Metal active site loaded halogen and nitrogen co-doped graphene composite material, hydrogen evolution electrode, preparation method and application

Abstract

The invention discloses a metal active site loaded halogen and nitrogen co-doped graphene composite material, a hydrogen evolution electrode, a preparation method and application. The preparation method comprises the following steps: (1) under the protection of inert gas, reacting a mixture of an alkali metal elementary substance and / or an alkaline earth metal elementary substance, condensed halogenated hydrocarbon, a non-oxygen high-molecular polymer and a non-oxygen amine organic matter in a closed container to prepare halogen and nitrogen co-doped graphene; and (2) uniformly mixing a metal salt solution and a dispersion liquid containing the halogen and nitrogen co-doped graphene and a surfactant, and reacting to obtain the metal active site loaded halogen and nitrogen co-doped graphene composite material. The halogen and nitrogen co-doped graphene composite material loaded with the metal active sites, prepared by the method, has relatively high activity and relatively high stability in the process of electrolyzing marine water to produce hydrogen, and can effectively reduce the hydrogen evolution overpotential in seawater or alkaline seawater.

Description

Technical Field

[0001] The present invention specifically relates to a halogen and nitrogen co-doped graphene composite material loaded with metal active sites, a hydrogen evolution electrode, a preparation method thereof, and an application. Background Art

[0002] The severe challenges brought about by the intensifying energy and environmental risks have prompted the transformation of the energy structure from traditional fossil fuels to emerging carbon-free energy sources. Hydrogen, as a storable clean fuel with a high energy density, has shown attractive potential. Currently, the vast majority of hydrogen is produced from the reforming of natural gas, inevitably resulting in huge energy consumption and air pollution. In contrast, green hydrogen production by water electrolysis, as a sustainable energy conversion technology, may help solve this problem. In addition, storing intermittent renewable energy in the form of H 2 is conducive to long-term seasonal energy storage.

[0003] Currently, mature low-temperature water electrolysis technologies, whether alkaline electrolyzers or proton exchange membrane (PEM)-based electrolyzers, use high-purity water as raw material. If water electrolysis is used to produce the vast majority of the world's energy in the near future, problems of water resource allocation and shortage may occur. In contrast, seawater accounts for 96.5% of the earth's water resource reserves, is an almost infinite resource, and is also a natural electrolyte raw material. However, due to the complexity of natural seawater, direct decomposition of seawater is still in its infancy. Public literature reports that the coupling of seawater reverse osmosis systems with traditional electrolyzers is feasible for seawater electrolysis, while the consensus in the field is that additional purification systems are still needed to make the treated seawater reach the water quality level required by traditional electrolyzers. Although it is currently uncertain which method is more preferable, research on direct seawater electrolysis may also provide practical solutions for more generally treating impurities in water raw materials.

[0004] However, compared with the well-developed alkaline electrolysis and the emerging PEM electrolysis using fresh water, the progress of direct seawater electrolysis technology is relatively slow. The main challenges include in near-neutral conditions (pH about 8.0) The efficiency of the lower electrolysis system is low and its stability is poor. More importantly, there are high concentrations of catalysts for electrochemical energy conversion and storage systems in seawater. The carrier and the catalyst can be adjusted to form a composite. harmful chloride ions and unwanted cations, including Mg2+ and Ca 2 +. Specifically, compared with alkalized water, the catalytic activities of both the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER) are very low under neutral seawater conditions. Therefore, a higher external applied voltage is required in actual operation to obtain an ideal current density. In this case, harmful chlorine oxidation / corrosion will be triggered, further reducing the overall electrolysis efficiency and severely eroding the catalyst. In addition, the pH value of the seawater near the cathode during the electrolysis process increases significantly. Due to the presence of a large amount of Mg2+ and Ca in natural seawater 2+ cations, leading to the formation of a large amount of insoluble precipitates (such as magnesium hydroxide and calcium hydroxide), which physically block the cathode and cover the active sites for hydrogen evolution catalysis.

[0005] Therefore, strong bases (800 US dollars per ton of KOH) still have to be added in seawater electrolysis. Currently, the hydrogen current density of alkalized seawater electrolysis using transition metal-based catalysts can reach 100 mA cm-2 to 400 mA cm-2 at 1.80 V to 1.90 V (60 °C to 80 °C), while under the same conditions, the hydrogen current density of natural seawater electrolysis is at least one order of magnitude lower (about 10 mA cm|2). More importantly, the performance of seawater electrolysis lags far behind that of freshwater electrolysis. For example, a PEM electrolyzer can reach a current density of 1.0 A cm|2 to 1.5 A cm|2 at about 1.80 V (80 °C), but it requires high-purity water as a raw material; poor water quality will cause the electrolyzer stack to fail due to poisoning of noble metal catalysts. Therefore, direct seawater electrolysis without a purification process and chemical additives is extremely attractive and has been studied for about 40 years, but the key challenges of this technology still lie in catalyst engineering and device design.

[0006] Although some catalysts such as NiFeSP show activity at low current densities, the hydrogen production rate is very low (Adv. Funct. Mater. 2022, 32, 2206138), far lower than the high-current hydrogen production conditions required for industrial water electrolysis. To address this bottleneck problem, various strategies have been developed, including selective active site engineering (Nat. Energy 2020, 5, 367), three-dimensional structure design, and carbon layer protection (Angew. Chem. Int. Ed. Engl. 2022, 61, e202209703). Recently, Guo et al. (Angew. Chem. Int. Ed. Engl. 2016, 55, 6702–6707) proposed an innovative strategy in which they enhanced the kinetic process by generating an in-situ local alkaline environment and obtained excellent seawater catalytic performance at 60 °C.

[0007] Supported catalyst materials have strong electrocatalytic activity, so efforts have been made to design and develop used for electrochemical energy conversion and storage systems. The interfacial effect between them is used to control the electron distribution, regulate the intermediate adsorption, prevent the dense aggregation of the catalyst, and improve the stability. Due to the large surface area, porous structure, and high electrical conductivity of carbon materials, they are widely used as carrier catalysts for various electrocatalytic reactions. However, during the long-term electrocatalytic hydrogen evolution from seawater splitting, the carbon support may be corroded by the complex environment in seawater, resulting in unstable interfaces. This causes the destruction of the porous structure, the shedding and aggregation of the catalyst, and the reduction of catalytic activity. The production of green hydrogen fuel by electrolyzing water is crucial for the future of renewable energy. Therefore, how to modify the surface of the carbon substrate to regulate the double-layer structure during the electrocatalytic hydrogen evolution from seawater splitting to inhibit the influence of complex ions in seawater on the electrocatalytic process is the key to the current development of seawater electrolysis hydrogen production technology. Summary of the Invention

[0008] The technical problem solved by the present invention is to overcome the defect in the prior art that during the electrocatalytic hydrogen evolution from seawater splitting, due to the easy destruction of the catalyst material structure and poor stability, the catalytic activity is poor, and to provide a halogen and nitrogen co-doped graphene composite material loaded with metal active sites, a hydrogen evolution electrode, a preparation method, and an application thereof. The halogen and nitrogen co-doped graphene composite material loaded with metal active sites prepared by the present invention has high activity and high stability during the process of electrolyzing seawater to produce hydrogen, and can effectively reduce the hydrogen evolution overpotential in seawater or alkaline seawater.

[0009] The present invention first reacts "alkali metal simple substance and / or alkaline earth metal simple substance", condensed halogenated hydrocarbon, carbon chain polymer compound, and non-oxygen amine organic matter to prepare a halogen and nitrogen co-doped graphene material, and then adds a noble metal salt solution to a dispersion liquid containing the halogen and nitrogen co-doped graphene and a surfactant for reaction, thereby preparing a halogen and nitrogen co-doped graphene material loaded with noble metal. The prepared halogen and nitrogen co-doped graphene material has micropores, and halogen atoms are doped at the micropores. At the same time, during the process of loading metal active sites, some carbon atoms in the graphene plane are replaced by nitrogen atoms. The halogen in the halogen-doped graphene composite material can anchor the active metal, which can not only avoid its agglomeration but also improve its stability. In the halogen and nitrogen co-doped graphene composite material loaded with metal active sites of the present invention, the halogen content is high, and the microenvironment during the electrolysis of seawater is regulated by the doping of halogen elements to resist Cl - , Br - , ClO - and other plasma corrosion and Ca 2+ , Mg 2+ ion deposition to improve the stability of the electrocatalyst; at the same time, the doped nitrogen elements improve the activity of the electrocatalyst by regulating the electronic structures of graphene and active metal elements, realizing high activity and high stability.

