Graphene Based Functional Composites Loading Of The Solid Or Liquid Components And Their Supercapacitor And Fenton Reaction Performances

Graphene has attracted intense interest all over the world in recent years due to its single-atom thickness and flexible two-dimensional?2D?structure.Such characteristic structures can serve as an ideal vehicle to load various solid and liquid components,which has been widely used in the fields of catalyst and supercapacitor.In this thesis,the synthesis of three composites has been studied including graphene macroforms?GMs?,graphene macroforms/Mn₃O₄?GM/Mn₃O₄?and graphene/Ferrite/C₃N₄?RGO/MnFe₂O₄/C₃N₄?composites.The supercapacitor performance of GMs was examined,and GM/Mn₃O₄ and RGO/MnFe₂O₄/C₃N₄ composites were used as the catalysts for the degradation of dyes to investigate their Fenton catalytic activities.The main contents are as follows:1.Dense 3D graphene macroforms with nano-tuned pore sizes have been synthesized using graphene oxide as the precursor and aqueous H₂SO₄ as the mediator by coupling hydrothermal method with evaporation drying process.The advantages of the method are summarized as follows:?1?H₂SO₄ as the catalyst can remove the oxygenic and hydric groups of GO through dehydration;?2?The concentrated H₂SO₄ trapped in the GMs after the evaporation of water plays an important role on tailoring of the pore sizes of GMs;?3?Liquid H₂SO₄ trapped in GMs acts as the electrolyte in supercapacitor;?4?The shaped GMs can be fabricated directly as an electrode for the assembly of a supercapacitor device free of any additives.The research shows that the graphene macroform with the average pore size of 4.8 nm is the excellent electrode material in H₂SO₄ electrolyte.Its specific capacitance is up to 230 F g^-1 at the current density of 0.1 A g^-1,and the specific energy density and power density are up to 8,3 Wh kg^-1 and 1000 W kg^-1 in two-electrode cell,respectively.2.GM/Mn₃O₄ hybrids have been synthesized using neutral GO suspension and Mn²⁺ as the precursors.Depending on the contents of concentrated Mn?2+?,the different content of Mn₃O₄ in GM/Mn₃O₄ can be obtained.The result indicates that the composite with the different content of Mn₃O₄ has exhibited the excellent catalytic performance as the Fenton catalyst.Among of them,the GM/Mn₃O₄ composite with the Mn₃O₄ content of 74%has the high Fenton catalytic performance for MB dye,and the degradation rate reaches 100% within 120 min.It is shown that GM/Mn₃O₄-74 composite can degradate other dyes including malachite green,magenta etc.Besides,GM/Mn₃O₄ with the dense macrostructure can avoid the loss of Mn₃O₄,and increase the recycling performance of the catalyst.3.RGO/MnFe₂O₄/C₃N₄ hybrids have been in situ synthesized for the catalytic degradation of dyes using pristine GO suspension,Fe²⁺ and g-C₃N₄ as the raw materials in the presence of KOH.The result shows that the degradation of MB for RGO/MnFe₂O₄-75/C₃N₄-5:1 reaches 100%within 80 min under visible light.Compared with other reports about the Fenton catalysts,we get more advantages in this work as followed:?1?The manganese salt of pristine GO suspension derived from Hummers method has been fully utilized with high efficiency;?2?The RGO/MnFe₂O₄/C₃N₄ composite can be recycled due to its magnetism;?3?The composite has exhibited the excellent catalytic activity under visible light;?4?The chemical interaction between RGO,MnFe₂O₄ and g-C₃N₄ exited in the RGO/MnFe₂O₄/C₃N₄ composite can increase the stability of the Fenton reaction,which still retains 96%within 80 min after fourth cycles.