Preparation method and application of non-metallic edge-doped graphene nanosheet electrocatalyst

Abstract

This invention provides a method for preparing and applying a non-metallic edge-doped graphene nanoplate electrocatalyst. The method for preparing the non-metallic edge-doped graphene nanoplate electrocatalyst includes the following steps: (1) Mixing and loading: Graphite powder, non-metallic dopant precursor, and organic solvent are added to a reactor in a predetermined ratio, mixed evenly, and then the reactor is sealed; (2) Mechanical exfoliation and doping: A predetermined mechanical shear force is applied to the reaction system of step (1) to exfoliate the graphite interlayers to form graphene nanoplates, and non-metallic dopant elements are simultaneously doped onto the edges of the graphene nanoplates during the exfoliation process; (3) Purification and collection: The mixture after step (2) is collected, washed to remove impurities, and then dried to obtain the non-metallic edge-doped graphene nanoplate electrocatalyst. This invention has the advantages of low cost, broad spectrum, high activity, and high two-electron oxygen reduction selectivity.

Description

Technical Field

[0001] This invention relates to the preparation of hydrogen peroxide, and particularly to a non-metallic edge-doped graphene nanoplate electrocatalyst, its preparation, and its application. Background Technology

[0002] Hydrogen peroxide (H2O2), as a high-value, environmentally friendly oxidant and disinfectant, holds an irreplaceable strategic position in fields such as chemical synthesis, metallurgical purification, electronic cleaning, paper bleaching, and environmental remediation. Currently, over 95% of the world's H2O2 is produced on a large scale through the traditional anthraquinone process. However, this process suffers from problems such as complex procedures, high energy consumption, and the generation of organic waste liquid; furthermore, high-concentration H2O2 poses significant safety hazards during centralized storage and transportation, making it difficult to meet the growing demands of modern industry for small-scale, decentralized, and on-demand production.

[0003] To break through the limitations of traditional production models, novel decentralized preparation methods such as direct hydrogen-oxygen synthesis and photocatalysis have been extensively studied in recent years. Although these methods align with the concept of "on-demand production" to some extent, they still have fundamental drawbacks: direct hydrogen-oxygen synthesis requires the use of flammable and explosive hydrogen-oxygen mixtures, posing a severe explosion risk; while photocatalysis is limited by problems such as high recombination rates of photogenerated carriers and low solar energy conversion efficiency, making it difficult to achieve large-scale application.

[0004] In contrast, based on the two-electron oxygen reduction reaction (2e... - The electrocatalytic synthesis of H2O2 using ORR (Organic Oxygen Reduction) technology requires only air (or oxygen) and water as raw materials and can achieve efficient, safe, and in-situ production of H2O2 under ambient temperature and pressure driven by electricity. It is considered the most promising green alternative. However, electrocatalytic 2e2… - The efficiency of ORR (Organic Reactive Catalyst) is highly dependent on the performance of the catalyst. Currently, there are three main approaches to address the technical requirements for the electrocatalytic synthesis of hydrogen peroxide, all of which have significant drawbacks: First, using precious metal catalysts such as palladium and platinum, which, although highly active, are expensive and prone to causing secondary pollution from heavy metals; second, modifying carbon materials through strong acid oxidation, which severely damages the conjugated network of the graphene substrate, leading to a sharp drop in conductivity, and also results in significant waste acid pollution and poor catalytic stability; third, using traditional high-temperature pyrolysis to prepare heteroatom-doped carbon materials, which is not only energy-intensive, but also often involves heteroatoms randomly doped within the carbon substrate, easily inducing four-electron side reactions to generate water, resulting in extremely poor selectivity for hydrogen peroxide. In summary, none of the existing technologies can simultaneously meet the requirements of low cost, high selectivity, and environmentally friendly large-scale production.

[0005] Therefore, developing a novel non-metallic electrocatalyst that is low-cost, broad-spectrum, highly active, and has high two-electron oxygen reduction selectivity has become a key technical challenge that needs to be addressed to achieve efficient and green in-situ production of H2O2.

[0006] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a low-cost, broad-spectrum, highly active non-metallic edge-doped graphene nanoplate electrocatalyst with high two-electron oxygen reduction selectivity, as well as its preparation and application.

[0008] The present invention adopts the following technical solution:

[0009] In a first aspect, a method for preparing a non-metallic edge-doped graphene nanoplate electrocatalyst is provided, comprising the following steps:

[0010] (1) Mixing and loading: Graphite powder, non-metallic dopant precursor and organic solvent are added to the reactor in a predetermined ratio, mixed evenly and then the reactor is sealed.

[0011] (2) Mechanical exfoliation and doping: A predetermined mechanical shear force is applied to the reaction system of step (1) to exfoliate the graphite interlayer to form graphene nanoplates, and the non-metallic doping elements in the non-metallic doping element precursor are simultaneously doped into the edge of the graphene nanoplates during the exfoliation process.

