The Preparation Study Of Porous Nickel Oxide By Anodic Oxidation

Due to its surface structure and excellent properties,nanoporous nickel oxide is considered as one of the materials with great research value and application potential in the fields of supercapacitors and photocatalysis.Compared with other methods of preparation of nickel oxide,anodic oxidation is simple and efficient,and the oxide film has good adhesion with the substrate.Oxide films with different morphologies have been successfully prepared on Al,Ti,Nb,Mg and other metals in this way.However,there are few studies on the anodic oxidation of nickel,the only research on anodic oxidation of nickel mainly focuses on the theoretical study of acidic aqueous/alkaline solution.Therefore,it is of great value to study the composition,morphology and performance characterization of the oxide film formed by direct current anodic oxidation of nickel in different electrolytes.In this paper,the pure metal nickel was anodized in three different electrolytes by means of two-electrode system and direct current anodic oxidation.The anodic oxidation process of nickel was investigated by changing the applied voltage,initial current density,reaction time and other parameters in combination with annealing process.SEM,XPS and water contact angle test and photocatalytic performance test methods were used to observe the surface micro-structure of the samples and to detect the components of the samples after anodic oxidation and annealing.The photocatalytic properties of some samples after anodic oxidation and annealing were investigated.After nickel was anodized in the acidic organic solution of ethylene glycol and ammonium fluoride,no porous structure was observed and analyzed by SEM.After anodic oxidation,the surfaces of the samples were hydrophilic and the water contact angle was affected by the initial current density.The NiO films prepared by anodizing and annealing have certain photocatalytic properties,but the XPS analysis results show that the NiO films obtained are not pure and contain a small amount of fluoride impurities.After nickel was anodized in strongly alkaline aqueous solution of sodium hydroxide,the anodic oxidation time and voltage had a great influence on the surface microstructure of the sample after anodic oxidation.As time goes on or voltage goes up,the lamellar structure with porosity gradually appears on the micro surface.XPS analysis showed that the main component of the surface film was Ni(OH)2.The surfaces of the samples were hydrophilic after anodizing,and the water contact angle was significantly affected by anodizing time and initial current density.However,even under the same condition,it was found in the experiment that the surface morphology of the sample was different after anodizing,and the experimental results were not easy to repeat.Nickel anodized at voltage 3 V,4 V,5 V respectively,under the initial current density of 200 mA/cm2 for 2 h in weakly alkaline aqueous solution of boric acid-borax.After anodic oxidation,the sample surface presented hydrophobicity,and with the increase of voltage or initial current density,the water contact Angle decreased,while it increased with the anodic oxidation time enlarged.And successfully prepared porous NiO films on nickel substrate combined with annealing,which presents certain photocatalytic performance towards rhodamine B solution...