Enhanced interfacial electron transfer by constructing NiCo-LDH hollow nanocages decorated N-doped graphene quantum dots heterojunction for high-performance supercapacitors

Nickel-cobalt layered double hydroxides (NiCo-LDHs) are highly promising materials for energy storage elec-trodes. However, the poor conductivity and easy agglomeration limit their practical application. Herein, the novel hollow nanocage architecture of NiCo-LDH nanosheets (H-NiCo-LDH) decorated N-doped graphene quantum dots (N-GQDs) is constructed using zeolitic imidazolate framework-67 (ZIF-67) as self-sacrificed tem-plate. The hollow nanocage structure suppresses the agglomeration of nanosheets and enlarges the electro-chemical interface, while the decoration of N-GQDs effectively improves electrical conductivity and provides more abundant active sites. More importantly, HRTEM characterization shows the construction of hetero-junctions between H-NiCo-LDH and N-GQDs, and the interfacial charge redistribution through p-n hetero-junction promotes interfacial electron transfer and enhances redox activity. Consequently, the N-GQD/H-NiCo-LDH electrode delivers a high specific capacitance of 2347 F g-1 (326 mA h g-1) at 1 A g-1 with excellent rate performance (82% capacitance retention at 10 A g-1). The assembled asymmetric supercapacitor by N-GQD/H-NiCo-LDH and active carbon exhibits an energy density of 52.1 W h kg -1 at a power density of 770 W kg -1 with remarkable cycling stability (80.5% capacitance retention after 5000 cycles). The hollow nanocage structure and enhanced electrical conductivity of N-GQDs make the N-GQD/H-NiCo-LDH a highly promising material for electrochemical energy storage applications.

Automated summary

By constructing a hollow nanocage structure of H-NiCo-LDH nanosheets and decorating them with N-GQDs, this study improves the conductivity and active sites of the material, resulting in high specific capacitance and excellent rate performance. Furthermore, the heterojunction between H-NiCo-LDH and N-GQDs promotes interfacial electron transfer and redox activity.