[0012] (3) Purification and collection: The mixture after step (2) is collected, washed to remove impurities, and then dried to obtain the non-metallic edge-doped graphene nanoplate electrocatalyst.

[0013] In a second aspect, a non-metallic edge-doped graphene nanoplate electrocatalyst prepared by the preparation method described in the first aspect is provided.

[0014] Thirdly, an electrode is provided, comprising a conductive substrate and a non-metallic edge-doped graphene nanoplate electrocatalyst as described in the second aspect, supported on the conductive substrate.

[0015] Fourthly, the application of the non-metallic edge-doped graphene nanoplate electrocatalyst described in the second aspect in the two-electron oxygen reduction to generate hydrogen peroxide is provided.

[0016] The non-metallic edge-doped graphene nanoplate electrocatalyst of this invention effectively promotes the selective occurrence of the oxygen reduction reaction along a two-electron path by doping the edges of the graphene nanoplates with non-metallic elements, thereby significantly improving the generation efficiency and selectivity of electrochemical hydrogen peroxide. It is suitable for decentralized, on-demand production scenarios. Specifically, this invention mainly has the following advantages:

[0017] 1. Non-metallic high-selectivity catalytic system: Eliminating the need for expensive precious metal components such as platinum and palladium fundamentally reduces catalyst manufacturing costs. The heteroatom-doped structure at the edges of graphene nanoplatelets allows for precise control of local electron distribution, effectively optimizing the adsorption energy of key intermediates, thereby stably and efficiently catalyzing the two-electron oxygen reduction reaction.

[0018] 2. High intrinsic activity of in-situ edge doping: Unlike traditional carbon-based surface doping, which destroys the conductivity of the carbon framework, the non-metallic elements of this invention are selectively anchored at the edges of the graphene nanoplatelets. This not only perfectly preserves the highly conductive network of the graphene surface, but also highly exposes the edge active sites, significantly improving the effective contact and reaction kinetics between oxygen molecules and catalytic sites.

[0019] 3. Green, low-cost, and scalable preparation: Using inexpensive graphite powder and non-metallic dopant precursors, a predetermined mechanical shear force (sufficient to exfoliate graphite layers to form graphene nanoplates, while simultaneously in-situ doping of non-metallic dopant elements at the edges of the graphene nanoplates) is applied, achieving graphite layer exfoliation and in-situ doping of edge non-metallic elements in one step. This mechanochemical method instantly breaks carbon bonds to create highly active edge dangling bonds and guides the non-metallic dopant precursor to complete edge-dominant doping in a closed microenvironment. This achieves simultaneous physical exfoliation of carbon layers and bonding of non-metallic elements, eliminating complex liquid-phase redox steps, avoiding the generation of large amounts of strong acids and waste liquids, and making the process extremely simplified and easily achievable for large-scale industrial production.

[0020] 4. Wide Environmental Adaptability and Distributed Production Potential: This non-metallic edge-doped graphene nanoplate electrocatalyst exhibits high structural stability, demonstrating excellent performance not only in conventional alkaline systems but also maintaining extremely high two-electron oxygen reduction performance in neutral and high-salt environments. When loaded onto conductive substrates (such as hydrophobic carbon paper or carbon cloth), it is perfectly suited for on-site electrolysis devices, meeting the distributed production needs of hydrogen peroxide in modern industry and environmental protection sectors for "on-demand" production. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope (SEM) image of a region of the non-metallic edge-doped graphene nanoplate electrocatalyst of Example 1.

[0022] Figure 2The image shows a scanning electron microscope (SEM) image of another region of the non-metallic edge-doped graphene nanoplate electrocatalyst of Example 1, along with the corresponding carbon and nitrogen elemental energy-dispersive X-ray spectra.

[0023] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) analysis of the non-metallic edge-doped graphene nanoplate electrocatalyst of Example 1.

[0024] Figure 4a , 4b 4c and 4c are respectively the LSV curves, hydrogen peroxide selectivity and apparent electron transfer number graphs of the electrocatalysts of Examples 1-3 and Comparative Example 1 under alkaline electrolyte conditions tested by rotating ring disk electrode in Example 4.

[0025] Figure 5a , 5b 5c and 5c are respectively the LSV curves, hydrogen peroxide selectivity and apparent electron transfer number graphs of the electrocatalyst of Example 1 under neutral electrolyte conditions tested by rotating ring disk electrode in Example 4.

[0026] Figure 6 This is a yield graph of hydrogen peroxide production using the electrocatalysts of Examples 1-3 and Comparative Example 1 in Example 5.

[0027] Figure 7 The diagram shows the Faraday current efficiency of the electrocatalysts used in Examples 1-3 and Comparative Example 1 for the production of hydrogen peroxide in Example 5. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0029] The core principle of this invention lies in using a mechanochemical method to achieve physical exfoliation of graphite and "in-situ edge doping" of non-metallic dopants in one step through mechanical shearing force. Without destroying the high conductivity of the graphene substrate, a catalytic active center with extremely high two-electron oxygen reduction selectivity is precisely constructed, thereby realizing a decentralized electrochemical hydrogen peroxide production that is suitable for low material cost and wide environmental adaptability.

