1074 results about "Nitrogen doped graphene" patented technology

The invention provides nitrogen mixed grapheme hydrogel of which the water content is 90 to 99.5 percent, the electric conductivity is 10-3-100 S / m, and the molar ratio of N and C is 1 to 25 percent. The invention further provides nitrogen mixed aerogel of which the molar ratio of N and C is 2 to 20 percent, the molar ratio of C and O is 15 to 5, nitrogen atoms existing in the form of amidogen nitrogen accounts for 40 to 70 percent, pyridine type nitrogen accounts for 10 to 40 percent, graphite type nitrogen accounts for 10 to 30 percent, the specific area is 300 to 1500 m<2> / g, the apertures which are micropore account for 10 to 20 percent, the apertures which are mesoporous 20 to 50 percent, the apertures which are macropore 30 to 70 percent, the apparent density is 0.01 to 0.2 g / cm<3>, the pore volume is 5 to 20 cm<3> / g, and the electric conductivity is 1 to 1000 S / m. The nitrogen mixed grapheme hydrogel or aerogel and preparation method thereof provided by the invention has the characteristics that the operation is simple, the equipment requirement is low, the production efficiency is high, the scale-up of the technology is easy, the nitrogen mixed content is controllable and the compounding with other functional substances is simple.

The invention discloses a preparation method of a novel three-dimensional nitrogen doped graphene composite material system. The method comprises the following steps: 1, uniformly dispersing graphene oxide in a solvent at room temperature, adding a selected material and a nitrogen-containing compound, and uniformly mixing to form a mixed solution; 2, reacting the mixed solution at a temperature from room temperature to 150DEG C for 0-8h; and 3, cooling the above obtained product to room temperature, centrifuging, collecting the obtained product, washing, and drying to obtain the nitrogen doped graphene composite material. The three-dimensional nitrogen doped graphene composite material system with the nitrogen content of 8-19% can be efficiently and controllably prepared through the method, and the nitrogen content of the system can be controlled by changing the kind and the amount of the added nitrogen-containing compound, the reaction temperature and the reaction time; and the method is simple, is easy to enforce, allows the yield to be greater than 98.9%, and can be widely used in fields of water treatment, biomedicines, energy generation, conversion and storage devices, electrostatic prevention, heat management, heat conduction and dissipation, sensors, electromagnetic shielding, wave absorption and catalysis.

The invention relates to a method for preparing nitrogen-doped graphene, in particular to a novel simple, convenient and scale method for preparing nitrogen-doped graphene at high temperature under the protection of inert gas by taking melamine as a nitrogen source. In the method, graphene oxide and the melamine are taken as raw materials, wherein the melamine is taken as the nitrogen source and the graphene oxide is taken as a carbon source; high temperature annealing is carried out in the atmosphere of inert gas, and the reduction of the graphene oxide and the nitrogen doping of graphene are realized; and by controlling reaction conditions such as temperature, time, the ratio of the raw materials and the like, graphene products with different nitrogen doping ratios can be prepared. The preparation method is simple and practicable; catalysts are not needed; the reaction process is easy to control; special requirements on equipment do not exist; the cost is low; and the method is easy to promote and use.

The invention discloses a method for preparing nitrogen-doped graphene which comprises the following steps of: drying a mixture of a carbon-containing precursor and a carbon-nitrogen-containing precursor; raising the temperature of the dried mixture to be 450-600 DEG C, and keeping the temperature to generate gray solid; and continuously raising the temperature of the gray solid to be 700-1000 DEG C, introducing protective gas, keeping the temperature to generate black solid, and obtaining the nitrogen-doped graphene. According to the method for preparing nitrogen-doped graphene in the embodiment, the nitrogen-doped graphene is obtained under normal pressure and high temperature through a solid-phase reaction, the whole preparation method is simple in process, the nitrogen-doped graphene can be obtained without complex equipment, and industrial production is easily performed. In addition, the invention also provides nitrogen-doped graphene.

