With the rapid improvement of the global economy, the role of energy has become even more vital in the 21st century. In this regard, energy storage/conversion devices have become a major, worldwide research focus. In response to this, we have prepared two-dimensional (2D)-hierarchical sheet-like ZnCo₂O₄ microstructures for supercapacitor applications using a simple hydrothermal method. The 2D-hierarchical sheet-like morphologies with large surface area and smaller thickness enhanced the contact area of active material with the electrolyte, which increased the utilization rate. We investigated the electrochemical performance of sheet-like ZnCo₂O₄ microstructures while using Cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analysis. The electrochemical results demonstrated that the ZnCo₂O₄ electrode possesses 16.13 mF cm⁻² of areal capacitance at 10 µA cm⁻² of current density and outstanding cycling performance (170% of capacitance is retained after 1000 cycles at 500 µA cm⁻²). The high areal capacitance and outstanding cycling performance due to the unique sheet-like morphology of the ZnCo₂O₄ electrode makes it an excellent candidate for supercapacitor applications.

Due to modernization and the scarcity of fossil fuel resources, energy demand is continuously increasing. In this regard, it is essential and necessary to create a renewable energy source that can meet future energy demands. Recently, the production of H₂ by water splitting and removing pollutants from the water has been essential for issues of energy and environmental demands. Herein, g-C₃N₄ and Ag-g-C₃N₄ composite structures have been successfully fabricated by the ultrasonication method. The physio/photochemical properties of prepared g-C₃N₄ and Ag-g-C₃N₄ were examined with different analytical techniques such as FTIR, XRD, UV-DRS, SEM, TEM, PL, and XPS analyses. The silver quantum dots (QDS) anchored to g-C₃N₄ structures performed the profound photocatalytic activities of H₂ production, dye degradation, and antimicrobial activity under visible-light irradiation. The Ag/g-C₃N₄ composite with an Ag loading of 0.02 mole has an optimum photoactivity at 335.40 μmol g⁻¹ h⁻¹, which is superior to other Ag loading g-C₃N₄ composites. The synthesized Ag/g-C₃N₄ nanoparticles showed potential microbial inhibition activity during the preliminary screening, and the inhibition zones were comparable to the commercial antibiotic chloramphenicol. The loading of Ag into g-C₃N₄ paves the suppression, recombination and transfer of photo-generated electron-hole pairs, leading to the enhancement of hydrogen production, the diminishment of pollutants in water under visible light irradiation, and antimicrobial activity against multidrug-resistant pathogens.