Preparation method of waste plastic recycling electrocatalyst for carbon sequestration utilization

Abstract

The invention relates to an electrocatalyst based on a Joule heat high-temperature flash evaporation plastic material and application of the electrocatalyst in hydrogen peroxide electrosynthesis. The preparation method of the electrocatalyst comprises the following steps: mixing plastic powder, metal chlorate and carbon black, carrying out uniform ball milling, carrying out multiple times of high-voltage Joule heat flash evaporation treatment, and then carrying out pickling purification and drying to obtain the porous carbon-based electrocatalyst containing the metal nanocluster or atom dispersion structure. The catalyst is loaded on hydrophobic carbon paper and can efficiently catalyze a two-electron reduction reaction of oxygen on a gas-liquid-solid three-phase interface, so that stable and high-selectivity hydrogen peroxide electrosynthesis is realized. Compared with a traditional catalytic material, the catalyst has the advantages of being simple and convenient in preparation process, low in raw material cost, high in resource recycling rate, excellent in electro-catalytic performance and the like, is suitable for a green distributed hydrogen peroxide synthesis system and has good environmental and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalytic materials and green energy chemistry, and particularly relates to a carbon-based electrocatalyst prepared by a Joule heat high-temperature flash method using plastic waste and an application method thereof in synthesizing hydrogen peroxide in a two-electron oxygen reduction reaction, and especially relates to a novel technical path coupling plastic carbon sequestration resource utilization and electrocatalytic functional materials. BACKGROUND

[0002] Based on the electrocatalytic process, the two-electron oxygen reduction reaction is used to prepare hydrogen peroxide, which is considered to be one of the sustainable alternative paths of the traditional anthraquinone method due to its environmental friendliness, distributed hydrogen and oxygen co-production, and other advantages. In this process, the development of cheap, efficient and sustainable electrocatalytic materials is the key to improving the yield and Faraday efficiency of hydrogen peroxide.

[0003] At the same time, the problem of plastic pollution is increasingly serious. Polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), polyvinyl chloride (PVC), polycarbonate (PC) and other polymer materials have strong chemical stability and poor biodegradability, and remain in the environment for a long time, causing great pressure on the ecosystem. Traditional plastic recycling technologies (such as mechanical crushing and pyrolysis gasification) have low conversion efficiency, high equipment energy consumption and complex by-products, and new efficient plastic carbon resource conversion technologies need to be developed.

[0004] In recent years, the Joule heat-induced high-temperature instantaneous flash technology has gradually become an important means for high-value conversion of waste carbon sources. This technology applies a strong current to a high-resistance material (such as a plastic precursor loaded on a conductive substrate) for a short time, instantaneously raises the local temperature to 1000-3000°C, and realizes the rapid cracking and carbonization of plastics. In the absence of inert gas protection, carbon materials with good electrical conductivity, rich defects and microporous structures can be obtained, which are particularly suitable for oxygen reduction reactions at the gas-liquid-solid three-phase interface. However, the pyrolysis process is highly dependent on temperature, heating rate, holding time and other heat treatment parameters, and fine tuning of these parameters is crucial for improving the selectivity of target products, reducing the amount of by-products and controlling the reaction rate. The pyrolysis behavior of different plastics shows significant differences. For example, PVC is prone to release hydrogen chloride (HCl) at high temperatures, which poses a great risk of corrosion to equipment and the environment.

[0005] How to use the Joule heat technology to realize the high-value carbonization of plastics and prepare hydrogen peroxide electrocatalysts with excellent selectivity and activity provides a clean energy path for plastic pollution control, and has significant scientific research value and application prospect. SUMMARY

[0006] In view of the key issues of the background technology, the purpose of the present invention is to provide an electrocatalyst based on Joule heat high-temperature flash evaporation of plastic materials and a method for its use in the electrosynthesis of hydrogen peroxide.

