Vanadium Oxide Foams: An Insight into the Structure of the Vanadium Oxide Walls

Vanadium oxide foams have been prepared by mixing V 2 O 5 with hydrogen peroxide and a solution of 1-hexadecylamine. The resulting yellow foams (YF) have been characterized by different methods including X-ray diffraction, thermal analyses, scanning and transmission electron microscopy, infrared spectroscopy, electron spin resonance, and 51 V MAS NMR spectroscopy. The local environment of vanadium probed by 51 V MAS NMR consists of tetrahedral and octahedral vanadium sites corresponding to the decavanadate [H x V 10 O 28 ] (6 - x ) - and [V 4 O 10 ] 4 - /[V 2 O 7 ] 4 - polyanions. This composition is in fair agreement with the reactivity of YF under acidic or basic conditions. Finally, a model for the YF structure based on amine layers intercalated with [H x V 10 O 28 ] (6 - x ) - and [V 4 O 10 ] 4 - /[V 2 O 7 ] 4 - polyanions is proposed.