Síntese eletroquímica de compósito do tipo óxido de grafeno reduzido e hexacianoferrato de lantânio visando a aplicação em supercapacitores.

Abstract

Reduced graphene oxide and lanthanum hexacyanoferrate (rGO/LaHCF) nanocomposite thin film was synthesized in a single step on a glassy carbon electrode (GCE), and subsequently, its performance as a cathodic material in energy storage devices, such as supercapacitors, was evaluated. The synthesis was carried out through the electroreduction of an aqueous dispersion of graphene oxide (GO) at 1.0 mg mL⁻¹, containing 2.0 mmol L⁻¹ potassium ferricyanide K₃[Fe(CN)₆] and 2.0 mmol L⁻¹ lanthanum nitrate hexahydrate La(NO₃)₃.6H₂O, using 0.1 mol L⁻¹ potassium chloride (KCl) as the supporting electrolyte. The film was characterized by electrochemical techniques such as cyclic voltammetry, where it was observed that at pH= 2, the material exhibited the highest charge accumulation and a pseudocapacitive profile. Scanning electron microscopy revealed the presence of the rGO/LaHCF film, where LaHCF particles coated with rGO sheets could be identified. Energy-dispersive X-ray spectroscopy confirmed the presence of all expected elements in the formation of the nanocomposite. Raman spectroscopy showed the typical D and G bands of carbonaceous materials, as well as the signal corresponding to the vibrational mode associated with the triple bond of the cyanide group. Fourier transform infrared spectroscopy results corroborated those observed in Raman spectroscopy. The specific capacitance was successfully evaluated, yielding values of 81 and 62 F g⁻¹ under current densities of 0.5 and 1.0 A g⁻¹, respectively. Additionally, the chargedischarge tests presented a coulombic efficiency of 93.37%, demonstrating that the nanocomposite has good potential for use in supercapacitors.