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Issue 20, 2010
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Investigation of proton dynamics and the proton transport pathway in choline dihydrogen phosphate using solid-state NMR

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Abstract

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.

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

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Publication details

The article was received on 11 Aug 2009, accepted on 12 Mar 2010 and first published on 08 Apr 2010


Article type: Paper
DOI: 10.1039/B916422G
Citation: Phys. Chem. Chem. Phys., 2010,12, 5431-5438
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    Investigation of proton dynamics and the proton transport pathway in choline dihydrogen phosphate using solid-state NMR

    L. S. Cahill, U. A. Rana, M. Forsyth and M. E. Smith, Phys. Chem. Chem. Phys., 2010, 12, 5431
    DOI: 10.1039/B916422G

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