Estudo eletroquímico e espectroeletroquímico de catalisadores para oxidação de etileno glicol em células a combustível

Abstract

The development of alternative sources of energy is extremely important for the Brazilian energy scenario. Direct alcohol fuel cells (DAFCs) have aroused great interest as an alternative source of energy for automobiles and portable electronic equipment. Ethylene glycol (EG) can be produced from biomass and in recent decades has become a promising candidate for use as fuel in these cells because of its energetic potential, easy storage, low toxicity, relatively high energy density (5,2 kW h Kg-1) and high boiling point (197 °C). However, the oxidation reaction process of this alcohol still needs to be defined. Thus, the objective of this work is to study ternary and binary electrocatalysts for ethylene glycol oxidation having as base metals Pt and Pd targeting fuel cell application. The physical characterization by XRD proved that synthesis by ethylene glycol reduction was efficient for the formation of ternary and binary electrocatalysts and the use of MEV and MET techniques showed surface morphology with dispersed particles and, in some cases, with formation of agglomerates. The mean particle sizes were between 2 and 4 nm for Pt-based materials and 8 to 12 nm for Pd-based materials. Electrochemical tests identified higher activity and stability for the PtPd/C binary alloys in the 48:52 composition that obtained an energy density of 6.41 mA cm-2. The in situ infrared spectroscopy results of the ethylene glycol oxidation in alkaline media showed that these materials are selective to glycolic acid.