Conversion of Amazonian Biomass (Tucumã Bark) into Porous Carbon Electrodes for Energy Storage

Abstract

The valorization of biomass is a key strategy for producing high-value materials aimed at sustainability. In this study, waste from tucumã (Astrocaryum aculeatum), a native fruit of the Amazon region, was investigated as a precursor for the fabrication of porous carbon electrodes intended for energy storage applications. The synthesis process involved the initial pyrolysis of the biomass, followed by chemical activation using potassium hydroxide (KOH) at varying biochar/KOH ratios (1:1, 1:3, and 1:5). The resulting materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and nitrogen adsorption–desorption analysis. Electrochemical performance was evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy in a 1 M KOH electrolyte within a potential window of −1.0 to 0.0 V. All samples exhibited characteristic (002) and (101) planes in the XRD patterns and D and G bands in the Raman spectra. The specific surface areas were 636, 1932, and 2468 m2 g–1, while the specific capacitances, calculated from GCD measurements, were 84, 146, and 298 F g–1, respectively. The electrode with the highest capacitance also demonstrated excellent cycling stability, retaining 98% of its initial capacitance after 7000 cycles at a current density of 7 A g–1 in KOH electrolyte. These results highlight that increasing the KOH dosage during activation is a critical factor in achieving carbon electrodes with optimized structural and electrochemical properties, emphasizing the potential of Amazonian biomass waste as a sustainable raw material for high-performance supercapacitor development.