Controllable Transformation of Metal-Organic Framework Nanosheets into Oxygen Vacancy NiCo_3-O₄ Arrays for...

The amino-functionalized bimetal NH₂-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 (NiCo_3-O₄/NF) achieves high capacitance (2484 F g^-1 at 1 A g^-1), excellent rate performance (91.4%), and long cycling life when assessed as promising electrode material for supercapacitors. Notably, the existing oxygen vacancy in NiCo_3-O₄ promotes the electrochemical performance of NiCo_3-O₄/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^-1 at a power density of 800.2 W kg^-1, which still remains 32.2 W h kg^-1 even at a high power density of 7994.5 W kg^-1. 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.