Construction of polypyrrole nanotubes interconnected ZIFs-templated nickel-cobalt layered double hydroxide via varying the mass of ZIF-67 for supercapacitors with tunable performance

Abstract Reasonable construction of electrodes materials with heterostructures is a very effective way to enhance the electrochemical performance. Herein, a series of hybrid electrodes materials (PPy/Ni–Co LDH) based on nickel-cobalt layered double hydroxide (Ni–Co LDH) with zeolitic imidazolate framework-67 (ZIF-67) as the template and polypyrrole (PPy) nanotubes have been synthesized. Various precursors PPy/ZIF-67 based on polypyrrole nanotubes with the same amount have been prepared, where the mass ratio of polypyrrole nanotubes to ZIF-67 are varied in the process of crystallization. As-synthesized precursors PPy/ZIF-67 serve as sacrificial templates and give birth to various hybrid electrodes materials PPy/Ni–Co LDH with the core-shell structure, where Ni–Co LDH is closely coated on the external surface of polypyrrole nanotubes. The experimental findings reveal the electrochemical performance of PPy/Ni–Co LDH becomes better and better with increasing masses of Ni–Co LDH. Benefiting from their core-shell structure and the synergy effect between polypyrrole nanotubes and Ni–Co LDH, the optimized sample displays a specific capacitance of 13.0 F cm−2 (1858.3 F g−1) at 1 mA cm−2 and a favorable rate capability. Furthermore, a symmetric coin-type hybrid supercapacitor based on the optimized sample has also been fabricated, and exhibits an energy density of 10.425 mWh·cm−2 at the power density of 0.25 mW cm−2.