Electrodeposition synthesis of reduced graphdiyne oxide/NiCo2S4 hierarchical nanosheet arrays for small size and light weight aqueous asymmetry supercapacitors

Abstract

Reduced graphdiyne oxide/NiCo2S4 hierarchical nanosheet array (r-GDYO/NiCo2S4) electrodes are successfully synthesized by electrodeposition and hydrothermal method. The r-GDYO/NiCo2S4 electrode has high capacity, high rate and high stability. At 30 mA cm−2, the area-specific capacity is 3.09 F cm−2, and the capacitance retention rate is 93.10% after 5000 cycles. Density functional theory can reveal the mechanism of graphdiyne enhancing pseudocapacitance of NiCo2S4 electrode. On the one hand, carbon repulsion promotes hydroxyl ion (OH−) to approach cobalt atoms (Co), which enhances NiCo2S4’s binding ability to OH−. On the other hand, the strong electronegativity of the carbon layer enhances the binding ability of NiCo2S4 to external electrons and increases the surface reactivity, thus accelerating the redox reaction and improving the charge storage capacity. Finally, r-GDYO/NiCo2S4 is the positive electrode, activated carbon (AC) is the negative electrode, and melamine foam is assembled as a membrane and storage electrolyte container to form a small volume and light weight aqueous asymmetric supercapacitor. This work not only provides ideas for the design of high-performance NiCo2S4 electrode materials, but also provides a new direction for the application of supercapacitors.