[0030] This invention provides a method for preparing a non-metallic edge-doped graphene nanoplate electrocatalyst, comprising the following steps:

[0031] (1) Mixing and loading: Graphite powder, non-metallic dopant precursor and organic solvent are added to the reactor in a predetermined ratio, mixed evenly and then the reactor is sealed.

[0032] (2) Mechanical exfoliation and doping: A predetermined mechanical shear force is applied to the reaction system of step (1) to exfoliate the graphite interlayer to form graphene nanoplates, and the non-metallic doping elements in the non-metallic doping element precursor are simultaneously doped into the edge of the graphene nanoplates during the exfoliation process.

[0033] (3) Purification and collection: The mixture after step (2) is collected, washed to remove impurities, and then dried to obtain the non-metallic edge-doped graphene nanoplate electrocatalyst.

[0034] In some embodiments, in step (1), the particle size of the graphite powder is 10-5000 mesh. More preferably, the particle size of the graphite powder is 100 mesh. In some embodiments, in step (1), the mass ratio of the graphite powder to the non-metallic dopant precursor is 1:(1~10); the organic solvent is anhydrous ethanol.

[0035] In some embodiments, in step (1), the reactor is a ball mill jar containing grinding media; in step (2), a predetermined mechanical shear force is applied by mechanically ball milling the reaction system.

[0036] In some embodiments, the mass ratio of the grinding media to the graphite powder is (50~150):1; the mechanical ball milling speed is 100 rpm to 500 rpm, and the continuous ball milling time is 8~48 hours. By controlling parameters such as the rotation speed, the mass ratio of the grinding media to the material, and the ball milling time, sufficient mechanical energy is applied to achieve graphite exfoliation and edge doping.

[0037] In some embodiments, the abrasive media may be, for example, stainless steel beads, zirconia beads, agate beads, alumina beads, etc.

[0038] In some embodiments, the specific operation of washing and removing impurities in step (3) is as follows: sequentially washing with anhydrous ethanol, immersing in acid solution, and rinsing with ultrapure water; the acid solution is a 1 M HCl solution.

[0039] In some embodiments, the drying in step (3) can be performed by vacuum freeze drying.

[0040] In some embodiments, in step (1), the non-metallic dopant element in the non-metallic dopant precursor is at least one of N, P, S, B, and F; the non-metallic dopant precursor is solid or gaseous.

[0041] In some embodiments, when the non-metallic dopant precursor is solid, the process further includes physically refining the non-metallic dopant precursor (e.g., grinding) to 10-5000 mesh, drying it under vacuum to remove moisture, and then adding it to the reactor along with the moisture-removed graphite powder and organic solvent.

[0042] In some embodiments, solid nonmetallic dopant precursors include urea, thiourea, ammonium chloride, boric acid, and red phosphorus; gaseous nonmetallic dopant precursors include ammonia or hydrogen sulfide gas.

[0043] More preferably, the non-metallic dopant precursor is urea, and the doped nitrogen exists mainly in the form of pyridine nitrogen and graphitic nitrogen (in these two forms, nitrogen is mainly in the form of pyridine nitrogen, which exists at the boundary of the graphene lattice in the graphene nanoplate) in the non-metallic edge-doped graphene nanoplate electrocatalyst.

[0044] The present invention also provides a non-metallic edge-doped graphene nanoplate electrocatalyst prepared by the above preparation method.

[0045] A specific embodiment of the present invention also provides an electrode, which includes a conductive substrate and the non-metallic edge-doped graphene nanoplate electrocatalyst supported on the conductive substrate.

[0046] In some embodiments, the non-metallic edge-doped graphene nanoplate electrocatalyst is loaded at a concentration of 0.1 mg / cm² on the conductive substrate. 2 Up to 0.5 mg / cm 2 .

[0047] The present invention also provides an application of the non-metallic edge-doped graphene nanoplate electrocatalyst in the two-electron oxygen reduction to generate hydrogen peroxide.

[0048] In some embodiments, the application includes: providing an electrolytic cell, the cathode of the electrolytic cell comprising a conductive substrate and the non-metallic edge-doped graphene nanoplate electrocatalyst supported on the conductive substrate; introducing an oxygen-containing gas and injecting an electrolyte into the cathode chamber of the electrolytic cell; applying a reduction potential to the cathode to carry out an electrolytic reaction, thereby generating hydrogen peroxide in the cathode chamber.

[0049] In some embodiments, the applications include: directly integrating an electrode loaded with the non-metallic edge-doped graphene nanoplate electrocatalyst into an electro-Fenton advanced oxidation system, utilizing the in-situ efficiently generated hydrogen peroxide to synergistically trigger the generation of highly oxidizing hydroxyl radicals with iron-based materials in the system, thereby applying it to the efficient degradation of antibiotic-resistant organic compounds (such as sulfamethoxazole) or the development of novel consumable-free advanced washing technologies.

