A series of hydrous ruthenium oxide (RuO 2 ‚xH 2 O) samples annealed at different temperatures have been studied by solid-state 1 H NMR spectroscopy. The proton dynamics of the RuO 2 ‚xH 2 O samples was characterized for the first time through variable-temperature 1 H spin-lattice relaxation time (T 1 ) measurements. For the RuO 2 ‚xH 2 O samples annealed at temperatures lower than 100 °C and higher than 200 °C, a high proton activation energy was obtained, implying that the proton dynamics/diffusive motion is relatively restrained, whereas the samples annealed at temperatures between 100 and 200 °C exhibited relatively low proton activation energies, indicating that the protons can easily diffuse into the bulk of the material. Therefore, the proton activation energy correlates strongly with the hydrogen transfer and storage ability of the proton-conducting materials. In combination with electrochemical measurements, our NMR data also suggest that the coexistence of the Ru 2+ , Ru 3+ , and Ru 4+ valency states in the local structure of the RuO 2 ‚xH 2 O is crucial for hydrogen transfer and storage ability.
13C chemical shift tensor data from 2D FIREMAT spectra are reported for 4,7-di-t-butylacenaphthene and 4,7-di-t-butylacenaphthylene. In addition, calculations of the chemical shielding tensors were completed at the B3LYP/6-311G** level of theory. While the experimental tensor data on 4,7-di-t-butylacenaphthylene are in agreement with theory and with previous data on polycyclic aromatic hydrocarbons, the experimental and theoretical data on 4,7-di-t-butylacenaphthene lack agreement. Instead, larger than usual differences are observed between the experimental chemical shift components and the chemical shielding tensor components calculated on a single molecule of 4,7-di-t-butylacenaphthene, with a root mean square (rms) error of +/-7.0 ppm. The greatest deviation is concentrated in the component perpendicular to the aromatic plane, with the largest value being a 23 ppm difference between experiment and theory for the 13CH2 carbon delta11 component. These differences are attributed to an intermolecular chemical shift that arises from the graphitelike, stacked arrangement of molecules found in the crystal structure of 4,7-di-t-butylacenaphthene. This conclusion is supported by a calculation on a trimer of molecules, which improves the agreement between experiment and theory for this component by 14 ppm and reduces the overall rms error between experiment and theory to 4.0 ppm. This intermolecular effect may be modeled with the use of nuclei independent chemical shieldings (NICS) calculations and is also observed in the isotropic 1H chemical shift of the CH2 protons as a 4.2 ppm difference between the solution value and the solid-state chemical shift measured via a 13C-1H heteronuclear correlation experiment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.