Synthesis of Ni(OH)₂ Nanoflakes Through a Novel Ion Diffusion Method Controlled by Ion Exchange Membrane and Electrochemical Supercapacitive Properties

Highlights: • We synthesized β-Ni(OH)₂ nanoflakes through a novel ion diffusion method. • The possible formation mechanism of the Ni(OH)₂ nanoflakes was discussed. • The temperature influence on growth of Ni(OH)₂ nanocrystals and its subsequent effect on electrochemical supercapacitive properties were examined. • The β-Ni(OH)₂ nanoflakes prepared at 50 °C for 12 h exhibits the highest specific capacitance of 2102 F g⁻¹. - Abstract: A novel method, ion diffusion method controlled by ion exchange membrane was reported for the synthesis of Ni(OH)₂ nanomaterials in the absence of any template or organic surfactant. The structure and morphology of as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), BET specific surface area and pore size distribution analyzer. It can be observed that β-Ni(OH)₂ nanoflake-like structure was obtained, and the sheet size, thickness and pore size of as-prepared samples can be controlled by altering reaction time and reaction temperature. The BET specific surface area of Ni(OH)₂ nanomaterials obtained by this method can be up to 280.5 m²/g at 30 °C. The electrochemical supercapacitive properties of Ni(OH)₂ nanostructures have been investigated by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy techniques. All these Ni(OH)₂ samples exhibit good capacity for electrochemical supercapacitor in KOH electrolyte. The flake nanostructures synthesized at 50 °C for 12 h exhibit a highest specific capacitance of 2102 F g⁻¹ at a current density of 20 mA cm⁻² within the potential range of 0.5 V and the Ni(OH)₂ sample retains 85.1% of the initial capacitance even after 1000 continuous charge–discharge cycles. The results indicate that ion diffusion method controlled by ion exchange membrane is a useful method for synthesizing inorganic nanomaterials.