[0050] In some embodiments, the application includes using an electrode loaded with the non-metallic edge-doped graphene nanoplate electrocatalyst in the field of consumer products, for example, by generating hydrogen peroxide in situ and on demand in the washing water stream to achieve thorough detergent-free stain removal and sterilization.

[0051] In some embodiments, the application includes using electrodes loaded with the non-metallic edge-doped graphene nanoplate electrocatalyst to develop distributed agricultural irrigation or aquaculture water treatment terminals, utilizing in-situ generated hydrogen peroxide to kill pathogens and oxidize harmful organic matter, and the hydrogen peroxide decomposes to produce only water and oxygen, achieving truly zero-residue green agriculture, thereby solving the problem of toxic residues easily generated by traditional agricultural bactericides and aquatic disinfectants.

[0052] The paper and textile industries are traditional major consumers of hydrogen peroxide, and have long been constrained by the dangerous centralized storage and transportation of high-concentration hydrogen peroxide. In some embodiments, the application includes: directly integrating the electrode loaded with the non-metallic edge-doped graphene nanoplate electrocatalyst of the present invention into the bleaching production line of the factory in the form of an electrode array, which can realize the "production and use" of bleaching agent, eliminate the risk of hazardous chemical storage, and at the same time significantly reduce logistics and procurement costs.

[0053] In some embodiments of the present invention, the 2e of the non-metallic edge-doped graphene nanoplate electrocatalyst (which may be simply referred to as the "electrocatalyst") is... - ORR performance testing can be conducted in the following ways:

[0054] A1. A predetermined mass of electrocatalyst is dispersed in a mixed solvent system containing low-carbon alcohol and water, and an appropriate amount of high molecular weight ionic polymer is added as a binder. The mixture is then ultrasonically or mechanically dispersed to form a uniform catalyst slurry. Subsequently, a quantitative volume of the slurry is uniformly coated onto the test disk electrode end face of a rotating ring electrode and dried to serve as a working electrode.

[0055] A2. Construct a standard three-electrode electrochemical testing system comprising the aforementioned working electrode, counter electrode, and reference electrode. Before data acquisition, perform multiple cyclic voltammetric scans on the working electrode within a specific potential window to perform in-situ cleaning and activation of the electrode surface until a stable electrochemical baseline is obtained.

[0056] A3. In an oxygen-saturated electrolyte solution environment, a preset rotation speed (which can be set to 900~2500 rpm, e.g., 1600 rpm) is applied to the rotating ring-disc electrode. Linear sweep voltammetry (LSV) is used to record the oxygen reduction polarization curve of the working electrode within the reduction potential range to obtain the disk current intensity. Simultaneously, a constant anodic oxidation potential is applied to the ring electrode to obtain the corresponding ring current intensity. Preferably, the scan rate is set to 5~20 mV / s (e.g., 10 mV / s) during testing; preferably, the ring electrode is maintained at a constant potential of 1.2~1.5 V vs. RHE (e.g., 1.5 V vs. RHE).

[0057] A4. Extract the absolute value of the disk current and the ring current value under steady-state conditions during the test, and combine them with the inherent collection efficiency of the rotating ring-disk electrode system used. Based on the law of conservation of mass and Faraday's law, quantitatively calculate the hydrogen peroxide selectivity (H2O 2%) and apparent electron transfer number of the electrocatalyst. n This serves as the core basis for judging the two-electron oxygen reduction performance of the catalyst.

[0058] In some embodiments of the present invention, the hydrogen peroxide production performance test of the non-metallic edge-doped graphene nanoplate electrocatalyst can be conducted in the following manner:

[0059] B1. A predetermined amount of electrocatalyst is coated onto the surface of a conductive substrate (such as hydrophobic carbon paper or carbon cloth), and after drying and curing, it serves as the working electrode; preferably, the loading of the electrocatalyst is 0.1 ~ 0.5 mg / cm³. 2 (For example, specifically 0.2 mg / cm) 2 This ensures that the catalytic active sites are fully exposed.

[0060] B2. Using a compartmentalized electrolytic cell (e.g., an H-type dual-chamber electrolytic cell (H-Cell)) separated by ion exchange membranes (such as proton exchange membranes or anion exchange membranes), the working electrode prepared above is placed in the cathode chamber, the counter electrode is placed in the anode chamber, and a reference electrode is added to jointly construct a test circuit for the production of hydrogen peroxide by two-electron oxygen reduction.

[0061] B3. Inject equal volumes of test electrolyte into the cathode and anode chambers, respectively. During the test, pure oxygen is continuously introduced into the electrolyte in the cathode chamber using a gas flow control device, with the gas flow rate controlled between 10 and 100 sccm to maintain oxygen saturation in the solution and provide sufficient reactants.

