Chlorine-doped five-membered ring defect carbon catalyst as well as preparation method and application thereof

Abstract

The invention provides a chlorine-doped five-membered ring defect carbon catalyst and a preparation method and application thereof.The preparation method comprises the steps that a structure induction and defect engineering synergistic strategy is adopted, a precursor rich in five-membered rings is subjected to high-temperature recombination through a fused salt heat treatment method, and a carbon network with highly-bent and edge active sites is constructed; chlorine or hydrogen chloride gas is introduced into an inert atmosphere for chlorine doping, so that the electronic structure regulation and control capability of the catalyst and the corrosion resistance to chloride ions are improved, and the chlorine-doped five-membered ring defect carbon catalyst has excellent electrocatalytic activity and can accurately regulate and control the electronic structure and surface reaction activity. According to the preparation method, the stability and corrosion resistance of the chlorine-doped five-membered ring defect carbon catalyst are remarkably improved, and the chlorine-doped five-membered ring defect carbon catalyst shows excellent performance in seawater electrolyte containing high-concentration Cl <->.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrocatalyst materials, in particular to a chlorine-doped five-membered ring defect carbon catalyst, a preparation method thereof and application thereof in seawater electrolysis for hydrogen production, oxygen production and hydrogen peroxide synthesis. BACKGROUND

[0002] With the continuous growth of global energy demand and the increasing scarcity of freshwater resources, seawater, as the most abundant liquid resource on earth, has gradually become an important medium for electrochemical energy conversion and resource synthesis. Seawater-based electrochemical synthesis technologies, such as seawater electrolysis for hydrogen production (HER), oxygen production (OER), and electrocatalytic synthesis of H2O2 (2e - ORR), have significant advantages such as wide resource availability, low cost, and environmental friendliness, and have become a hot research direction in the field of new energy and green chemical industry.

[0003] However, the existing seawater electrochemical synthesis system still faces a series of technical bottlenecks that need to be solved, mainly including the following aspects: First, the electrode material has insufficient corrosion resistance. Seawater contains high concentrations of chloride ions (Cl - ), which can easily cause electrode corrosion and catalyst deactivation during electrochemical reactions, resulting in a significant decrease in electrode life and severely restricting the long-term stable operation of the system. Second, the chlorine evolution side reaction on the anode is highly competitive, and Cl - is easily oxidized to chlorine gas (Cl2), resulting in a decrease in energy utilization efficiency and the production of harmful byproducts, increasing the safety risk and processing cost of the system. Third, the existing catalysts have insufficient activity and selectivity. Traditional metal catalysts (such as Pt, IrO2, RuO2, etc.) perform well in pure water systems, but their high preparation cost and poor structure controllability limit their large-scale application.

[0004] Carbon-based catalysts, especially carbon materials with specific modifications, have shown good application prospects in seawater electrochemical synthesis due to their electrical neutrality, low cost, and high electrical conductivity. For example, nitrogen-doped carbon materials can significantly improve their catalytic activity and stability for ORR, OER, and HER. However, existing carbon-based catalysts still have deficiencies in terms of Cl - corrosion resistance, and it is difficult to balance catalytic activity and long-term stability. Therefore, there is an urgent need to develop an electrocatalytic material that has high activity, excellent selectivity, and chlorine corrosion resistance. SUMMARY

[0005] In view of the above, the present invention aims to solve the problems of insufficient selectivity, poor chlorine corrosion resistance, and low stability of existing catalysts in seawater electrolysis systems, and provide a chlorine-doped five-membered ring defect carbon catalyst with high selectivity, high current adaptability and excellent chlorine corrosion resistance. The present invention adopts a synergistic strategy of structure induction and defect engineering to perform high-temperature reorganization on a five-membered ring-rich precursor to construct a carbon network with highly curved and edge active sites, introduce chlorine doping in an inert atmosphere, and accurately control its electronic structure and surface reaction activity, thereby significantly improving the stability and corrosion resistance of the catalyst. - The results show excellent performance in seawater electrolyte.

