Desenvolvimento de eletrocatalisadores Pt/Nb²O5/Ti para a eletro-oxidação de glicerol.

Abstract

Glycerol, an abundant co-product in biodiesel production, has attracted interest due to its potential as a feedstock with high added-value chemical properties. Glycerol electro-oxidation is a promising route for the delivery of these products, using electrocatalysts that can operate under different conditions and with high selectivity. In this work, electrocatalysts platinum (Pt) based on deposited niobium pentoxide (Nb2O5) supported on titanium substrate (Ti) were developed, and evaluated in the electro oxidation of glycerol. The electrocatalysts were prepared in two main steps: thermal deposition of a precursor resin containing Nb, obtained by the Pechini method, and Pt electrodeposition by cyclic voltammetry. Material characterization included thermal analysis (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The electrocatalytic activity was evaluated by cyclic voltammetry and chronoamperometry in acidic and basic media. Thermal analysis showed that the complete decomposition of the precursor resin occurs above 500°C. X-ray diffractograms indicated the formation of amorphous Nb2O5 at 450°C and a transition to pseudo-hexagonal and orthorhombic crystalline phases at higher temperatures. SEM micrographs revealed that the surface of the electrocatalysts becomes rougher with increasing heat treatment temperature, and EDS analyses confirmed the presence of Pt, Ti, and Nb, as well as the atomic percentage in each electrocatalyst. The voltammograms showed that the electrocatalysts containing Nb2O5 presented higher activity in the electro-oxidation of glycerol compared to Pt/Ti, with emphasis on the electrocatalysts treated at 550°C and 450°C, which presented the highest current densities and lower poisoning by intermediaries. This work demonstrated that the incorporation of Nb2O5 in Pt electrocatalysts improved the activity in the electro-oxidation of glycerol, making them promising for applications in glycerol valorization processes. Furthermore, electrocatalysts demonstrated better performance in acidic media than in basic media.