Selective Synthesis of 3D Aligned VO₂ and V₂O₅ Carbon Nanotube Hybrid Materials by Chemical Vapor Deposition

3D carbon nanotube hybrid materials containing VO₂ and V₂O₅ evenly distributed onto vertically aligned carbon nanotubes (VACNTs) is reported. Adjustable loading of particles in controllable sizes and shapes onto the VACNTs was developed via a stepwise chemical vapour deposition (CVD) approach. Solid VO(acac)₂ is chosen as vanadium source. CO₂ acts as reactive gas for the pre‐functionalisation of the VACNTs. The process temperature was identified as key parameter to control the deposited vanadium oxide phase. A temperature of 550 °C results in monoclinic VO₂, while 600 °C results in the deposition of V₂O₅ onto the VACNT support. The morphology and the amount of deposited material was found to be dependent on the reactor dimensions and the degree of functionalisation of the carbon support. An increase of the D/G ratio of the VACNT from 0.75 to 1.08 caused by a CO₂ treatment step within the process led to an increase of the particle coverage from a scarce coverage without prior CO₂ treatment to a dense coverage of the VACNT support after 15 min of CO₂ exposure time. Size and crystallinity of the as deposited particles can be further adjusted by a controlled heat treatment after VO(acac)₂ precursor deposition.