The energy industry has been challenged by the current high population and high energy consumption, forcing the development of effective and efficient supercapacitor devices. The crucial issues until now have been high production cost, deprived cyclic stability, and squat energy density. To resolve these problems, various approaches have been taken, such as the development of long-life electrode materials with high capacity, rapid charging, and slow discharging to overcome poor life cycle stability. In the present work we focus on fabricating cost-effective unique-morphology, high-surface-area alpha-Co(OH)₂ for application in an aqueous-electrolyte symmetric supercapacitor. In this study, hierarchical nanoflakes assembled in three-dimensional (3D) flower-shaped cobalt hydroxide (HN-3DF-α-Co(OH)₂) electrode were synthesized using the solvothermal method with sodium dodecylbenzene sulfonate (SDBS) and methanol as solvents. Spectroscopic and microscopic techniques were used to characterize fabricated HN-3DF-Co(OH)₂, which revealed that the materials electrode exhibited the alpha phase with a hierarchical flower-like structure. A half-cell electrochemical assembly (three-electrode assemble cell) and symmetric full cell (two-electrode assemble cell) were examined in an aqueous electrolyte. In three-electrode assembly cells, HN-3DF-α-Co(OH)₂ exhibited 719.5 Fg^-1 specific capacitance (C_sp) at 1 Ag^-1 with excellent cyclic retention stability of approximately 88% after 3000 cycles. In two-electrode symmetric supercapacitive systems, HN-3DF-α-Co(OH)₂ achieved a maximum C_sp of 70.3 Fg^-1 at 0.4 Ag^-1 with the highest energy density of approximately 6.25 Wh/kg at a power density of 328.94 W/kg. The fabricated two-electrode assembly cell with the HN-3DF-α-Co(OH)₂ electrode retained cyclic stability of approximately 85% after 5000 repeated charge and discharge cycles. Solvothermally-synthesized, optimized HN-3DF-α-Co(OH)₂ showed outstanding electrochemical performance results in three- and two-electrode systems. This unique aqueous symmetric supercapacitor can be used to design cost-effective symmetric capacitors based on metal hydroxide.

The manufacturing techniques, structural features, and optical attributes of titanium dioxide (TiO₂) nanoparticles are highlighted in this study. These nanoparticles are notable for their remarkable photocatalytic activity, cheap cost, chemical stability, and biocompatibility. TiO₂ consists of three polymorph structures: anatase, rutile, and brookite. Because of its electrical characteristics and large surface area, anatase is the most efficient for photocatalysis when exposed to UV light. The crystallinity, size, and shape of titania nanoparticles (NPs) are influenced by diverse production techniques. Sol-gel, hydrothermal, solvothermal, microwave-assisted, and green synthesis with plant extracts are examples of common methods. Different degrees of control over morphology and surface properties are possible with each approach, and these factors ultimately affect functioning. For example, microwave synthesis provides quick reaction rates, whereas sol-gel enables the creation of homogeneous nanoparticles. XRD and SEM structural investigations validate nanostructures with crystallite sizes between 15 and 70 nm. Particle size, synthesis technique, and annealing temperature all affect optical characteristics such as bandgap (3.0–3.3 eV), fluorescence emission, and UV-visible absorbance. Generally speaking, anatase has a smaller crystallite size and a greater bandgap than rutile. TiO₂ nanoparticles are used in gas sensing, food packaging, biomedical coatings, dye-sensitized solar cells (DSSCs), photocatalysis for wastewater treatment, and agriculture. Researchers are actively exploring methods like adding metals or non-metals, making new composite materials, and changing the surface to improve how well they absorb visible light.

The development of efficient materials for energy storage applications has attracted considerable attention, especially for supercapacitors and batteries that are the most promising and important power sources in everyday life. For this purpose, a suitable and efficient current collector must be determined and its behavior with respect to various solvents when it is used as an electrode material for energy storage applications should be understood. In this work, we studied the effect of washing three-dimensional nickel foam using different concentrations of hydrochloric acid and ethanol on the surface characteristics, electrochemical behavior, and storage performance of the foam. Additionally, we observed the different types of acidic treatments that improved the electrochemical and storage performances of the three-dimensional nickel foam. The surface characterization results show that acidic conditions with a concentration of 3M changes the surface morphology from a flat/hill-like structure to a nanosheet/nanoflake-like structure without any further treatment. This structure provides a nano-channel and a large number of surface charges during the electrochemical reaction. The results of this study show that pretreatment of 3D-NF is highly important and recommended. The present work also contributes to the knowledgebase on pretreatment of 3D-NF and its optimization.