Study On The Preparation And Properties Of Graphene Oxide Composites

Graphene,a one atom thick and two dimensional carbon materials,has been extensively studied due to the remarkable physical and chemical properties.However,the high cost and complex preparation processes hinder its application in many fields.As an important derivative of Graphene,Graphene oxide?GO?can be considered as an important precursor for mass synthesis of Graphene due to its low cost of production.Besides,GO consists of abundant oxygen-containing functional groups such as hydroxyl,epoxy,carboxy and carbonyl groups and large specific surface area,which provides much active sites to form GO composites combined with various materials.Recently,the GO composites have been in the application of adsorption and electrochemical energy storage.Environment and energy are the two most important issues,which are key steps in achieving sustainable development strategy.Recently,heavy-metal pollution and energy shortage have become two serious problems that bother people.For example,the bivalent cadmium ion pollution seriously harm people's health.In addition,in terms of energy conversion,Li₃VO₄ as a promising anode material for Lithium ion batteries,however,the poor electronic conductivity seriously hinder it's wide application.In this paper,starting from the above research background,the main contents of the research are as follows:?1?The natural flake graphite was adopted as raw materials to prepare graphene oxide via an improved Hummers method.The GO-starch composite was prepared through a facile esterification method.The chemical composition and morphology of GO and GO-starch were investigated by scanning electron microscopy?SEM?,fourier transform infrared spectroscopy?FT-IR?,Raman spectroscopy and BET.GO-starch was used as a novel adsorbent for the removal of Cd?II?in waste water.The characterization results demonstrated that the soluble starch had been grafted onto the surface of GO successfully.To evaluate the effects of the adsorption of Cd?II?by GO-starch,batch adsorption studies were optimize the major parameters such as contact time,initial pH of Cd?II?,initial concentrations of Cd?II?and temperature.The maximum uptake capacity of Cd?II?by GO-starch was 43.20 mg/g under the optimal conditions.Furthermore,the adsorption kinetics,isotherms and thermodynamics of Cd?II?on GO-starch were also investigated.The experimental results showed that the adsorption kinetics and isotherms of Cd?II?on GO-starch were fitted by pseudo-second-order kinetic model and Langmuir isotherm model,respectively.Moreover,the thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic reaction and the entropy increased in the adsorption process.?2?The pure Li₃VO₄ and Li₃VO₄/GO composites were prepared by a sol-gel and heat treatment subsequently.The chemical composition and morphology of Li₃VO₄and Li₃VO₄/GO were investigated by XRD,SEM and TG.The electrochemical tests demonstrated that Li₃VO₄/GO delivers the initial coulombic efficiency of 74.6%in the first cycle and the specific charge capacity is 209 mAh g^-11 after 100 cycles and presents a retention rate of 72.5%at the specific current density of 100 mA g^-1.Meanwhile,even at a high specific current density of 2000 mA g^-1,the charge capacity of Li₃VO₄/GO anode still presents a retention rate of 67%after 500 cycles.The rate tests also show that Li₃VO₄/GO anode delivers excellent rate performance.In addition,compared with the pure Li₃VO₄,the Li₃VO₄/GO delivers more superior electrochemical performance as an anode material for Lithium ion batteries.