Preparation Of Ferrite/Graphene-based Nanocomposite Film Electrode And The Capacitive Deionization Applications

Capacitive deionization technology（CDI）is a new type of green environmental desalination technology based on electric double layer theory,which is wide-ranging,energy saving,environment recycled,no secondary pollution and providing a good application prospect in seawater desalination.CDI is a technology using the capacitance principle of electrode material to form an electric double layer by the absorption of cationic and anionic in salt solution to achieve the purpose of desalination.The focus of CDI technology is the preparation of electrode material with renew ability and higher specific capacitance.At present,the research is mainly based on the carbon nanomaterials for CDI electrode material,and in order to improve the performance of carbon electrode and the desalination rate of CDI,it is effective way to mix other components with carbon materials,such as conducting polymer,metal oxide,or other carbon material,thereby exhibiting the advantages of the components.Among them,iron-based composite oxide（ferrite）is a new type of inorganic functional material,and the addition of a small amount of ferrite will greatly improves the specific capacitance of the electrode material,which is widely used in the field of supercapacitors.Therefore,the preparation of electrode materials with high specific surface area,reasonable pore size distribution,high conductivity,high mechanical strength and high specific capacitance will play an important role in capacitance deionization technology.In this paper,the ferrite and nanocomposites of rGO/ferrite was prepared by coprecipitation method and hydrothermal method,which were introduced into the carbon materials respectively,and prepared large-area porous electrode films with high capacitance and reproducibility by rolling process,then applied them to the capacitor deionization technology,with the potential of large-scale production.The research contents and achievements in this paper are as follows:Using coprecipitation method to combine oxalic acid with other metal ions to form complex precursor,and calcining it to prepare ferrite nanometer material with uniform particle size.The ferrite particles are uniformly grown by hydrothermal method on Graphene surface to prepare rGO/ferrite nanocomposites with excellent performance.The two methods do not need to adjust the PH value of the solution,and the operation steps are simple.The results show that both methods can prepare pure nano-materials with uniform particle size.However,ferrite nanoparticles are prone to agglomeration due to magnetic properties,thus forming large particles.The structure of rGO/ferrite nanocomposites prevents the ferrite from self-agglomeration which is created by magnetism in ferrite and van der Waals forces in graphene,thus making ferrite nanoparticles homogeneously flattening in the wrinkles of the graphene.These two methods laid the foundation for the preparation of electrode material film.Fe₂ZnO₄,Fe₂CoO₄ and rGO/Fe₂CoO₄ nanomaterials were combined with carbon materials（activated carbon as the main raw materials and one-dimensional carbon nanotubes,twodimensional graphite Olefins and carbon particles with smaller particle size）by rolling method and the three-dimensional network structure ferrite/carbon nanocomposite films were prepared by rolling with polytetrafluoroethylene as binder.The addition of Fe₂ZnO₄,Fe₂CoO₄ and rGO/ Fe₂CoO₄ nanomaterials makes the carbon material film have a higher specific capacitance,specific surface and reasonable pore size distribution,ensuring good mechanical properties,electricity Chemical properties,cycling stability and capacitance deionization of the electrode material.In the CDI test of the same carbon material component electrode film,under the condiction of 2.0V applied voltage,30 r / min peristaltic pump rotation speed,100 mol / L the initial concentration of salt solution,the maximum desalination rate of the Fe₂ZnO₄ and the carbon material electrode film was 47.5% and the maximum salt adsorption capacity was 5.57 mg / g.The maximum desalination rate of Fe₂CoO₄ and carbon material was 55.5%.The maximum salt adsorption was 6.74 mg / g.The maximum desalination rate of rGO/ Fe₂CoO₄ and carbon electrode films is 65.4% and the maximum adsorption capacity is 10.25 mg / g.Through the comparative analysis,it can be concluded that the electrode films with nano-materials prepared by hydrothermal method and carbon materials have a better performance.In short,large area complete films can be prepared by the rolling method,which is a good electrode material with large specific capacitance and specific surface area,ensuring the CDI performance and renewable capacity of the electrode material.