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Supercatalysis by superexchange

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journal contribution
posted on 02.12.2016, 11:44 by Stephen Fletcher, Nicholas J. Van Dijk
In modern transition state theory, the rate constant for an electron transfer reaction is expressed as the product of four factors: an exponential factor, a pre-exponential factor, an electronic transmission coefficient, and a nuclear transmission coefficient. The activation energy of the reaction manifests inside the exponential factor, and on the conventional view, catalysis occurs by decreasing this activation energy below its catalyst-free value. In the present work we report the discovery of an unusual counter-example in which catalysis occurs by increasing the electron transmission coefficient far above its catalyst-free value. The mechanism involves the formation of a superexchange bridge between an electron donor (a graphite cathode) and an electron acceptor (a pentasulfide ion). The bridge consists of a dz2 orbital inside a cobalt phthalocyanine molecule. The dramatic result is the acceleration of the reduction of pentasulfide ions by more than 5 orders of magnitude compared with the catalyst-free case.

Funding

This work was sponsored by the EPSRC (UK) Grant Number: EP/M009394/1, “Electrochemical Vehicle Advanced Technology” (ELEVATE). N.J.V.D. also thanks Regenesys Technologies Ltd. for a scholarship.

History

School

  • Science

Department

  • Chemistry

Published in

The Journal of Physical Chemistry C

Pages

26225 - 26234

Citation

FLETCHER, S. and VAN DIJK, N.J., 2016. Supercatalysis by Superexchange. The Journal of Physical Chemistry C, 120 (46), pp 26225–26234.

Publisher

American Chemical Society

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/

Acceptance date

28/10/2016

Publication date

2016

Notes

ACS AuthorChoice - This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.

ISSN

1932-7447

eISSN

1932-7455

Language

en

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