The invention provides preparation and application of a nitrogen doped graphene fuel cell catalyst, wherein a preparation method of the nitrogen doped graphene fuel cell catalyst is characterized by comprising the following steps: dispersing graphene oxide into a solvent, and carrying out ultrasonic treatment, thereby obtaining a graphene solution; dispersing at least one of non-noble metal salt as well as hydrate thereof and nitrogenous small organic molecules into the solvent, thereby obtaining a mixed solution; dropping the graphene oxide solution into the mixed solution, drying the solvent by distillation, thereby obtaining a nitrogen doped graphene precursor, warming to 600-1000 DEG C under the protection by inert gases, keeping the temperature for 1-4 hours, and cooling naturally, thereby obtaining the doped graphene catalyst. The nitrogen doped graphene preparation process provided by the invention is simple; required raw materials are low in cost, high in yield, can achieve industrial production easily, have very high oxygen reduction catalytic activity, can be applied to the fields of fuel cells, metal-air cells as well as microorganism fuel cells and the like.

The invention discloses a nitrogen-doped graphene / molybdenum disulfide composite material, and a preparation method and application thereof. The nitrogen-doped graphene / molybdenum disulfide composite material is obtained by mixing a graphite oxide solution, a nitrogen-containing precursor, a sulfur-containing precursor and a molybdenum-containing precursor in a solution, removing the solvent or hetero-ion to obtain a precursor material, performing heat treatment on the precursor material under the protection of an inert gas, and performing nitrogen doping and crystallization. The nitrogen-doped graphene / molybdenum disulfide composite material is applicable to lithium ion batteries, sodium cells, magnesium cells, hydrogen generation under electrocatalysis, hydrogen generation under photocatalysis and super capacitors, and is capable of improving the capacity of an anode material and also enhancing the cycling performance and the rate performance of the anode material when being used as a lithium ion battery anode material.

The invention discloses a preparation method of a nitrogen doped graphene / metal oxide nanometer composite material. The preparation method comprises the following steps of: weighing graphene and metal salt the cation of which is trivalent or quadrivalent to be added in a dispersant, and then carrying out ultrasonic dispersion to obtain mixed liquor; (2), reacting the mixed liquor obtained in the step (1) with alkaline air on a gas-liquid interface for 3-12hours at the temperature of 60-200 DEG C, cooling, centrifuging, washing a precipitate and drying to obtain powder; and (3) introducing the alkaline air or a mixed gas of the alkaline air and inert gas, maintaining the powder to be at the constant temperature of 600-900 DEG C for 2-6 hours, and cooling to room temperature to obtain the nitrogen doped graphene / metal oxide nanometer composite material. According to the invention, the conductibility and interface action of the composite material obtained by the method provided by the invention are improved due to the doping of nitrogen; and the method provided by the invention has the advantages of simple process, cheap cost, high productive rate, short cycle and the like, and is environment-friendly, and can be suitable for industrialization large-scale production.

The invention discloses a method for preparing nitrogen-doped graphene with high nitrogen doping amount. The method comprises the following steps: (1) dispersing of graphene; (2) ultrasonic dispersion; (3) microwave heating; and (4) filtering and drying. The nitrogen doping amount of the nitrogen-doped graphene prepared by the method disclosed by the invention is 10%-15.0%, the density of free carriers in graphene is greatly increased by the high nitrogen doping amount, the interaction of graphene and metal is enhanced, no oxidation pretreatment is carried out, no toxic solvent is used in the reaction process, reactants are simple in component, reaction conditions are mild, and the prepared nitrogen-doped graphene has excellent electrochemical property and can be used for preparation of new energy materials such as lithium ion battery, lithium-air battery, super capacitor electrode material and fuel cell oxygen reduction catalysts. According to the method disclosed by the invention, a high-pressure kettle is heated by using microwaves without high temperature; the method is low in energy consumption, is carried out in an airtight environment and therefore hardly causes environment pollution; in addition, the method is simple in process and convenient to operate and needs less production equipment, thus, the cost is further reduced.

