Functionalized Nanomaterials as Supercapacitor Devices: Current Trends and Beyond

At present, energy storage and the development of new energy sources are of great importance. Due to their high-power density, good cyclic stability, quick charging and discharging rate (within seconds), and low maintenance cost, supercapacitors are crucial energy storage technologies. Numerous scientists focus on developing electrochemical energy storage devices like supercapacitors (SCs) for a variety of applications. The development of electrochemically active materials in electrodes possesses significantly advanced in recent years. Supercapacitors are divided into two categories based on their charge storage mechanisms: (a) electrical double-layer capacitors (EDLCs) and (b) pseudo capacitors. EDLC stores charge electrostatically via reversible ion adsorption at the electrode/electrolyte interface, whereas fast reversible redox reactions occur at electro-active materials such as transition metal oxides and conductive polymers that are linked to pseudo-capacitance. Flexible energy storage devices which serve as ontogenesis to flexible electronics; whether it is for wearable consumer electronics, soft robotics, photonics, or integrated sensors, are a potential means of achieving this goal. The functionalized material electrode has a higher specific capacitance than that of an unfunctionalized material electrode. For example, TiO2-WO3, g-C3N4-rGO/LDH, graphene/MnO2, etc. are proven to be highly efficient electrode materials for SCs. The surface area, durability, and specific capacitance of the functionalized materials can be tuned to achieve maximum efficacy. The strategy for functionalized materials and facile and in situ synthetic methodologies are used to prepare the electrode materials. The energy conversion and storage properties of a supercapacitor device will be needed for the next generation of electronics. The huge potential of functionalized materials is used in electronic devices with high capacitance and good retention time. Future challenges and current trends beyond these functionalized nanoparticles as an efficient, fast charge–discharge and stability toward energy storage devices such as supercapacitors are addressed in this chapter.