Electrical conductivity and Raman characterization of V2O5 grown by sol–gel technique inside nanoscale pores

• V2O5 xerogel grown inside the pores (200 nm large) of an Al2O3 membrane, 60 μm thick
• Complex impedance in the range 1 Hz–40 MHz for confined and unconfined gels
• Micro-Raman analysis on confined gels, unconfined gels and crystallized regions
• All the data indicates a more amorphous structure for the confined gels.

Vanadium pentoxide, V2O5, is one of the most widely studied electrode materials. A promising way to improve its conduction properties is to grow V2O5 gels confined in nanoporous structures. In this work Al2O3 filtration membranes with 200 nm pores were used as template for the growth of nanopore-confined V2O5·nH2O xerogels. Impedance spectroscopy was performed in the range from 1 Hz to 40 MHz to study their conductivity and micro-Raman spectroscopy was also performed to investigate their structural evolution. Two kinds of proton conduction could be observed: one for water confined in the bulk crystal lattice and a second one associated with water intercalated in the ribbon-like structures associated with V2O5 xerogels. Both types of conduction were found to be increased in xerogels confined in nanopores. This increase in proton conduction was attributed to better orientation of V2O5 in the pores and to the more amorphous nature of the confined xerogel.