Study On The Performance Of Capacitive Deionization Of The Nitrogen-Enriched Carbon Electrode Derived From Porous Organic Frameworks

Capacitive Deionization is a desalination technology that was based on the electrical double layer(EDL).With the advantages including low energy consumption and environmentally friendly,CDI is considered to have a good application prospect.Electrode materials play an important role in the performance of CDI.However,the traditional porous carbon materials suffer from the low salt remove capacity which limits the further application of CDI.Nitrogen doping is regarded as a kind of the best way to improve the electrochemical performance of carbon materials since nitrogen doping can bring some favorable differences to the structure and physical and chemical properties of carbon materials.Besides,there are abundant availability and low cost of nitrogenous sources.Therefore,nitrogen-doped carbon material is one of the perfect materials for CDI.Melamine is a cheap chemical reagent from a wide range of sources,and has a very high nitrogen content(66%).At the same time,the structure contains a rigid triazine ring structure,which is very suitable as a monomer to prepare organic polymers.In this study,we firstly prepared the Schiff base network-1(SNW-1)via one-port synthesis and then the nitrogen-enriched micro-mesoporous carbon(NMC)electrode was fabricated by carbonizing the Schiff base network-1 at 500°C,600°C and 700°C.Fourier transform infrared spectroscopy,thermogravimetry,high-resolution emission scanning electron microscopy,X-ray diffraction,Raman spectroscopy,X-ray photonic energy spectrum,nitrogen adsorption/desorption and contact Angle test were used to characterize the nitrogen-doped carbon materials.constant current charge-discharge(GCD),electrochemical impedance spectroscopy(EIS)and Cyclic voltammetry(CV)tests were carried out on the nitrogen-doped derived carbon materials with an electrochemical workstation.NMCs electrodes were carried out series of desalination under different operating conditions.The experimental results show that the porous organic polymer SNW-1 is a very ideal carbon precursor,and the nitrogen-doped carbon materials prepared by its carbonization have very good adsorption properties.The main reason is that the original perforated structure of SNW-1 is destroyed and reorganized during the heating process,and many mesopores are generated.The micropores serve as a conductive network,and the mesopores facilitate the transmission and adsorption of charged particles.Abundant nitrogen elements increase the electrochemical performance of the material as well as the specific adsorption of some ions.Among them,the specific capacitance of NMC600 prepared at 600°C is as high as 152.33 F/g at a scan rate of 1 mv/s,which is the best performance among the prepared samples.This is because it has a large specific surface area of 312 m~2/g,and also contains 15.57%nitrogen content.The element composition and internal structure have reached a relatively good balance,which maximizes the synergistic effect.When the solution concentration is 500 mg/L and the external voltage is 1.2 V,the adsorption capacity is as high as 25.53 mg/g,the maximum adsorption rate of salt ion is 1.91 mg/g/min,the charge efficiency is 0.58 and the energy consumption is 0.75 k Wh/kg.It also showed good regeneration performance in the cyclic adsorption-desorption experiment.It shows that the nitrogen doped carbon electrode prepared by porous organic polymer has a excellent application prospect in CDI.