Marcela Alejandra Bavio

This paper examines the electrochemical performance of humic acids extracted from natural water and fertile soil, like electrode materials for supercapacitors, as proposed and evaluated. Humic acids come from the decomposition of organic matter in the humus formation process, therefore they are considered renewable resources. The humic acids are characterized by Fourier transform infrared spectroscopy, UV–vis spectroscopy, optical microscopy, and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy. Electrochemical techniques are used to evaluate the behavior of humic acids like electrode materials for supercapacitors. Cyclic voltamperometry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy are performed in H₂SO₄ 0.5 mol L⁻¹. The highest capacitance, energy, and power values are found with humic acids from the soil. Thus, the specific capacitance of 87.15 F g⁻¹ at 0.040 A g⁻¹, maximum power of 32680 W kg⁻¹, and energy of 60.52 W h kg⁻¹ are obtained. The humic acids from soil have good cycling stability and high energy efficiency, placing them as promising materials in energy storage.

Developing technological solutions using regional lignocellulosic waste as precursors is key to reducing the environmental impact of the lack of ecological disposal treatments on them, such as on-site burning and accumulation in landfills. These residues can be used to develop activated carbons. Activated carbon is a versatile material with a high surface area that can be used for energy storage.In this work, were value yerba mate residues by producing chemically activated carbon to be used as electrode material in supercapacitors. A process of carbonization, impregnation, activation with KOH and subsequent washing and drying is carried out for their development. Variables such as impregnation radius and activation temperature are studied. The developed carbons were characterized by physicochemical and electrochemical techniques. They were found to have high surface areas, up to 1800 m2g-1, with a hierarchical porous distribution. A maximum specific capacitance of 644 Fg-1 at 0.1 Ag-1, and power values of ca 32000 Wkg-1, at 33 Ag-1 were found. All the synthesized carbons have excellent electrochemical properties and are suitable for use as active material in supercapacitors.

Los compuestos orgánicos presentes en efluentes industriales son en su mayoría resistentes a los tratamientos biológicos y químicos convencionales. La industria textil ha presentado notables problemas medioambientales vinculados principalmente al uso y la gestión del recurso hídrico, tiene un alto consumo de agua potable y subterránea en sus procesos. Sus aguas residuales son las más contaminantes de los sectores industriales.

In this paper, the study of double perovskite La2NiMnO6 as electrode material for supercapacitors is presented. The mixed oxide was prepared by citrate precursor route (CIT). The sample was calcined for 4 hours at 800 degrees C. The material was characterized by PXRD, SEM and FTIR spectroscopy. Cyclic voltammetry and galvanostatic charge/discharge measurements were used to study the capacitive behavior of the nanomaterial in alkaline and acid solutions. I/V profiles were obtained at varying the scan rates from 10 to 100 mV/s. The galvanostatic charge/discharge curves were recorded at different current density values in the 3-17 A/g range. The higher capacitance values were obtained in alkaline medium. Thus, a specific capacitance of 1681 F/g at a current density of 3 A/g, and a power and an energy specific of 2903 W/kg and 378 Wh/kg, were obtained in KOH. While in acid solution these values were 492 F/g, 3225 W/kg and 137 Wh/kg, respectively. These promising results promote the use of the double perovskites for electrode materials in supercapacitors.

In this work, the construction of electrochemical capacitors using polyaniline–carbon black nanocomposites as electrode material is described. Symmetric and asymmetric cells were assembled. The active material was supported on carbon cloth acting as current collector as well. The electrolyte was H₂SO₄ 0.5 M, and the selected potential range was 1 V. The electrochemical behavior of the arrayed supercapacitors was studied by cyclic voltammetry and galvanostatic charge/discharge runs. At a constant current density of 0.3 A/g, a specific capacitance value of 1039 F/g was obtained for a symmetric assembly using both electrodes prepared with polyaniline and carbon black nanocomposites. When the set is asymmetric, being the positive electrode made of polyaniline and carbon black nanocomposites, the specific capacitance value is 1534 F/g. For the latter array, the specific power and energy density values are 300 W/kg and 426 Wh/kg at 0.3 A/g, and 13 700 W/kg and 28 Wh/kg at 13.7 A/g. These results suggest a good capacity of fast energy transfer. Moreover, this asymmetric supercapacitor demonstrated a high stability over 1000 cycles being the loss of only 5%. Copyright © 2015 John Wiley & Sons, Ltd.