Preparation And Desalination Characteristics Of Electro-sorption MXene Electrode

In recent years,desalination technologies have been intensively studied to collect recycle clean water from seawater or brackish water in order to solve the freshwater scarcity crisis.Electro-sorption technology,also known as Capacitive Deionization(CDI),has received much attention because of its advantages,such as no secondary pollution,no additional oxidant or flocculant,along with low cost and energy consumption.The principle is that by applying a voltage to the electrode,the anions and cations in the water are acted by the electric field force,move towards the electrode with the opposite electric charge,and are absorbed by the electric double layer to remove the ions in the aqueous solution.Under the condition of open circuit or applying opposite voltage,The adsorbed ions are released and discharged,and the electrodes are regenerated at the same time.The core of capacitive deionization technology is the selection and preparation of electrode materials.Capacitive deionization materials that have been widely used include activated carbon fibers,graphene,metal oxides,carbon nanotubes and other materials.In recent years,two-dimensional transition metal carbides,nitrides and carbon nitrides,or MXene,are attracting attention in the fields of heavy metal ion adsorption,energy storage devices,catalysis,electromagnetic interference shielding,and gas sensors.With the outstanding features of high specific surface area,high metal conductivity,easy functionalization,biocompatibility,activated metal hydroxide sites,and good hydrophilicity,MXene is of bright future for application in capacitive deionization technology.In this paper,the synthesis method of MXene materials,the application of MXene in asymmetric supercapacitors,the related application of MXene in capacitive deionization technology and its challenges and problems are studied.Specific studies include.(1)A flexible asymmetric supercapacitor device based on pseudocapacitive materials was prepared,and nanowire structured V₂O₅ hydrate was prepared by hydrothermal decomposition as the positive electrode material;delaminated layer less Ti₃C₂T_x MXene with terminal groups of-OH,-O and-F was used as the negative electrode material to assemble the asymmetric supercapacitor.The microscopic morphology and electrochemical properties of the two materials were separately characterized and tested.The asymmetric Ti₃C₂T_x MXene//V₂O₅ device was operated at a potential window of-1.1 V-0.1 V for Ti₃C₂T_x MXene up to 1.5 V,and the energy density of the device was significantly increased up to 8.33 m Wh cm^-3.In addition,the prepared solid-state flexible device could be used for light-emitting diodes(LEDs)for up to 7 s.(2)The application of MXene in asymmetric supercapacitors proved its excellent performance,and later MXene was directly configured with conductive carbon black and binder in proportion to the slurry applied in CDI.The conductivity was tested by using NaCl solution at a certain flow rate and at a certain concentration as a salt solution.The results proved that the ion adsorption rate of Ti₃C₂T_x MXene to NaCl solution reached 17.84 mg g^-1,which proved the superior adsorption performance of MXene.