Compostos de coordenação aplicados como catalisadores na eletro-oxidação de álcool

Abstract

Direct ethanol fuel cells (DEFCs) are considered a viable alternative power source for both stationary and mobile applications. Obstacles to widespread use of DEFCs include the slow kinetics of ethanol electro-oxidation, which has been countered by using Pt-based electrocatalysts. Pt-based electrocatalysts are produced by partially or totally replacing the alloying platinum with other less expensive materials such as transition metal complexes. This study describes the synthesis and characterization of the electrochemical properties of two new complexes containing salen-type Schiff base coordinates to the metallic center UO2, whose molecular structure was previously elucidated by FTIR, elemental analysis (CHN) and RMN and 1H. Its cyclic voltammogram indicates two reversible redox pairs at 0.69/0.56 V (E1/2 = 0.63 V) and 0.85/0.77 V (E1/2 = 0.81 V) vs. ERH, attributed to ligand processes such as two successive oxidations of phenolate to phenoxyl radicals. The use of complexes UO2(3-OMe-t-salcn)H2O and UO2(3-OMe-c-salcn)H2O called C1 and C2, as a catalyst for ethanol oxidation reaction in acidic media was also investigated via cyclic voltammetry and chronoamperometry varying mass ratios between complex PtSn/C; system pH, scan speed and ethanol concentration. Six PtSn-based catalysts were produced with different PtSn:Complex mass ratios. For all catalysts obtained in this work, direct scanning of the samples indicated that the peak current density for the 6:1 PtSn/C:C1 catalysts was the highest . In addition, it exhibited better catalystic activity for ethanol electro-oxidation, exhibited better catalytic activity for ethanol electro-oxidation; i.e., it decreased the onset potential during the oxidation of ethanol. Moreover, this catalyst exhibited peak-current densities (j) at 34.53 mA.cm-2; i.e., ~5.2-fold that of PtSn/C. In addition, chronoamperometry data indicated higher catalytic activity at 0.6 V for PtSn/C:[UO2(3-OMe-t-salcn)H2O]-based catalysts.