Three-Dimensional Graphene-Decorated Copper-Phosphide (Cu₃P@3DG) Heterostructure as an Effective Electrode for a Supercapacitor

Transition metal phosphides already emerged with great interest due to their energy storage capacitance, superior metalloid characteristics, and decent electrical conductivity. To achieve a commercially viable outcome, these electrodes are fabricated with interconnected carbonaceous materials. Herein, we have synthesized hexagonal copper phosphide (Cu₃P) platelets using chemical vapor deposition (CVD) and integrated it with highly conducting three-dimensional graphene (3DG), leading to a nanohybrid (Cu₃P@3DG) as a coulombic efficient supercapacitor. This nanohybrid has exhibited a specific capacitance (C_sp) of 1,095.85 F/g at 10 mV/s scan rate along with a cycling stability of 95% capacitive retention after 3,000 cycles at a current density of 8.97 A/g. The C_sp is almost four times higher and the stability is 1.2 times higher compared to the bare Cu₃P platelets. We have fabricated an asymmetric supercapacitor (ASC) using Cu₃P@3DG on graphite as cathode and activated carbon (AC) on graphite as anode (Cu₃P@3DG//AC) that has shown high specific capacity (108.78 F/g), energy density (8.23 Wh/kg), and power density (439.6 W/kg). Moreover, this ASC has exhibited an excellent life cycle (5,500 consecutive charge–discharge with 96% coulombic efficiency). Therefore, the proposed all-solid-state hybrid device can be considered as a route for next-generation high-performing energy storage devices.