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Nanostructured electrocatalysts for application in direct alkaline-acid fuel cells of glycerol

Abstract

This project aims at the application of nanostructured electrocatalysts such as anodes and cathodes of alkaline-acid direct glycerol fuel cells. The combination of the materials proposed for glycerol oxidation/hydrogen peroxide reduction have never been studied for such a purpose. The anodic reaction will be the oxidation of glycerol in alkaline medium. The cathodic reaction will be the hydrogen peroxide reduction reaction in an acidic medium, to completely replace oxygen. Tokuyama alkaline membranes and Nafion membranes treated for basic media will be used. In all fuel cells as anodes will be used binary systems (Fe, Nb and Bi nanooctahedra with Pd and Au nanoparticles) ternary systems (Pd and Au nanocubes decorated with Fe, Nb and Bi nanoparticles) and (Bi, Fe or Nb nanoparticles with Pd or Au nanoparticles), supported in carbon XC72. In the cathode part, the catalysts may be Au/C with or not nanostructures of the metals of Ce and Nb and in carbon XC72. The oxidation reaction of Glycerol will be studied by cyclic voltammetry and chronoamperometry techniques, and all better materials will be studied in alkaline-acid direct glycerol fuel cells. The oxidation mechanism of Glycerol will be studied by means of the in-situ infrared technique in half-cell experiments. The products formed during oxidation in single fuel cells will be evaluated by the ex-situ Raman technique (FT Raman). The materials will be characterized by physical techniques such as X-ray Diffraction (XRD), X-ray Dispersive Energy (EDX), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Infrared Spectrophotometry (FTIR), Raman spectroscopy and contact angle, where aspects such as: particle size, phases, formation of nanostructures, oxygenated species, defects and surface hydrophilicity will be evaluated. The electrocatalysts will be tested in their stability by ICP- MS to measure the dissolution of metals in long operating times. The clear problems, which have not yet been solved in the literature for glycerol and the use of the oxygen reduction reaction, to be solved in this project with the nanostructures studied are: 1) oxidize glycerol to carbonate in greater quantity to extract the greatest amount of electrical energy from this fuel in alkaline-acid direct glycerol fuel cells, 2) decrease the amount of Pd (Au as substitute with low amount) with nanostructures to decrease the cost of electrocatalysts, 3) to study the reaction mechanism, checking the best electrocatalysts, for the formation of more carbonate, 4) to replace the oxygen reduction reaction by the hydrogen peroxide reduction reaction in fuel cells that presents a faster kinetics and a higher cell overpotential (Ec-Ea) and 5) to evaluate the stability of anode and cathode electrocatalysts in accelerated stress tests for operation in alkaline-acid direct glycerol fuel cells. Specifically, to increase the selectivity for the formation of carbonate from glycerol according to what has been observed in the literature it is proposed to form nanostructures (electrocatalysts) that increase the number of defects, acidic oxygenated species, hydrophilicity and the number of active sites, improvement of electronic properties in the vicinity of electrocatalyst atoms, modification of crystallinity, lattice parameters, interatomic distances, binding energies and stability. If the structures do not promote carbonate formation, another goal is the formation of high value-added products such as hydroxypyruvate, 1,3 dihydroxyl 2 propanone, and glyceraldehyde in which electrocatalysts can be selective. It is expected with the development of the project to find higher open circuit potentials, higher current densities, higher power densities in alkaline-acid direct glycerol fuel cells, never studied before using the materials that will be prepared in this project. (AU)

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