Preparation Of Polydopamine Functionalized Graphene Composite And Its Adsorption And Sodium Storage Properties

Graphene has been extensively studied in the fields of basic research and engineering applications in recent years because of its excellent properties.However,the excellent properties of graphene cannot be maximized due to the irreversible stacking and poor dispersion of graphene sheets,which greatly hinders the practical application of graphene.It is urgent to develop an effective strategy to functionally modify graphene to impart its multi-functional properties,thereby-maximizing the excellent properties of graphene.In this work,the polydopamine functionalized graphene composite system is designed and constructed using graphene oxide(GO)as the matrix material.Three technical approaches of covalent modification,nano-composite engineering,and construct assemblies are proposed to maximize the outstanding properties of graphene and endow it with multi-functional properties,which can effectively solve the bottleneck problem of graphene materials in practical applications.Polydopamine(PDA)is used to chemically reduce and functionally modify the GO sheets,and a unique structural design is introduced to realize the composite of graphene with carbon nanotubes(MWCNT),antimony sulfide(Sb2S3),and molybdenum disulfide(MoS2)nanomaterials.The constructed functionalized graphene composite material is applied to the fields of pollutant adsorption and sodium ion batteries(SIBs).(1)The ultra-lightweight and robust three-dimensional carbon nanotube/reduced graphene oxide hybrid aerogels are prepared via a viable green route and applied to efficient heavy adsorption of heavy metal ions.PDA functionalized multi-walled carbon nanotubes(MW CNT-PDA)were introduced into the GO system.The reducibility and adhesion of PDA can effectively promote self-assembly and realize the functional modification of GO sheets.No additional reducing agents were required during the molding of the hybrid aerogel,thereby greatly reducing the pollution emissions.The MWCNTPDA in the right amounts provided the hybrid aerogels with excellent structural stability and effectively prevented the stacking of GO sheets,as well as provided sufficient active sites to improve the adsorption of Cu(Ⅱ)and Pb(Ⅱ).Benefiting from the large specific surface area,porous structure,and competent active sites,the resulting hybrid aerogels showed superior adsorption performance,and the saturated adsorption capacities were as large as 318.47 and 350.87 mg g-1 for Cu(Ⅱ)and Pb(Ⅱ),respectively.The research revealed that the dominant adsorption mechanisms of hybrid aerogel involved chemical adsorption and intraparticle diffusion.Therefore,high adsorption capacity and the advantage of easy separation made the hybrid aerogel an ideal adsorbent for pollutant adsorption in practical application.(2)The carbon nanotube/graphene composite aerogels with hierarchical porous structure(GCPCA)are constructed through the combination of hydrothermal self-assembly,pore structure design,and thermal annealing treatment,which is used to efficiently remove organic pollutants in water.MWCNT-PDA was creatively introduced into the graphene aerogel framework to promote self-assembly of GO sheets and realize the functional modification of GO sheets.The MWCNTs in moderate amounts can provide the composite aerogels with desirable structure stability,hydrophobicity,and extra specific surface area.Meanwhile,the eventual absorption performance of GCPCAs can be improved by optimizing the microporous structure.In particular,a novel"cabbage-like" hierarchical porous structure was obtained as the pre-freezing temperature was decreased to-80℃.The miniaturization of pore size around the periphery of GCPCA enhanced the capillary flow in aerogel channels and the super absorption capacity for organic solvents was up to 501 times(chloroform)of its mass.The GCPCA exhibited outstanding repeatable compressibility,ultra-lightweight,hydrophobic nature,and fatigue durability,which were crucial for highly efficient organic pollution absorption.The GCPCA showed excellent reusable performance in absorption-squeezing,absorption-combustion,and absorption-distillation cycles.Therefore,the GCPCA with unique performance possessed broad and important application prospects,such as oil pollutions cleanup and treatment of chemical industrial wastewater.(3)The unique Sb2S3@nitrogen-doped carbon nanotubes were uniformly encapsulated by graphene sheets to construct functional composite aerogels,which can be used as high-performance anode materials for SIBs.The composite aerogel with ingenious structure was creatively designed by coating PDA onto the Sb2S3 nanorods.The PDA was not only a precursor of nitrogendoped carbon layer adjusting volume change of Sb2S3 during storage Na+ but also act as a reducing agent assisting to create graphene aerogel.Moreover,the nitrogen-doped carbon layer formed a strong interaction between the Sb2S3 and graphene to maintain the structural integrity of the aerogel anode material.Importantly,the composite aerogel synergized the superior electrical conductivity,abundant porous channels,and excellent electrochemical reactivity into one.As a result,the optimized composite aerogel showed a high specific capacity of 368 mA h g-1 after 200 cycles at 0.2 A g-1,and exhibited excellent fast charge performance and long cycle stability.Furthermore,the full cell was constructed from the optimized composite aerogel anode and Na3V2(PO4)3(NVP)cathode,displaying a high specific capacity of 388 mA h g-1 at 0.1 A g-1 with a remarkable energy density of 189 Wh kg-1,thereby showing great practical application potential.(4)All-in-one MoS2 nanosheets tailored by porous nitrogen-doped graphene(N-RGO)are designed and fabricated as high-performance anode materials for SIBs.The novel MoS2@N-RGO composite anode exhibited enhanced electronic conductivity and excellent structural stability as well as high cycling reversibility of conversion reaction,resulting from the restricted growth of MoS2 nanosheets on the porous N-RGO through a strong coupling effect.In particular,the all-in-one MoS2 nanosheets synergistically combined all the desirable characteristics of vertical alignment,ultrathin layer,vacancy defect,and enlarged interlayer spacing,thereby effectively improving the electrochemical kinetics and improve the utilization of the active material.With these merits,the MoS2@N-RGO composite anode displayed a high specific capacity of 329 nA h g-1 after 200 cycles at 0.2 A g-1 and showed a specific capacity of 219 and 149 mA h g-1 at 10 and 20 A g-1,respectively.Moreover,the full cell constructed from MoS2@N-RGO composite anode and NVP cathode displayed high specific capacity and remarkable energy density,thereby exhibiting great potential for practical application.