SCHEDULED MAINTENANCE
NiCo2S4/tryptophan-functionalized graphene quantum dot nanohybrids for high-performance supercapacitors†
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Abstract
This paper reports a new NiCo2S4/tryptophan-functionalized graphene quantum dot nanohybrid (NiCo2S4/Trp-GQDs). NiCo2S4 was fabricated by a one-step hydrothermal reaction and then hybridized with Trp-GQDs to form NiCo2S4/Trp-GQDs. The result shows that the NiCo2S4 offers better structural stability and specific surface area compared to NiCo2S4 prepared by the traditional two-step method. The introduction of Trp-GQDs greatly enhances the electron/ion conductivity of NiCo2S4 and the mechanical properties of the binder layer. The hybrid of NiCo2S4 with Trp-GQDs achieves significant electrochemical synergy. The NiCo2S4/Trp-GQD electrode for supercapacitors provides high specific capacitance (1453.1 F g−1 at a current density of 1 A g−1) and rate-capability (455.6 F g−1 at a current density of 20 A g−1) in a 3.0 M KOH electrolyte using a three-electrode test system. The asymmetric supercapacitor of NiCo2S4/Trp-GQDs/activated carbon exhibits an energy density of 157.1 W h kg−1 at a power density of 800 W kg−1 and 103.2 W h kg−1 at a power density of 4000 W kg−1 in a 3.0 M KOH electrolyte. The energy density is much higher than that of a single NiCo2S4 electrode (67.9 W h kg−1 at a power density of 800 W kg−1 and 37.5 W h kg−1 at a power density of 4000 W kg−1). The excellent capacitive performance means the nanohybrid can be applied in next-generation high-performance supercapacitors.
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