Investigations of Vanadium Dioxide as a Catalytic Electrode and Support

Abstract

Vanadium dioxide (VO2) is a material that undergoes a phase transition at 68 °C which corresponds to interesting changes in its optical and electronic properties, including a decrease in resistivity of up to five orders of magnitude. While the physical properties of this material have long been studied, the ability of VO2 to detect various analytes has been largely ignored. This work utilizes films and particles of VO2 and related materials in the study of two analytes with potential real-world applicability, 2,4,6-trinitrotoluene (TNT) and carbon monoxide. The electrochemical reduction of TNT was investigated using films of vanadium dioxide. Three distinct reduction peaks were observed in the potential range of −0.50 to −0.90 V (vs Ag/AgCl), corresponding to the electrochemical reduction of the three nitro-groups on the TNT molecule and demonstrating a linear response to TNT concentration. Furthermore, the use of adsorptive stripping voltammetry allowed detection of TNT as low as 1 μg/L (4.4 nM), which is comparable to the lowest concentrations of TNT detection currently available in the literature. Vanadium dioxide materials were further used as supports for the gold-catalyzed oxidation of carbon monoxide. Although other metal oxides such as titanium dioxide (TiO2) have been well documented in their ability to act as supports for this reaction at temperatures close to or at room temperature, VO2 has not yet been pursued as a possible support. This work demonstrates for the first time the ability of VO2 to act as a support for gold nanoparticle catalysts, using V2O4 and TiO2 as controls. The findings of this work reveal catalytic activity of these materials that does not directly correlate to gold nanoparticle size, despite what has been published previously. The basis for this discrepancy is still unclear and warrants further investigation. However, the results described in this work are the first describing the use of VO2 materials as gold nanoparticle supports for CO oxidation, and open further avenues of research using this unique material.