Controlled Reduction of Vanadium Oxide Nanoscrolls: Crystal Structure, Morphology, and Electrical Properties

Abstract

The systematic and controlled reduction of vanadium oxide nanoscrolls results in routes to the large-scale preparation of nanostructures of the interesting and useful materials rutile VO 2 and corundum V 2 O 3 . Vanadium oxide (V 2 O 5−δ ) nanoscrolls, prepared by the hydrothermal treatment of aged suspensions of V 2 O 5 and dodecylamine, were reduced in a furnace in an atmosphere of 5% H 2:95% N 2 under different time and temperature conditions to monitor systematic trends in the structure and morphology of the resulting oxides. The products were characterized by X-ray diffraction (XRD), electron microscopy, N 2 sorption measurements, and electrical transport studies. We find that the reduction conditions (time and temperature) play a significant role in determining the crystal structure and morphology of the products. At short times and low temperatures, the reduction products are rutile VO 2 . These convert to corundum V 2 O 3 when temperatures are increased. In all cases, the appearance of crystalline Bragg peaks in XRD is associated with the breaking up of the starting high-aspect nanostructures into small, dense crystallites. Under certain reduction conditions, porous materials with ill-defined X-ray structures are obtained as intermediates.