Oxygen Storage in Transition Metal-Doped Bixbyite Vanadium Sesquioxide Nanocrystals

Bixbyite vanadium sesquioxide (V₂O₃) is a metastable polymorph of vanadium oxide that has been shown to have a significant oxygen storage capacity with very low temperature oxidation onset. In this work, bixbyite V₂O₃ nanocrystals were synthesized with titanium and manganese dopants. Doped materials with varied dopant concentration were synthesized, and all were incorporated as aliovalent metal ions. The oxygen storage capacity of these nanocrystal materials was evaluated over ten oxidation and reduction cycles. It was found that over these ten cycles, the oxygen storage capacity of all the materials fell drastically. In situ X-ray diffraction evidence shows that manganese-doped materials degrade into an amorphous manganese-containing vanadate, while titanium-doped materials form crystalline degradation products. In all cases, this degradation causes an increase in the minimum mass achieved during oxygen release, indicating irreversible oxidation.