The invention provides a nitrogen-doped graphene catalyst and a preparation method and application thereof. The nitrogen-doped graphene catalyst is characterized by being prepared by roasting a nitrogen-doped graphene precursor; the nitrogen-doped graphene precursor is prepared from the raw materials including at least one of non-precious metal salt and hydrate thereof, graphite oxide and nitrogen-containing small organic molecules; in the raw materials, the mass percent of the graphite oxide is 10-89wt%, the mass percent of the nitrogen-containing small organic molecules is 10-89wt%, and the mass percent of at least one of non-precious metal salt and hydrate thereof is 1-10wt%. The preparation process of the nitrogen-doped graphene provided by the invention is simple, the process is easy to operate, the activity is high, the cost is low, and industrial production is easy to implement; the nitrogen-doped graphene can be applied to the fields of fuel cells, metal-air cells, microbial fuel cells and the like.

The invention provides a graphene and a preparation method thereof, belonging to the technical field of grapheme synthesis. Nitrogen-doped grapheme can be prepared by using a direct current electric arc method and taking mixed gas of ammonia gas and helium gas as reaction atmosphere. The nitrogen-doped grapheme with high yield can be prepared by adopting the preparation method of the grapheme under low pressure and low current and has high production safety. The purity of the prepared grapheme is over 97 percent; by the characterization of a transmission electron microscope, the layer number of the prepared grapheme is between 2 and 6, the size of grapheme sheets is between 100 and 200 nanometers and the interlayer spacing is about 0.4 nanometer. The produced nitrogen-doped grapheme has favorable application prospect in catalyst carriers, lithium ion batteries, conductive thin films and other aspects.

The invention relates to a novel composite material, and particularly relates to a preparation method and application of a nitrogen-doped graphene and cobaltosic oxide hollow nanosphere composite material. The novel composite material comprises a doped graphene substrate and cobaltosic oxide hollow nanospheres which is attached to the surface of the doped graphene substrate. Melamine resin is taken as a cross-linking reagent for integrating graphite oxide with Co<2+> into a single coordination precursor. The preparation method comprises the following steps: in a pyrolysis process of the precursor, taking the melamine resin as a new nitrogen source to uniformly dope the graphene with nitrogen, fixing cobalt oxide which is generated in situ, and finally preparing the nitrogen-doped graphene / Co3O4 hollow nanosphere composite material with a sandwich structure. The composite material has a graded porous structure, is high in specific surface area, more in active sties, good in electron conductivity and ion conductivity, and good in application prospect in the field of new energy resources and catalysis.

The invention provides a preparation method of nitrogen doped graphene and an application of the nitrogen doped graphene in super capacitors. The preparation method of the nitrogen doped graphene specifically comprises the following steps: putting a carbon material and a compound containing active nitrogen elements in an enclosed container, and heating to a temperature of 100 to 300 DEG C so as to obtain the nitrogen doped graphene. In the preparation process of the nitrogen doped graphene, under a heating condition, nitrogen elements in the compound containing active nitrogen elements are mixed into the carbon material so as to obtain the nitrogen doped graphene. The nitrogen doped graphene preparation method mentioned above avoids adopting a high reaction temperature, and has the advantages of mild preparation conditions and low production cost. The prepared nitrogen doped graphene is used as an electrode material of a super capacitor, and the specific capacity of the super capacitor can reach 190 F / g, when the electric current density is 5 A / g. The capacity retention ratio is 96.3% after 10000 times of circulation.

The invention relates to a method for preparing nitrogen-doped graphene. The method comprises the steps: (1) with foam nickel as a substrate, making dopamine monomers undergo a polymerization reaction on the surface of the substrate to form polydopamine, and thus obtaining PDA-Ni; (2) with the generated PDA-Ni as a solid precursor and the foam nickel as a catalyst and a template, carrying out high temperature annealing in closed inert gas, finally cooling to the room temperature in the closed inert gas, and thus obtaining a foam nickel block NG-Ni coated with the nitrogen-doped graphene product; and (3) etching away the foam nickel template by hydrochloric acid, and thus obtaining a three-dimensional porous nitrogen-doped graphene material without support. By controlling the annealing temperature, a nitrogen doping type can be regulated and controlled. The preparation method is simple and easy to implement, allows the reaction process to be easy to control, has no special requirements on equipment, is low in cost, and is easy to popularize and use.