[0010] The present invention solves the above technical problems through the following technical solutions:

[0011] The present invention provides a method for preparing a halogen and nitrogen co-doped graphene composite material loaded with metal active sites, which comprises the following steps:

[0012] (1) Under the protection of an inert gas, a mixture of "alkali metal element and / or alkaline earth metal element", condensed halogenated hydrocarbon, non-oxygen polymer and non-oxygen amine organic compound is reacted in a closed container to obtain a halogen and nitrogen co-doped graphene;

[0013] (2) A dispersion liquid containing a metal salt, the halogen and nitrogen co-doped graphene and a surfactant is mixed evenly and then reacted to obtain the halogen and nitrogen co-doped graphene composite material loaded with metal active sites.

[0014] In step (1), the alkali metal element may be one or more of K, Na, Rb and Cs. The alkaline earth metal element may be one or more of Mg, Ca, Ba and Sr.

[0015] In step (1), the condensed halogenated hydrocarbon generally refers to a solid or liquid halogenated hydrocarbon.

[0016] In step (1), the types of halogen atoms in the condensed halogenated hydrocarbon may be one or more of F, Cl, Br and I, preferably one or more of F, Cl and Br. The number of halogen atoms in the condensed halogenated hydrocarbon is at least one.

[0017] In step (1), the condensed halogenated hydrocarbon may be one or more of condensed haloalkanes, condensed halogenated alicyclic hydrocarbons, halogenated chain unsaturated hydrocarbons and condensed halogenated aromatic hydrocarbons.

[0018] Among them, the condensed haloalkane is preferably one or more of carbon tetrachloride (CCl 4 ), carbon tetrabromide (CBr 4 ), hexachlorobenzene (CCl 6 ), chloroform (CHCl 3 ), dichloromethane (CH 2 Cl 2 ) and decafluoropentane (C 5 H 2 F 10 ).

[0019] Among them, the condensed halogenated alicyclic hydrocarbon may be 1,2,3,4-tetrachlorocyclopentane (C 5 H 6 Cl 4 ), 1,2,3,4-tetrafluorocyclopentane (C 5 H 6 F 4 ), 1,2,3,4-tetrabromocyclopentane (C 5H 6 Br 4 )、1,3,5 - trichlorocyclohexane (C 6 H 9 Cl 3 )、1,3,5 - tribromocyclohexane (C 6 H 9 Br 3 )、1,3,5 - trifluorocyclohexane (C 6 H 9 F 3 )、1,2,4,5 - tetrachlorocyclohexane (C 6 H 8 Cl 4 )、1,2,4,5 - tetra Bromocyclohexane (C 6 H 8 Br 4 ), 1,2,4,5 - tetrafluorocyclohexane (C 6 H 8 F 4 ), 1,2,3,4,5 - pentachlorocyclohexane (C 6 H 7 Cl 5 )、1,2,3,4,5 - pentabromocyclohexane (C 6 H 7 Br 5 )、1,2,3,4,5 - pentafluorocyclohexane (C 6 H 7 F 5 )、1,2,3,4,5,6 - hexafluorocyclohexane (C 6 H 6 F 6 )、1,2,3,4,5,6 - hexachlorocyclohexane (C 6 H 6 Cl 6 )、1,2,3,4,5,6 - hexabromocyclohexane (C 6 H 6 Br 6 ) or more than one of them.

[0020] Among them, the halogenated chain - unsaturated hydrocarbon can be vinyl chloride (C 2 H 3 Cl), vinyl bromide (C 2 H 3 Br), vinyl fluoride (C 2 H 3 F), 3 - chloropropene (C 3 H 5 Cl), 3 - bromopropene (C 3 H 5 Br), 3 - fluoropropene (C 3 H 5 F), 3,3 - dichloropropene (C 3 H 4 Cl 2 ), 3,3 - dibromopropene (C 3 H 4Br 2 )、3,3-difluoropropene (C 3 H 4 F 2 )、3,3,3-trichloropropene (C 3 H 3 Cl 3 )、3,3,3-tribromopropene (C 3 H 3 Br 3 )、3,3,3-trifluoropropene (C 3 H 3 F 3 )、4-chloro-1-butene (C 4 H 7 Cl)、4-bromo-1-butene (C 4 H 7 Br)、4-fluoro-1-butene (C 4 H 7 F)、3-chloro-1-butene (C 4 H 7 Cl)、3-bromo-1-butene (C 4 H 7 Br)、3-fluoro-1-butene (C 4 H 7 F)、4,4-dichloro-1-butene (C 4 H 6 Cl 2 )、4,4-dibromo-1-butene (C 4 H 6 Br 2 )、4,4-difluoro-1-butene (C 4 H 6 F 2 )、3,4-dichloro-1-butene (C 4 H 6 Cl 2 )、3,4-dibromo-1-butene (C 4 H 6 Br 2 )、3,4-difluoro-1-butene (C 4 H 6 F 2 )、3,3-dichloro-1-butene (C 4 H 6 Cl 2 )、3,3-dibromo-1-butene (C 4 H 6 Br 2 )、3,3-difluoro-1-butene (C 4 H 6 F 2) 4,4,4-trichloro-1-butene (C 4 H 5 Cl 3 ) 4,4,4-tribromo-1-butene (C 4 H 5 Br 3 ) 4,4,4-trifluoro-1-butene (C 4 H 5 F 3 ) 3,4,4-trichloro-1-butene (C 4 H 5 Cl 3 ) 3,4,4-tribromo-1-butene (C 4 H 5 Br 3 ) 3,4,4-trifluoro-1-butene (C 4 H 5 F 3 ) 3,3,4-trichloro-1-butene (C 4 H 5 Cl 3 ) 3,3,4-tribromo-1-butene (C 4 H 5 Br 3 ) 3,3,4-trifluoro-1-butene (C 4 H 5 F 3 ) 3,4,4,4-tetrachloro-1-butene (C 4 H 4 Cl 4 ) 3,4,4,4-tetrabromo-1-butene (C 4 H 4 Br 4 ) 3,4,4,4-tetrafluoro-1-butene (C 4 H 4 F 4 ) 3,3,4,4-tetrachloro-1-butene (C 4 H 4 Cl 4 ) 3,3,4,4-tetrabromo-1-butene (C 4 H 4 Br 4 ) 3,3,4,4-tetrafluoro-1-butene (C 4 H 4 F 4 ) or more than one of them.

[0021] Among them, the condensed halogenated aromatic hydrocarbon may be hexachlorobenzene (C 6 Cl 6 ) hexabromobenzene (C 6 Br6 )), hexafluorobenzene (C 6 F 6 ), 1,3,5-trichlorobenzene (C 6 H 3 Cl 3 ), 1,3,5-tribromobenzene (C 6 H 3 Br 3 ), 1,3,5-trifluorobenzene (C 6 H 3 F 3 ), 1,2,4,5-tetrachlorobenzene (C 6 H 2 Cl 4 ), 1,2,4,5-tetrabromobenzene (C 6 H 2 Cl 4 ), 1,2,4,5-tetrafluorobenzene (C 6 H 2 F 4 ) or more than one of them.

[0022] In step (1), the non-oxygen-containing high molecular polymer generally refers to a high molecular polymer that does not contain oxygen element. The non- oxygen polymer is preferably a non-oxygen carbon chain polymer and / or a non-oxygen cyclic linear high molecular polymer.

