Controllable Transformation of Metal-Organic Framework Nanosheets into Oxygen Vacancy NiCoO Arrays for Ultrahigh-Capacitance Supercapacitors with Long Lifespan.

The amino-functionalized bimetal NH-NiCo-MOF nanosheet array is first fabricated on Ni foam substrates and then controllably transformed into oxygen vacancy bimetal oxide arrays by simply thermal annealing in air. This NiCo-based oxide array (NiCoO/NF) achieves high capacitance (2484 F g at 1 A g), excellent rate performance (91.4%), and long cycling life when assessed as promising electrode material for supercapacitors. Notably, the existing oxygen vacancy in NiCoO promotes the electrochemical performance of NiCoO/NF due to the enhancement of electrical conductivity and capture capability for OH. In addition, the assembled asymmetric supercapacitor (ASC) device exhibits an excellent energy density of 39.3 W h kg at a power density of 800.2 W kg, which still remains 32.2 W h kg even at a high power density of 7994.5 W kg. Furthermore, a light-emitting diode can be lightened for more than 6 min, demonstrating a great potential for practical application of ASC devices. This work knocks on the door of a feasible strategy for designing and synthesizing 2D metal oxide nanosheet arrays with excellent electrochemical properties.