TY - JOUR

T1 - Investigation of proton dynamics and the proton transport pathway in choline dihydrogen phosphate using solid-state NMR

AU - Cahill, Lindsay S.

AU - Rana, Usman Ali

AU - Forsyth, Maria

AU - Smith, Mark E.

PY - 2010

Y1 - 2010

N2 - 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 H-1 solid-state NMR and 2D NMR pulse sequences, including P-31 and C-13 CODEX and H-1 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.

AB - 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 H-1 solid-state NMR and 2D NMR pulse sequences, including P-31 and C-13 CODEX and H-1 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.

KW - Choline -- Transport properties

KW - Protons -- Transport properties

KW - Nuclear magnetic resonance spectroscopy

U2 - 10.1039/b916422g

DO - 10.1039/b916422g

M3 - Journal article

VL - 12

SP - 5431

EP - 5438

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9084

IS - 20

ER -