[0006] To this end, in a first aspect, an embodiment of the present invention provides a chlorine-doped five-membered ring defect carbon catalyst, wherein the chlorine-doped five-membered ring defect carbon catalyst is mainly composed of a five-membered ring structure, carbon defects, and a surface-enriched chlorine-doped structure, wherein the five-membered ring structure accounts for 5%-20% of the total carbon ring structure, the carbon defects include at least one of vacancy defects, edge defects, and topological defects, and the carbon defect density ranges from 10×10 14 -20×10 14 cm -2 The chlorine atom content accounts for 4%-8% of the total atomic number of the chlorine-doped five-membered ring defect carbon catalyst, and the surface concentration is higher than the internal concentration and forms a gradient distribution.

[0007] Preferably, the five-membered ring structure interacts with the carbon defects to form a three-dimensional porous carbon network with a porosity range of 15%-25%, an average pore size of 10-60 nm, and a specific surface area of ​​≥500 m 2 / g; having a continuous conductive channel and an electrical conductivity of not less than 20S / cm; the active site density on the surface and inside of the porous carbon network is not less than 10×10 15 cm -2 .

[0008] Preferably, the chlorine source is at least one of chlorine gas, hydrogen chloride, or organic chlorine sources such as methyl chloride, ethyl chloride, and carbon tetrachloride.

[0009] In a second aspect, an embodiment of the present invention provides a method for preparing the chlorine-doped five-membered ring defect carbon catalyst provided in the first aspect above, and the preparation method includes: step S1: after uniformly mixing a carbon precursor rich in a five-membered ring structure and a molten salt system in a certain proportion, placing the mixture in the tubular furnace, heating and keeping the mixture warm for a period of time under a protective atmosphere to obtain a solid product; step S2: introducing chlorine element gas into the protective atmosphere, reheating the solid product and keeping the mixture warm for a period of time to uniformly embed the chlorine element into the edge or defect site of the carbon skeleton to form a precursor-loaded complex; step S3: taking out the above-mentioned precursor-loaded complex, cleaning it with ultrasonic stirring with an acidic solution, and then washing it with deionized water until it is neutral and then drying it to obtain a chlorine-doped five-membered ring defect carbon catalyst.

[0010] Preferably, in step S1, the carbon precursor is at least one of fullerene 60, fullerene 70, or indene and other aromatic compounds containing high-density five-membered rings, and the purity of the carbon precursor is ≥98%.

[0011] Preferably, the molten salt system is a KCl-NaCl eutectic system, a LiCl-KCl eutectic system or a ZnCl2 single molten salt system; and the mass ratio of the carbon precursor to the molten salt is controlled between 1:5 and 1:20.

[0012] Preferably, in step S1, the protective atmosphere is argon or nitrogen with a purity of ≥99.99%, and the flow rate is controlled at 100-300 mL min -1 The heating temperature is 700-1000 ° C, and the holding time is 2-4 hours.

[0013] Preferably, in step S2, the chlorine gas is at least one of volatile organic chlorine source gases such as chlorine gas, hydrogen chloride gas or chloromethane vapor; the chlorine gas content is 5%-10% (volume fraction); the secondary heating temperature is 500-800°C, and the holding time is 0.5-2 hours.

[0014] Preferably, in step S3, the acidic solution is dilute hydrochloric acid with a concentration of 1 mol / L or sulfuric acid with a concentration of 0.5 mol / L; the drying method is vacuum drying, the drying temperature is 80° C., and the drying time is 12-24 hours.

[0015] In a third aspect, an embodiment of the present invention provides a method for synthesizing H2O2 by electrolysis of seawater, the method comprising: coating the chlorine-doped five-membered ring defect carbon catalyst provided by the embodiment of the first aspect of the present invention on the surface of carbon paper or carbon cloth as a cathode electrode, using a titanium mesh or iridium oxide coated electrode as an anode, using natural seawater as the electrolyte, and achieving efficient synthesis of H2O2 at a constant potential of -0.8V-0.2Vvs.RHE.