[0023] Among them, the non-oxygen-containing carbon chain high molecular polymer can be polyolefin plastics and / or polyhalogenated olefins. The polyolefin plastics are preferably PE and / or PP. The polyhalogenated olefins are preferably one or more of PVDF, PTFE, PVC and PVDC.

[0024] Among them, the non-oxygen-containing cyclic high molecular polymer can be polystyrene and / or polychlorostyrene.

[0025] In step (1), the non-oxygen-containing amine organic compounds generally refer to hydrocarbon group substitution products of ammonia, preferably one or more of fatty amines, aromatic amines and cyanamide compounds.

[0026] Among them, the fatty amines can be higher fatty amines and / or lower fatty amines. The higher fatty amines generally refer to organic amine compounds with the number of carbon atoms in the range of C8 to C22 (including C8), such as polyetheramines. The lower fatty amines generally refer to organic amine compounds with the number of carbon atoms in the range of C2 to C8 (excluding C8), preferably one or more of propylamine, butylamine, butanediamine and pentanediamine.

[0027] Among them, the aromatic amines generally refer to amine compounds containing benzene rings, preferably one or more of aniline, β-naphthylamine and benzidine.

[0028] Among them, the cyanamide compounds generally refer to organic compounds containing a cyano group and an amino group, preferably one or more of cyanamide, dicyandiamide, and melamine.

[0029] In step (1), the mass ratio of the "alkali metal element and / or alkaline earth metal element" to the condensed halogenated hydrocarbon can be 1:(0.5 - 100), preferably 1:(3 - 40), such as 1:6, 1:10, 1:20, or 1:25.

[0030] In step (1), the mass ratio of the "alkali metal element and / or alkaline earth metal element" to the non-oxygen-containing polymer can be 1:(0.05 - 10), preferably 1:(0.1 - 2), such as 1:0.3, 1:0.5, or 1:1.

[0031] In step (1), the mass ratio of the "alkali metal element and / or alkaline earth metal element" to the non-oxygen-containing amine organic compound can be 1:(0.5 - 10), preferably 1:(0.5 - 2), such as 1:0.8, 1:1, 1:1.5, or 1:2.

[0032] In step (1), it is preferable to clean the surface of the "alkali metal element and / or alkaline earth metal element" before use. The cleaning method is, for example, to wipe the surface clean with a dry and dust-free paper, then cut off the surface oxide layer with a knife and cut it into chips to increase the contact area between the reactants.

[0033] In step (1), the inert gas is generally a gas that does not react with the reaction system, such as nitrogen or a noble gas (argon).

[0034] In step (1), the closed container is preferably a closed container that is resistant to high temperature, high pressure, and corrosion, such as a hydrothermal autoclave or a cartridge-type high-pressure stainless steel tank.

[0035] In step (1), according to the routine in the art, generally, the mixture of the "alkali metal element and / or alkaline earth metal element", condensed halogenated hydrocarbon, non-oxygen-containing polymer, and non-oxygen-containing amine organic compound is mixed under the protection of an inert gas and then placed in a closed container filled with an inert gas for reaction.

[0036] In step (1), the temperature of the reaction can be 30 - 220 °C, such as 40 °C, 60 °C, 80 °C, 100 °C, 130 °C, 140 °C, 150 °C, 160 °C, or 180 °C. The reaction time can be 3 - 24 h, preferably 4 - 12 h, such as 6 h, 10 h, or 12 h.

[0037] In step (1), according to the routine in the art, after the reaction ends, washing and drying are generally required. The solvent used for washing can be conventional in the art, for example, ethanol and / or deionized water. The number of washing times can be 3 - 6 times.

[0038] In step (1), the pore size of the halogen and nitrogen co-doped graphene is preferably 1 - 2 nm. In the halogen and nitrogen co-doped graphene, the doping atomic ratio of the halogen can be 5 at% - 40 at%, such as 10 at%, 14 at% or 34 at%, preferably 5 at% - 15 at%; the doping atomic ratio of nitrogen can be 0.5 at% - 10 at%, such as 1 at%, 5 at%, 8 at%, preferably 2 at% - 5 at%. The doping atomic ratio refers to the proportion of the number of doping atoms in the total number of atoms in the halogen and nitrogen co-doped graphene.

[0039] In step (2), the metal in the metal salt can be a noble metal and / or a transition metal.

[0040] Among them, the noble metal is preferably one or more of Ru, Pt, Rh, and Pd. The transition metal is preferably one or more of Fe, Co, Ni, and Cu. The metal salt is generally one or more of the hydrochloride, nitrate, and sulfate of the corresponding metal. When the metal is a noble metal, the metal salt can be ruthenium trichloride (RuCl 3 ), chloroplatinic acid (H 2 PtCl 6 ), potassium chlororhodate, sodium chlororhodate, and palladium chloride. When the metal is a transition metal, the metal salt can be one or more of ferric chloride, cobalt chloride, nickel chloride, and copper chloride.

[0041] In step (2), the surfactant is preferably cetyltrimethylammonium bromide. (CTAB), dodecyltrimethylammonium bromide (DTAB), and sodium dodecylbenzenesulfonate (SDBS).

[0042] In step (2), the mass ratio of the halogen and nitrogen co-doped graphene to the surfactant is preferably (0.5 - 4):1, such as 1:1 or 2:1.

[0043] In step (2), the mass ratio of the metal in the metal salt to the halogen and nitrogen co-doped graphene is preferably 1:(10 - 20), such as 1:10, 1:12, 1:13, 1:15, 1:16, 1:17, or 1:18.

[0044] In step (2), the solvent in the dispersion can be conventional in the art, for example, one or more of water, ethanol, ethylene glycol, propylene glycol, and glycerol.

[0045] In step (2), preferably, after uniformly mixing the metal salt solution and the "dispersion containing the halogen and nitrogen co-doped graphene and the surfactant", the halogen and nitrogen co-doped graphene composite material loaded with metal active sites is prepared through a reaction; more preferably, the metal salt solution is added to the "dispersion containing the halogen and nitrogen co-doped graphene and the surfactant".

[0046] Among them, the concentration of the metal salt solution can be 1-10 mg / mL, preferably 1-5 mg / mL, such as 3 mg / mL. The solvent in the metal salt solution can be deionized water and / or alcohol solvents. The alcohol solvents can be one or more of ethanol, ethylene glycol, propylene glycol, and glycerol.

[0047] Among them, in the dispersion containing the halogen and nitrogen co-doped graphene and the surfactant, the solvent can be one or more of aqueous ethanol solution, aqueous ethylene glycol solution, ethylene glycol, aqueous propylene glycol solution, and aqueous glycerol solution, such as aqueous ethylene glycol solution. The volume concentration of the aqueous ethylene glycol solution can be 5%-50%, such as 20%, and the volume concentration refers to the volume ratio of ethylene glycol to the total volume of the aqueous ethylene glycol solution. In the dispersion containing the halogen and nitrogen co-doped graphene and the surfactant, the sum of the mass concentrations of the halogen and nitrogen co-doped graphene and the surfactant can be 1-10 g / L, such as 3 g / L, 6 g / L, or 8 g / L.

[0048] In step (2), the mixing method can be conventional in the art, such as stirring and / or ultrasonic treatment. The mixing time can be 1-5 h, such as 2 h or 3 h.

[0049] In step (2), when the metal in the metal salt includes a transition metal, preferably, it is also necessary to A reducing agent is added. The types of the reducing agent can be conventional in the art, preferably one or more of ascorbic acid, formaldehyde, glucose, sodium borohydride, and hydrazine hydrate. The dosage of the reducing agent generally only needs to completely reduce the metal in the metal salt. Preferably, the molar ratio of the reducing agent to the metal salt is not less than 3:1, more preferably (3-8):1, such as 3:1.

