Vacuum Topotactic Conversion Route to Mesoporous Orthorhombic MoO3 Nanowire Bundles with Enhanced Electrochemical Performance

The growth of mesoporous bundles composed of orthorhombic MoO3 nanowires with diameters ranging from 10 to 30 nm and lengths of up to 2 inn by topotactic chemical transformation from triclinic alpha-MoO3 center dot H2O nanorods under vacuum condition at 260 C is achieved. During the process of vacuum topotactic transformation, the nanorod frameworks of the precursor alpha-MoO3 center dot H2O can be preserved. The crystal structures, molecular structures, morphologies, and growth behavior of the precursory, intermediate and final products are characterized using powder X-ray diffraction (PXRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). Detailed studies of the mechanism of the mesoporous MoO3 nanowire bundles formation indicate topotactic nucleation and oriented growth of the well-organized orthorhombic MoO3 nanowires inside the nanorod frameworks. MoO3 nanocrystals prefer [001] epitaxial growth direction of triclinic alpha-MoO3 center dot H2O nanorods due to the structural matching of [001] alpha-MoO3 center dot H2O//[100] MoO3. The electrochemical measurement of the mesoporous MoO3 nanowire bundles indicates that their galvanostatic Li storage performance can be significantly improved. The high reversible capacities of 954.8 mA h g(-1) can be retained over 150 cycles. The topotactic growth under vacuum based on the crystal structural relationship of hydrated metal oxide and related metal oxide will provide an effective and all-purpose route to controlled preparation of novel micro/nanostructured oxides (such as V2O5 and WO3 nanowires, etc.) with enhanced properties (energy storage/conversion, organic electronics, catalysis, gas-sensor, and so on).