[0016] The chlorine-doped five-membered ring defect carbon catalyst and its preparation method provided in the embodiment of the present invention adopt a synergistic strategy of structure induction and defect engineering. The five-membered ring-rich precursor is subjected to high-temperature reorganization by molten salt heat treatment to construct a carbon network with highly curved and edge active sites; chlorine or hydrogen chloride gas is introduced into an inert atmosphere for chlorine doping, which improves the catalyst's electronic structure regulation ability and corrosion resistance to chloride ions, and makes the chlorine-doped five-membered ring defect carbon catalyst have excellent electrocatalytic activity and accurately regulate its electronic structure and surface reaction activity. This preparation method significantly improves the stability and corrosion resistance of the chlorine-doped five-membered ring defect carbon catalyst, and in the presence of high concentrations of Cl - The results show excellent performance in seawater electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of the preparation method of the chlorine-doped five-membered ring defect carbon catalyst provided in an embodiment of the present invention;

[0018] Figure 2 This is a transmission electron microscope image of the chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention;

[0019] Figure 3 The chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention has a 2e - ORR performance curve;

[0020] Figure 4 This is the OER performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention in seawater;

[0021] Figure 5 HER performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention in seawater;

[0022] Figure 6 This is a comparison chart of the yield and Faraday efficiency of the chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention for the electrosynthesis of H2O2 from seawater at different current densities. DETAILED DESCRIPTION

[0023] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0024] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will appreciate the reusability of other processes and / or the use of other materials.

[0025] The purpose of the present invention is to provide a chlorine-doped five-membered ring defect carbon catalyst and its preparation method. The preparation method adopts a synergistic strategy of structure induction and defect engineering. The five-membered ring-rich precursor is subjected to high-temperature reorganization by molten salt heat treatment to construct a carbon network with highly curved and edge active sites; chlorine or hydrogen chloride gas is introduced into an inert atmosphere for chlorine doping, and its electronic structure and surface reaction activity are precisely controlled. This preparation method significantly improves the stability and corrosion resistance of the chlorine-doped five-membered ring defect carbon catalyst. - The results show excellent performance in seawater electrolyte.

[0026] The first embodiment of the present invention provides a chlorine-doped five-membered ring defect carbon catalyst, which is mainly composed of carbon elements and is collaboratively constructed by a five-membered ring structure, carbon defects, and a surface-enriched chlorine-doped structure. The five-membered ring structure accounts for 5% to 20% of the total carbon ring structure, and the carbon defects include at least one of vacancy defects, edge defects, and topological defects, and the carbon defect density ranges from 10×10 14 -20×10 14 cm -2 The five-membered ring structure interacts with the carbon defects to form a three-dimensional porous carbon network with a porosity range of 15%-25%, an average pore size between 10-60nm, and a specific surface area of ​​≥500m 2 / g (determined by BET method), and has a continuous conductive channel with an electrical conductivity of not less than 20S / cm; there are abundant active sites on the surface and inside of the porous carbon network, and the density of the active sites is not less than 10×10 15 cm -2; the content of the chlorine atoms accounts for 4-8% of the total number of atoms of the chlorine-doped five-membered ring defect carbon catalyst, and the surface concentration is higher than the internal and forms a gradient distribution, wherein the chlorine element source can be chlorine (Cl2), hydrogen chloride (HCl), or organic chlorine sources such as chloromethane, chloroethane, carbon tetrachloride, etc. The chlorine element doping improves the electronic structure regulation ability of the catalyst and the corrosion resistance to chlorine ions, and makes the chlorine-doped five-membered ring defect carbon catalyst have excellent electrocatalytic activity.

[0027] The second aspect of the present application provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, as shown in Figure 1 The preparation method comprises the following steps:

[0028] Step S1: uniformly mix the carbon precursor rich in five-membered ring structure and the molten salt system according to a certain proportion, then place it in the tube furnace, heat and keep warm for a period of time under a protective atmosphere to obtain a solid product.