[0050] In step (2), the reaction method can be a solvothermal reaction or an atmospheric pressure reaction. When the metal in the metal salt includes noble metals, the reaction is preferably a solvothermal reaction. When the metal in the metal salt only includes transition metals, the reaction can be a solvothermal reaction or an atmospheric pressure reaction. When the metal in the metal salt only includes transition metals, the solvothermal reaction preferably includes the following steps: uniformly mixing the metal salt solution, the reducing agent, and the "dispersion containing graphene co-doped with halogen and nitrogen elements and surfactant", and then carrying out a solvothermal reaction; the atmospheric pressure reaction preferably includes the following steps: first mixing the "dispersion containing metal salt, graphene co-doped with halogen and nitrogen elements and surfactant" for 10 - 60 min (such as 20 min), then carrying out solid-liquid separation, redispersing the obtained precipitate into a solvent (such as deionized water), adding the reducing agent, and then reacting at 0 - 100 °C (such as 25 °C, 40 °C, 50 °C or 80 °C) for 1 min - 1 h (such as 10 min, 30 min or 50 min), and then filtering, washing, and drying. When the metal in the metal salt only includes transition metals and the reaction is carried out in the form of a solvothermal reaction, the solvent in the reaction system is preferably ethylene glycol.

[0051] Among them, the solvothermal reaction generally needs to be carried out in a high-temperature and high-pressure resistant closed container, such as a hydrothermal autoclave. The temperature of the solvothermal reaction can be 100 - 180 °C, preferably 100 - 140 °C, such as 120 °C, 130 °C, 140 °C or 150 °C. The time of the solvothermal reaction can be 6 - 48 h, preferably 3 - 24 h, such as 6 h, 12 h, 18 h or 24 h. According to the routine in the art, after the solvothermal reaction is completed, washing and drying are generally required. The solvent used for washing can be conventional in the art, such as ethanol and / or deionized water. The number of washing times can be 3 - 6 times.

[0052] The present invention also provides a graphene composite material co-doped with halogen and nitrogen elements and loaded with metal active sites prepared by the preparation method as described above.

[0053] In the present invention, the graphene composite material co-doped with halogen and nitrogen elements and loaded with metal active sites In the material, the loading of precious metal atoms is preferably 3% - 10%, such as 6.25%. This loading refers to The ratio of the mass of metal atoms to the total mass of the graphene composite material co-doped with halogen and nitrogen elements and loaded with metal active sites.

[0054] In the graphene composite material co-doped with halogen and nitrogen elements and loaded with metal active sites of the present invention, the dispersion state of the metal is preferably "single-atom simple substance and / or alloy" dispersion or uniform dispersion of clusters with a diameter of less than 10 nm.

[0055] The present invention also provides a hydrogen evolution electrode, which comprises a current collector layer and a catalytic layer located on the surface of the current collector layer. The catalytic layer comprises the halogen and nitrogen co-doped graphene composite material loaded with metal active sites as described above and a binder.

[0056] In the present invention, the current collector layer can be carbon paper, carbon felt, nickel foam or titanium felt. The thickness of the current collector layer can be 0.05 mm - 0.5 mm.

[0057] In the present invention, the binder can be conventional in the art, such as perfluorosulfonic acid resin.

[0058] In the present invention, on the surface of the hydrogen evolution electrode, the areal density of the halogen and nitrogen co-doped graphene material loaded with noble metal can be 0.5 - 4 mg / cm 2 , for example, 2 mg / cm 2 .

[0059] The present invention also provides a preparation method of the hydrogen evolution electrode as described above, which comprises the following steps:

[0060] The halogen and nitrogen co-doped graphene composite material loaded with metal active sites and the binder are made into a slurry and then coated on the surface of the current collector layer, and then dried.

[0061] In the present invention, the binder is generally a perfluorosulfonic acid resin solution. The solid content of the perfluorosulfonic acid resin solution is preferably 5 - 10 wt%, for example, 5 wt% and 8 wt% are the percentages of the mass of the perfluorosulfonic acid resin solid in the total mass of the perfluorosulfonic acid resin solution.

[0062] In the present invention, the binder generally needs to be further diluted before use, for example, diluted with ethanol.

[0063] In the present invention, in the slurry, the concentration of the halogen and nitrogen co-doped graphene composite material loaded with metal active sites can be 5 - 15 mg / mL, for example, 10 mg / mL.

[0064] In the present invention, the solvent in the slurry can be conventional in the art, such as ethanol and / or deionized water.

[0065] The present invention also provides a halogen and nitrogen element co-loaded with metal active sites as described above. Application of the doped graphene composite material or the hydrogen evolution electrode as described above in hydrogen production by electrolyzing seawater.

[0066] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0067] The reagents and raw materials used in the present invention are all commercially available.

[0068] The positive and progressive effects of the present invention are as follows:

[0069] (1) The preparation method of the halogen and nitrogen co-doped graphene composite material loaded with metal active sites provided by the present invention is simple, the method is clear, and the operation cost is low;

[0070] (2) The halogen and nitrogen co-doped graphene composite material loaded with metal active sites provided by the present invention can well improve the hydrogen evolution stability in a seawater environment or an alkaline seawater environment during the electrolysis of seawater to produce hydrogen, and effectively reduce the hydrogen evolution overpotential in seawater or alkaline seawater. Description of the Drawings

[0071] Figure 1 SEM and EDS characterization diagrams of Cl and N co-doped graphene prepared in Example 1;

[0072] Figure 2 SEM diagram of Br and N co-doped graphene prepared in Example 2;

[0073] Figure 3 SEM diagram of Cl, F, and N co-doped graphene prepared in Example 3;

[0074] Figure 4 Transmission electron microscope structure characterization diagram of Ru-loaded Cl and N co-doped graphene prepared in Example 10;

[0075] Figure 5 Transmission electron microscope element distribution diagram of Ru-loaded Cl and N co-doped graphene prepared in Example 10;

[0076] Figure 6 XRD diagrams of Cl and N co-doped graphene (GCl) prepared in Example 1 and Ru-loaded Cl and N co-doped graphene (Ru@GCl) prepared in Example 10;

[0077] Figure 7 Adsorption / desorption curves of BET tests for Cl and N co-doped graphene (before Ru loading) prepared in Example 1 and Ru-loaded Cl and N co-doped graphene (after Ru loading) prepared in Example 10;

[0078] Figure 8 The Cl and N co-doped graphene (GCl) prepared in Example 1 and the example Pore size distribution diagram of Ru-loaded Cl and N co-doped graphene (Ru@GCl) prepared in Example 10;

[0079] Figure 9 Raman diagram of Ru-loaded Cl and N co-doped graphene prepared in Example 10;

[0080] Figure 10Hydrogen evolution polarization curves of the catalysts prepared in Example 10, Comparative Example 1 and Comparative Example 2 in an alkaline seawater environment;

[0081] Figure 11 500 mA / cm of the Ru-loaded Cl, N co-doped graphene electrocatalyst prepared in Example 10 in an alkaline seawater environment 2 Schematic diagram of the stability curve at a high current density;

[0082] Figure 12 Hydrogen evolution polarization curve of the Ru-loaded Cl, N co-doped graphene electrocatalyst prepared in Example 10 in natural seawater environment;

[0083] Figure 13 100 mA / cm of the Ru-loaded Cl, N co-doped graphene electrocatalyst prepared in Example 10 in natural seawater environment 2 Hydrogen evolution stability curve at the current density of;

[0084] Figure 14 Polarization curves of an anion exchange membrane electrolyzer with the Ru-loaded Cl, N co-doped graphene electrocatalyst (Ru@GCl) prepared in Example 10 and commercial PtC catalyst as the cathode in an environment with alkaline seawater as the electrolyte;

[0085] Figure 15 1000 mA / cm of the Ru-loaded Cl, N co-doped graphene electrocatalyst (Ru@GCl) prepared in Example 10 and commercial PtC catalyst as the cathode in an environment with alkaline seawater as the electrolyte 2 Stability test chart at the current density of;

[0086] Figure 16 1000 mA / cm of the anion exchange membrane electrolyzer with the Ru-loaded Cl, N co-doped graphene electrocatalyst (Ru@GCl) prepared in Example 10 as the cathode in an environment with alkaline seawater as the electrolyte 2 Faraday efficiency test curve at the current density of;

[0087] Figure 17 Hydrogen evolution polarization curves of the materials prepared in Example 15 and Example 16 in 1 M KOH pure aqueous solution and 1 M KOH Bohai seawater solution respectively. Detailed implementation mode

[0088] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0089] The raw material information used in the following examples and comparative examples is shown in Table 1:

[0090] Table 1

[0091]

[0092] Example 1

[0093] Preparation of Cl and N co-doped graphene:

[0094] (1) In an Ar atmosphere, the clean metal K, CCl 4 , PVC and melamine were mixed in a mass ratio of 1:6:1:1 and placed in a hydrothermal autoclave with a polytetrafluoroethylene liner filled with Ar atmosphere;

[0095] (2) The hydrothermal autoclave containing potassium metal, CCl 4 , PVC and melamine was placed in an oven at 150 °C for reaction for 6 hours to obtain a black powder;

[0096] (3) The black powder obtained in step 2 was ultrasonically washed 3 times each in ethanol and water, and then dried to obtain Cl and N co-doped graphene powder.

