Simple deposition of mixed α, β-nickel hydroxide thin film onto nickel foam as high-performance supercapacitor electrode material

Abstract

Here, uniform thin nanosheets’ film of mixed α- and β-Ni(OH)₂ phases was cathodically electrodeposited onto nickel foam support and the fabricated electrode was utilized as binder-free electrode for supercapacitor applications. An additive-free aqueous electrolyte of 0.05 M nickel nitrate was used as the deposition bath, where the hydroxide film was prepared with only applying direct current of 10 mA/cm² in a two-electrode system while a uniform electrical field was established through using two counter electrodes parallel to nickel foam cathode. The morphology, crystalline phase and also specific surface area of the deposited nickel hydroxide film onto Ni foam were analyzed using field-emission scanning electron (FE-SEM) and X-ray diffraction (XRD) techniques as well as BET and FT-IR spectroscopy. These analyses proved that a mixed alpha and beta phases of Ni(OH)₂ with uniform nanosheets’ morphology are grown onto the nickel foam cathode. The electrochemical investigations using CV, GCD and electrochemical impedance spectroscopy (EIS) manifested the designed electrode provides specific capacitance of 2143 F g⁻¹ at a current density of 0.5 A g⁻¹ with high rate capability of 65% by increasing the current density from 0.5 to 20 A g⁻¹ as well as 90% and 74% cycling stability at the current densities of 5 and 15 A/g, respectively. The excellent electrochemical performance of the as-prepared electrode is ascribed to the simultaneous deposition of both α and β phases through using a facile electrochemical deposition method. The presence of α and β phases guarantees the high specific capacitance and high cycling stability of the prepared electrode, respectively.