[0007] The technical problem of the present invention is solved by the following technical solutions:

[0008] A method for preparing an electrocatalyst for recycling waste plastics for carbon sequestration comprises the following steps:

[0009] S1. Mix plastic powder, metal chloride and carbon black in proportion, add stainless steel grinding balls and perform ball milling in a ball mill to obtain a mixed powder;

[0010] S2. The mixed powder is subjected to multiple rapid heating processes using Joule heat and high-temperature flash evaporation to obtain a carbonized precursor. The flash evaporation is performed under an inert atmosphere (e.g., nitrogen, argon) or vacuum to inhibit oxidation and the release of toxic gases. The exhaust gas is treated in an alkaline solution (e.g., NaOH) absorption tower before being discharged.

[0011] S3. Leaching and washing the carbonized precursor obtained in step S2 with an acid solution, and then drying to obtain the electrocatalyst powder.

[0012] In some embodiments, the present invention also has the following technical features:

[0013] The plastic powder is selected from at least one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), polyvinyl chloride (PVC), and polycarbonate (PC), with a particle size range of 0.1-500 μm. Among them, PVC adopts multiple pulse currents of progressive intensity, and the flash evaporation is carried out in an inert atmosphere (such as nitrogen, argon) or under vacuum. The exhaust gas is treated in an alkaline solution (such as NaOH) absorption tower before being discharged. PET adopts high-energy pulse rapid flash evaporation. PE / PP adopts medium-intensity, short-time multiple pulse heating. PS uses a medium-temperature single pulse. PU / PC adopts a staged heating strategy. The first stage is preheating to release organic ammonia and hydroxyl intermediates, and the second stage is high-temperature carbonization to achieve directional transformation of the skeleton.

[0014] In some embodiments, the present invention also has the following technical features:

[0015] The metal chloride is selected from at least one of nickel chloride, ferric chloride, cobalt chloride and zinc chloride, and the added amount is 1%-20% of the mass of the plastic powder.

[0016] In some embodiments, the present invention also has the following technical features:

[0017] The added amount of the carbon black is 1%-20% of the mass of the plastic powder.

[0018] In some embodiments, the present invention also has the following technical features:

[0019] The ball mill uses stainless steel grinding balls with a diameter of 5-10 mm and a number of 4-8 balls; the ball milling time is 30-90 min and the ball milling frequency is 20-40 Hz.

[0020] In some embodiments, the present invention also has the following technical features:

[0021] The Joule heat high-temperature flash evaporation process is performed 1-10 times by controlling 40-200V capacitor discharge under the protection of an inert gas atmosphere.

[0022] In some embodiments, the present invention also has the following technical features:

[0023] The acid solution is at least one of 0.5-1 mol / L sulfuric acid or hydrochloric acid, the leaching time is 0.5-1 hour, the drying temperature after washing is 50-80° C., and the drying time is 6-12 hours.

[0024] Compared with the prior art, the present invention has the following advantages and outstanding effects:

[0025] The present invention uses Joule heat high-temperature flash evaporation technology for the first time to rapidly carbonize common waste plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) under non-inert atmosphere conditions to prepare conductive carbon materials rich in defect structures, realizing the green conversion of polluted plastics into electrocatalytic functional materials, and having the dual benefits of carbon fixation and resource recovery. Compared with traditional pyrolysis or chemical vapor deposition methods, the Joule heat flash evaporation process has the advantages of fast heating rate, no reliance on complex equipment, and no need for inert gas protection, which greatly reduces the material preparation cost and energy consumption, and has significant industrialization potential. The carbon material formed during the flash evaporation process has a loose structure and a large interlayer spacing, and has good electron transport performance and reaction site exposure rate, which is suitable for constructing a gas-liquid-solid three-phase reaction interface. Heterogeneous atoms such as nitrogen, phosphorus, and sulfur or loaded transition metals can be introduced as needed to improve the selectivity and stability of the catalyst for the two-electron oxygen reduction pathway. It can be directly used in the electrosynthesis process of hydrogen peroxide, exhibits excellent reaction stability and catalytic activity in the flow cell system, is suitable for neutral or weakly alkaline electrolytes, and has the ability to continuously produce hydrogen peroxide, meeting various application scenarios such as on-site preparation, green water treatment and distributed energy systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a method for preparing an electrocatalyst for recycling waste plastics for carbon sequestration in an embodiment of the present invention.

