Estudio Electroquímico de electrodos de Carbón Vítreo modificados con el sistema Cu-ZSM5 inmovilizados con PMMA/MA

Abstract

In this work the commercial zeolite NH4-ZSM5 (Zeolite Molecular Sieve of porosity-5) was calcined in air to produce the protonated zeolite H-ZSM5, the copper incorporation into H-ZSM5 was performed by ion exchange obtained the zeolite Cu-ZSM5. The solids prepared were characterized by X-ray diffraction (XRD), Nuclear Magnetic Resonance (NMR), scanning electron microscopy (SEM), nitrogen physisorption (NF), temperature programmed reduction with hydrogen (TPR-H2) and Function Radial Distribution (FRD). The Cu-ZSM5 was mixed with a polymer solution of polymethyl methacrylate (PMMA) and methyl acrylate (MA), the material obtained (Cu-ZSM5/PMMA/MA) was immobilized on a glassy carbon surface, obtaining the zeolite modified electrode. These electrodes were characterized by infrared spectroscopy (IR), Raman spectroscopy and electrochemical techniques as cyclic voltammetry (CV), open circuit potential (OCP) and chronoamperometry (CA). The presence of copper in the zeolite was confirmed by TPR-H2 and FDR. The spectra of XRD and NMR result, indicates not structural changes in the zeolite H-ZSM5 due to the presence of Cu2+. Whereas the results of nitrogen physisorption suggest that the Cu2+ cations occupying the exchange sites in zeolite ZSM5. On the other hand, spectroscopic techniques revealed the presence of groups C=O and C=C in the mix zeolite / polymer. The electrochemical responses showed that in the presence of chloride the reduction of Cu2+ to Cu0 happens in two steps: Cu2+/Cu+ and Cu+/Cu0, due to the stabilization of the species CuCl2-. Experiments at different potential inversion put in evidence that these two redox processes not occur on the surface of glassy carbon but occurs in the interface carbon/zeolite. The exchange rate between the Cu2+ ion of the zeolite and the cations present in the solution is given by the following sequence Li+> K+> Na+. Experiments based on the anion present in the electrolyte propose that redox processes Cu2+/Cu(I) and Cu(I)/Cu0 are carried out with zeolites modified electrodes even in the presence of nitrates and sulfates. The stabilization of Cu(I) is associated with the interaction between Cu (I) with C=C. The electrocatalytic activity in this modified electrodes were evaluated in two reactions, electrochemical oxidation of ascorbic acid and electrochemical reduction of nitrites.