A Neutron Diffraction Study of the Electrochemical Double Layer Capacitor Electrolyte Tetrapropylammonium Bromide in Acetonitrile
Humphreys, Elizabeth K
Welbourn, Rebecca JL
Youngs, Tristan Gerard Alfred
Soper, Alan Kenneth
The Journal of Physical Chemistry B
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Humphreys, E. K., Allan, P., Welbourn, R. J., Youngs, T. G. A., Soper, A. K., Grey, C., & Clarke, S. (2015). A Neutron Diffraction Study of the Electrochemical Double Layer Capacitor Electrolyte Tetrapropylammonium Bromide in Acetonitrile. The Journal of Physical Chemistry B, 119 15320-15333. https://doi.org/10.1021/acs.jpcb.5b08248
Neutron diffraction with isotopic substitution has been used to characterise the bulk liquid structure of the technologically relevant electrolyte solution, 1 M tetrapropylammonium bromide (TPA Br) in acetonitrile (acn), and of pure deuterated acetonitrile. Empirical potential structure refinement modelling procedures have been used to extract detailed structural information about solvent-solvent, solvent-ion and ion-ion correlations. Analysis of the refined data shows the expected local dipolar conformation of acn in the pure solvent. This short range dipolar ordering is also present within the solutions of TPA Br in acn, and it affects how the solvent orders itself around the ions. The solvation numbers of the TPA cations and the bromide anions are deduced – 8 and 5 respectively – as are the orientations of the solvent molecules surround the ions. Evidence for ion association is also presented, with nearly two thirds of the ions in the system being in associated pairs or clusters.
Neutrons, neutron diffraction, neutron scattering, electrochemical double layer capacitors, empirical potential structure refinement, EPSR, partial structure factors, partial pair distribution functions
E.K.H. acknowledges the European Research Council ERC Grant ERC-2009-AdG-247411 for funding. P.K.A acknowledges a Junior Research Fellowship from Gonville and Caius College, an Oppenheimer Fellowship from the University of Cambridge. R.J.L.W. acknowledges the EPSRC Grant 11220426 for funding.
External DOI: https://doi.org/10.1021/acs.jpcb.5b08248
This record's URL: https://www.repository.cam.ac.uk/handle/1810/252496