[0029] The carbon precursor can be one or more of fullerene 60 (C 60 ), fullerene 70 (C 70 ) or indene, etc. aromatic compounds containing high-density five-membered rings, and the purity of the carbon precursor is ≥98%; the molten salt system can be a KCl-NaCl eutectic system (NaCl and KCl are composed according to a 1:1 molar ratio), a LiCl-KCl eutectic system (LiCl and KCl are composed according to a 1:1 molar ratio) or a ZnCl2 single molten salt system; the mass ratio of the carbon precursor to the molten salt is controlled between 1:5 and 1:20; the protective atmosphere can be argon or nitrogen with a purity of ≥99.99%, and the flow rate is controlled between 100-300 mL min -1 ; the heating temperature can be 700-1000℃, and the holding time can be 2-4 hours. In this step, the five-membered ring structure in the solid product is induced to be enriched, the graphite layer is broken and restructured, and micropores are formed by high-temperature molten salt.

[0030] Step S2: introduce chlorine element gas in a protective atmosphere, and secondarily heat and keep warm the solid product for a period of time to make the chlorine element uniformly embedded in the edge or defect site of the carbon skeleton to form a precursor-loaded composite;

[0031] The chlorine element gas can be at least one of chlorine, hydrogen chloride gas or volatile organic chlorine source gas such as chloromethane vapor; the content of the chlorine element gas can be 5-10% (volume fraction); the second heating temperature can be 500-800℃, and the holding time can be 0.5-2 hours. In this step, doping chlorine element can effectively regulate the surface electronic structure of the catalyst, improve its corrosion resistance and catalytic stability in high Cl - concentration seawater environment.

[0032] Step S3: The precursor-loaded complex is taken out, washed with an acid solution under ultrasonic stirring, washed with deionized water until neutral, and dried to obtain a chlorine-doped five-membered ring defect carbon catalyst.

[0033] The acid solution can be dilute hydrochloric acid with a concentration of 1 mol / L or sulfuric acid with a concentration of 0.5 mol / L; the drying method can be vacuum drying, the drying temperature can be 80℃, and the drying time can be 12-24 hours.

[0034] The preparation method of the chlorine-doped five-membered ring defect carbon catalyst provided in the embodiments of the present application adopts a structure induction and defect engineering synergistic strategy, recombines a five-membered ring precursor rich in five-membered rings at high temperature by a molten salt heat treatment method, constructs a carbon network with high bending and edge active sites, and introduces chlorine or hydrogen chloride gas in an inert atmosphere for chlorine doping to accurately control the electronic structure and surface reactivity. The preparation method significantly improves the stability and corrosion resistance of the chlorine-doped five-membered ring defect carbon catalyst, and the catalyst exhibits excellent performance in a seawater electrolyte containing a high concentration of Cl - .

[0035] The third aspect of the present application provides a method for synthesizing H2O2 by electrolysis of seawater, which comprises: coating the chlorine-doped five-membered ring defect carbon catalyst provided in the first aspect of the present application on the surface of carbon paper or carbon cloth as a cathode electrode, using a titanium mesh or an iridium oxide coated electrode as an anode, and using natural seawater as an electrolyte to realize efficient synthesis of H2O2 at a constant potential. The range of the constant potential can be-0.8V-0.2V vs. RHE; the control current density is 100-1000mA·cm -2 , and the control electrolyte temperature is 20-40℃.

[0036] The yield of H2O2 prepared by the method provided in the embodiments of the present application can reach 50 mol·g -1 ·h -1 , and the Faraday efficiency is more than 96%.

[0037] The following further details the specific process and effects of the preparation method of the chlorine-doped five-membered ring defect carbon catalyst of the present application with reference to some specific embodiments, but is not limited to the protection scope of the present application.

