Rational construction of triangle-like nickel-cobalt bimetallic metal-organic framework nanosheets arrays as battery-type electrodes for hybrid supercapacitors

Reasonably designing self-supported metal-organic framework (MOF) nanoarrays is profound for applications in energy storage and conversion. Herein, we construct a triangle-like nickel-cobalt bimetallic metal-organic framework nanosheet array on nickel foam (NiCo-MOF/NF) via facile one-step hydrothermal reaction, served as battery-like electrode material for hybrid supercapacitors. By adjusting the molar ratio of Ni and Co, the optimal NiCo-MOF/NF with Ni/Co = 3:2 (3-2 NiCo-MOF/NF) produces an impressive specific capacity of 1003.5 C/g (2230 F/g) at 1 A/g, surpassing most of the previously reported MOF based electrode materials. The superior electrochemical performances may be related to their 3D well-aligned MOF nanosheets arrays, which provides enlarged electroactive areas. Meanwhile, the tight junction of electrode materials and conductive substrate nickel foam (NF) can guarantee their sufficient electric contact, contributing to fast electron transfer from electrodes to conductive substrates. Finally, a hybrid supercapacitor fabricated by the 3-2 NiCo-MOF/NF against active carbon (AC) delivers an advantageous energy density of 34.3 Wh/kg at a power density of 375 W/kg. These results certificate that such bimetallic NiCo-MOF nanosheets arrays hold great potential as novel electrode materials for hybrid supercapacitors.