[0097] According to Figure 1 it can be known that in the Cl and N co-doped graphene prepared in this example, the atomic ratio of Cl element is about 14%, and the atomic ratio of N element is about 5%.

[0098] Example 2

[0099] Preparation of Br and N co-doped graphene:

[0100] (1) In an Ar atmosphere, the clean metal K, CBr 4 , PE and melamine were mixed in a mass ratio of 1:25:0.3:1 and placed in a hydrothermal autoclave with a polytetrafluoroethylene liner filled with Ar atmosphere;

[0101] (2) The hydrothermal autoclave containing potassium metal, CBr 4 , PE and melamine was placed in an oven at 150 °C for reaction for 6 hours to obtain a black powder;

[0102] (3) The black powder obtained in step 2 was ultrasonically washed 3 times each in ethanol and water, and then dried to obtain Br and N co-doped graphene powder.

[0103] The SEM image of the Br and N co-doped graphene prepared in Example 2 is as shown in Figure 2As shown, through EDS characterization analysis, it can be known that the atomic ratio of Br element is about 10%, and the atomic ratio of N element is about 5%.

[0104] Example 3

[0105] Preparation of Cl, F, and N co-doped graphene:

[0106] (1) In an Ar atmosphere, the surface-cleaned metal K, CCl 4 , PVDF, and melamine were mixed at a mass ratio of 1:6:1:1 and placed in a hydrothermal autoclave lined with polytetrafluoroethylene filled with an Ar atmosphere;

[0107] (2) The hydrothermal autoclave containing metal K, CCl 4 , PVDF, and melamine was placed in an oven at 150 °C for reaction for 6 hours to obtain a black powder;

[0108] (3) The black powder obtained in step 2 was ultrasonically washed 3 times each in ethanol and water in sequence, and then dried to obtain Cl, F, and N-doped graphene powder.

[0109] The SEM image of the Cl, F, and N co-doped graphene prepared in Example 3 is as Figure 3 shown. Through EDS characterization analysis, it can be known that the atomic ratio of Cl element is about 20%, the atomic ratio of F element is about 14%, and the atomic ratio of N element is 4%.

[0110] Example 4

[0111] Compared with Example 1, except that PVC in step (1) was replaced with polystyrene, the remaining operations and conditions were the same as those in Example 1.

[0112] Example 5

[0113] Compared with Example 1, except that metal K in step (1) was replaced with metal Mg, the remaining operations and conditions were the same as those in Example 1.

[0114] Example 6

[0115] Compared with Example 1, except that metal K in step (1) was replaced with metal Ca, the remaining operations and conditions were the same as those in Example 1.

[0116] Example 7

[0117] Compared with Example 1, except that the hydrothermal temperature in step (2) was adjusted to 130 °C, the remaining operations and conditions were the same as those in Example 1.

[0118] Example 8

[0119] Compared with Example 1, except that the hydrothermal temperature in step (2) was adjusted to 180 °C, the remaining operations and conditions were the same as those in Example 1.

[0120] Example 9

[0121] Compared with Example 1, except that the hydrothermal reaction time in step (2) was adjusted to 12 h, the remaining operations and conditions were the same as those in Example 1.

[0122] Example 10

[0123] Preparation of Ru-loaded Cl, N co-doped graphene:

[0124] (1) The Cl, N co-doped graphene prepared in Example 1 and cetyltrimethylammonium bromide CTAB were dispersed in an ethylene glycol aqueous solution with a volume concentration of 20% at a mass ratio of 1:1, and ultrasonically stirred sufficiently to make them uniformly dispersed to obtain a dispersion liquid, and the sum of the mass concentrations of Cl, N co-doped graphene and CTAB was 6 g / L;

[0125] (2) An aqueous solution of 3 mg / mL RuCl 3 was added to the dispersion liquid in step 1, and the mass ratio of Ru element to Cl, N co-doped graphene was 1:15. After mixing evenly, it was transferred into a hydrothermal autoclave and subjected to a solvothermal reaction in an oven at 120 °C for 12 hours of heat preservation. After cooling, it was filtered, and washed 3 times with ethanol and deionized water in sequence, and then separated and dried to obtain a Cl, N co-doped graphene material loaded with noble metal Ru.

[0126] According to Figure 4 and Figure 5 it can be known that in the Cl, N co-doped graphene material loaded with noble metal Ru prepared in Example 10, the distribution state of Ru is mainly single atoms and clusters with a diameter of less than 5 nm, and they are uniformly dispersed.

[0127] Example 11

[0128] Compared with Example 10, except that the solvothermal temperature in step (2) was adjusted to 150 °C, the remaining operations and conditions were the same as those in Example 10.

[0129] Example 12

[0130] Compared with Example 10, except that the solvothermal heat preservation time in step (2) was adjusted to 24 h, the remaining operations and conditions were the same as those in Example 10.

[0131] Example 13

[0132] Compared with Example 10, except that the mass ratio of Ru element and Cl, N co-doped graphene in step (2) is adjusted to 1:12, the remaining operations and conditions are the same as those in Example 10.

[0133] Example 14

[0134] Compared with Example 10, except that the mass ratio of Ru element and Cl, N co-doped graphene in step (2) is adjusted to 1:18, the remaining operations and conditions are the same as those in Example 10.

[0135] Example 15

[0136] Compared with Example 10, except that the 3 mg / mL RuCl 3 aqueous solution in step (2) is replaced with a 3 mg / mL chloroplatinic acid aqueous solution, the remaining operations and conditions are the same as those in Example 10, and the mass ratio of Pt element and Cl, N co-doped graphene is 1:15.

[0137] Example 16

[0138] Compared with Example 10, except that the 3 mg / mL RuCl 3 aqueous solution in step (2) is replaced with a mixed aqueous solution of chloroplatinic acid and RuCl 3 , the remaining operations and conditions are the same as those in Example 10. In the mixed aqueous solution of chloroplatinic acid and RuCl 3 , the concentrations of chloroplatinic acid and RuCl 3 are both 1.5 mg / mL, and the mass ratio of the sum of Pt and Ru elements to Cl, N co-doped graphene is 1:15.

[0139] Example 17

[0140] Step (1): Disperse the Cl, N co-doped graphene prepared in Example 1 and cetyltrimethylammonium bromide CTAB in ethylene glycol at a mass ratio of 1:1, and fully stir by ultrasonic to make it evenly dispersed to obtain a dispersion liquid. The sum of the mass concentrations of Cl, N co-doped graphene and CTAB is 6 g / L;

[0141] Step (2): Add a 3 mg / mL iron chloride ethylene glycol solution and An appropriate amount of ascorbic acid. The mass ratio of Fe element, Cl, and N co-doped graphene is 1:15, and the mass ratio of ascorbic acid and the molar ratio of iron chloride is 3:1 to the dispersion liquid in step 1. After mixing evenly, transfer it into a hydrothermal kettle and carry out a solvothermal reaction in an oven at 120 °C for 12 hours. After cooling, filter it, and wash it 3 times with ethanol and deionized water in turn, and then separate and dry it to obtain a Cl, N co-doped graphene material loaded with metal Fe.

