Electrochemical preparation of Ni(OH)2/CoOOH bilayer films for application in energy storage devices

CoOOH/Ni(OH)2 and Ni(OH)2/CoOOH bilayer films were obtained through electrochemical deposition of Ni(OH)2 and Co(OH)2 single layers onto steel plate substrate, with subsequent electrochemical oxidation of Co(OH)2 to form CoOOH. The films were structurally characterized using X-ray diffraction and Raman spectroscopy techniques. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques were used to perform the electrochemical characterization of the prepared bilayers. It was verified that during the electrochemical oxidation, CoOOH formation occurs without Ni(OH)2 oxidation. Ni(OH)2 films deposited on CoOOH (CoOOH/Ni(OH)2) showed a superior electrochemical performance, with 324.27 mA h g−1 and 96.82% at 1.0 mA cm−2 for the specific capacity and capacity retention respectively. It was also determined that the relaxation time constant under this condition is 17.05 s. These results suggested that the CoOOH/Ni(OH)2 bilayer films might be potential candidates for application as electrode in energy storage devices.