The invention relates to a preparation method of nitrogen-doped graphene. According to the invention, urea is adopted as a reducing agent, and is subjected to a hydro-thermal reaction with graphene, such that the nitrogen-doped graphene is obtained. According to the invention, the hydro-thermal method is adopted, a relatively high temperature is not required, requirements on equipment are low, and energy can be saved. During the preparation process, urea is adopted as the reducing agent. Urea is advantaged in non-toxicity and low environment pollution. The preparation method is advantaged in simple process, short reaction time, and relatively high efficiency. With the method, the prepared nitrogen-doped graphene is advantaged in good performance.

The present invention provides a preparation method for a nitrogen-doped graphene hydrogel. The preparation method comprises the following steps: (1) adding an oxidized graphite to water according to a certain ratio, and carrying out ultrasonic dispersion to obtain an oxidized graphene aqueous solution; (2) adding an organic amine to the oxidized graphene aqueous solution obtained from the step (1) in a dropwise manner, and stirring for a certain time to form an oxidized graphene and organic amine compounded intermediate product; and (3) carrying out a hydrothermal synthesis reaction on the intermediate product obtained from the step (2) to obtain the nitrogen-doped graphene hydrogel. The method of the present invention is a new and easy method for synthesis and regulation of the three dimensional structure of the graphene, and has characteristics of simple operation, easy control, low cost, no pollution and easy industrialization. With application of the graphene hydrogel of the present invention as a super-capacitor electrode material, results show that good specific capacitance and high power density are provided under the very high charge and discharge current circumstance.

The invention belongs to the technical field of new energy materials and preparation thereof, and relates to a mesoporous graphite type carbon nitride / nitrogen doped graphene sol nanocomposite and a method for preparing the same. The method comprises the following steps that: graphene oxide and a surfactant are added into deionized water and are ultrasonically mixed uniformly to obtain a colloidal solution; mesoporous graphite type carbon nitride is added to be continuously and ultrasonically treated, and a nitrogen-containing compound is then added to be stirred at constant temperature to form a mixed solution; and hydrothermal reaction and natural cooling are then carried out, ammonia which is adsorbed to a material surface is removed through washing, and the material is dried. The yield of the prepared mesoporous graphite type carbon nitride / nitrogen doped graphene sol nanocomposite is high, and the mesoporous graphite type carbon nitride / nitrogen doped graphene sol nanocomposite has a wide application scope, can be applied to fuel cells, photodegradation reactors and the like. The method has the advantages of simplicity in technology, low cost, high yield, short period and environmental friendliness, and can be suitable for industrially producing the mesoporous graphite type carbon nitride / nitrogen doped graphene sol nanocomposite in a large scale.

The invention discloses a three-dimensional nitrogen-doped graphene composite material as well as a preparation method and an application thereof to electrochemical biosensors. By means of the characteristics such as high specific surface area, good biocompatibility and high conductivity of the three-dimensional nitrogen-doped graphene, the three-dimensional nitrogen-doped graphene composite material is constructed; the preparation method comprises the following steps: obtaining substrate-containing three-dimensional nitrogen-doped graphene by taking a foam material as a substrate and utilizing a chemical vapor deposition (CVD) method in the presence of inert gas, hydrogen, a carbon source and a nitrogen source, and obtaining the three-dimensional nitrogen-doped graphene composite material by etching and cleaning the three-dimensional nitrogen-doped graphene. By compounding the three-dimensional nitrogen-doped graphene with enzyme / non-enzyme materials, corresponding three-dimensional nitrogen-doped graphene composite materials can be obtained; the three-dimensional nitrogen-doped graphene composite materials are prepared into electrodes and have the characteristics of being high in current corresponding sensitivity, good in stability and wide in application range when being used for detecting a plurality of molecules such as glucose, dopamine, paracetamol and the like.

