Desenvolvimento de eletrocatalisadores a base de óxidos de Sn, Co e Cu para a eletrorredução de CO2
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Data
2024-03-04
Autores
Garcia, Robson Roella
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Universidade Federal do Espírito Santo
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The electrochemical reduction of CO2 (RECO2) using electrocatalysts could be an alternative to overcome the problems generated by high CO2 emission rates. To catalyze RECO2 in the formation of other products, there are several metal oxides described in the literature, such as SnO2, Co3O4 and CuO. SnO2, Co3O4 are able to catalyze RECO2 to formate, CuO to reduce CO2 to methane, formate, ethanol and carbon monoxide. The aim of this work was to synthesize electrocatalysts based on pure Sn, Co and Cu oxides supported on Vulcan XC 72 carbon by the simple ion coprecipitation method. In order to characterize the crystal structures of the synthesized materials, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Raman techniques were used. Initially, the XRD data confirmed the formation of the synthesized oxides. However, the carbon-supported materials did not show any characteristic peaks using this technique, probably due to their amorphous structure. The Raman technique made it possible to identify carbon in the samples supported on Vulcan XC 72 carbon. SEM and MET data made it possible to identify the morphology of the particles. Thus, it was possible to observe the formation of spherical agglomerates with an average size of 11.0 nm for SnO2 and 13.0 nm for SnO2/C. In the case of Co3O4, Co3O4/C, polygonal particles with an octahedral shape were formed with an average size of 15.7 nm for Co3O4 and 20.6 nm for Co3O4/C. For CuO and CuO/C, agglomerates of particles with an average size of 30.0 nm and 40.0 nm were formed. The electrocatalysts were characterized using the cyclic voltammetry (CV) technique. The oxidation and reduction peaks of the oxides were observed at −1.5 V to 1 V (versus Ag/AgCl (KCl 3.0 mol L−1)). Linear scanning voltammetry (LSV) was then used to study the electrochemical behavior of the oxides synthesized in the presence of CO2. VVL showed that the Co and Cu materials presented a higher current in an N2-saturated medium than in a CO2-saturated solution, indicating that there was competition in the hydrogen evolution reactin was favored. Among the materials studied, CuO/C was the electrocatalyst that showed the best current density when saturated with CO2, at a potential of −1.6 V (versus Ag/AgCl (KCl 3.0 mol L−1)). This material was then used in RECO2 using the chronoamperometry technique, applying a fixed potential of −1.6 V (versus Ag/AgCl (KCl 3.0 mol L−1)) for 30 min, in a solution with a constant flow of CO2. Finally, aliquots of this solution were removed and analyzed via nuclear magnetic resonance, which indicated the formation of some products from the reduction of CO2 such as ethane, acetone and acetate. These studies have therefore demonstrated the potential use of electrocatalysts synthesized by simple ion coprecipitation for the electrochemical reduction of CO2
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