[0062] B4. Apply a preset constant reduction potential to the working electrode using an electrochemical testing system, perform continuous electrolysis tests using the chronoamperometry method, and record the current-time response curve.

[0063] B5. After electrolysis is completed, a quantitative electrolyte sample is extracted from the cathode chamber and pre-acidified (for example, an appropriate amount of dilute sulfuric acid can be added to the extracted electrolyte sample to create a strongly acidic environment). Then, a redox titration is performed using a potassium permanganate standard solution of known accurate concentration. When the titration solution turns slightly red and does not fade within a predetermined time (e.g., 30 seconds), the titration endpoint is determined to have been reached.

[0064] B6. Based on the volume of potassium permanganate standard solution consumed, the amount of hydrogen peroxide generated is calculated. Combined with the total volume of electrolyte in the cathode chamber and the total amount of electricity passing through the working electrode during the test, the actual hydrogen peroxide yield and Faraday current efficiency of the electrocatalyst are quantitatively calculated.

[0065] The following describes specific embodiments of the present invention.

[0066] Example 1

[0067] The preparation method of the non-metallic edge-doped graphene nanoplate electrocatalyst in this embodiment includes the following steps:

[0068] S1. Grind the graphite powder and the non-metallic dopant precursor (urea is specifically used in this embodiment) to about 100 mesh, and then place them in a vacuum drying oven for drying (e.g., drying for 8 hours) to completely remove free moisture.

[0069] S2. Accurately weigh 1 g of pretreated graphite powder and 5 g of urea, and add them together with 5 ml of anhydrous ethanol into a ball mill jar containing 100 g of grinding media (stainless steel beads with a diameter of 6 mm). Mix them thoroughly and then seal the ball mill jar tightly.

[0070] S3. Place the sealed ball mill jar in a planetary ball mill for mechanical ball milling at room temperature, set the ball milling speed to 500 rpm, and the continuous ball milling time to 48 hours.

[0071] S4. Collect the solid mixture after ball milling and wash it repeatedly by centrifugation with anhydrous ethanol, acid (1 M HCl solution), and ultrapure water to remove unreacted urea and residual metal impurities. Finally, place the washed product in a vacuum freeze dryer for 48 hours to obtain the non-metallic edge-doped graphene nanoplate electrocatalyst, specifically a nitrogen-edge-doped graphene nanoplate electrocatalyst in this example, which will be referred to as the electrocatalyst below.

[0072] A scanning electron microscope image of a region of the electrocatalyst prepared in Example 1 is shown below. Figure 1As shown, the particle size of the ball-milled graphene nanoplatelets can reach the nanoscale (<1000 nm), much smaller than the 100-mesh (150 μm) of graphite powder. This is because the ball milling process utilizes high-energy mechanical shear force to drive physical exfoliation between graphite layers, and simultaneously promotes the doping of non-metallic doping elements (N element in this example) mainly at the edge defect sites of the newly formed graphene nanoplatelets. Figure 2 The image shown is a scanning electron microscope (SEM) image of another region of the electrocatalyst from Example 1, along with the corresponding carbon and nitrogen elemental energy-dispersive X-ray spectra. Figure 2 It can be seen that nitrogen is widely and uniformly distributed in the electrocatalyst. For example... Figure 3 As shown, further X-ray photoelectron spectroscopy analysis reveals that the doped nitrogen mainly exists in the form of pyridine nitrogen and graphitic nitrogen, with pyridine nitrogen being the predominant form. This allows for the manipulation of the local electronic structure for 2e... - The effective adsorption of oxygen in ORR, and the nitrogen element introduced by mechanical ball milling in this embodiment, does not exist in a loose physical adsorption state, but is deeply reconstructed and embedded in the sp2 hybrid network of carbon, forming high bond energy CN covalent bonds (such as stable pyridine nitrogen and graphitic nitrogen configurations). Under aqueous electrolyte and room temperature electrocatalytic environment, this strong covalent lattice is extremely difficult to be destroyed, fundamentally eliminating the possibility of active heteroatoms "dissolving" or "leaking" into the electrolyte, and has high stability.

[0073] Example 2

[0074] The difference from Example 1 is that the non-metallic dopant precursor used in Example 2 is sodium sulfide, while the rest is the same as in Example 1, resulting in a sulfur-edge-doped graphene nanoplate electrocatalyst.

[0075] Example 3

[0076] The difference from Example 1 is that the non-metallic dopant precursor used in Example 3 is sodium dihydrogen phosphate, while the rest is the same as in Example 1, resulting in a phosphorus edge-doped graphene nanoplate electrocatalyst.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that no non-metallic dopant precursor was used in Comparative Example 1, but otherwise it is the same as Example 1, that is, only graphite powder was ball-milled to obtain graphene nanoplate electrocatalyst.