The invention relates to the technical field of synthesizing of graphene materials and provides a preparation method of nitrogen-doped graphene. The preparation method includes: using an improved Hummers method to prepare continuous large-piece graphene oxide; using a hydrothermal method to prepare the graphene oxide into graphene of a porous three-dimensional structure; ultrasonically dispersing the graphene of the porous three-dimensional structure into an acid solution with the pH being 1-5, adding aniline, well mixing, adding ammonium persulfate, well mixing, and transferring the obtained mixed liquid into a teflon container for hydrothermal reaction so as to obtain a porous three-dimensional graphene-polyaniline compound; performing high-temperature treatment under nitrogen protection to allow polyaniline to decompose out nitrogen sources so as to obtain the nitrogen-doped porous three-dimensional graphene. The method has the advantages that the nitrogen-doped graphene with high nitrogen content can be prepared, the structure of the three-dimensional graphene can be kept, the obtained nitrogen-doped porous three-dimensional graphene is good in electrochemical performance and quite suitable for being used for producing a super capacitor, and the method is convenient to operate and beneficial to industrial popularization.

The invention relates to a chemical preparation method for a nitrogen-doped graphene quantum dot, belonging to the technical field of nano materials. The invention particularly relates to a preparation method for the nitrogen-doped graphene quantum dot. The method comprises the following steps: firstly, by taking graphite oxide as a carbon source and glycine as a nitrogen source, preparing a nitrogen-doped graphene sheet under a high-temperature annealing condition; then, cutting the deeply oxidized nitrogen-doped graphene sheet into an oxidized nitrogen-doped graphene nano sheet; preparing the nitrogen-doped-graphene quantum dot with super-strong blue fluorescence by way of a hydrothermal reaction. The synthetic method of the nitrogen-doped graphene quantum dot provided by the invention is simple in synthetic process, all raw materials are cheap and easy to get in the market, and the prepared nitrogen-doped graphene quantum dot is high in purity and yield, mono-dispersible and good in water solubility, has a very strong blue fluorescence performance and has a very good application prospect in the application fields of lithium batteries, micro supercapacitors, biological fluorescent labels, solar batteries and the like.

The invention discloses nitrogen doped graphene with a regular morphology and a preparation method thereof. The nitrogen doped graphene is prepared by adopting a chemical vapor deposition method. The preparation method comprises the following steps of: placing a metal catalyst into a reactor; heating in the non-oxidizing atmosphere to ensure the temperature of the catalyst rises to 200 to 600 DEG C; and then filling carbon and nitrogen sources into the reactor to perform the reaction to obtain the nitrogen doped graphene. The nitrogen doped graphene prepared by the invention is regular nitrogen doped graphene with a quadrangular structure. The layer number of the nitrogen doped graphene can be 1 to 10. The nitrogen doped graphene not only can be of a polycrystal structure, but also can be of a single crystal structure. The method for preparing the nitrogen doped graphene with the regular morphology, which is provided by the invention, has simple process and low economic cost and is environmental-friendly. The nitrogen doped graphene with the regular morphology can be produced in a large scale.

A preparation method for a water phase of nitrogen-doped graphene (NG) is characterized in that the preparation method comprises the following steps: mixing 0.5-5mg / mL oxidized graphene water suspension and solid urea as raw materials and dissolving, wherein the mass ratio of the oxidized graphene to the urea is 1 to 0.01; transferring the mixture into a stainless steel reaction kettle; feeding the stainless steel reaction kettle in a drying oven and carrying out constant temperature hydrothermal reaction at the reaction temperature of 150-200DEG C for 5-20 hours; naturally reducing the temperature to room temperature; taking out a sample and soaking or dialyzing with secondary deionized water; and removing the un-reacted urea; freezing and drying to obtain the nitrogen-doped graphene, wherein the nitrogen doping amount is 2.05-8.47 percent and the specific surface area is 450-550m<2> / g. According to the preparation method disclosed by the invention, the control over effective reduction of the nitrogen-doped graphene and the nitrogen doping ratio in the product can be realized by regulating and controlling the conditions such as the reaction temperature, the time, the ratio of a reactant and the like according to the requirement on the properties of products.

