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

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.