Boosting Charge Storage via Extrinsic Pseudocapacitance in NiMoO ₄ -rGO/NCP Ternary Hybrid Nanostructures

The ternary composite materials composed of metal oxides and phosphates supported on a carbon scaffold exhibit remarkable synergistic effects, combining rich redox-active sites with excellent electrical conductivity. In this work, we have developed the hierarchical hybrid architecture integrating nickel molybdate (NiMoO 4 ) and nickel cobalt phosphate (NCP) with conductive reduced graphene oxide (rGO) as extrinsic pseudocapacitive material using the sol−gel method. Notably, the incorporation of NCP induces pronounced extrinsic pseudocapacitance, which significantly enhances the overall specific capacity of the composite by increasing the number of accessible active sites, improving charge transport and redox kinetics, and ultimately delivering superior electrochemical performance. The NiMoO 4 -rGO/NCP composite exhibits pore size in the range of 20−30 nm with a high specific surface area of 162.4 m 2 g −1 and higher conductivity. The electrochemical evaluation reveals that the NiMoO 4 -rGO/NCP electrode delivers an impressive specific capacity of 353.8 mAh g −1 at 1 A g −1, with excellent rate capability and a capacity retention of 75% over 10000 cycles. Later, the hybrid supercapacitor (HSC) was assembled using NiMoO 4 -rGO/NCP as the positive electrode and activated carbon (AC) as the negative electrode. The HSC cell delivered a capacitance of 276.6 F g −1 at 2 A g −1 with a specific energy of 98.35 Wh kg −1 and a specific power of 2086.9 W kg −1 . The device also delivered excellent cyclic stability with negligible loss after 14000 cycles at a very high current density of 80 A g −1 . Our investigation presents a unique hierarchical design of electrode material for next-generation energy storage systems.