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Investigation of proton dynamics and the proton transport pathway in choline dihydrogen phosphate using solid-state NMR

journal contribution
posted on 01.01.2010, 00:00 authored by L Cahill, U Rana, Maria ForsythMaria Forsyth, M Smith
Choline dihydrogen phosphate has previously been shown to be a good ionic conductor as well as an excellent host for acid doping, leading to high proton conductivities required for e.g., electrochemical devices including proton membrane fuel cells and sensors. A combination of variable-temperature 1H solid-state NMR and 2D NMR pulse sequences, including 31P and 13C CODEX and 1H BaBa, show that the proton conduction mechanism primarily involves assisted transport via a restricted three-site motion of the phosphate unit around the P–O bond that is hydrogen bonded to the choline and exchange of protons between these anions. In other words, proton transport at ambient temperatures appears to occur most favorably along the crystallographic b axis, from phosphate dimer to dimer. At elevated temperatures exchange between the protons of the hydroxyl group on the choline cation and the hydrogen-bonded dihydrogen phosphate groups also contributes to the structural diffusion of the protons in this solid state conductor.

History

Journal

Physical chemistry chemical physics

Volume

12

Issue

20

Pagination

5431 - 5438

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