PROTONIC DIFFUSION IN VANADIUM PENTOXIDE XEROGELS

Vanadium pentoxide gels appear to be mixed conductors. Electronic conduction arises from the hopping of small polarons between vanadium ions in different valence state. It mainly depends on the V(IV)/V(V) ratio. Ionic conduction arises from the diffusion of protons through the gel. A very high ac conductivity is observed in the V//2O//5, 1. 6 H//2O xerogel. The ionic conductivity strongly depends on the amount of water in the V//2O//5,nH//2O gel. It decreases quite fast when the water content decreases. The gel should actually be considered as a polyvanadic acid hydrate in which lamellar oxide particles are held together by water layers.