[0079] Example 4

[0080] In Example 4, the electrocatalysts of Examples 1-3 and Comparative Example 1 were subjected to 2e oxidation. - ORR performance testing includes the following steps:

[0081] S1. Take 5.0 mg of electrocatalyst and disperse it in a mixed solution of 490 μL isopropanol / water (volume ratio 1:1) and 10 μL 5 wt.% Nafion solution. Add an appropriate amount of high molecular weight ionic polymer (5 wt.% Nafion solution) as a binder and disperse it by ultrasonic or mechanical means for 1 hour to form a uniform catalyst slurry.

[0082] S2. Take 10 μL of catalyst slurry and coat it evenly on the test disk electrode end face of the rotating ring disk electrode, and let it dry naturally to serve as the working electrode.

[0083] S3. Construct a standard three-electrode electrochemical testing system comprising the aforementioned working electrode, counter electrode (such as a graphite rod), and reference electrode (preferably, an Hg / HgO reference electrode for testing in alkaline electrolyte; and an Ag / AgCl reference electrode for testing in neutral electrolyte). Before formal data acquisition, perform multiple cyclic voltammetry scans on the working electrode within a specific potential window (0 ~ 0.8V vs. RHE in this embodiment) to perform in-situ cleaning and activation of the electrode surface until a stable and consistent electrochemical baseline is obtained.

[0084] S4. In an oxygen-saturated electrolyte environment (preferably, pure oxygen is continuously introduced into the electrolyte for more than 30 minutes to saturate the electrolyte with oxygen, and oxygen is continuously introduced during the test; in this embodiment, the gas flow rate is specifically set to 50 sccm to maintain the oxygen saturation state in the solution and provide sufficient reactants), a preset rotation speed is applied to the rotating ring electrode; in this embodiment, it is specifically set to 1600 rpm.

[0085] S5. The oxygen reduction polarization curve of the working electrode in the reduction potential range is recorded using LSV. The scan rate is specifically set to 10 mV / s during the test to obtain the disk current intensity. A constant anodic oxidation potential is simultaneously applied to the ring electrode. In this embodiment, it is specifically maintained at 1.5 V vs. RHE (relative to the reversible hydrogen electrode) to obtain the corresponding ring current intensity.

[0086] S6. Extract the absolute value of the disk current and the ring current value under steady-state conditions during the test, and combine them with the inherent collection efficiency of the rotating ring-disk electrode system used (the collection efficiency is measured after calibration). N =0.46), based on the law of conservation of mass and Faraday's law, the hydrogen peroxide selectivity (H2O2%) and apparent electron transfer number of the electrocatalyst were quantitatively calculated using equations (1) and (2), respectively. n This serves as the core criterion for judging the two-electron oxygen reduction performance of the electrocatalyst:

[0087]

[0088] In equations (1) and (2), I R and I D These represent the ring current and disk current, respectively. The 2e⁻ under alkaline and neutral conditions was measured. - ORR performance is as follows: Figures 4a-4c and Figures 5a-5c As shown, where, Figure 4a , 4b Figures 4c show the LSV curves, hydrogen peroxide selectivity, and apparent electron transfer number of the electrocatalysts from Examples 1-3 and Comparative Example 1, respectively, under alkaline electrolyte (0.1 M KOH) conditions tested using a rotating ring-disk electrode. Figure 5a , 5b Figures 5 and 5c show the LSV curves, hydrogen peroxide selectivity, and apparent electron transfer number plots obtained by rotating atomic disk electrode testing with the electrocatalyst of Example 1 under two neutral electrolyte conditions (0.1 M Na2SO4 and 0.5 M NaCl simulating seawater). Figures 4a-4c It can be seen that under alkaline conditions (0.1 M KOH), nitrogen doping is most effective in increasing the 2e- content of nonmetallic substrates. - The ORR catalyst exhibits superior activity and selectivity in H2O2 production, particularly maintaining a selectivity of 75% or higher even at high overpotentials (0–0.3 V vs. RHE). In contrast, undoped, S-doped, and P-doped electrocatalysts show minimum H2O2 selectivity of 40–60% within the 0–0.3 V vs. RHE range. Furthermore, from… Figures 4a-4c It can be seen that the onset voltage of the electrocatalysts in Examples 1-3 and Comparative Example 1 is: N-doped (0.766V) = P-doped (0.766V) > S-doped (0.743V) > undoped (0.714V), and the H2O2 selectivity (0V vs RHE to onset voltage) is: N-doped (74.7%~98.3%), S-doped (50.2%~94.2%), P-doped (54.3%~95.2%), undoped (43.7%~96.9%). Furthermore, from... Figures 5a-5c It can be seen that under neutral conditions (0.1 M Na2SO4 and 0.5 M NaCl simulating seawater), the electrocatalyst of Example 1 also maintains good selectivity for H2O2 generation, both favoring 2e. - The pathway involves reducing oxygen to produce H2O2.

