon Ensemble using constrained ab initio molecular dynamics. Calculated barriers for these elementary steps on unsolvated, uncharged Pt(111) are similar to results for climbing-image nudged elastic band calculations from the literature. Solvation reduces the barrier for both C-H and O-H bond activation steps with respect to their vapor phase values, though the effect is more pronounced for C-H bond activation due to less disruption of the hydrogen-bond network. The calculated activation energy barriers show that breaking the C-H bond of methanol is more facile than the O-H bond on solvated negatively biased, or uncharged Pt(111). Furthermore, with positive bias, O-H bond activation is enhanced,more » becoming slightly more facile than C-H bond activation.« less

Authors:
 [1];  [2];  [1]
  1. Univ. of Wisconsin-Madison, Madison, WI (United States)
  2. Osaka Univ., Osaka (Japan)
Publication Date:
Research Org.:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1405318
Grant/Contract Number:
FG02-05ER15731
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 34; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; AIMD; DFT; methanol; Pt(111); electrocatalysis

Citation Formats

Herron, Jeffrey A., Morikawa, Yoshitada, and Mavrikakis, Manos. Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces. United States: N. p., 2016. Web. doi:10.1073/pnas.1604590113.
Herron, Jeffrey A., Morikawa, Yoshitada, & Mavrikakis, Manos. Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces. United States. doi:10.1073/pnas.1604590113.
Herron, Jeffrey A., Morikawa, Yoshitada, and Mavrikakis, Manos. 2016. "Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces". United States. doi:10.1073/pnas.1604590113. https://www.osti.gov/servlets/purl/1405318.
@article{osti_1405318,
title = {Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces},
author = {Herron, Jeffrey A. and Morikawa, Yoshitada and Mavrikakis, Manos},
abstractNote = {Using ab initio molecular dynamics (as implemented in periodic, self-consistent (GGA-PBE) density functional theory (DFT) we investigated the mechanism of methanol electro-oxidation on Pt(111). We investigated the role of solvation and electrode potential on the energetics of the first proton transfer step, methanol electro-oxidation to methoxy (CH3O) or hydroxymethyl (CH2OH). The results show that solvation weakens the adsorption of methoxy to uncharged Pt(111), while the binding energy of methanol and hydroxymethyl are not significantly affected. The free energies of activation for breaking the C-H and O-H bonds in methanol were calculated through a Blue Moon Ensemble using constrained ab initio molecular dynamics. Calculated barriers for these elementary steps on unsolvated, uncharged Pt(111) are similar to results for climbing-image nudged elastic band calculations from the literature. Solvation reduces the barrier for both C-H and O-H bond activation steps with respect to their vapor phase values, though the effect is more pronounced for C-H bond activation due to less disruption of the hydrogen-bond network. The calculated activation energy barriers show that breaking the C-H bond of methanol is more facile than the O-H bond on solvated negatively biased, or uncharged Pt(111). Furthermore, with positive bias, O-H bond activation is enhanced, becoming slightly more facile than C-H bond activation.},
doi = {10.1073/pnas.1604590113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 34,
volume = 113,
place = {United States},
year = 2016,
month = 8
}

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  • We report a photoelectron spectroscopy and computational study of hydrated N3- anion clusters, N3-(H2O)n (n=0-16), in the gas phase. Photoelectron spectra of the solvated azide anions were observed to consist of a single peak, similar to that of the bare N3-, but the spectral width was observed to broaden as a function of cluster size due to solvent relaxation upon electron detachment. The adiabatic and vertical electron detachment energies were measured as a function of solvent number. The measured electron binding energies indicate that the first four solvent molecules have much stronger interactions with the solute anion, forming the firstmore » solvation shell.« less
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