Energy storage is one of the leading problems being faced globally, due to the population explosion in recent times. The conventional energy sources that are available are on the verge of extinction, hence researchers are keen on developing a storage system that will face the upcoming energy needs. Supercapacitors, also known as ultracapacitors or electrochemical capacitors, are advanced energy storage devices characterised by high power density and rapid charge–discharge cycles. Unlike traditional batteries, supercapacitors store energy through electrostatic separation, offering quick energy release and prolonged operational life. They hold exceptional performance in various applications, from portable electronics to electric vehicles, where their ability to deliver bursts of energy efficiently complements or replaces conventional energy storage solutions. Ongoing research focuses on enhancing energy density and overall efficiency, positioning supercapacitors as pivotal components in the evolving landscape of energy storage technologies. A novel electrode material of NiO/CuO/Co3O4/rGO was synthesized which when used as a supercapacitor, the highest value of CS is 873.14 F/g which is achieved for a current density of 1 A/g under with an energy density of 190 Wh/kg and the highest power density of 2.5 kW/kg along with 87.3% retention after 5000 GCD cycles under 1 M KOH.

The development of biocomposites using renewable resources is a cost-effective and long-term solution to environmental and resource issues. Hydrogels [Poly Sodium Acrylate (PSA)] were created by variable percentages of crosslinker concentration, and banana–cellulose microfibril (CMF) was used as a filler in this study for better reinforcement. When the concentration of crosslinker is increased, the number of covalent crosslinks increases, limiting the movement of water molecules and lowering the diffusion coefficient, equilibrium water content, the initial rate of swelling, and the theoretical equilibrium swelling ratio. The swelling behaviour of reinforced PSA with high concentrations of CMF was unexpected; the hydrophilic OH groups of CMF increase the diffusion of water molecules from the swelling medium to inside the PSA, allowing for better mechanical behaviour of gels without sacrificing the swelling response. The swelling behaviour and swelling exponent of a hydrogel were determined at various temperatures, pH levels, and physiological fluid models. The swelling exponent's maximum value was discovered to be 0.5, which suggests that the hydrogel's water diffusion was non-Fickian in nature. The swelling ratio was found to rise with rising temperature and to have a lower value than that at room temperature. It was also proven that elevating the pH of the medium from 1 to 7 improved the PSA/CMF hydrogels' swelling response. The swelling behaviour of PSA/CMF hydrogels was also investigated as the concentration of CMF rose from 0.2 to 1%. The equilibrium water content, swelling kinetics, and water transport mechanisms were all investigated. The Flory–Rehner equation was applied to determine crosslinking density, polymer mesh size, and molecular weight between crosslinks.