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

Reduced graphdiyne oxide/NiCo ₂S ₄ hierarchical nanosheet array (r-GDYO/NiCo ₂S ₄ ) electrodes are successfully synthesized by electrodeposition and hydrothermal method. The r-GDYO/NiCo ₂S ₄ 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 NiCo ₂S ₄ electrode. On the one hand, carbon repulsion promotes hydroxyl ion (OH ⁻ ) to approach cobalt atoms (Co), which enhances NiCo ₂S ₄’s binding ability to OH ⁻ . On the other hand, the strong electronegativity of the carbon layer enhances the binding ability of NiCo ₂S ₄ to external electrons and increases the surface reactivity, thus accelerating the redox reaction and improving the charge storage capacity. Finally, r-GDYO/NiCo ₂S ₄ 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 NiCo ₂S ₄ electrode materials, but also provides a new direction for the application of supercapacitors.