The invention relates to a method for preparing a low-temperature nitrogen-doped graphene supported nano Pd hydrogenation catalyst. The method comprises the following steps: ultrasonically stripping graphite oxide, thereby obtaining an aqueous solution of highly dispersed graphite oxide; selecting different nitrogen sources, and synthesizing nitrogen-doped graphene at low temperature through a hydrothermal method; and performing ultrasonic treatment on the nitrogen-doped graphene, adding a certain amount of PdCl2 solution, and adding a reducing agent, thereby preparing the highly dispersed supported nano Pd hydrogenation catalyst by a chemical reduction method. Because nitrogen atoms, which contain lots of lone pair electrons and can achieve a coordination effect with metal nanoparticles, are mixed into a carbon skeleton of graphene, runoff and conglomeration of the metal nanoparticles are effectively avoided, and the dispersity of the metal nanoparticles on the surface of graphene is improved. The catalyst is used for a hydrogenation reaction of olefins and has extremely high catalytic activity and high reusability. The catalyst is simple in preparation method and low in cost, the nitrogen content is high, doped nitrogen is controllable, and industrial production is easily realized.

The invention provides a preparation method of a nitrogen-doped graphene aerogel supported non-precious metal oxygen reduction catalyst. The method comprises the following steps: stirring a mixed solution of organic amine and aldehyde for 0.5-2 hours at the temperature of 50-90 DEG C, adding graphene oxide and a non-precious salt solution, stirring for 1-24 hours at the temperature of 60-99 DEG C to obtain organogel, performing freezing or supercritical drying, heating to 500-1000 DEG C under protection of inert gas, preserving heat for 1-6 hours, and naturally cooling to room temperature, thereby obtaining the nitrogen-doped graphene aerogel supported non-precious metal oxygen reduction catalyst. The preparation method of the nitrogen-doped graphene aerogel supported non-precious metal oxygen reduction catalyst is simple, the production can be easily expanded, the cost is low, the oxygen reduction catalysis activity is high, and the commercial popularization is facilitated.

The invention provides a transition metal nitride / nitrogen-doped graphene nanometer composite material and a preparation method and application thereof. In the composite material, transition metal nitride nanoparticles with sizes being 5-20 nanometers are embedded into a nitrogen-doped graphene framework, and the composite material is relatively large in specific area, contains mesopores uniformlydistributed and has favorable electrical conductivity. The preparation method of the composite material comprises the steps of (1) mixing a template precursor, a carbon source and a metal source to obtain a mixed material; and (2) placing the mixed material of the step (1) in an atmosphere furnace, and performing calcination in a non-oxidization atmosphere to obtain the transition metal nitride / nitrogen-doped graphene nanometer composite material. The composite material is used for the supercapacitor, a fuel cell or a lithium ion battery and has excellent application prospect. Compared with the prior art, the preparation method of the composite material is simple in process, low in equipment requirement and low in energy consumption, the raw material is low in cost, and mass production iseasy.

Disclosed is a preparation method of nitrogen-doped graphene-loaded metal single atom catalysts. As a compounding agent, ethylenediamine tetraacetic acid disodium salt is subjected to an ion exchange reaction with metal ions in liquid phases to form a stable compound, the compound is fully and evenly mixed with alkali metal salt after drying by distillation, and the nitrogen-doped graphene-loaded metal single atom catalysts are obtained through simultaneous pyrolysis conversion. The prepared catalysts have the appearance characteristics of two-dimensional microstructures which are super-thin and large in area, the thickness is 0.5-2 nm, the number of graphene layers is 1-8, the metal load is within 0.01-10 wt%, and the catalysts can be applied to the field of catalysis synthesis of energy, catalysis, medicine and biology. The method can be widely applied to the synthesis of various metal single atom catalysts, obtained metal single atoms can all be firmly riveted on the surface of graphene, the load amount is high, and the thermal stability is good. The method has the advantages of being simple and safe in operation process, low in cost, controllable to prepare, large in synthesis amount, suitable for industrialized production and large-scale application and the like.

