Sulfuric
acid is a ubiquitous compound for industrial processes,
and aqueous sulfate solutions also play a critical role as electrolytes
for many prominent battery chemistries. While the thermodynamic literature
on it is quite well-developed, comprehensive studies of the solvation
structure, particularly molecular-scale dynamical and transport properties,
are less available. This study applies a multinuclear nuclear magnetic
resonance (NMR) approach to the elucidation of the solvation structure
and dynamics over wide temperature (−10 to 50 °C) and
concentration (0–18 M) ranges, combining the 17O
shift, line width, and T
1 relaxation measurements, 33S shift and line width measurements, and 1H pulsed-field
gradient NMR measurements of proton self-diffusivity. In conjunction,
these results indicate a crossover between two regimes of solvation
structure and dynamics, occurring above the concentration associated
with the deep eutectic point (∼4.5 M), with the high-concentration
regime dominated by a strong water–sulfate correlation. This
description was borne out in detail by the activation energy trends
with increasing concentration derived from the relaxation of both
the H2O/H3O+ and H2SO4/HSO4
–/SO4
2–
17O resonances and the 1H self-diffusivity.
However, the 17O chemical shift difference between the
H2O/H3O+ and H2SO4/HSO4
–/SO4
2– resonances across the entire temperature range is nevertheless strikingly
linear. A computational approach coupling molecular dynamics simulations
and density functional theory NMR shift calculations to reproduce
this trend is presented, which will be the subject of further development.
This combination of multinuclear, dynamical NMR, and computational
methods, and the results furnished by this study, will provide a platform
for future studies on battery electrolytes where aqueous sulfate chemistry
plays a central role in the solution structure.