[0038] Embodiment 1

[0039] The present embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is boron atom, and the preparation method comprises the following steps:

[0040] Step S1: 1g of C 60Mixing with 5g molten salt precursor (KCl-NaCl) into appropriate solvent (water + ethanol), evaporating dry, and then placing in a tube furnace and heating to 900℃ under argon protection, and keeping the temperature for 2 hours, to obtain a solid product with rich five-membered ring defect structure by high-temperature treatment by the molten salt method;

[0041] Step S2: introducing 5% chlorine in argon, and heating the solid product to 700℃ again, and keeping the temperature for 1 hour, so that chlorine elements are uniformly embedded into the edge or defect site of the carbon skeleton, to form a precursor loaded composite;

[0042] Step S3: taking out the precursor loaded composite, cleaning with an acidic solution under ultrasonic stirring, and repeatedly washing with deionized water until the washing liquid is neutral, and drying in a vacuum drying oven at 60℃ for 12 hours, to obtain a chlorine-doped five-membered ring defect carbon catalyst.

[0043] Figure 2 The transmission electron microscope image of the chlorine-doped five-membered ring defect carbon catalyst prepared in the embodiment is shown.

[0044] Embodiment 2

[0045] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the molten salt precursor (KCl-NaCl) in step S1 is modified to a molten salt precursor (KCl-LiCl), and the remaining steps are the same as in embodiment 1.

[0046] Embodiment 3

[0047] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the heating temperature in step S1 is modified to 700℃, and the remaining steps are the same as in embodiment 1.

[0048] Embodiment 4

[0049] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the heating temperature in step S1 is modified to 1000℃, and the remaining steps are the same as in embodiment 1.

[0050] Embodiment 5

[0051] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the heating temperature in step S2 is modified to 500℃, and the remaining steps are the same as in embodiment 1.

[0052] Embodiment 6

[0053] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the heating temperature in step S2 is modified to 800 DEG C, and the remaining steps are the same as those in embodiment 1.

[0054] Embodiment 7

[0055] The embodiment provides a preparation method of a chlorine-doped five-membered ring defect carbon catalyst, wherein the heteroatom is a boron atom, and in the embodiment, only the heating temperature in step S2 is modified to 800 DEG C, and the remaining steps are the same as those in embodiment 1. 60 Mixed with KCl-NaCl molten salt precursor at a mass ratio of 1:8, that is, 1g C 60 Mixed with 8g of molten salt precursor (KCl-NaCl), and the remaining steps are the same as those in embodiment 1.

[0056] In order to verify the finished product quality of the chlorine-doped five-membered ring defect carbon catalyst prepared by the preparation method provided in the embodiments of the application, the chlorine-doped five-membered ring defect carbon catalyst prepared in the above embodiments 1-7 is coated on a carbon paper electrode, Nafion solution is used as a binder, an iridium oxide coated titanium mesh is selected as an anode, natural seawater is filled into an electrolytic tank as an electrolyte for electrolysis experiment, and test results are shown in Table 1.

[0057] Wherein, Figure 3 Fig. 2 shows the 2e- ORR performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in embodiment 1 of the application in seawater. - Fig. 3 shows the OER performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in embodiment 1 of the application in seawater. Figure 4 Fig. 4 shows the HER performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in embodiment 1 of the application in seawater. Figure 5 Fig. 4 shows the HER performance curve of the chlorine-doped five-membered ring defect carbon catalyst prepared in embodiment 1 of the application in seawater.

[0058] Table 1, test items and test results of embodiments 1-7

[0059] Example No. H2O2 yield (mol g -1 ·h -1 )]]> Faraday efficiency Example 1 65.4 99.3 Example 2 50.2 98.7 Example 3 37.6 92.5 Example 4 45.8 98.3 Example 5 33.2 94.5 Example 6 39.6 95.7 Example 7 46.8 96.8

[0060] The test results show that the chlorine-doped five-membered ring defect carbon catalyst prepared by the preparation method of the chlorine-doped five-membered ring defect carbon catalyst provided in the embodiments of the application can achieve H2O2 yield of 30-70 mol·g -1 ·h -1 , and Faraday efficiency is greater than or equal to 90% in the potential range of-0.8V to 0.2V vs. RHE.

