Ni(OH)2–NiO–NiF Compound Film on Nickel with Superior Pseudocapacitive Performance Prepared by Anodization and Post-hydrothermal Treatment Methods

Abstract

An Ni(OH)2–NiO–NiF compound film was successfully fabricated on a nickel foil by combining two-electrode anodization and hydrothermal treatment methods. The structure and morphology of the films before and after hydrothermal treatment were studied by using X-ray diffraction analysis, X-ray photoelectron spectrum, surface area and porosity analyzer, and scan electron microscopy, while the electrochemical performances of the resultant films were carried out using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge procedures. The results showed that no crack was found in the resulting film achieved by this two-step technology. This film consisted of nano-plate crystals with porous morphology, and exhibited a high specific capacitance (1,984 F/g at 10 A/g), high capability and good cycling stability (capacitance close to 1,680 F/g at 100 A/g after 2,000 cycles). The reasons for excellent pseudocapacitive performance of this compound film on nickel foil were discussed. It is suggested that the excellent pseudocapacitive performance of this compound film is related to the hydrothermal effects.