[0027] Figure 2aThis is the voltage diagram of the flash Joule heating process in Experimental Example 1.

[0028] Figure 2b This is the current diagram of the flash Joule heating process in Experimental Example 1.

[0029] Figure 2c This is the temperature diagram of the flash Joule heating process in Experimental Example 1.

[0030] Figure 3a ] and XRD patterns of the appropriately acid-washed catalyst prepared in Experimental Example 1.

[0031] Figure 3b This is a scanning electron microscope image of the catalyst prepared in Experimental Example 1.

[0032] Figure 3c This is a high-magnification scanning electron microscope image of the catalyst prepared in Experimental Example 1.

[0033] Figure 4a ] and XRD patterns of the non-acid-washed catalyst prepared in Experimental Example 1.

[0034] Figure 4b ] and XRD patterns of the completely acid-washed catalyst prepared in Experimental Example 1.

[0035] Figure 5a Diagram of the device for electrocatalytic synthesis of high-concentration hydrogen peroxide.

[0036] Figure 5b Graph showing the selectivity of hydrogen peroxide to the catalyst at different potentials for the appropriate acid wash.

[0037] Figure 5c Diagram of the number of electrons transferred for oxygen reduction at different potentials for a properly acid-washed catalyst.

[0038] Figure 6a The graph shows the hydrogen peroxide selectivity of the un-acid-washed and fully-acid-washed catalysts at different potentials.

[0039] Figure 6b Figure 2 is a diagram of the oxygen reduction transfer electron number of the un-acid-washed and fully-acid-washed catalysts at different potentials. DETAILED DESCRIPTION

[0040] The following examples of the present invention are based on the discovery that optimizing pyrolysis parameters (such as temperature gradient, pyrolysis cycle, and atmosphere) for different plastic types not only improves pyrolysis efficiency but also effectively controls product composition, enabling high-value-added conversion pathways. Proper pyrolysis control can also inhibit coking, mitigate coking and blockage, and improve system stability. Furthermore, it can be combined with the condensation and recovery of volatile organic compounds (VOCs) in the reaction system to improve energy efficiency.

[0041] The present invention is further described below through some specific examples.

[0042] The embodiment of the present application provides a kind of solid carbon utilization-oriented waste plastic resourceization electrocatalyst preparation method, as shown in Figure Figure 1 S1, plastic powder, metal chloride salt, carbon black are uniformly mixed, and planet ball mill is used for sufficient ball milling;S2, the mixed powder is treated by using flash joule heat high temperature flash process multiple rapid heating, to obtain carbonized precursor (carbon material and metal particle mixture before pickling, carbon material and metal small particle cluster after pickling, large particle metal is dissolved by acid, and metal small particle cluster is protected by carbon material and is not easy to be washed out and is retained.);S3, powder is carried out acid leaching washing (the purpose is to wash away large particle metal element, so that metal large particle can catalyze hydrogen peroxide decomposition), and solid is washed and dried, to obtain catalyst powder (carbon material and metal small particle cluster).Carbon material and metal small particle cluster after pickling.

[0043] Specifically, the plastic powder in the step S1 includes but is not limited to one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), polyvinyl chloride (PVC), polycarbonate (PC), and the particle size range is 0.1-500 μm.