[0089] Example 5

[0090] Example 5 tested the electrocatalyst hydrogen peroxide production performance of Examples 1-3 and Comparative Example 1, including the following steps:

[0091] S1. The electrocatalyst is coated onto the surface of a conductive substrate (such as hydrophobic carbon cloth or hydrophobic carbon paper), and after drying and curing, it serves as the working electrode. In this embodiment, the electrocatalyst loading is set to 0.2 mg / cm³. 2 This ensures that the catalytically active sites are fully exposed.

[0092] S2. A compartmentalized electrolytic cell separated by ion exchange membranes (such as proton exchange membranes or anion exchange membranes) is used (in this embodiment, an H-type dual-chamber electrolytic cell, i.e., H-Cell, is used).

[0093] S3. Place the working electrode prepared in S1 in the cathode chamber, the counter electrode in the anode chamber, and supplement it with a reference electrode (preferably, an Hg / HgO reference electrode is used for testing in an alkaline electrolyte; an Ag / AgCl reference electrode is used for testing in a neutral electrolyte) to jointly construct a test circuit for the two-electron oxygen reduction to produce hydrogen peroxide. In this embodiment, the electrolyte used is an alkaline electrolyte (0.1 M KOH).

[0094] S4. Inject equal volumes of electrolyte into the cathode chamber and anode chamber respectively.

[0095] S5. Before the test, pure oxygen is continuously introduced into the electrolyte in the cathode chamber for more than 30 minutes using a gas flow control device to saturate the electrolyte with oxygen. During the test, pure oxygen is continuously introduced into the electrolyte in the cathode chamber. In this embodiment, the gas flow rate is specifically set to 50 sccm to maintain the oxygen saturation state in the solution and provide sufficient reactants.

[0096] S6. Apply a preset constant reduction potential to the working electrode using an electrochemical testing system, perform continuous electrolysis testing using the chronoamperometry method, and record the current-time response curve.

[0097] S7. After electrolysis for the predetermined time (15 minutes in this embodiment), a quantitative electrolyte sample is extracted from the cathode chamber. The extracted electrolyte sample is pre-acidified. In this example, to construct the strongly acidic environment required for the potassium permanganate redox reaction, an appropriate amount of dilute sulfuric acid is added to the extracted electrolyte sample for pre-acidification. Then, a potassium permanganate standard solution of known and accurate concentration is used for titration. When the titrated solution turns slightly red and does not fade within the predetermined time (e.g., 30 seconds), the titration endpoint is determined to have been reached.

[0098] S8. Calculate the amount of H2O2 produced based on the volume of potassium permanganate standard solution consumed. n H2O2 As shown in equation (3), the Faraday current efficiency (FE) of the electrocatalyst in the production of H2O2 was quantitatively calculated by combining the total volume of the electrolyte in the cathode chamber and the total amount of electricity passing through the working electrode during the test. H2O2 ).

[0099]

[0100]

[0101] In equations (3) and (4), C KMnO4 This indicates the concentration of KMnO4 consumed during the titration process; V KMnO4 This indicates the volume of KMnO4 consumed during the titration process; I and t The figures represent the current and time consumed during the electrolysis process, respectively. Under alkaline conditions (0.1 M KOH), the yields and Faraday current efficiencies of the electrocatalysts used in Examples 1-3 and Comparative Example 1 for producing H₂O₂ are shown below. Figure 6 , Figure 7 As shown, the H2O2 yield and Faradaic current efficiency of the electrocatalysts doped with non-metallic elements (Examples 1-3) are higher than those of the undoped electrocatalyst (Comparative Example 1). Furthermore, the electrocatalyst of Example 1 exhibits the highest H2O2 yield (5.76 mol / (g·h)) and Faradaic current efficiency (92%), which is consistent with the aforementioned 2e - The ORR performance test results are consistent.

[0102] The above embodiments illustrate the use of urea, sodium sulfide, and sodium dihydrogen phosphate as precursors for non-metallic dopant elements. In other embodiments, solid powders such as thiourea and ammonium chloride can be used. Alternatively, the solid non-metallic dopant element precursor can be replaced with a gaseous precursor, such as by filling a ball mill jar with a certain pressure of ammonia or hydrogen sulfide gas. The extremely high local energy generated during mechanical bond breaking directly captures and breaks down gas molecules, achieving purer edge gas-phase doping and eliminating the need for subsequent washing away of solid residues. Furthermore, single non-metallic doping can be extended to binary or ternary co-doping (such as NP, NS, or NBF co-doping). Alternatively, by introducing non-metallic elements with greater electronegativity differences (such as adding boric acid or red phosphorus), a "push-pull electron effect" can be constructed at the graphene edge, further breaking the local charge symmetry and approaching the theoretical adsorption energy limit of the two-electron oxygen reduction reaction.

[0103] The reactor in the above embodiments is a ball mill jar, which is a room-temperature ball mill. In other embodiments, the room-temperature ball mill can be improved to a cryogenic mechanical ball mill in a liquid nitrogen environment. This utilizes the brittle fracture characteristics of carbon materials at extremely low temperatures to maximize the "edge / inside" ratio, thereby multiplying the absolute amount of edge doping. Alternatively, a supercritical carbon dioxide or high-pressure fluid-assisted high-shear reactor can be used to replace the traditional steel ball mill. This utilizes the powerful shear force and cavitation effect generated when the fluid releases energy during instantaneous decompression to tear the carbon layer and promote edge reactions in the precursor. This approach is more easily implemented for continuous industrial mass production.