[0142] Example 18

[0143] Compared with Example 17, except that the 3 mg / mL aqueous ferric chloride solution in step (2) is replaced with a mixed ethylene glycol solution of cobalt chloride and RuCl 3 , the remaining operations and conditions are the same as those in Example 17. In the mixed ethylene glycol solution of cobalt chloride and RuCl 3 , the concentrations of cobalt chloride and RuCl 3 are both 1.5 mg / mL. The mass ratio of the sum of Co and Ru elements to the mass of Cl, N co-doped graphene is 1:15. The molar ratio of ascorbic acid to metal salts (cobalt chloride and RuCl 3 ) is 3:1.

[0144] Example 19

[0145] Compared with Example 10, except that the Cl, N co-doped graphene prepared in Example 1 in step (1) is replaced with the Br, N co-doped graphene prepared in Example 2, the remaining operations and conditions are the same as those in Example 10.

[0146] Example 20

[0147] Compared with Example 10, except that the Cl, N co-doped graphene prepared in Example 1 in step (1) is replaced with the Cl, F, N co-doped graphene prepared in Example 3, the remaining operations and conditions are the same as those in Example 10.

[0148] Example 21

[0149] Compared with Example 10, except that the Cl, N co-doped graphene prepared in Example 1 in step (1) is replaced with the Cl, N co-doped graphene prepared in Example 4, the remaining operations and conditions are the same as those in Example 10.

[0150] Example 22

[0151] Compared with Example 10, except that the Cl, N co-doped graphene prepared in Example 1 in step (1) is replaced with the Cl, N co-doped graphene prepared in Example 5, the remaining operations and conditions are the same as those in Example 10.

[0152] Example 23

[0153] (1) Preparation of Cl, N co-doped graphene: Compared with Example 1, except that melamine in step (1) is replaced with aniline, the remaining operations and conditions are the same as those in Example 1;

[0154] (2) Preparation of Ru-loaded Cl and N co-doped graphene: Except that the Cl and N co-doped graphene prepared above was used to replace the Cl and N co-doped graphene prepared in Example 1, the other operations and conditions were the same as those in Example 10.

[0155] Embodiment 24

[0156] (1) Preparation of Cl and N element co-doped graphene: Compared with Example 1, except that the melamine in step (1) is replaced by butylamine, the other operations and conditions are the same as those in Example 1;

[0157] (2) Preparation of Ru-loaded Cl and N co-doped graphene: Except that the Cl and N co-doped graphene prepared above was used to replace the Cl and N co-doped graphene prepared in Example 1, the other operations and conditions were the same as those in Example 10.

[0158] Embodiment 25

[0159] Step (1): same as Example 17;

[0160] Step (2): adding 3 mg / mL of ferric chloride ethylene glycol solution to the dispersion of step 1, wherein the mass ratio of Fe element to Cl-doped graphene is 1:15, stirring for 20 min and centrifuging, dispersing the precipitate obtained after centrifugation into deionized water, adding an appropriate amount of sodium borohydride, wherein the molar ratio of sodium borohydride to ferric chloride is 3:1, mixing well and stirring in a beaker for reaction, the stirring speed is 300 rpm, the reaction temperature is 50°C, the reaction time is 30 min, filtering after the reaction is completed, and washing with ethanol and deionized water for 3 times in sequence, and then separating and drying to obtain a Cl-doped graphene material loaded with metal Fe.

[0161] Comparative Example 1

[0162] Preparation of commercial graphene materials loaded with precious metal Ru:

[0163] (1) dispersing commercial graphene and hexadecyltrimethylammonium bromide (CTAB) in a 20% ethylene glycol aqueous solution at a mass ratio of 1:1, and fully ultrasonically stirring to uniformly disperse them to obtain a dispersion, wherein the mass concentration of commercial graphene and CTAB is 6 g / L;

[0164] (2) Add 3 mg / ml RuCl to the dispersion in step 1 3 Solution, Ru element and commercial stone to graphene is 1:15. After ultrasonic treatment for 3 hours and uniform dispersion, it is transferred into a high-temperature and high-pressure In a sealed container, a hydrothermal reaction was carried out at 120° C. and kept warm for 12 hours. After cooling, the product was filtered and washed three times with ethanol and deionized water respectively, and then separated and dried to obtain a graphene material loaded with the precious metal Ru.

[0165] Comparative Example 2

[0166] High temperature dechlorination treatment of Cl-doped graphene and preparation method of loading precious metal Ru after dechlorination:

[0167] (1) The Cl and N co-doped graphene obtained in Example 1 was annealed in an Ar environment at a temperature of 900° C. for a holding time of 12 h to completely remove the doped Cl and obtain Cl-doped graphene (rGCl);

[0168] (2) dispersing the reduced Cl-doped graphene and hexadecyltrimethylammonium bromide (CTAB) in a 20% ethylene glycol aqueous solution at a mass ratio of 1:1, and fully ultrasonically stirring to uniformly disperse them to obtain a dispersion, wherein the mass concentration of the reduced Cl-doped graphene and CTAB is 6 g / L;

[0169] (3) Add 3 mg / ml RuCl to the dispersion in step 2 3 The solution, the mass ratio of Ru element and Cl-doped graphene is 1:15, and ultrasonic treatment is carried out for 3 hours. After uniform dispersion, it is transferred into a closed container resistant to high temperature and pressure, and a hydrothermal reaction is carried out at 120°C. The temperature is kept for 12 hours, and the solution is filtered after cooling. It is washed with ethanol and deionized water for 3 times in sequence, and then separated and dried to obtain a reduced Cl-doped graphene material loaded with precious metal Ru.

[0170] Effect Example

[0171] 1. XRD test

[0172] Figure 6 XRD patterns of Cl, N co-doped graphene (GCl) prepared in Example 1 and Ru-loaded Cl, N co-doped graphene (Ru@GCl) prepared in Example 10. A relatively broad lamellar peak appears at about 10° for Cl, N co-doped graphene, indicating that the doping of Cl increases the interlayer spacing of graphene. After loading Ru, no weak and broad characteristic peak of Ru single substance appears, indicating that the size of Ru is very small and has not been obviously crystallized.

[0173] 2. Pore size and specific surface area test: The specific surface area and pore size distribution of the Cl and N element co-doped graphene in Example 1 and the Ru loaded Cl and N co-doped graphene in Example 10 were tested by BET specific surface area method. The test results are shown in Figure 7 and Figure 8 .according to Figure 8 It can be seen that the Cl-doped graphene is distributed The 1.2 nm micropores disappear after Ru loading, indicating that the Ru particles are very likely to cover the original micropores. location.

[0174] 3. Raman test

[0175] Figure 9 This is the Raman graph of Ru-loaded Cl and N co-doped graphene prepared in Example 10. The Raman spectrum is at 1350 cm -1 , 1580cm -1 and 2680cm -1 The characteristic peaks of graphene appear on the left and right, namely D peak, G peak and G' peak, among which the G' peak is sharper, indicating that the number of layers is smaller.

[0176] 4. Electrolysis of alkaline seawater test, electrolysis of seawater test, electrolysis of alkaline seawater anion exchange membrane electrolyzer test:

[0177] Preparation of hydrogen evolution electrode: (a) The clear solution obtained by ultrasonically mixing the perfluorosulfonic acid resin Nafion solution and anhydrous ethanol is used as a binder; the Nafion solution used is an aqueous solution with a solid content of 5%. The volume ratio of Nafion solution to anhydrous ethanol is 1:19; (b) The catalyst materials prepared in the examples are respectively added to the prepared binders, and the concentration of the catalyst in the obtained coating is 10 mg / mL. The hydrogen evolution electrode coating is obtained by thorough ultrasonic mixing. After applying the coating on carbon paper, the electrode coated with the coating is placed in an infrared low-energy baking apparatus, maintained at 60°C for vacuum heating for 10 hours, and the hydrogen evolution electrode is obtained after the solvent is completely evaporated. The obtained hydrogen evolution electrode catalyst loading surface density is 2 mg / cm 2 .