[0044] Particle size plays a key role in the present invention, affecting the heating rate, carbonization degree, structural uniformity and final catalytic performance: 1. Ensure uniform temperature rise and rapid heat conduction. Joule heat heating is an instantaneous, volumetric heat generation method. Plastic powder with small particle size has a larger specific surface area and heat exchange efficiency, which can significantly improve the uniformity of temperature rise and avoid local overheating or incomplete carbonization. Too large a particle size will lead to delayed heat conduction, resulting in insufficient carbonization or residual intermediate products (such as tar, wax), affecting the purity and structural quality of the final carbon material. 2. Promote graphitization and the formation of ordered structures. Under high temperature, rapid heating and rapid cooling conditions, small particle size is conducive to the uniform breaking of carbon chains and the rapid recombination of carbon atoms, thereby increasing the degree of graphitization and obtaining a layered, ordered graphene-like structure. On the contrary, large particles tend to form irregular agglomerates, resulting in distortion of carbon sheets and disordered stacking, thereby reducing conductivity and catalytic activity. 3. Improve the uniformity of the catalyst's composition. If plastic powder is used simultaneously with an auxiliary agent (such as a metal precursor), consistent particle size can also prevent uneven component distribution, thereby ensuring uniform heterogeneous structure, doping distribution, or active site uniformity in the final catalyst, which is beneficial for improving the repeatability and stability of electrocatalytic performance. 4. Ease of processing and feeding. Controlling the particle size within the range of 0.1–500 μm can also prevent scattering or sticking during heating, facilitating feed control and experimental safety, and is particularly suitable for rapid batch processing and continuous device operation. ); Metal salts include but are not limited to at least one of nickel chloride, ferric chloride, cobalt chloride, or zinc chloride, with an addition amount of 1%–20% of the plastic; the carbon black is added in an amount of 1%–20% of the plastic. Preferably, the grinding balls in step S1 are stainless steel grinding balls with a diameter of 5–10 mm and a number of 4–8. The grinding in step S1 is performed in a grinder for 30–90 minutes, with grinding parameters set at 20–40 Hz.

[0045] The Joule heating process described in step S2 is controlled by capacitor voltage. Ar gas is introduced to evacuate the air, and the reaction chamber is sealed. Multiple flash evaporation processes are performed at voltages ranging from 40–200 V. The exhaust gas is treated in an alkaline solution (such as NaOH) absorption tower before being discharged. A condensation module is integrated into the reaction system to collect volatile organic compounds (VOCs) for reuse.

[0046] The acid in step S3 is at least one of sulfuric acid and hydrochloric acid, with a concentration of 0.5–1 mol / L. During the pickling process, some metal nanoparticles are coated with a carbon-rich mesophase or graphite layer during the high-temperature precursor conversion or carbonization process, forming a "core-shell" structure that physically isolates the metal core from the external acidic solution. This carbon coating has excellent chemical stability and acid resistance, effectively preventing direct acid attack on the metal and reducing its dissolution rate during the pickling process, thereby achieving selective retention of the metal species.

[0047] The electrocatalyst prepared above was used to efficiently synthesize hydrogen peroxide via a two-electron oxygen reduction reaction. First, the catalyst was evenly coated on a hydrophobic carbon paper surface, polytetrafluoroethylene (PTFE) was added as a binder, and the resulting material was dried in an infrared oven to form a working electrode. Subsequently, in a flow cell system with simultaneous circulation of the anode and cathode electrolytes, oxygen was directly aerated onto the working electrode surface, and the electrolysis reaction was carried out under constant current density conditions. During the experiment, the electrolyte was regularly replaced, and the cumulative concentration of hydrogen peroxide generated was measured to evaluate the catalyst's actual hydrogen peroxide synthesis capacity and stability.

[0048] In a preferred embodiment, the reserved electrode area on the cathode plate is 1–4 cm 2 , the air flow channel width is 0.5-2mm, and the channel spacing is 0.1-1cm.

[0049] In a preferred embodiment, the carbon paper area used for the cathode is 1–4 cm 2 The amount of catalyst used is 0.2–1.5 mg; the amount of binder used in polytetrafluoroethylene (PTFE) is 0.01–0.075 g.

[0050] In a preferred embodiment, the electrolyte concentration is at least one of KOH and Na2SO4 at 0.5-4 mol / L; the electrolyte is circulated to obtain high-concentration hydrogen peroxide.

[0051] In a preferred embodiment, the flow rate of oxygen is 20-100 mL / min; the current density is 25-200 mA / cm 2 .

[0052] The embodiment of the present invention needs to be equipped with an exhaust gas treatment system (such as alkali washing + carbon adsorption) when it is industrialized, and comply with the H2O2 production safety standards (OSHA guidelines). For laboratory scale operation, it is recommended to operate in an inert glove box.

