Preparation And Properties Of Porous Graphene Oxide Carbon Aerogels

In recent years,capacitor deionization(CDI)has received increasing attention as a reliable,energy-efficient and cost-effective desalination technology.Carbon aerogels(CAs)is a special class of material derived from the sol-gel method and is considered as one of the most promising CDI electrode materials.Due to its unique high electrical conductivity,environmental compatibility and chemical stability,it has broad prospects in the field of CDI.Porous graphene oxide is a new carbon material which has high specific surface area,excellent physical and chemical properties.However,the graphene sheet is prone to agglomeration and its performance is far from ideal.In order to prepare the CDI electrode material with excellent properties,this subject added porous graphene oxide on the basis of resorcinol-formaldehyde carbon aerogel,and combined the advantages of both to prepare the high-performance porous graphene oxide aerogel.Based on this research,we doped heteroatoms or metal oxides to improve its electrosorption and electrochemical performance of the material.The details are as follows.(1)Preparation of graphene oxide by improved hummers method,and the porous graphene oxide(HGO)was prepared by chemically etching pores with hydrogen peroxide.An organic gel was prepared by mixing HGO with resorcinol,formaldehyde,and a catalyst uniformly using a one-step sol-gel method.A porous graphene oxide carbon aerogel was obtained after freeze drying and carbonization.The obtained carbon aerogel has a rich pore structure and a large specific surface area.Electrochemical tests found that the carbon aerogel HGC8-2 prepared at an HGO addition amount of 2 wt%and a carbonization temperature of 800? had the best electrochemical performance,with a specific capacity of 130.52 F g-1 at 0.1 A g-1.Compared with GC8,the specific capacitance is improved by about 8.6%.When applied to the CDI desalination test,the maximum adsorption capacity reached 20.20 mg g-1 at a voltage of 1.4 V and an initial conductivity of 1600 ?s cm-1 NaCl solution,which was 11.6%higher than GC8,and the maximum adsorption rate reached 0.36 mg g-1 s-1.(2)It was determined that the added amount of HGO was 2wt%,and urea and ammonium fluoride were used as nitrogen and fluorine sources.The organic gel was also synthesized by the sol-gel method in one step.The nitrogen-fluorine co-doped porous graphene oxide carbon aerogel was obtained after freeze-drying and carbonization.The introduction of nitrogen and fluorine atoms increases the conductivity and wettability of the material,and greatly improves its electrochemical performance.When the mass ratio of ammonium fluoride to HGO is 5:1,the prepared FNHGC-2 has the best electrochemical performance,and the specific capacity reaches 173.3 F g-1 at a current density of 0.1 A g-1,compared with the undoped HGC8-2 performance improved by 32.78%.In the CDI desalination test,the maximum adsorption capacity reached 49.12 mg g-1 at a voltage of 1.4 V and an initial conductivity of 1600 ?s cm-1 NaCl solution,and the performance was improved by 1.43 times.(3)The added amount of HGO is still 2wt%,and metal-doped porous graphene oxide carbon aerogel is prepared by using manganese nitrate and cobalt nitrate hexahydrate as metal sources.When the mass ratio of manganese nitrate to HGO is 2:2,the prepared MnCo/HGC-2 has the best electrochemical performance,the specific capacity reaches 164.18 F g-1 at 0.1 A g-1,and the performance is improved by 25.79%.In the CDI desalination test,the maximum adsorption capacity reached 30.20 mg g-1 at a voltage of 1.4 V and an initial conductivity of 1600?s cm-1 NaCl solution,and the performance was improved by 49.5%.