[0104] The embodiments of the present invention solve the following technical problems in existing products or methods:

[0105] 1. Solve the technical problems of high cost of existing precious metal electrocatalysts and poor selectivity of two-electron oxygen reduction in traditional non-metallic carbon-based materials. Among the existing electrocatalysts for the synthesis of hydrogen peroxide based on two-electron oxygen reduction, precious metal catalysts (such as palladium, platinum, and gold) are difficult to apply on a large scale due to their high price and scarcity; while conventional non-metallic carbon materials are prone to four-electron side reactions (producing water) during the catalytic process, resulting in generally low selectivity and yield of hydrogen peroxide, which is difficult to meet the actual production needs.

[0106] 2. Solve the technical problem of decreased conductivity and limited intrinsic catalytic activity in traditional heteroatom-doped carbon materials due to "basal-plane doping". Existing heteroatom doping techniques often dope non-metallic elements (such as nitrogen and sulfur) within the basal plane of carbon materials. This basal-plane doping not only destroys the original conjugated large π-bond structure of graphene, significantly reducing the macroscopic conductivity of the material, but also the basal-plane defects often trigger unfavorable four-electron oxygen reduction reactions, greatly limiting the intrinsic activity and energy conversion efficiency of the catalyst.

[0107] 3. Solve the technical problems of complex preparation processes, severe pollution, and difficulty in large-scale mass production of existing graphene-based electrocatalysts. Traditional graphene and doped graphene preparation processes (such as the Hummers process and subsequent high-temperature liquid-phase reactions) are usually cumbersome and require large amounts of strong acids, strong oxidants, or toxic solvents, easily generating large amounts of difficult-to-treat heavy metals and acidic waste liquids. Such methods are not only costly and polluting, but also difficult to achieve green, low-cost large-scale mass production in industry.

[0108] 4. This invention addresses the technical bottlenecks of traditional hydrogen peroxide production methods, which are ill-suited to modern decentralized, on-demand industrial scenarios and the limited environmental adaptability of existing electrochemical hydrogen peroxide synthesis technologies. Traditional anthraquinone methods for hydrogen peroxide production suffer from complex processes, high energy consumption, and significant organic waste, and the high concentrations of hydrogen peroxide produced pose significant safety and explosion risks during centralized storage and transportation. This invention, through the development of a highly efficient electrocatalyst, overcomes the limitations of traditional centralized production methods, providing a technical pathway for in-situ, efficient, safe, and environmentally adaptable hydrogen peroxide production at ambient temperature and pressure, requiring only water, air (or oxygen), and electricity.

[0109] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative 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 suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. The application of a non-metallic edge-doped graphene nanoplate electrocatalyst in the two-electron oxygen reduction to hydrogen peroxide, characterized in that, The preparation method of the non-metallic edge-doped graphene nanoplate electrocatalyst includes the following steps: (1) Mixed loading: Graphite powder, non-metallic dopant precursor and organic solvent are added to the reactor in a predetermined ratio, mixed evenly and then the reactor is sealed; the organic solvent is anhydrous ethanol; the non-metallic dopant in the non-metallic dopant precursor is N; (2) Mechanical exfoliation and doping: The reaction system of step (1) is subjected to mechanical ball milling to apply a predetermined mechanical shear force to exfoliate the graphite interlayer to form graphene nanoplates, and during the exfoliation process, the non-metallic dopant elements in the non-metallic dopant precursor are simultaneously doped into the edge of the graphene nanoplates. (3) Purification and collection: The mixture after step (2) is collected, washed to remove impurities, and then dried to obtain the non-metallic edge-doped graphene nanoplate electrocatalyst.

2. The application according to claim 1, characterized in that, In step (1), the particle size of the graphite powder is 10-5000 mesh.

3. The application according to claim 1, characterized in that, In step (1), the mass ratio of the graphite powder to the non-metallic dopant precursor is 1: (1~10).

4. The application according to claim 1, characterized in that, In step (1), the reactor is a ball mill jar containing grinding media.

5. The application according to claim 4, characterized in that, The mass ratio of the grinding media to the graphite powder is (50~150):1; the rotation speed of the mechanical ball milling process is 100 rpm to 500 rpm, and the continuous ball milling time is 8~48 hours.

6. The application according to claim 1, characterized in that, In step (3), the specific operation of washing and removing impurities is as follows: sequentially cleaning with anhydrous ethanol, immersing in acid solution, and rinsing with ultrapure water; the acid solution is a 1 M HCl solution.

7. The application according to claim 1, characterized in that, In step (1), the non-metallic dopant precursor is in solid or gaseous state.

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