STRUCTURE OF С@Al2O3 BY MULTINUCLEAR SOLID-STATE NMR SPECTROSCOPY
D. F. Khabibulin1,2, A. M. Volodin1, O. B. Lapina1,2
1Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk National Research State University, Novosibirsk, Russia
Keywords: Оі-AlO, Оґ-AlO, графеновое покрытие, наночастицы оксида алюминия, Н Al ЯМР
, ОН-группы, graphene coating, aluminum oxide nanoparticles, ОН groups
Abstract
The 27Al, 1H MAS NMR method is used to study initial nanosized metastable aluminum oxides of a pseudoboehmite series (g- and d-Al2O3) after being coated with graphene (С@Al2O3) and annealed in the air (С@Al2O3-Т). It is demonstrated that aluminum nanoparticles coated with graphene and annealed at high temperatures (to 750°C for g and 1180°C for d) preserve their phase composition but differ from initial oxides by a very low concentration of defects (ОН groups). After the annealing of the graphene coating the hydroxyl cover of oxides is reduced, however, the set of ОН groups differs greatly from that of the initial oxides. Only one type of terminal ОН groups with a ~0.2 ppm shift and one type of bridging m2-ОН groups with a 1.8 ppm shift for g-Al2O3 from OH-m2-AlVAl n and 2.1 ppm for d-Al2O3 OH-m2-AlIVAl n are observed. The data obtained make it possible to characterize in detail the d-Al2O3 pure phase.
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