Estudo eletroquímico de filme bicamada de óxido de manganês e hidróxido de níquel para aplicação em supercapacitores híbridos

Abstract

The high energy demand caused by population growth has led to the development and improvement of new energy conversion and storage systems. The hybrid supercapacitor is one of the energy storage devices that has been gaining more and more ground in the energy storage market, mainly due to advances in materials research. The aim of this work was to evaluate the electrochemical and synergistic behavior of MnO2 and Ni(OH)2 films obtained by galvanostatic electrodeposition for application in hybrid supercapacitors. X-ray diffraction (XRD) analysis suggested the δ-MnO2 phase for the MnO2 films and the presence of two polymorphs for the Ni(OH)2 films: α-Ni(OH)2 and β-Ni(OH)2, as well as the presence of metallic Ni. EDS analysis showed the presence of the main elements (Ni, Mn and O) that make up the MnO2 and Ni(OH)2 films, and the same elements were also identified in the Ni(OH)2/MnO2 bilayer film. Scanning Electron Microscopy (SEM) showed the formation of MnO2 films with cracks. The Ni(OH)2 films showed cracks with the formation of plates and microparticles, and these characteristics had a distinct influence on the electrochemical responses. The electrochemical characterization showed an improvement in the response of the bi-layer film in mixed electrolyte (KOH+Na2SO4), when compared to the response of the individual films. The Ni(OH)2 600 s / MnO2 1200 s bilayer film showed the best electrochemical properties for use in hybrid supercapacitors. This bi-layer film showed a significantly higher specific capacitance of 331.1 C.g1 , with a cyclic stability of 106.7% in retaining the specific capacitance after 5,000 cycles at a scan rate of 100 mV.s-1 . The improvement in electrochemical performance is due to the synergistic interaction between the layers, signaling a promising potential for use in energy storage devices, such as hybrid supercapacitors.