Preparation And Electrochemical Capacitance Properties Of Metal Oxide Nanoarrays

In recent decades,due to the rapid growth of global population and economic,the demand for energy is increasing.Therefore,it is important and urgent to develop new types of clean energy.At this time,supercapacitors as alternative energy and power sources have attracted great interests.In many supercapacitor electrode materials,we have found that the preparation of supercapacitors from cheap metal oxides can reduce costs and become environmentally friendly.It is easier to commercialize and becoming a current research hotspot.In this paper,the synthesis method of direct current electrochemical deposition combined with high temperature annealing and oxidation is adopted.With the help of gold-plated AAO template,a series of unique nanopore and nanowire array materials have been successfully prepared.Meanwhile,their relative performance have been systematically studied.The specific research contents of this paper are listed as follows:1.Preparation and electrochemical capacitance properties of NiO nanopore array filmsIn this paper,we sputtered a thin layer of gold on the surface of the self-made alumina template with an ion-sputtering device to completely cover the template pores as conductive electrodes.NiO nanopore array films were prepared on the AAO template by means of direct current electrochemical deposition and high temperature annealing and oxidation.In order to facilitate the performance test,we completely etched away the alumina with an alkaline solution to obtain a soft and continuous nanohole array film.Then nanohole array film was transferred to the conductive side of a unidirectionally conductive ITO glass and it was fixed by epoxy resin.An NiO electrochemical capacitor was constructed.The morphology,phase and composition of the NiO nanopore array was analyzed by SEM,XRD and EDS.The morphology and structural characteristics indicate that the nanohole array film is an ordered pore structure composed of minute particles,and along the direction of the holes,the film exhibits a peak-like structure.The electrochemical properties of the sample were tested with CHI660e.When the current density is 10 mA/cm²,NiO nanopore array exhibits excellent area specific capacitance with 57 mF/cm².Furthermore,the stability of NiO nanopore array film is 128%in 1000 cycles of charge and discharge.Analysis shows that NiO nanopore array film exhibite such good performance mainly due to the thin-film nanopore array structure.The structure of the NiO film material is relatively stable and its conductivity is good.On the other hand,the nanohole array structure of the thin film.2.Synthesis of ordered Ni/NiO nanocables for electrochemical capacitor applicationBased on the self-made AAO template,Ni/NiO nanowire array material with core-shell structure was successfully prepared by the combination of direct current electrochemical deposition and high temperature annealing.Taking the same method as in content 1,an Ni/NiO electrochemical capacitor was constructed by transferring the nanowire array onto ITO glass.The morphology and structure of Ni/NiO nanocables have been studied by SEM and HRTEM.The morphology and structure characteristics show that every nanotube has a Ni nanowire as the inner core and a thick layer of NiO as the external shell.The electrical properties of the Ni/NiO nanocables were tested by CHI660e,and the results show that Ni/NiO nanocables have a large capacity and high current ratio.When the current density is 1 mA/cm²,the area ratio capacitance of Ni/NiO nanocable is 398 mF/cm².Furthermore,the Ni/NiO nanowire array material has good cycle stability as high as 94.3%in 4000 times charge and discharge.The good electrochemical performance can be attributed to the special core-shell nano-architecture.The metal Ni nanowire cores achieve rapid electron transfer.The NiO shell with a larger surface area is conducive to enhance its sensing capacitance.3.Preparation of nickel-doped trioxide nanowire arrays for supercapacitor propertiesBased on AAO template,Ni-doped Co₃O₄ nanowire array was successfully fabricated by the combination of direct current electrochemical deposition and high temperature annealing.Like the above method,we adopted the method of suspension transfer to build Ni-doped Co₃O₄ electrochemical capacitors.The morphology and phase of the as-prepared nanowire arrays were characterized by TEM,SEM and XRD.The results show that the morphology and size of Ni doped Co₃O₄ nanowires are very uniform and vertically aligned on the substrate.Combined with XRD and EDS,we can conclude that the ratio of Co:Ni is about 20:1.The electrical properties of the Ni doped Co₃O₄ nanowires were tested by CHI660e.Results show that Ni doped Co₃O₄nanowires excellent electrochemical capacitance characteristic.When the current density is 10 mA/cm²,the area specific capacitance of the nanowire array is 173mF/cm²,and Ni doped Co₃O₄ nanowire material has good cycle stability as high as 98%in 1000 times.This excellent performance should be related to the special structure and composition of the material.Incorporating a small amount of Ni in the Co₃O₄ material can play a strong synergistic role to further enhance the specific capacitance value of the electrode material.