[0061] In addition, in order to verify the H2O2 yield and Faraday efficiency of the chlorine-doped five-membered ring defect carbon catalyst prepared by the preparation method provided in the embodiment of the present invention in seawater electrolysis at different current densities, the chlorine-doped five-membered ring defect carbon catalyst prepared in Example 1 of the present invention was coated on a carbon paper electrode and subjected to long-term electrolysis experiments in natural seawater. The current density range is 100-1000 mA·cm -2 , the test results are as follows Figure 6 shown.

[0062] from Figure 6 It can be seen that the chlorine-doped five-membered ring defect carbon catalyst has a high conductivity in the range of 100-1000 mA·cm -2 The H2O2 production rate increases gradually with the increase of current density, and reaches 900 mA·cm -2 At this current density, the H2O2 yield reaches 70 mol·g -1 ·h -1 And during the test, the Faraday efficiency always remained above 90%.

[0063] In summary, the preparation method provided by the present invention adopts a synergistic strategy of structural induction and defect engineering. The five-membered ring-rich precursor is subjected to high-temperature reorganization by molten salt heat treatment to construct a carbon network with highly curved and edge active sites. Chlorine or hydrogen chloride gas is introduced in an inert atmosphere for chlorine doping, and its electronic structure and surface reactivity are precisely regulated. The chlorine-doped five-membered ring defect carbon catalyst prepared by this preparation method has high stability and strong corrosion resistance. It has high electrochemical stability in chloride ion systems. Under natural seawater conditions, the catalyst exhibits excellent stability and corrosion resistance, and is suitable for long-term continuous operation.

[0064] In addition, the chlorine-doped five-membered ring defect carbon catalyst prepared by the preparation method of the present invention is not only suitable for the electrolysis of seawater to synthesize H2O2, but can also be used in multiple fields such as seawater disinfection, marine anti-fouling and degradation of marine pollutants. Specific application scenarios include:

[0065] (1) In-situ sterilization of seawater: H2O2 synthesized by seawater electrolysis is directly released into the seawater pipe network and aquaculture systems. Due to its strong oxidizing properties, H2O2 can destroy bacteria and algae cells, inhibit their reproduction, reduce the number of microorganisms in the water, create a healthy seawater aquaculture environment, reduce the risk of disease, and increase aquaculture returns.

[0066] (2) Marine pollution control: Synthesized H2O2 works synergistically with photocatalysis and Fenton systems. In the photocatalytic system, H2O2 acts as an electron acceptor, accelerating the separation of photogenerated electrons and holes, and enhancing the oxidative decomposition of organic pollutants in marine plastic microparticles. In the Fenton system, it reacts with ferrous ions to generate hydroxyl radicals, which efficiently degrade organic pollutants and heavy metal chelates, protecting the ecological balance of the ocean.

[0067] (3) Antifouling of hulls and marine equipment: Utilizing the slow-release properties of H2O2, it can be applied to the surface of equipment. The continuously released H2O2 can effectively inhibit the attachment of marine organisms such as algae and shellfish, reduce biofouling, lower equipment energy consumption and maintenance costs, extend equipment life, and ensure efficient and safe marine operations.

[0068] (4) Distributed green energy system: The chlorine-doped five-membered ring defect carbon catalyst prepared by the present invention is integrated into an offshore floating electrochemical system. With the help of solar energy or wind energy, H2O2 is synthesized from seawater as a raw material to achieve chemical energy storage and on-site energy conversion.

[0069] (5) Polar and offshore emergency oxygen supply and water purification systems: Synthetic H2O2 can be used for emergency water disinfection, killing pathogens and providing safe drinking water. At the same time, the oxygen produced by the decomposition of H2O2 can meet emergency oxygen supply needs, providing strong support for deep-sea scientific research and island disaster prevention.

