Template-directed in situ grown bimetallic nanoarchitectures with hydroxide active site enriched multi-charge transfer routes for energy storage

Abstract

Cobalt metal-organic frameworks were used as templates to obtain densely stacked two-dimensional ultrathin nanosheets of nickel/cobalt metal-organic frameworks on carbon cloth via in situ deposition at room temperature. The freestanding electrodes made of ultra-thin nanosheets and quasi-one-dimensional pores exhibited a unique electronic structure with Ni(OH)(2) anchored to the surface. With distinctive structural superiority, multiple charge transfer routes, and Ni(OH)(2) moieties as active sites, the electrode showcased a high areal capacity (C-a) of 2041 mC cm(-2) (2 mA cm(-2)), a specific capacity of (C-s) 671 C g(-1), a volumetric capacitance (C-vc) of 1033 F cm(-3) (2 A g(-1)) and a prolonged cycling life of 5000 cycles with an appreciable capacity retention of 91.5% in 6 M KOH. The asymmetric supercapacitor device assembled (CC/CoNi-MOF@Ni(OH)(2)//CC/O,N,S@AC) delivered a superior specific capacity (C-s) of 284 C g(-1), a specific capacitance (C-sp) of 189 F g(-1), a volumetric capacitance (C-vc) of 128 F cm(-3), a maximum specific energy (E-s) of 75.0 W h kg(-1), and an excellent specific power (P-s) of 17.13 kW kg(-1), and withstood 10 000 charge/discharge cycles with a decline of 11.3% in the initial capacity. The proposed method with DFT analysis underpins a strategy to custom-design economically viable freestanding electrodes with a large surface area per volume/mass, a synergy effect at the interface, and multiple charge transfer pathways for potential application in energy storage.