Unlocking the potential of a novel hierarchical hybrid (Ni–Co)Se2@NiMoO4@rGO–NF core–shell electrode for high-performance hybrid supercapacitors

Abstract

Nano-hybridization of a core–shell structure integrating a transition metal selenide with transition metal oxides on the surface of a carbonaceous material embellished 3D substrate results in the formation of high-capacity electrode materials for use in energy storage devices thanks to the ample electroactive sites and relatively high electronic conductivity of the resultant materials compared to their individual components. Herein, oxalic acid templated and selenization processed porous Ni–Co–Se (NCSe) nanorods are vertically grown on the surface of an rGO–nickel foam (NF) substrate, followed by the embellishing of the surface of the NCSe nanorods with hydrothermally-prepared NiMoO₄ (NMO) nanosheets to prepare a hierarchical NCSe@NMO@rGO–NF hybrid core–shell structure. The as-prepared NCSe@NMO@rGO–NF hybrid electrode exhibits tremendous electrochemical performance in terms of a high specific capacity (396.1 mA h g⁻¹) at a current density of 1 A g⁻¹, along with excellent capacity retention (87.6%) after 8000 consecutive charge–discharge (GCD) cycles. A hybrid supercapacitor (HSC) device was also assembled by sandwiching the NCSe@NMO@rGO–NF electrode with oxalic acid and metal–organic framework derived porous carbon/CNT coated NF (OA-MOF-PC-CNTs@NF) to unveil its practical applicability. The as-fabricated HSC shows a high energy density (63.2 W h kg⁻¹) and power density (7983.5 W kg⁻¹) alongside 89.4% capacitance retention after 8000 GCD cycles. Owing to their unique structural features and superlative electrochemical properties, the proposed method and selected materials can mitigate the issues related to electrochemical capacitors.