[0070] In the description of this specification, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0071] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A chlorine-doped five-membered ring defect carbon catalyst, characterized in that: The chlorine-doped five-membered ring defect carbon catalyst is mainly composed of carbon elements and is collaboratively constructed by a five-membered ring structure, carbon defects, and a surface-enriched chlorine-doped structure. The five-membered ring structure accounts for 5% to 20% of the total carbon ring structure, and the carbon defects include at least one of vacancy defects, edge defects, and topological defects. The carbon defect density range is 10×10 14 -20×10 14 cm -2 The chlorine atom content accounts for 4%-8% of the total atomic number of the chlorine-doped five-membered ring defect carbon catalyst, and the surface concentration is higher than the internal concentration and forms a gradient distribution.

2. The chlorine-doped five-membered ring defect carbon catalyst according to claim 1, characterized in that The five-membered ring structure interacts with the carbon defects to form a three-dimensional porous carbon network with a porosity range of 15%-25%, an average pore size between 10-60nm, and a specific surface area of ​​≥500m 2 / g; having a continuous conductive channel and an electrical conductivity of not less than 20S / cm; the active site density on the surface and inside of the porous carbon network is not less than 10×10 15 cm -2 ; 3. The chlorine-doped five-membered ring defect carbon catalyst according to claim 1, characterized in that The chlorine element source is at least one of chlorine gas, hydrogen chloride or organic chlorine sources such as methyl chloride, ethyl chloride, and carbon tetrachloride.

4. A method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 1, characterized in that: The preparation method comprises: Step S1: uniformly mixing a carbon precursor rich in a five-membered ring structure and a molten salt system in a certain proportion, placing the mixture in the tube furnace, heating and keeping the mixture warm for a period of time under a protective atmosphere to obtain a solid product; Step S2: introducing chlorine gas into a protective atmosphere, reheating the solid product and keeping it warm for a period of time to allow the chlorine to be evenly embedded in the edges or defect sites of the carbon skeleton to form a precursor-loaded complex; Step S3: taking out the above-mentioned precursor-loaded composite, cleaning it with an acidic solution by ultrasonic stirring, then washing it with deionized water until it is neutral and then drying it to obtain a chlorine-doped five-membered ring defect carbon catalyst.

5. The method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 4, characterized in that: In step S1, the carbon precursor is at least one of fullerene 60, fullerene 70, or an aromatic compound containing a high density of five-membered rings, such as indene, and the purity of the carbon precursor is ≥98%.

6. The method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 4, characterized in that: The molten salt system is a KCl-NaCl eutectic system, a LiCl-KCl eutectic system or a ZnCl2 single molten salt system; the mass ratio of the carbon precursor to the molten salt is controlled between 1:5 and 1:

20.

7. The method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 4, characterized in that: In step S1, the protective atmosphere is argon or nitrogen with a purity of ≥99.99%, and the flow rate is controlled at 100-300 mL min -1 The heating temperature is 700-1000 ° C, and the holding time is 2-4 hours.

8. The method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 4, characterized in that: In step S2, the chlorine gas is at least one of volatile organic chlorine source gases such as chlorine, hydrogen chloride gas or chloromethane vapor; the chlorine gas content is 5%-10% (volume fraction); the secondary heating temperature is 500-800°C, and the holding time is 0.5-2 hours.

9. The method for preparing the chlorine-doped five-membered ring defect carbon catalyst according to claim 4, characterized in that: In step S3, the acidic solution is dilute hydrochloric acid with a concentration of 1 mol / L or sulfuric acid with a concentration of 0.5 mol / L; the drying method is vacuum drying, the drying temperature is 80° C., and the drying time is 12-24 hours.

10. A method for synthesizing H2O2 by electrolysis of seawater, characterized in that: The method comprises: coating the chlorine-doped five-membered ring defect carbon catalyst according to any one of claims 1 to 3 on the surface of carbon paper or carbon cloth as a cathode electrode, using a titanium mesh or iridium oxide coated electrode as an anode, using natural seawater as an electrolyte, and achieving efficient synthesis of H2O2 at a constant potential of -0.8V-0.2V vs. RHE.

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