Controllable In Situ Transformation of Layered Double Hydroxides into Ultrathin Metal-Organic Framework Nanosheet Arrays for Energy Storage

Ultrathin two-dimensional metal-organic frameworks (MOFs) have convincing performances in energy storage, which can be put down to their accessible active sites with rapid charge transfer. Herein, NiCo-layered double hydroxide (LDH) nanosheet arrays are used as self-sacrificial templates to in situ fabricate ultrathin NiCo-MOF nanosheet arrays on Ni foam (NS/NF) by using organic ligands without adding metal sources. Two ultrathin MOF nanosheets with different ligands, terephthalate (BDC) and 2-aminoterephthalate (NH2-BDC), are synthesized, characterized, and discussed in detail. Specifically, NiCo-NH2-BDC-MOF NS/NF exhibits the best electrochemical performance as a battery-type electrode for supercapacitors, achieves an areal capacitance of 12.13 F cm(-2) at a current density of 2 mA cm(-2), and retains the original capacitance of 73.08 % after 5000 cycles at a current density of 50 mA cm(-2). Furthermore, when NiCo-NH2-BDC-MOF NS/NF is assembled with activated carbon (AC) to form an asymmetric supercapacitor (ASC), an energy density of 0.81 mWh cm(-2) can be provided at a power density of 1.60 mW cm(-2). These results offer an effective and controllable synthetic strategy to in situ prepare ultrathin MOF nanosheet arrays with different ligands and metal ions from LDH precursors.

Automated summary

The study successfully synthesized ultrathin NiCo-MOF nanosheet arrays on Ni foam using NiCo-layered double hydroxide nanosheets as sacrificial templates, showing excellent energy storage performance. The NiCo-NH2-BDC-MOF NS/NF exhibited the best electrochemical performance as a battery electrode for supercapacitors, with an areal capacitance of 12.13 F cm(-2) and retaining 73.08% of its original capacitance after 5000 cycles at a current density of 50 mA cm(-2).