[0178] (1) Electrolysis of alkaline seawater test: The prepared hydrogen evolution electrode was subjected to electrochemical experiments. The electrochemical experiments were carried out on a Gamery electrochemical workstation using a standard three-electrode test system. The corresponding working electrode was the hydrogen evolution electrode prepared above, the counter electrode was a graphite rod electrode, and the reference electrode was mercury / mercury oxide (Hg / HgO) (0.098V vs. RHE). All electrodes in this experiment were relative to RHE, and all electrochemical tests were carried out at 25°C. In each experiment, all modified electrodes were heated at N 2 The test was carried out in saturated 1M KOH seawater, N 2 Saturated 1 M KOH seawater was obtained by adding potassium hydroxide to Bohai seawater (purchased from Taobao, manufacturer: Bohai) and introducing nitrogen.

[0179] Test results such as Figure 10 As shown in Table 2, the Ru-loaded reduced chlorine co-doped graphene in Comparative Example 2, the Ru-loaded commercial graphene in Comparative Example 1, and the Ru-loaded Cl and N co-doped graphene samples in Example 10 were 2 The overpotentials in 1M KOH seawater are 120 mV, 43 mV and 7.8 mV respectively. The experimental results show that the halogen and N element co-doped graphene material loaded with precious metals provided by the present invention can effectively reduce the hydrogen evolution overpotential in alkaline seawater.

[0180] Meanwhile, according to Figure 17 it can be seen that the hydrogen evolution polarization curves of the catalyst based on Cl, N co-doped graphene in alkaline pure aqueous solution and alkaline seawater almost coincide, indicating that the Cl, N co-doped graphene prepared in the present invention can well resist the influence of Cl - plasma on the hydrogen evolution activity of the catalyst.

[0181] Table 2

[0182] Sample Overpotential Sample Overpotential Example 10 7.8 mV Example 19 8.1 mV Example 11 8.3 mV Example 20 8.3 mV Example 12 8.5 mV Example 21 8.0 mV Example 13 7.6 mV Example 22 7.9 mV Example 14 11.7 mV Example 23 39 mV Example 15 11.2 mV Example 24 10.7 mV Example 16 12 mV Example 25 9.6 mV Example 17 47 mV Comparative Example 1 43 mV Example 18 15 mV Comparative Example 2 120 mV

[0183] Meanwhile, referring to Figure 11 it can be seen that the hydrogen evolution electrode prepared by using the product prepared in Example 10 can stably operate in 1M KOH seawater with a current density of 500 mA / cm 2 for more than 200 hours.

[0184] (2) Electrolysis of seawater test: The hydrogen evolution electrode prepared from Ru-loaded Cl-doped graphene obtained in Example 10 was subjected to an electrochemical experiment. The electrochemical experiment was carried out on a Gamery electrochemical workstation, using a standard three-electrode test system. The corresponding working electrode was the above-prepared hydrogen evolution electrode, the counter electrode was a graphite rod electrode, and the reference electrode was silver / silver chloride (Ag / AgCl) (0.2224 V vs. RHE). All electrodes in this experiment were relative to RHE, and all electrochemical tests were carried out at 25 °C. Each time an experiment was carried out, all modified electrodes were tested in Bohai seawater (purchased on Taobao, manufacturer: Bohai).

[0185] The experimental results are as Figure 12 and Figure 13 shown. The hydrogen evolution overpotential of Example 10 in non-alkalized seawater is 180 mV, and it can stably operate at a current density of 100 mA / cm 2 for more than 24 hours.

[0186] (3) Electrolysis of alkaline seawater anion exchange membrane electrolyzer test:

[0187] The hydrogen evolution electrodes prepared from the materials prepared in Example 10 and commercial 20% PtC materials (manufacturer: Macklin) were used as the cathode, commercial CoFe MOF@Ni sheet was used as the anode, and commercial anion exchange membrane (brand: PiperIOn, model A60-HCO 3, the merchant: Shengnuo Technology) is encapsulated into an alkaline anion exchange membrane electrolyzer, which includes a cathode end plate, a cathode plate, a gasket, an anode plate, and an anode end plate. 1M KOH Bohai seawater is pumped into the encapsulated electrolyzer as the electrolyte using a circulating peristaltic pump. The polarization curve of the electrolyzer is obtained by performing two-electrode CV performance tests on the electrolyzer using a Gamery electrochemical workstation. Subsequently, the stability test of the electrolyzer for electrolyzing alkaline seawater is carried out on a Blue Electric test system (constant current mode, current density is 1000 mA / cm 2 ).

[0188] According to Figure 14 and Figure 15 , it can be seen that the electrolyzer prepared using the Ru-loaded Cl, N co-doped graphene material of Example 10 can reach a current density of 1000 mA / cm 2 at a voltage of 1.94 V, and can stably operate for more than 700 h at a current density of 1000 mA / cm 2 . While the electrolyzer prepared using commercial PtC material can reach 1000 mA / cm 2 only at 2.2 V, and fails after operating for 25 h at a current density of 1000 Ma / cm 2 .

[0189] According to Figure 16 , it can be seen that the Ru-loaded Cl, N co-doped graphene hydrogen evolution catalyst has a very high Faraday efficiency (>95%) during the process of electrolyzing alkaline seawater at a high current density (1000 mA / cm 2 ).

[0190] Although the specific implementation manners of the present invention have been described above, those skilled in the art should understand that this is only an example. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these implementation manners, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a halogen and nitrogen co-doped graphene composite material loaded with metal active sites, characterized in that: The steps include: (1) Under the protection of an inert gas, a mixture of "alkali metal element and / or alkaline earth metal element", condensed halogenated hydrocarbon, non-oxygen high molecular polymer and non-oxygen amine organic matter is reacted in a closed container to obtain halogen and nitrogen co-doped graphene; (2) After uniformly mixing a dispersion containing a metal salt, the halogen and nitrogen co-doped graphene and a surfactant, the halogen and nitrogen doped graphene composite material carrying metal active sites is obtained through reaction.

2. The method for preparing the halogen and nitrogen co-doped graphene composite material carrying metal active sites according to claim 1, characterized in that: Step (1) satisfies one or more of the following conditions: (1) The alkali metal element is one or more of K, Na, Rb and Cs; (2) The alkaline earth metal element is one or more of Mg, Ca, Ba and Sr; (3) The condensed halogenated hydrocarbon is one or more of condensed halogenated alkanes, condensed halogenated alicyclic hydrocarbons, halogenated chain unsaturated hydrocarbons and condensed halogenated aromatic hydrocarbons; (4) The non-oxygen high molecular polymer is a non-oxygen carbon chain high molecular polymer and / or a non-oxygen cyclic high molecular polymer; The non-oxygen carbon chain high molecular polymer is preferably polyolefin plastic and / or polyhalogenated olefin; The non-oxygen cyclic polymer is preferably polystyrene and / or polychlorostyrene; (5) The non-oxygen amine organic matter is one or more of aliphatic amines, aromatic amines and cyanamide compounds; The fatty amine is preferably a higher fatty amine and / or a lower fatty amine; the higher fatty amine is, for example, a polyetheramine; the lower fatty amine is preferably one or more of propylamine, butylamine, butanediamine and pentamethylenediamine; The aromatic amine is preferably one or more of aniline, β-naphthylamine and benzidine; The cyanamide compound is preferably one or more of cyanamide, dicyandiamide and melamine; (6) The mass ratio of the "alkali metal element and / or alkaline earth metal element" to the condensed halogenated hydrocarbon is 1:(0.5-100), preferably 1:(3-40), for example 1:6, 1:10, 1:20 or 1:25; (7) The mass ratio of the "alkali metal element and / or alkaline earth metal element" to the non-oxygen high molecular polymer is 1:(0.05-10), preferably 1:(0.1-2), for example 1:0.3, 1:0.5 or 1:1; (8) The mass ratio of the "alkali metal element and / or alkaline earth metal element" to the non-oxygen amine organic matter is 1:(0.05-10), preferably 1:(0.5-2), for example 1:0.8, 1:1, 1:1.5 or 1:2; (9) The sealed container is a sealed container that is resistant to high temperature, high pressure and corrosion, such as a hydrothermal kettle or a ferrule-type high-pressure stainless steel tank; (10) The reaction temperature is 30-220°C, for example, 40°C, 60°C, 80°C, 100°C, 130°C, 140°C, 150°C, 160°C or 180°C; (11) The reaction time is 3-24 hours, preferably 4-12 hours.

