Obtenção de nanoestruturas core-shell para aplicação na eletrocatálise da reação de oxidação de glicerol

Abstract

This work aimed to synthesize and evaluate core-shell nanocatalysts based on platinum (Pt) combined with less noble metals—cobalt (Co), nickel (Ni), and tin (Sn)—in a Pt:M molar ratio of 1:1 (M = Co, Ni, and Sn), denoted as Co@Pt/C, Ni@Pt/C, and Sn@Pt/C, respectively. The catalysts were obtained through a sequential reduction method designed to deposit Pt onto preformed metallic cores. Characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) revealed nanoparticles ranging from 8 to 14 nm with surfaces predominantly composed of Pt. High-resolution TEM images confirmed the overlapping of metallic phases, supporting the formation of a core-shell architecture. The electrocatalytic performance of the materials was investigated for the glycerol oxidation reaction (GOR) in alkaline media under three conditions: (i) 0.1 mol.L-1 KOH + 0.1 mol.L-1 glycerol; (ii) 0.5 mol.L-1 KOH + 1.0 mol.L-1 glycerol; and (iii) 1.0 mol.L-1 KOH + 1.0 mol.L-1 glycerol. In all cases, Co@Pt/C, Ni@Pt/C, and Sn@Pt/C exhibited superior activity compared to commercial Pt/C, showing lower onset potentials, higher current densities, and greater tolerance to catalytic poisoning. Under 0.1 mol.L-1 KOH + 0.1 mol.L-1 glycerol, chronoamperometric tests (0.6 V vs. RHE, 1800 s) showed that Sn@Pt/C achieved a final current density 1.3 times higher than Pt/C. Under 1.0 mol.L-1 KOH + 1.0 mol.L-1 glycerol, Co@Pt/C reached a current density 7.5 times greater than Pt/C after 3600 s. In situ Fourier-transform infrared spectroscopy (FTIR) studies identified reaction intermediates and products such as glyceraldehyde, 1,3-dihydroxyacetone, tartronate, formate, and carbonate ions, indicating both partial and complete oxidation of glycerol. These results demonstrate that introducing a second metallic core significantly alters the electronic structure and surface properties of Pt, enhancing its catalytic performance and selectivity toward glycerol oxidation in alkaline medium.