Niobium Pentoxide Nanorods for the Determination of Dissolved Oxygen in Aqueous Media

Niobium oxides are a group of materials with great potential for applications within various research fields. The wide variety of Nb-O bonds, structures and allotropic forms results in unique properties, extensively described in literature as catalyst for various chemical reactions. Since this material has shown itself promising for catalytical applications, the goal of this study was to investigate its performance for the fabrication of a sensor device for the electrochemical determination of dissolved oxygen, which is of fundamental importance in areas such as environmental monitoring. Thus, a hydrothermal synthesis was used to obtain the niobium oxide and samples that, beyond the hydrothermal process, underwent calcination heat treatment, were compared. The obtained niobium oxides were morphologically analyzed through SEM and Raman spectroscopy. The hydrothermal synthesys produced amorphous niobium pentoxide nanorods, while the calcination heat treatment resulted in crystalline niobium pentoxide. The electrochemical behavior was studied through cyclic voltammetry and the pH effect over the oxygen reduction reaction was taken into consideration. The amperometric response of the sensor between the working electrode and a saturated calomel reference electrode was measured in a 0,5 M lithium perchlorate (LiClO 4 ) solution. Results have shown that the synthesized niobium pentoxide is a promising material for the determination of the dissolved oxygen in aqueous media since it showed and electrocatalytic activity towards the oxygen reduction reaction. The amperometric response has shown itself linearly related to the concentration of the dissolved oxygen and detected concentrations below 1mg/L.