[0053] Experimental Example 1

[0054] Flash Joule Heat Plastics for Catalyst Preparation

[0055] 1g of PVC with a particle size of 0.1μm, 50mg of NiCl2, 50mg of ZnCl2 and 100mg of carbon black were mixed evenly and further mixed using a planetary ball mill. The grinding balls were 5 stainless steel grinding balls with diameters of 5, 8 and 10mm, and the number was 5. The grinding time was 90min and the grinding parameters were set to 40Hz. Figure 2a As shown, the mixed powder was flash evaporated multiple times using Joule heat in a capacitor voltage range of 40-160V, Ar gas was introduced to evacuate the air, and the reaction chamber was sealed. The voltage interval was 20V. Figure 2bThe exhaust gas is treated by NaOH absorption before being discharged. Figure 2c The temperature was shown, wherein the highest temperature could reach above 3000° C. The obtained powder was acid-washed in 1 mol / L hydrochloric acid for 1 h to obtain a catalyst. Figure 3a The X-ray diffraction (XRD) pattern of the prepared material shows that the carbon material prepared by the present invention is composed of a small amount of metal and silicon carbide. The silicon carbide may be introduced into the quartz tube during the high-temperature flash evaporation process (silicon carbide is generally inert and has no catalytic activity, so it does not affect the catalytic activity). Figure 3b and Figure 3c This is a scanning electron microscope (SEM) image of the catalyst. It can be seen that the prepared catalyst has many defects and void structures. The metal cluster particles are evenly dispersed on the defective carbon surface due to the protective effect of the carbon coating generated by Joule heat. Figure 4a The X-ray diffraction (XRD) pattern of the sample without acid washing is shown, showing strong metal diffraction peaks, indicating that the material still contains a large amount of metal residues (metal elements, not single atoms) that have not been removed. These metals originate from the metal elements generated by the high-temperature flash reduction process of the precursor and remain on the surface or in the pores of the carbon support without treatment. Figure 4b The XRD pattern of the sample after complete acid washing is shown below. As can be seen, the acid washing process essentially removes the metal components, causing the metal diffraction peaks to significantly weaken or even disappear. However, the removal of the metal also partially destroys the carbon structure, rendering the material more disordered and amorphous, lacking clear crystalline features. This structural degradation weakens the charge transport capacity and the synergistic effect of the active sites, potentially leading to a decrease in catalytic performance.

[0056] Experimental Example 2

[0057] By constructing a flow cell system with simultaneous circulation of anode and cathode electrolytes, the practical application potential of hydrogen peroxide synthesis based on the two-electron oxygen reduction reaction was evaluated ( Figure 5a ). The catalyst was evenly coated on 1 cm 2 0.25 wt% polytetrafluoroethylene was added as a binder on the hydrophobic carbon paper, and the catalyst loading was 0.2 mg / cm 2 The sample was dried in an infrared oven to obtain a working electrode. The electrolyte concentration was 1 mol / L KOH, and a circulating flow method was used to obtain a high concentration of hydrogen peroxide. The oxygen flow rate was 60 mL / min; the current density was 100 mA / cm 2In the hydrogen peroxide test, first mix 272mL of concentrated sulfuric acid with 300mL of distilled water, then add 35.4g of potassium titanium oxalate, and finally adjust the volume to 1L. Take 1mL of the prepared colorimetric reagent, 3mL of deionized water, and 1mL of sample and add them to the digestion tube. Use a UV-visible spectrophotometer at a wavelength of 400nm to measure the absorbance and calculate the hydrogen peroxide selectivity and electron transfer number. Based on Figure 5b and Figure 5c The catalyst has a high selectivity for hydrogen peroxide in the voltage range of 0-0.65 V and a number of electron transfer close to 2, indicating that it has high activity and selectivity for the two-electron oxygen reduction synthesis of hydrogen peroxide. Figure 6a As shown, the catalysts without acid washing and fully acid washing were also evaluated, and the selectivity of hydrogen peroxide in the fully acid washed catalyst was above 80%, while the selectivity in the non-acid washed catalyst was around 75%. Figure 6b As shown in the figure, the electron transfer number of oxygen reduction after complete acid washing and no acid washing is about 2.5. The results show that the catalyst after moderate acid washing exhibits the highest hydrogen peroxide selectivity and the electron transfer number closest to 2, and the overall performance is better than that of the complete acid washing and no acid washing samples. This phenomenon shows that moderate acid washing can effectively remove some excess metal clusters on the surface and reduce the non-selective 4e - The ratio of ORR channels is improved, while retaining some of the interface structures formed between the metal and the carbon support. These interfaces may play a role in promoting O2 activation and stabilizing 2e - The metal content in the un-acid-washed sample is relatively high, which easily forms excessive metal active centers, promoting the breakage of O–O bonds, resulting in HO becoming the main product and a decrease in hydrogen peroxide selectivity. While complete acid washing improves selectivity, the complete removal of metal components weakens the interfacial synergy, reduces charge transfer efficiency, and results in catalytic activity slightly lower than that of the moderately acid-washed sample. Compared with the prior art, the embodiments of the present invention also have the following advantages:

