A hybrid supercapacitor assembled by reduced graphene oxide encapsulated lollipop-like FeNi2S4@Co9S8 nanoarrays

Abstract

Mixed metal sulfides (MMSs) combined with carbonaceous materials are considered effective electrode materials for supercapacitors owing to their satisfactory capacity and rate capability. Herein, lollipop-like FeNi2S4@Co9S8 nanoarrays wrapped by reduced graphene oxide on nickel foam (NF\\L-FNSCS-rGO) are manufactured for a hybrid supercapacitor. Briefly, FeNi layered double hydroxide (FeNi-LDH) nanowires are first prepared by a hydrothermal route. Afterward, zeolitic imidazolate framework-67 (ZIF-67) nanocages welding on the top of FeNi-LDH nanowires are designed at room temperature. Then, sulfidation of the obtained nanoarrays in the presence of thioacetamide leads to the formation of FeNi2S4@Co9S8 nanostructures. Finally, the L-FNSCS-rGO nanoarrays were constructed on NF by coating graphene oxide (GO) sheets on amino-propyltriethoxysilane (APTES)-modified FeNi2S4@Co9S8 nanoarrays, followed by reduction of the GO by thermal treatment. Benefiting from this peculiar architecture, the designed NF\\L-FNSCS-rGO possesses sufficient electrochemical active sites as well as developed diffusion pathways for electrolyte ions. Therefore, the NF\\L-FNSCS-rGO reveals a large capacity of 1308C/g, splendid rate performance (e.g., 1093.5C/g at 36 A/g), and high longevity (93.75% retention after 8500 cycles). The corresponding hybrid supercapacitor device (NF\\L-FNSCS-rGO//NF\\activated carbon (AC)) delivers a good energy density of 68.85 Wh kg−1 at 860.7 W kg−1 with the NF\\L-FNSCS-rGO (cathode electrode) and NF\\activated carbon (AC) (anode electrode), demonstrating the potential for the real applications. More importantly, the new structural design can be extended to the fabrication of other materials for extensive applications.