Preparation And Capacitive Desalination Performance Of Cu-Al Layered Double Hydroxide

Carbon material is often employed as electrode for capacitive deionization(CDI),leading to undesired salt removal capacity and charge efficiency in high concentrated brine.In this thesis,layered double hydroxides(LDHs)and its derivatives and carbons were separately used as chloride ion intercalation electrodes and sodium ion adsorption electrodes to build a hybrid CDI(HCDI)system.In relation to HCDI,chloride ions are inserted within LDH layers,and sodium ions are adsorbed by electrostatic action,resulting in desalination.In this thesis,the preparation,physio-chemical properties and CDI behavior of layered double hydroxides and its derivatives will be explored and discussed deeply.Thus,the research contents are stated as follows:1?In this work,laminated CuAl-mixed metal oxide(CuAl-LDO)has been prepared and proposed as chloride ions interaction electrode for Pesudo-CDI(P-CDI).To constitute full P-CDI cell,CuAl-LDO and HNO3 treated activated carbon(AC-HNO3)were employed as anode and cathode,respectively.When operated at constant voltage mode,the CuAl-LDO?AC-HNO3 P-CDI shows high salt removal capacity of 39.08 mg/g in NaCl solutions with an initial concentration of 500 mg/L at applied voltage of 1.2 V.After 20 cycles.The capacity retening is?19%while the charge efficiency is 80.72%.Moreover,the crystal phase evolution of CuAl-LDO as well as corresponding electrochemical spectra during the P-CDI process illustrated that chloride ion was intercalated into the CuAl-LDO electrode via chemical bond.Besides,it is found that Cu(OH,CI)2·2H2O may be formed as the P-CDI cycling increases which is responsible for the salt removal capacity decay after long cycling.2?This work aims to improve the desalination capacity of CuAl-LDO.Thus,the vertical-aligned CuAl-LDO grown on reduced graphene oxide(CuAl-LDO/rGO)is proposed as high-performance anode for HCDI.It is found that the morphology of CuAl-LDO is ultimately dependent on the loading mass of urea.As a result,the optimized CuAl-LDO/rGO exhibits relatively high specific surface area,3D porous structure and electrochemical behavior.As anode for HCDI,it demonstrated high salt removal capacity of 64.0 mg/g at cell voltage of 1.2 V in NaCl with an initial concentration of 1000 mg/L.After 20 cycles,the capacity remains at 58.0 mg/g which is?90%of initial value,suggesting the superior cycling ability.Moreover,the phase transformation of CuAl-LDO/rGO at various stages indicates that the Cu(OH,Cl)2·2H2O may responsible for the capacity decay upon the cycling.However,the morphology characterization realizes that the aggregation of Cu(OH,Cl)2·2H2O nanoparticles can be effectively inhibited within CuAl-LDO/rGO by compared to that of random oriented CuAl-LDO,which is accounted for superior salt removal capacity retention.Besides,a comparison is performed on HCDI performance among different anodes,highlighting the advances of CuAl-LDO/rGO.