NiO–MnO2 and NiO–CuO anchored on rGO as ternary electrode materials for energy storage applications

Abstract

The development of new electrode materials is critical for advancing supercapacitor technologies. This study presents the design and synthesis of metal oxide-based hybrid capacitive nanocomposites comprising NiO–MnO₂ and NiO–CuO ternary hybrids anchored on reduced graphene oxide (rGO) via a green hydrothermal method as advanced electrode materials for high-performance supercapacitors. XRD analysis results revealed the successful formation of binary and ternary metal oxide-based composites with cubic NiO, monoclinic CuO and tetragonal MnO₂. The unique morphology of MnO₂ nanorods and NiO nanoflowers, coupled with the conductive rGO framework, facilitates efficient redox reactions. The presence of rGO within the composites facilitates rapid electron transport, mitigates particle agglomeration, and prevents volumetric and structural degradation during charge–discharge cycles. Notably, NiO/MnO₂/rGO and NiO/CuO/rGO as ternary composite electrodes achieved specific capacitances of 107 F g⁻¹ and 413 F g⁻¹, respectively, at a scan rate of 5 mV s⁻¹ within a 0.6 V potential window. A fabricated NiO/MnO₂/rGO‖rGO all-solid-state asymmetric supercapacitor device using PVA–KOH as a solid-state gel electrolyte delivered a specific and areal capacitance of 1866.7 mF g⁻¹ and 10.82 mF cm⁻², respectively, at 10 mA g⁻¹. Furthermore, the device delivered an energy and power density of 75.6 mWh kg⁻¹ (438.5 μWh cm⁻²) and 17500 mW kg⁻¹ (39.5 mW cm⁻²), respectively, at 10 mA g⁻¹ and 74% capacity retention after continuous charge–discharge for 3000 cycles.