[0058] The embodiment of the present invention uses Joule heat technology to heat waste plastics at high temperature and quickly, and the heating rate can reach 10 3 –10 4 K / s, with peak temperatures reaching 2000–3000°C, far exceeding the heating capabilities of conventional pyrolysis or carbonization methods. The long-chain hydrocarbons in the plastic precursor rapidly break and recombine, facilitating the orderly accumulation of carbon atoms in a very short period of time, forming a highly graphitized graphene-like structure.

[0059] In addition, the method of the embodiment of the present invention has the characteristics of "fast cooling and fast heating", which can freeze the intermediate structure in a very short time, inhibit the excessive stacking and agglomeration of graphite sheets, and thus obtain a graphene-like carbon material with a high specific surface area, rich defect sites and a conductive network structure.

[0060] In contrast, traditional pyrolysis or tubular furnace carbonization processes often result in a disordered carbon skeleton, low degree of graphitization, and difficulty in controlling the interface microstructure due to their slow heating rates (typically several K / s) and long heating times. Therefore, the present invention achieves dual optimization of material structure and performance through high-temperature rapid thermal treatment using Joule heat, representing a key technological path for realizing the "carbon resourceization" of plastics and enabling high-performance electrocatalytic applications.

[0061] This method is the first to use Joule thermal flash evaporation technology to prepare waste plastic carbon resource catalysts, breaking through the problems of low efficiency and disordered structure of traditional low-temperature pyrolysis or tubular furnace carbonization, and achieving instantaneous pyrolysis at high temperatures of several thousand degrees.

[0062] Rapid graphitization forms an ordered graphene-like structure; significantly improves electronic conductivity and oxygen adsorption capacity, which is beneficial to 2e - ORR selectivity.

[0063] The electrocatalyst prepared by the method for electrocatalytic synthesis of hydrogen peroxide in the embodiment of the present invention has a graphene-like structure and abundant edge active sites, which can effectively regulate the adsorption configuration of oxygen and promote 2e - Reduction channel, inhibition of 4e - Complete reduction, thereby improving the Faradaic efficiency and selectivity of hydrogen peroxide; some existing carbon catalysts (such as commercial carbon black, carbon nanotubes, etc.) have disordered structures and random distribution of active sites, which can easily lead to unstable reaction pathways and more side reactions.

[0064] The carbon materials synthesized using the Joule heat high-temperature rapid heating and rapid cooling method have a high degree of order and conductivity, which is conducive to rapid electron transport; at the same time, a multi-level pore structure (micropores + mesopores) is formed, which enhances the oxygen transmission efficiency in the catalytic layer and reduces the mass transfer resistance; in contrast, traditional carbon catalysts or doped catalysts may have problems with poor conductivity or pore blockage.

[0065] The graphene-like carbon skeleton has the characteristics of high chemical stability and strong resistance to oxidative corrosion; it is adaptable to a variety of reaction electrolytes; compared with some metal-based or doped catalysts, this catalyst has no dissolution risk and has a higher activity retention rate after long-term use.

