Multinuclear PFGSTE NMR description of 39 K, 23 Na, 7 Li, and 1 H specific activation energies governing diffusion in alkali nitrite solutions

• Published in: Journal of magnetic resonance (1997) 2024-07, Vol.364, p.107707
• Main Authors: Graham, Trent R, Kennedy, Ashley R, Felsted, Robert G, Colina-Ruiz, Roberto A, Nienhuis, Emily T, Reynolds, Jacob G, Pearce, Carolyn I
• Format: Article
• Language: English
• ISSN: 1096-0856
• DOI: 10.1016/j.jmr.2024.107707

While pulsed field gradient stimulated echo nuclear magnetic resonance (PFGSTE NMR) spectroscopy has found widespread use in the quantification of self-diffusivity for many NMR-active nuclei, extending this technique to uncommon nuclei with unfavorable NMR properties remains an active area of research. Potassium-39 ( K) is an archetypical NMR nucleus exhibiting an unfavorable gyromagnetic ratio combined with a very low Larmor frequency. Despite these unfavorable properties, this work demonstrates that K PFGSTE NMR experiments are possible in aqueous solutions of concentrated potassium nitrite. Analysis of the results indicates that K NMR diffusometry is feasible when the nuclei exhibit spin-lattice and spin-spin relaxation coefficients on the order of 60-100 ms and 50-100 ms, respectively. The diffusivity of K followed Arrhenius behavior, and comparative Na, Li, and H PFGSTE NMR studies of equimolal sodium nitrite and lithium nitrite solutions led to correlations between the enthalpy of hydration with the activation energy governing self-diffusion of the cations and also of water. Realizing the feasibility of K PFGSTE NMR spectroscopy has a widespread impact across energy sciences because potassium is a common alkali element in energy storage materials and other applications.