Fabrication of a composite material of Gd₂O₃, Co₃O₄ and graphene on nickel foam for high-stability supercapacitors

The porous flower-like microsphere structure composite of gadolinium oxide (Gd₂O₃), tricobalt tetraoxide (Co₃O₄) and reduced graphene oxide (rGO) was prepared on the nickel foam (NF) substrate by a hydrothermal synthesis method and annealing process, which can be directly used as an electrode material for supercapacitors without any conductive adhesive or binder. This porous nanostructure not only improves the conductivity of the electrode, but also shortens the migration route of ions and electrons. The innovative electrode of Gd₂O₃/Co₃O₄/rGO/NF has a high specific capacitance of 3616 F g⁻¹ (1 A g⁻¹). The supercapacitor is assembled, with a specific capacitance of 442.5 F g⁻¹ (0.5 A g⁻¹) at room temperature (20 °C) and strong multiplicative performance (current density from 0.5 to 20 A g⁻¹, specific capacitance retention of 65.9%). At a power density of 300 W kg⁻¹, the energy density reaches 88.5 Wh kg⁻¹, and the performance stays relatively stable across a large working temperature range of 0 to 60 °C. The specific capacitance is 368.3 F g⁻¹ even at temperatures up to 60 °C and 415.0 F g⁻¹ at temperatures below 0 °C. Even after 40 000 cycles at a high current density of 10 A g⁻¹, the capacity retention is 93.3%, suggesting exceptional cycling stability. This study demonstrates the potential practical application of Gd₂O₃/Co₃O₄/rGO/NF electrodes in supercapacitors.