Binder-Free Defective Bimetallic Metal-Organic Framework Nanostructures with Lattice Distortion as Hybrid Supercapacitor Electrodes

Owing to their adaptable topologies and simplicity of functionalization, metal–organic frameworks (MOFs) are highly sought-after materials for battery-type electrodes. To improve the MOFs’ overall conductivity and instability, a Ni/Co-MOF nanostructure grows in situ on nickel foam (NF) with the controlled introduction of structural defects using a one-step solvothermal method. Benzoic acid (BA) is selected as the cost-effective regulator and ligand to compete with the original ligand terephthalic acid (TPA), for inducing lattice distortion. The incorporation of BA results in increased micropore volume and surface area. These characteristics improve the contact between the electrode and electrolyte, leading to a rapid redox reaction. Thus, the defective sample Ni/Co-MOF/NF with 10% BA exhibits an ultrahigh capacity of 352.3 mAh g–1 at a current density of 1 A g–1. Moreover, the assembled hybrid supercapacitor device (10% Ni/Co-MOF/NF//AC) demonstrates a suitable energy density of 33.5 Wh kg–1 at a power density of 404.6 W kg–1 and 90.3% capacitance retention after 8000 cycles. These findings provide valuable insights for developing ultrahigh-performance MOF nanostructures that can be directly used as supercapacitor electrodes.