On the Mechanism of Electrochemical Reduction of Niobium Halides in Ionic Liquids

In this paper we will discuss possible mechanisms of the charge transfer for the reduction of Nb halides in ionic liquids with pyrrolidinium cations. The reduction sequence starts from Nb(V) and seems to be relatively complex. Our experimental approach is mainly based on voltammetry combined with in-situ microgravimetry (quartz crystal microbalance) to study the mass-charge balance of the reduction process. There is strong indication for the occurance of at least one intermediate species, probably Nb(III). This intermediate can be detected in rotating ring disk electrode experiments. The rate constants of the individual charge transfer steps can be estimated from square wave voltammetry.