Resumo:
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.
