MOF-Derived Sheets Resembling NiO@MXene (2D/2D) Composites as Efficient Electrode Materials for Hybrid Supercapacitors

MOF-derived metal oxides combined with metal carbide composites are attracting research interest for enhancing the energy density of supercapacitors, owing to their excellent redox properties and high electrical conductivity. A MOF-derived NiO@MXene composite, synthesized by a hydrothermal method with 51.04 m2/g of surface area, delivered 1306 F/g (647 C/g) at 1 A/g. The enhanced capacitance stems from the rational design of the composite electrode to promote a synergistic effect, facilitate fast ion transport, and accelerate redox reaction kinetics. As a positive electrode of a solid-state hybrid supercapacitor versus a negative activated carbon electrode in a PVA-KOH hydrogel electrolyte, the device delivered 40 Wh/kg (energy density) and 1.2 kW/kg (power density) and retained 78% of its capacitance and 89.8% Coulombic efficiency after 10,000 cycles.