Construction And Modification Of C-N Binary System

Carbon is an element that is widely distributed in nature.Simple carbon materials,such as graphene,diamond,and carbon nanotubes,are popular materials that have been widely studied.The valence layer of carbon has 4 electrons,which makes it easy to bond with other atoms and makes up tens of thousands of substances.The doping of elements also brings many new and more excellent properties to carbon materials.B,N,Si,etc.are main elements used for doping modification of carbon materials,and an extensive attention has been received to nitrogen-doped carbon materials for their advantages of low cost,simple method and mild conditions to fabricate.Nitrogen-doped carbon materials include nitrogen-doped and nitrogen-enriched carbon materials,depending on the nitrogen content and the bonding modes.Nitrogen-doped carbon materials are widely used in electrochemistry,adsorption,and hydrogen storage for the advantages of the large specific surface area,cheapness,availability,non-toxicity,and lightweight.The typical graphite-like carbon nitride(g-C3N4)in nitrogen-enriched carbon materials is a new type of non-metallic photocatalytic semiconductor.It can be applied in photocatalytic hydrolysis production hydrogen,organic degradation,organic synthesis,sterilization and other fields for the advantages of stable chemical properties,easy preparation,and environmental friendliness.This dissertation takes the carbon-nitrogen binary material system as the research object to develop high-performance capacitors and photocatalysts.(1)Using sucrose as a carbon source,melamine as a nitrogen source,and NaHCO3 as a foaming agent,foam carbon was firstly prepared from precursors in a muffle furnace,and then heat-treated at a high temperature of 500-1000 ? in an Ar atmosphere to obtain nitrogen-doped porous carbon(NPC).The effects of the composition of the raw materials and the temperature of thermal treatment to the composition and structure of the NPC and the electrochemical performance were systematically studied.The results showed that the specific surface and the degree of graphitization of NPC gradually increased,while the N doping amount gradually decreased,with the increase of the heat treatment temperature.The obtained NPC had the best electrochemical properties as electrode materials,when the mass ratio of sucrose,melamine,and NaHCO3 was of 1:1:2/3,and the thermal treatment temperature was of 500 ?.The specific capacitance of the NPC reached up to 92.9 Fg-1 when the current density was of 2 Ag-1.(2)BiVO4 precursor nanofibers were prepared by using bismuth nitrate and vanadyl acetylacetonate as the precursors,and the evolution of the composition and the structure was analyzed.XRD spectra presented that the precursor could be converted into BiVO4 inorganic fiber via the pyrolysis above 400 ?,and the main crystal phase in the fiber was monoclinic scheelite BiVO4.SEM results showed that the surface roughness and the pores of the fiber increased as the temperature increased.The fiber of BiVO4-500 had the largest degree of roughness and pore structure,which were favorable for the load of g-C3N4.G-C3N4/BiVO4 composite fibers could be obtained with g-C3N4 being supported on BiVO4 fibers by thermal polymerization of urea.TEM,XRD and XPS results showed that the composite fiber was chemically bonded together to form a heterojunction structure rather than a physical mixture of g-C3N4 and BiVO4.The adsorption capacity,catalytic rate and catalytic effect of g-C3N4/BiVO4 composite fibers were significantly better than the pure g-C3N4 and pure BiVO4,compared with the catalytic degradation of methylene blue.(3)Ni2P of non-noble metal was prepared by pyrolysis,using NiCl2·6H2O as the Ni source and NaH2PO2·H2O as the P source.The effects of the raw material composition and the heat treatment temperature on the preparation of Ni2P were systematically studied.It was found that XRD pattern of Ni2P have the highest purity of the crystal phase when the ratio of Ni to P was 1:4 and the heat treatment temperature was 350 ?.Ni2O was supported on g-C3N4 through heat treatment and TEM,XPS,and FT-IR showed that g-C3N4 and Ni2P were bound together through chemical bonds.Those were strong interactions,forming a heterojunction structure.The prepared g-C3N4/Ni2P composite was applied for photocatalytic degradation of methylene blue.The results showed that g-C3N4/Ni2P had better photocatalytic degradation ability,and the lower the content of Ni2P in g-C3N4/Ni2P was,the better the g-C3N4/Ni2P was for photocatalysis.