3. The method for preparing the halogen and nitrogen co-doped graphene composite material carrying metal active sites as claimed in claim 2, characterized in that: The condensed halogenated alkane is one or more of carbon tetrachloride, carbon tetrabromide, hexachlorobenzene, chloroform, dichloromethane and decafluoropentane; The condensed halogenated alicyclic hydrocarbon is one or more of 1,2,3,4-tetrachlorocyclopentane, 1,2,3,4-tetrafluorocyclopentane, 1,2,3,4-tetrabromocyclopentane, 1,3,5-trichlorocyclohexane, 1,3,5-tribromocyclohexane, 1,3,5-trifluorocyclohexane, 1,2,4,5-tetrachlorocyclohexane, 1,2,4,5-tetrabromocyclohexane, 1,2,4,5-tetrafluorocyclohexane, 1,2,3,4,5-pentachlorocyclohexane, 1,2,3,4,5-pentabromocyclohexane, 1,2,3,4,5-pentafluorocyclohexane, 1,2,3,4,5,6-hexafluorocyclohexane, 1,2,3,4,5,6-hexachlorocyclohexane, and 1,2,3,4,5,6-hexabromocyclohexane; The halogenated chain unsaturated hydrocarbons are vinyl chloride, vinyl bromide, vinyl fluoride, 3-chloropropylene, 3-bromopropylene, 3-fluoropropylene, 3,3-dichloropropylene, 3,3-dibromopropylene, 3,3-difluoropropylene, 3,3,3-trichloropropylene, 3,3,3-tribromopropylene, 3,3,3-trifluoropropylene, 4-chloro-1-butene, 4-bromo-1-butene, 4-fluoro-1-butene, 3-chloro-1-butene, 3-bromo-1-butene, 3-fluoro-1-butene, 4,4-dichloro-1-butene, 4,4-dibromo-1-butene, 4,4-difluoro-1-butene, 3,4-dichloro-1-butene, 3,4-dibromo-1-butene, 3,4-difluoro-1-butene, 3,3-dichloro-1-butene, 3,3-dibromo- One or more of 1-butene, 3,3-difluoro-1-butene, 4,4,4-trichloro-1-butene, 4,4,4-tribromo-1-butene, 4,4,4-trifluoro-1-butene, 3,4,4-trichloro-1-butene, 3,4,4-tribromo-1-butene, 3,4,4-trifluoro-1-butene, 3,3,4-trichloro-1-butene, 3,3,4-tribromo-1-butene, 3,3,4-trifluoro-1-butene, 3,4,4,4-tetrachloro-1-butene, 3,4,4,4-tetrabromo-1-butene, 3,4,4,4-tetrafluoro-1-butene, 3,3,4,4-tetrachloro-1-butene, 3,3,4,4-tetrabromo-1-butene, and 3,3,4,4-tetrafluoro-1-butene; The condensed halogenated aromatic hydrocarbons are one or more of hexachlorobenzene, hexabromobenzene, hexafluorobenzene, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-trifluorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene and 1,2,4,5-tetrafluorobenzene; The polyolefin plastic is PE and / or PP; The polyhaloolefin is one or more of PVDF, PTFE, PVC, and PVDC.

4. The method for preparing the halogen and nitrogen co-doped graphene composite material carrying metal active sites according to claim 1, characterized in that: Step (2) satisfies one or more of the following conditions: (1) The metal in the metal salt is a noble metal and / or a transition metal; The noble metal is preferably one or more of Ru, Pt, Rh and Pd; the transition metal is preferably one or more of Fe, Co, Ni and Cu; (2) The metal salt is one or more of the hydrochloride, nitrate and sulfate of the corresponding metal; (3) The surfactant is one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide and sodium dodecylbenzene sulfonate; (4) In step (2), the mass ratio of the halogen-nitrogen co-doped graphene to the surfactant is (0.5-4):1, for example, 1:1 or 2:1; (5) In step (2), the mass ratio of the metal in the metal salt to the halogen-doped graphene is 1:(10-20), for example, 1:10, 1:12, 1:13, 1:15, 1:16, 1:17 or 1:18; (6) When the metal in the metal salt includes a transition metal, a reducing agent is also added; The type of the reducing agent is one or more of ascorbic acid, formaldehyde, glucose, sodium borohydride and hydrazine hydrate; the amount of the reducing agent used is preferably sufficient to reduce all the metals in the metal salt, more preferably, the molar ratio of the reducing agent to the metal salt is not less than 3:1, and further preferably is (3-8):

1.

5. The method for preparing the halogen and nitrogen co-doped graphene composite material carrying metal active sites according to claim 1, characterized in that: In step (2), the reaction is carried out by solvent thermal reaction or normal pressure reaction; When the metal in the metal salt includes a noble metal, the reaction is preferably a hydrothermal reaction; When the metal in the metal salt includes only transition metal, the reaction is preferably a solvothermal reaction or a normal pressure reaction; the solvothermal reaction preferably includes the following steps: the metal salt solution, the reducing agent and the "dispersion containing the halogen and nitrogen co-doped graphene and a surfactant" are mixed evenly and then a solvothermal reaction is performed; the normal pressure reaction preferably includes the following steps: the "dispersion containing the metal salt, the halogen and nitrogen co-doped graphene and a surfactant" is mixed for 10-60 minutes, solid-liquid separation is performed, and the obtained precipitate is redispersed in a solvent, the reducing agent is added, and then the reaction is performed at 0-100°C for 1 minute to 1 hour, and then filtered, washed and dried; Wherein, the temperature of the solvent thermal reaction is preferably 100-180°C, more preferably 100-140°C; The solvent thermal reaction time is preferably 6-48 hours, more preferably 3-24 hours.

6. The method for preparing the halogen and nitrogen co-doped graphene composite material carrying metal active sites according to claim 1, characterized in that: In step (2), the metal salt solution and the "dispersion liquid containing the halogen and nitrogen co-doped graphene and a surfactant" are mixed evenly, and then reacted to obtain the halogen and nitrogen co-doped graphene composite material carrying metal active sites; Wherein, the concentration of the metal salt solution is preferably 1-10 mg / mL; In the "dispersion liquid containing the halogen and nitrogen co-doped graphene and a surfactant", the solvent is preferably one or more of an ethanol aqueous solution, an ethylene glycol aqueous solution, an ethylene glycol, a propylene glycol aqueous solution and a glycerol aqueous solution; In the "dispersion containing the halogen and nitrogen co-doped graphene and a surfactant", the sum of the mass concentrations of the halogen and nitrogen co-doped graphene and the surfactant is preferably 1-10 g / L.

7. A halogen and nitrogen co-doped graphene material carrying metal active sites prepared by the method for preparing a halogen and nitrogen co-doped graphene composite material carrying metal active sites as described in any one of claims 1 to 6.

8. A hydrogen evolution electrode, characterized in that It comprises a current collector layer and a catalytic layer located on the surface of the current collector layer, wherein the catalytic layer comprises the halogen and nitrogen co-doped graphene composite material carrying metal active sites as claimed in claim 7 and a binder.

9. A method for preparing a hydrogen evolution electrode as claimed in claim 8, characterized in that: It includes the following steps: The halogen and nitrogen co-doped graphene composite material carrying metal active sites as claimed in claim 7 and the binder are made into slurry, which is then coated on the surface of the current collector layer and dried.

10. Use of the halogen and nitrogen co-doped graphene composite material loaded with metal active sites as claimed in claim 7, or the hydrogen evolution electrode as claimed in claim 8 in hydrogen production by electrolysis of seawater.

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