VICTORIA AMATHEUS MAIA
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Artigo IPEN-doc 30430 Optimizing PtSn composition in direct sugarcane extract fuel cells2024 - VILLARDI, BRUNO D.Q.; MAIA, VICTORIA A.; NANDENHA, JULIO; ZAMBIAZI, PRISCILLA J.; SOUZA, RODRIGO F.B. de; NETO, ALMIR O.Pt90Sn10/C composition exhibited a strong maximum power density value and a good sugar oxidation response in sugar extract solution in comparison with others electrocatalysts prepared. Pt90Sn10/C demonstrated a maximum power density approximately 93% higher than that of Pt80Sn20/C, which is the second most active material and more than 8 times bigger than Pt/C. The primary difference between the two lies in glucose consumption, which is approximately 90% higher in Pt90Sn10/C. It is important to highlight that in the more active materials; fructose consumption remains relatively constant, ranging between 7 and 8%. The enhanced performance could be attributed to both the altered electronic properties resulting from tin integration into the platinum crystal lattice and the activation of water at less positive potentials by a bifunctional mechanism. XRD results showed that the lattice parameters were expanded indicating the insertion of Sn to Pt, while that cyclic voltammetry showed that all materials present the hydrogen adsorption–desorption region over Pt (− 0.2 to 0.15 V); however, when increasing the tin content in the catalyst, the region decreases the definition and is associated with the presence of transition metals such as Sn. TEM images and histograms for PtSn showed the increase in the average particle size accompanying the tin enrichment in the composition; this effect could be tin oxide in material surface and is in agreement with other works.Artigo IPEN-doc 28867 PtSb/C electrocatalysts for glycerol oxidation in alkaline electrolyte2022 - PEREIRA, C.V.; MAIA, V.A.; ZAMBIAZI, P.J.; SOUZA, R.F.B. de; ANTOLINI, E.; NETO, A.O.Pt/C and PtSb/C catalysts in various atomic ratios were synthesized by the sodium borohydride reducing method and their activity for the glycerol oxidation reaction (GOR) was evaluated in alkaline media. Transmission Electron Microscopy (TEM) images showed that Pt particle size increases with increasing Sb content in the catalyst. X-ray photoelectron spectroscopy (XPS) showed that the ratio of Pt and Sb is close to that expected. By XPS measurements, the presence of Sb2O5 in Pt70Sb30/C and Pt50Sb50/C was observed. X-ray diffraction (XRD) analysis revealed the presence of the face-centered cubic (FCC) structure of Pt and PtSb and of some others phases that could be identified as Sb oxides. By linear sweep voltammetry (LSV) measurements, Pt80Sb20/C showed the highest activity for the GOR in alkaline media for potentials >−0.35 V vs. Ag/AgCl, while Pt50Sb50/C showed the highest GOR activity in the potential range between −0.60 and −0.35 V vs. Ag/AgCl. The direct glycerol fuel cells with Pt80Sb20/C as the anode catalyst showed the best performance. These results attest the beneficial effect of Sb addition to platinum: the activity enhancement in the presence of Sb atoms has to be ascribed to both a bifunctional mechanism related to the presence of Sb oxides, and an electronic effect between platinum and antimony in the PtSb alloy.