A MnO₂/AgNP nanocomposite was synthesized using a sonochemical method and investigated as an electrode material in a solid-state hybrid supercapacitor. Aquivion’s sodium and lithium electrolyte membrane serves as an electrolyte and separator. For comparison, MnO₂ was used as the active material. The developed supercapacitor containing a carbon xerogel as a negative electrode, the MnO₂/AgNP composite as a positive electrode and a Na⁺-exchange membrane demonstrated the highest performance characteristics. These results indicate that the incorporation of silver nanoparticles into the MnO₂ structure is a prospect for obtaining an active composite electrode material for solid-state supercapacitors.

In this study, the potential to modify the phase structure and morphology of manganese dioxide synthesized via the hydrothermal route was explored. A series of samples were prepared at different synthesis temperatures (100, 120, 140, and 160 °C) using KMnO₄ and MnSO₄·H₂O as precursors. The phase composition and morphology of the materials were analyzed using various physicochemical methods. The results showed that, at the lowest synthesis temperature (100 °C), an intercalation compound with composition K_1.39Mn₃O₆ and a very small amount of α-MnO₂ was formed. At higher temperatures (120–160 °C), the amount of α-MnO₂ increased, indicating the formation of two clearly distinguished crystal structures. The sample obtained at 160 °C exhibited the highest specific surface area (approximately 157 m²/g). These two-phase (α-MnO₂/K_1.39Mn₃O₆) materials, synthesized at the lowest and highest temperatures, respectively, and containing an appropriate amount of carbon xerogel, were tested as active mass for positive electrodes in a solid-state supercapacitor, using a Na₊-form Aquivion^® membrane as the polymer electrolyte. The electrochemical evaluation showed that the composite with the higher specific surface area, containing 75% manganese dioxide, demonstrated improved characteristics, including 96% capacitance retention after 5000 charge/discharge cycles and high energy efficiency (approximately 99%). These properties highlight its potential for application in solid-state supercapacitors.

Solid-state supercapacitors with gel electrolytes have emerged as a promising field for various energy storage applications, including electronic devices, electric vehicles, and mobile phones. In this study, nanocomposite gel membranes were fabricated using the solution casting method with perfluorosulfonic acid (PFSA) ionomer dispersion, both with and without the incorporation of 10 wt.% montmorillonite (MMT). MMT, a natural clay known for its high surface area and layered structure, is expected to enhance the properties of supercapacitor systems. Manganese oxide, selected for its pseudocapacitive behavior in a neutral electrolyte, was synthesized via direct co-precipitation. The materials underwent structural and morphological characterization. For electrochemical evaluation, a two-electrode Swagelok cell was employed, featuring a carbon xerogel negative electrode, a manganese dioxide positive electrode, and a PFSA polymer membrane serving as both the electrolyte and separator. The membrane was immersed in a 1 M Na₂SO₄ solution before testing. A comprehensive electrochemical analysis of the hybrid cells was conducted and compared with a symmetric carbon/carbon supercapacitor. Cyclic voltammetric curves were recorded, and galvanostatic charge–discharge tests were conducted at various temperatures (20, 40, 60 °C). The hybrid cell with the PFSA/MMT 10 wt.% exhibited the highest specific capacitance and maintained its hybrid profile after prolonged cycling at elevated temperatures, highlighting the potential of the newly developed membrane.

This study explores the synthesis and characterization of platinum (Pt), nickel (Ni), and cobalt (Co)-based electrocatalysts using the sol–gel method. The focus is on the effect of different support materials on the catalytic performance in alkaline media. The sol–gel technique enables the production of highly uniform electrocatalysts, supported on carbon-based substrates, metal oxides, and conductive polymers. Various characterization techniques, including X-ray diffraction (XRD) and scanning electron microscopy (SEM), were used to analyze the structure of the synthesized materials, while their electrochemical properties, which are relevant to their application in unitized regenerative fuel cells (URFCs), were investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). This hydrogen energy-converting device integrates water electrolyzers and fuel cells into a single system, reducing weight, volume, and cost. However, their performance is constrained by the electrocatalyst’s oxygen bifunctional activity. To improve URFC efficiency, an ideal electrocatalyst should exhibit high oxygen evolution (OER) and oxygen reduction (ORR) activity with a low bifunctionality index (BI). The present study evaluated the prepared electrocatalysts in an alkaline medium, finding that Pt25-Co75/XC72R and Pt75-Co25/N82 demonstrated promising bifunctional activity. The results suggest that these electrocatalysts are well-suited for both electrolysis and fuel cell operation in anion exchange membrane-unitized regenerative fuel cells (AEM-URFCs), contributing to improved round-trip efficiency.

The aim of this study is to explore the feasibility of using flotation wastewater from copper–porphyry ore processing to synthesize a gel that serves as a precursor for a polymer nanocomposite used in supercapacitor electrode fabrication. These wastewaters—characterized by high acidity and elevated concentrations of metal cations (Cu, Ni, Zn, Fe), sulfates, and organic reagents such as xanthates, oil (20 g/t ore), flotation frother (methyl isobutyl carbinol), and pyrite depressant (CaO, 500–1000 g/t), along with residues from molybdenum flotation (sulfuric acid, sodium hydrosulfide, and kerosene)—are byproducts of copper–porphyry gold-bearing ore beneficiation. The reduction of Ni powder in the wastewater induces the degradation and formation of a gel that captures both residual metal ions and organic compounds—particularly xanthates—which play a crucial role in the subsequent steps. The resulting gel is incorporated during the oxidative polymerization of aniline, forming a nanocomposite with a polyaniline matrix and embedded xanthate-based compounds. An asymmetric supercapacitor was assembled using the synthesized material as the cathodic electrode. Electrochemical tests revealed remarkable capacitance and cycling stability, demonstrating the potential of this novel approach both for the valorization of industrial waste streams and for enhancing the performance of energy storage devices.