Hydroxide diffuses slower than hydronium in water because its solvated structure inhibits correlated proton transfer

Mohan Chen, Lixin Zheng, Biswajit Santra, Hsin Yu Ko, Robert A. Distasio, Michael L. Klein, Roberto Car, Xifan Wu

Research output: Contribution to journalArticle

61 Scopus citations

Abstract

Proton transfer via hydronium and hydroxide ions in water is ubiquitous. It underlies acid-base chemistry, certain enzyme reactions, and even infection by the flu. Despite two centuries of investigation, the mechanism underlying why hydroxide diffuses slower than hydronium in water is still not well understood. Herein, we employ state-of-the-art density-functional-theory-based molecular dynamics - with corrections for non-local van der Waals interactions, and self-interaction in the electronic ground state - to model water and hydrated water ions. At this level of theory, we show that structural diffusion of hydronium preserves the previously recognized concerted behaviour. However, by contrast, proton transfer via hydroxide is less temporally correlated, due to a stabilized hypercoordination solvation structure that discourages proton transfer. Specifically, the latter exhibits non-planar geometry, which agrees with neutron-scattering results. Asymmetry in the temporal correlation of proton transfer leads to hydroxide diffusing slower than hydronium.

Original languageEnglish (US)
Pages (from-to)413-419
Number of pages7
JournalNature chemistry
Volume10
Issue number4
DOIs
StatePublished - Apr 1 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)

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