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Proton transport in choline dihydrogen phosphate/H3PO4 mixtures

journal contribution
posted on 01.01.2010, 00:00 authored by U Rana, Paul Bayley, R Vijayaraghavan, Patrick HowlettPatrick Howlett, D MacFarlane, Maria ForsythMaria Forsyth
Mixtures of the plastic crystal material choline dihydrogen phosphate [Choline][DHP] and phosphoric acid, from 4.5 mol% to 18 mol% H3PO4, were investigated and shown to have significantly higher proton conductivity compared to the pure [Choline][DHP]. This was particularly evident from the electrochemical hydrogen reduction reaction and the proton NMR diffusion measurements, in addition to ionic conductivity measured from the impedance spectroscopy. The ionic conductivity was observed to increase by more than an order of magnitude in phase I (i.e. the highest temperature solid phase in [Choline][DHP]) reaching up to 10−2 S cm−1. The multinuclear NMR spectroscopy data suggest that, at least on the timescale of the NMR measurement, the H+ cations and [DHP] anions are equivalent in both phases. The pulsed field gradient NMR diffusion measurements of the 18 mol% acid sample indicate that all three ions are mobile, however the H+ diffusion coefficient is an order of magnitude higher than for the [Choline] cation or the [DHP] anion, and therefore conduction in these materials is dominated by proton conductivity. The thermal stability, as measured by TGA, is unaffected with increasing acid additions and remains high; i.e. no significant mass loss below 200 °C.

History

Journal

Physical chemistry chemical physics

Volume

12

Issue

37

Pagination

11291 - 11298

Publisher

Royal Society of Chemistry

Location

Cambridge, England

ISSN

1463-9076

eISSN

1463-9084

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2010, Owner Societies