Low Temperature Plasma Induced Synthesis Of Boron And Nitrogen Co-doped Reduced Graphene Oxide And Its Electrochemical Performances

Due to its unique two-dimensional structure,graphene has many excellent properties,such as electrical,mechanical and optical,which makes it has broad application prospects in the electrode materials,sensors and other fields.However,there are some native defects,such as zero band gap and low active sites of graphene seriously limit its practical application,and it has reported that the surface modification and heteroatom doping can change the original charge distribution of graphene and bring more active sites,which can improve this problem to some extent.In this dissertation,the precursor graphene oxide was prepared via the modified Hummers method with natural graphite as raw material,and boric acid and ammonium bicarbonate were selected as dopant.The undoped reduced graphene oxide?rGO?,boron doped rGO?B-rGO?,nitrogen doped rGO?N-rGO?and co-doped rGO?BN-rGO?were synthesized heteroatom-doped reduced graphene oxide materials with excellent electrochemical properties by low-temperature plasma reactor via a REDOX method.And compared the electrochemical performance of supercapacitor and lithium ion battery of BN-rGO with rGO,B-rGO and N-rGO.The main contents of the dissertation are summarized as follows:The Scanning Electron Microscope?SEM?image showed that all the four materials prepared had the microscopic morphology as thin as bright yarn.Raman's results showed that the defects of the doped materials were somewhat reduced compared with the precursor,which belonged to sp² hybridization repair caused by heteroatom doping,and the conductivity and electrolyte infiltration effect of the materials were improved.The BET specific surface area of the prepared material is about 300 m²·g^-1 and the pore diameter is about 3.8 nm,which is a typical mesoporous structure material and has great benefits for charge transfer.The X-ray Photoelectron Spectroscopy results confirmed that the boron content in B-rGO and BN-rGO is 1.21 at%and 1.41 at%,respectively,while the nitrogen content in N-rGO and BN-rGO is 2.12 at%and 2.69at%,indicating that boron and nitrogen had synergistic effect in co-doping and could promote each other.A reasonable explanation is that as an electron acceptor,the introduction of boron in graphene can enhance the electron deficient holes around the nearby carbon atoms,making it easier for carbon atoms to further combine with electron-donating nitrogen atoms.BN-rGO shows the excellent specific capacitance of 350 F·g^-1 under the condition of current density of 0.5 A·g^-1 in the three-electrode system,which is 2.36,1.46 and1.21 times of rGO,B-rGO and N-rGO under the same condition,respectively.The R_ctt of BN-rGO is 20.91?,which are only a third of the rGO.It is shown that BN-rGO is not only has a higher capacitance,but also a small impedance,which makes it an ideal material for the electrode of super-capacitor.The initial charge-discharge specific capacity of BN-rGO reaches 2500 mAh·g^-1 when assembled as cathode materials of lithium ion batteries devices,which is 2.55,1.88 and 1.61 times of that of rGO,B-rGO and N-rGO,respectively.And BN-rGO shows the highest specific capacity under any current density.The specific capacity given a slightly lower after 100 cycles under the current density of 200 mA·g^-1,but it's Coulombic Efficiency?EC?still remained above 95%.All the results illustrated that the BN-rGO have excellent performance in both super-capacitor and lithium ion battery.