Synthesis Of Magnetic Oxide/graphene Composites And Their Application For Lithium Storage Properties And Adsorption Properties

Recently,nanoparticles with controllable size and morphology have caused much attention for their application in basic science and practical technology.Among them,a typical nanomaterial has been considered as anode material for lithium ion batteries and pollution treated material.Fe₃O₄ with a high theoretical capacity of 926 m Ah g^-1,is a kind of metal oxide that could be used as anode material for lithium ion batteries.However,it could suffer from a large volume change during lithiation/delithiation.As a result,its cycling performance becomes bad.The similar disadvantages are also there for the Fe₃O₄ when used as the sorbent.If the Fe₃O₄ nanoparticles were modified with graphene material,their structure would be stabilized,thus improving the electrochemcal properties and adsorbing performance to some extent.In this work,we adopted the solvent-thermal method to synthesize the porous Fe₃O₄ microspheres with uniform size.The obtained Fe₃O₄ microspheres were composited with graphene nanosheets through electrostatic cation or covalent action.The electrochemical properties of the modified Fe₃O₄ microspheres were studied as well as the adsorption of Pb?II?ions.The main study contents are lists as follows:1. Porous Fe₃O₄ microspheres with uniform size were prepared by a facile solvent-thermal method.They were modified with the coupling agent KH-550 to form positive charge on the surface.Through the electrostatic action,the obtained positive microspheres were composited with graphene oxide nanosheets.It is found that:the first specific discharge capacities of C-1,C-2 and C-3 samples can retain 1210,1236,and 1230 m Ah g^-1.After 100 cycles,the capacities was maintained at 670,763,and713 m Ah g^-1.At the 2 C rate,the C-2 samples can still be maintained at 395 m Ah g^-1.When the current density returns to 0.1C,the discharge capacity can be returned to821 m Ah g^-1.Therefore,when the mass ratio of GNSs to p-Fe₃O₄ is 1:4,the synthesized composites have the best electrochemical performance.2.A new type of composite was prepared by surface coating the p-Fe₃O₄microspheres with TEOS,then modified with APTES,and packed by graphene oxide through covalent action.It is found that:in the 0.1³ V voltage range,0.1 C current density,the first discharge capacity of p-Fe₃O₄-W-RGO samples is 1246 m Ah g^-1.In the first 50 times,the capacity gradually receded to 753 m Ah g^-1,and then,the cycle life curve of the material showed a gradual upward trend until the 100th cycle,the discharge capacity returned to 793 m Ah g^-1.At the 2 C rate,the p-Fe₃O₄-W-RGO samples can still be maintained at 478 m Ah g^-1.When the current density returns to0.1 C,the discharge capacity can be returned to 843 m Ah g^-1.3.GO-wrapped Fe₃O₄ microsphere?GO-W-MC?were prepared by optimizing the fabrication process,in which the effects of deionized water,APTES and p H value are studied.The optimic adsorption condition was obtained by measuring the adsorption performances under various p H values,different Pb?II?concentrations and different time.The results indicated that the as-prepared sample had a strong magnetism and stable structure.It can strongly absorb the Pb?II?ion in aqueous solution repeatedly.The maximum adsorption capacity of the composites was 225.6mg/g at p H=6,Ce=160 mg/L and 480 min.The adsorption capacity of the five adsorption cycles can still be maintained at about 89%.As a result,it would not pollute the solution secondarily,and can be developed to a promising absorbing material to remove the heavy metallic ions from the water.