[0066] Using waste plastics as raw materials, it achieves high-performance catalytic functions while taking into account resource recovery and carbon sequestration value; the synthesis route is short, energy consumption is low, no rare metals are required, and the preparation cost is much lower than traditional catalyst systems; it can be extended to large-scale green hydrogen peroxide production systems and has industrial potential

[0067] This method not only functionally achieves the efficient synthesis of hydrogen peroxide, but also realizes the carbon sequestration / carbon conversion process through the carbon resource utilization of waste plastics. It is environmentally friendly and is part of the green chemical industry path.

[0068] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an electrocatalyst for recycling waste plastics for carbon sequestration, characterized in that: The following steps are involved: S1. Mix plastic powder, metal chloride and carbon black in proportion, add stainless steel grinding balls and perform ball milling in a ball mill to obtain a mixed powder; S2. The mixed powder is subjected to multiple rapid heating treatments through a Joule heat high-temperature flash evaporation process to obtain a carbonized precursor; the flash evaporation is performed under an inert atmosphere or vacuum to inhibit oxidation and the release of toxic gases; the exhaust gas is treated in an alkaline solution absorption tower before being discharged; S3. Leaching and washing the carbonized precursor obtained in step S2 with an acid solution, and then drying to obtain the electrocatalyst powder.

2. The method according to claim 1, characterized in that The plastic powder is selected from at least one of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), polyvinyl chloride (PVC), and polycarbonate (PC), with a particle size range of 0.1–500 μm. PVC uses multiple pulse currents of progressive intensity, the flash evaporation is carried out under an inert atmosphere or vacuum, and the waste gas is treated in an alkaline solution absorption tower before being discharged. PET uses high-energy pulse rapid flash evaporation; PE / PP uses medium-intensity, short-duration multiple pulse heating; PS uses a medium-temperature single pulse; PU / PC uses a staged heating strategy, with the first stage being preheating to release organic ammonia and hydroxyl intermediates, and the second stage being high-temperature carbonization to achieve directional skeleton transformation.

3. The method according to claim 1, characterized in that The metal chloride is selected from at least one of nickel chloride, ferric chloride, cobalt chloride and zinc chloride, and the added amount is 1%-20% of the mass of the plastic powder.

4. The method according to claim 1, wherein The added amount of the carbon black is 1%-20% of the mass of the plastic powder.

5. The method according to claim 1, wherein The ball mill uses stainless steel grinding balls with a diameter of 5-10 mm and a number of 4-8 balls; the ball milling time is 30-90 min and the ball milling frequency is 20-40 Hz.

6. The method according to claim 1, characterized in that The Joule heat high-temperature flash evaporation process is performed 1-10 times by controlling 40-200V capacitor discharge under the protection of an inert gas atmosphere.

7. The method according to claim 1, characterized in that The acid solution is at least one of 0.5-1 mol / L sulfuric acid or hydrochloric acid, the leaching time is 0.5-1 hour, the drying temperature after washing is 50-80° C., and the drying time is 6-12 hours.

8. A method for electrocatalytic synthesis of hydrogen peroxide, characterized in that: The electrocatalyst prepared by the method according to any one of claims 1-7 is uniformly coated on the surface of hydrophobic carbon paper, and polytetrafluoroethylene (PTFE) is added as a binder. After drying, a working electrode is formed. In a flow cell system in which the anode and cathode electrolytes circulate, oxygen is introduced and an electrolysis reaction is carried out under constant current density conditions to achieve the electrosynthesis of hydrogen peroxide.

9. The method according to claim 8, characterized in that The working electrode area is 1–4 cm 2 The amount of the catalyst is 0.2-1.5 mg, and the amount of the PTFE binder is 0.01-0.075 g.

10. The method according to claim 8, characterized in that The electrolyte is a KOH or Na2SO4 solution with a concentration of 0.5-4 mol / L. The electrolyte circulates, the oxygen flow rate is 20-100 mL / min, and the current density is 25-200 mA / cm 2 .

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