Synthesis of nickel cobalt sulfide on Ni foam for improved electrochemical energy storage: Effect of binder-free reverse pulse potentiostatic electrodeposition and redox additive

Nickel cobalt sulfide (Ni-Co-S) was grown on 3D conductive Ni foam (NF) using binder-free electrochemical deposition to serve as a positive electrode (NCS@NF) for electrochemical energy storage application. Multiple cycles of reverse pulse potentiostatic electrochemical deposition (RPP-ED) were systematically applied to study their influence on the physico-chemical properties of NCS@NF. During the 300 optimized RPP-ED cycles uniform mesoporous interconnected nanoflakes of Ni-Co-S were formed on NF. The NCS@NF electrode demonstrated remarkable electrochemical storage performance, achieving a maximum areal capacity of 0.590 C cm-2 (590 C g-1) in 2 M KOH electrolyte. This remarkable property of NCS@NF can be associated with the improved ionic diffusion at the interconnected nanoflake structure and improved redox transitions at the active sites of nanoflakes. Moreover, the addition of K4(CN)6 as a redox additive improved the areal capacity of NCS@NF to 2.56 C cm-2 (2560 C g-1). Furthermore, an aqueous hybrid supercapacitor was assembled by integrating activated carbon on NF as the negative electrode, while employing NCS@NF as the positive electrode. The aqueous hybrid supercapacitor exhibited an enhanced charge-discharge potential of 1.5 V and demonstrated remarkable stability, maintaining 89% of its performance over 10,000 cycles. Notably, it achieved maximum energy and power densities, 33 mu Wh cm-2 and 6019 mu W cm-2, respectively. These results establish its suitability for hybrid supercapacitor applications.

Automated summary

In this study, nickel cobalt sulfide (Ni-Co-S) nanoflakes were successfully grown on 3D conductive nickel foam using binder-free electrochemical deposition. The resulting positive electrode demonstrated remarkable electrochemical storage performance, and when combined with activated carbon negative electrode, an aqueous hybrid supercapacitor with enhanced charge-discharge potential and remarkable stability was assembled. These findings highlight the potential of Ni-Co-S@NF for hybrid supercapacitor applications.