Preparation Of N,P Co-doped Porous Carbon Materials For Capacitive Deionization

The scarcity of water is a serious problem in the world.The demand for freshwater will increase with population growth,industrial development,and climate change.Seawater desalination is an effective way to solve the problem.Seawater and brackish water desalination is a promising way to solve the lack of water resources.Reverse osmosis and distillation as traditional desalination technologies have many defects such as high energy consumption as well as high cost.Recently,the deionization capacitors has become an attractive technique for desalination,which relies on the use of electric double layer capacitors(EDLC).The capacitive deionization(CDI)has got more and more attention and developed rapidly because of its low cost,low energy consumption,high efficiency and environment-friendliness.Carbon materials are the most widely used as electrode materials for deionization capacitors because of its special properties,some carbon materials such as activated carbon,graphene,carbon nanotubes and carbon carbon aerogel have been used as CDI electrode materials.However,finding novel electrode materials with simple preparation method and high CDI efficiency is still very urgent.Our reaearch concentrates on preparing novel heteroatoms-doped porous carbon materials and the studies of their morphology,structure,electrochemical performance and deionization performance.The main research contents are listed as follows:(1)Nitrogen and phosphorus co-doped meso-/microporous carbon derived from biomass materials has been designed and successfully fabricated as high-performance electrodes for deionization capacitors.The obtained materials were prepared by the pyrolysis of pomelo peel via a dual-activation strategy by using NH4H2PO4 and KHCO3.It is interesting that the as-prepared nitrogen and phosphorus co-doped meso-/microporous carbon possesses a high specific surface area of 2726 m2/g with high percentage of mesopores of 52 %.It has been demonstrated that the obtained electrode shows high specific capacitance,low inner resistance and good wettability.Consequently,the obtained electrode exhibits good deionization performance under various operating conditions.The electrode reveals an ultrahigh deionization capacity of20.78 mg/g with an initial NaCl concentration of 1000 mg/L at the cell voltage of 1.4 V.The obtained electrode also has a good regeneration performance.The good performance is ascribed to the high surface area,superior micro-/mesoporous structure and good wettability.Hence,the nitrogen and phosphorus co-doped meso-/microporous carbon should be a promising candidate as electrode materials for deionization capacitors.(2)Nitrogen and phosphorus co-doped grapheme-like porous carbon have been prepared via a simpleFe-catalyst approach and calcined melamine–phytic acid supermolecular aggregate at 900 oC for 2 h.The as-prepared nitrogen and phosphorus co-doped grapheme-like porous carbon possesses a high specific surface area of 1320 m2/g and shows good electrochemical performance as well as good wettability.The electrode reveals an ultrahigh deionization capacity of 21 mg/g with an initial NaCl concentration of 500mg/L at the cell voltage of 1.4 V.The obtained electrode also has a good regeneration performance.