Fabrication of Metal Sulfides/Graphene Nanocomposites for the Applications in Supercapacitors. II: Ni-Mn-S/Mn-Cu-O/Graphene

Background: Excessive use of fossil energy has exacerbated global warming, and the goal of carbon neutralization has been put on the agenda. In order to make full use of renewable energy and reduce greenhouse gas emissions, it is urgent to develop environment-friendly energy storage devices. We previously reported metal sulfides/ graphene nanocomposites for the applications in supercapacitors (I. NiS/graphene). Recent work was presented as the paper in the series (II. Ni-Mn-S/Mn-Cu-O/graphene). Objective: To synthesize graphene-supported multi-metal sulfides for electrochemical capacitance storage. Methods: The materials were prepared with a two-step hydrothermal method. Samples were characterized by field emission scanning electron microscopy, X-ray powder diffraction, and electrochemical measurements. Results: The as-fabricated electrode exhibited a specific capacitance of 566 F g^–1 at the current density of 1 A g^–1 and a rate of 68% at 10 A g^–1. The materials retained 75.8% of the initial capacitance after 1000 charge-discharge cycles at 5 A g^–1. The results suggest optimum Ni-Mn-S/Mn-Cu-O/graphene composites for supercapacitor applications. Conclusion: The Ni-Mn-S/Mn-Cu-O/graphene composites with nanosheet structures were prepared with a two-step hydrothermal method. The materials showed enhanced electrochemical capacitance performances superior to the individual components.