The present invention relates to a method of preparing a nitrogen-doped graphene comprising preparing a Edge-Functionalized Graphene by binding a graphite with a organic material having amino groups and functional groups such as carboxy acid group through an electrophilic substitution reaction, and heat treating the resultant Edge-Functionalized Graphene, and a nitrogen-doped graphene prepared thereby. According to the present invention, by a more inexpensive and simpler method, a nitrogen-doped graphene can be prepared at higher purity and higher yield. The nitrogen-doped graphene obtained by the present invention has very excellent physical and electric properties, and particularly has a superior oxygen reduction capability, compared with the platinum catalyst used at cathode of a H2 / O2 fuel cell so that it will replace the platinum to lower more the cost of a H2 / O2 fuel cell or to increase its life and further to provide a new turning point for the commercialization of a H2 / O2 fuel cell.

The invention discloses a nitrogen-doped graphene-metal oxide nanocomposite material as well as a preparation method and application thereof. The nitrogen-doped graphene-metal oxide nanocomposite material is obtained by performing reaction on nitrogen-doped graphene and a metal salt in an organic solvent in a solvothermal way, wherein the nitrogen-doped graphene is obtained by performing reaction on oxidized graphene or partially-reduced graphene and a nitrogen-enriched substance in a water solution. The nitrogen-doped graphene-metal oxide nanocomposite material is simple in process, relatively low in cost, and good in operability and repeatability; by the preparation method, the problems that the nitrogen doping content of a carrier in the composite material is not high, in-situ growth of metal oxide particles on the surface of the graphene is not uniform and the particle size is large are solved; the nitrogen-doped graphene-metal oxide nanocomposite material can be applied to lithium ion batteries and supercapacitors on a large scale.

The invention provides a method for preparing nitrogen-doped graphene with a combustion synthesis method. The method comprises steps as follows: (1) weighed magnesium powder, a solid carbon source and a nitrogen source are evenly mixed, mixed powder is obtained, and the mass ratio of the magnesium powder, the solid carbon source and the nitrogen source in the mixed power is (19.95-99):(40-79.95):(1-39.5); (2) the mixed powder obtained in Step (1) has a combustion synthesis reaction in a specific atmosphere, a reaction product is purified, and the nitrogen-doped graphene is obtained. With the adoption of the method, raw materials are wide in source, the prepared nitrogen-doped graphene is complete in sheet-like structure, good in dispersity in a solvent and large in effective specific surface area, and the nitrogen-doped graphene has the ferromagnetism through nitrogen doping.

The invention provides a graphene-coated lithium iron phosphate positive electrode material and a preparation method thereof, relating to the technical field of batteries. The graphene-coated lithium iron phosphate positive electrode material is a nitrogen-doped graphene-coated lithium iron phosphate positive electrode material. The preparation method comprises the following steps: preparing a mixture A of graphene oxide and nitrogen source dopant; preparing lithium source dispersion liquid, phosphorus source dispersion liquid and iron source dispersion liquid, mixing the lithium source dispersion liquid, the phosphorus source dispersion liquid and the iron source dispersion liquid with the mixture A, and drying to obtain a nitrogen-doped graphene-coated lithium iron phosphate precursor; preheating the precursor, and then sintering in an inert atmosphere to obtain the nitrogen-doped graphene-coated lithium iron phosphate positive electrode material. In a product prepared by the invention, a lithium iron phosphate surface is coated with nitrogen-doped graphene, so that a good electric channel is provided for lithium iron phosphate, so that lithium iron phosphate shows good rate capability.

The invention provides a nitrogen-doped graphene coated nano sulfur positive electrode composite material, a preparation method, and an application thereof. The composite material includes: an effective three-dimensional conductive network formed by overlapping of nitrogen-doped graphenes, and nano sulfur particles coated by nitrogen doped graphene layers evenly. The preparation method includes: dispersing nitrogen-doped graphenes in a liquid-phase reaction system including at least sulfur source and acid, and depositing nano sulfur particles by an in-situ chemical reaction of the sulfur source and the acid, thereby preparing the positive electrode composite material. The positive electrode composite material of the invention has a high conductivity, a high sulfur utilization rate, and a high rate, thereby restraining the dissolution and shuttle effect in the lithium sulfur batteries, and enhancing the cyclic performance of the batteries.