Synthesis and electrochemical properties of InVO4nanotube arrays

Abstract

This paper reports an experimental study on the synthesis and electrochemical properties of InVO₄ nanotube arrays fabricated by capillary-enforced sol-filling in templates in combination with solvent-evaporation induced deposition. InVO₄ sol was synthesized using the sol–gel route from vanadium oxoisopropoxide and indium nitrate with ethanol as the solvent. Nanotube arrays of InVO₄ were prepared by filling the sol into pores of polycarbonate membranes and pyrolyzing through sintering. Another type of InVO₄ nanotube array (InVO₄–acac) was obtained from the sol with the addition of acetyl acetone (acac). For comparison purposes, InVO₄ films were prepared by drop casting from the same InVO₄ sol. Films and the two types of nanotube array of InVO₄ annealed at 500 °C consisted of mixed monoclinic (InVO₄-I) and orthorhombic (InVO₄-III) phases. Scanning electron microscopy (SEM) characterization indicated that the nanotubes were aligned perpendicular to the substrate surface with an outer diameter of ∼200 nm for short InVO₄ nanotubes and ∼170 nm for long InVO₄–acac nanotubes. Chronopotentiometry results revealed that the InVO₄–acac nanotube array has the highest charge capacity (790 mAh g⁻¹), followed by the InVO₄ nanotube array (600 mAh g⁻¹) then the InVO₄ film (290 mAh g⁻¹). Such enhanced lithium-ion intercalation properties were ascribed to the large surface area and short diffusion distance offered by nanostructures and amorphisation caused by acetyl acetone in the case of InVO₄–acac nanotube arrays.