Preparation of oxygen-containing acid radical modified graphite-based cathode for electro-catalysis hydrogen peroxide synthesis

Abstract

The invention discloses a preparation method of an oxyacid radical modified graphite-based cathode for electro-catalysis hydrogen peroxide synthesis. An oxyacid (sulfuric acid or phosphoric acid) and nitric acid are compounded to form a mixed acid solution, and the graphite-based electrode is subjected to oxyacid radical modification by using the mixed acid solution. The preparation method of the oxygen-containing acid modified graphite-based electrode is simple and low in cost, does not need harsh conditions such as high temperature and the like, and has great industrial and large-scale production potential; the oxygen-containing acid radical modified graphite-based cathode prepared by an acid treatment method is used for reducing oxygen to produce hydrogen peroxide, the yield of the hydrogen peroxide exceeds 21.79 mg.cm <-2 >. H <-1 > and is increased by about 20 times compared with the yield (1.13 mg.cm <-2 >. H <-1 >) of oxygen oxidation by using unmodified original commercial carbon paper, and meanwhile, the highest selectivity of the hydrogen peroxide is up to 97.5%.

Description

Technical Field

[0001] The present invention relates to a method for preparing a graphite-based cathode with high-efficiency electrocatalytic hydrogen peroxide production performance by an acid treatment method, belongs to the field of electrochemistry and inorganic material synthesis, and specifically relates to the preparation of an oxygen-containing acid radical-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis. Background Art

[0002] Hydrogen peroxide (H2O2) is an efficient, clean oxidant and versatile chemical widely used in disinfection, bleaching, environmental remediation, chemical synthesis, and energy, playing an important role in industrial production and daily life. Currently, the industrial production of H2O2 mainly relies on the anthraquinone method, which is complex and costly, accompanied by the formation of a large number of harmful byproducts. Furthermore, H2O2 poses significant safety risks during storage and transportation. Therefore, the development of a green, efficient, and controllable H2O2 synthesis technology has become a key issue that needs to be addressed.

[0003] Electrocatalytic synthesis of H2O2 uses oxygen or water as raw materials and uses electricity to drive the two-electron oxygen reduction reaction (2e - -ORR), realizing an environmentally friendly, efficient and refined method for H2O2 synthesis. Although metal-based catalysts have high selectivity and stability, their high cost limits their application in large-scale H2O2 production. In contrast, graphite-based materials are considered to be ideal candidates for electrocatalytic H2O2 synthesis due to their high chemical stability, good electrical conductivity and low cost. At present, in order to improve the 2e --ORR activity, a variety of modification strategies have been adopted, such as heteroatom doping (N, B, etc.), defect engineering and composite material design. However, nitrogen or boron doping usually involves complex processes such as chemical vapor deposition (CVD) or high-temperature treatment, and defect engineering or composite material design methods often require precise nanostructure control, which increases the difficulty and uncertainty of preparation. Therefore, in practical applications, surface oxygen-containing group functionalization has become a preferred strategy to improve the electrochemical performance of graphite-based catalysts. The introduction of oxygen-containing groups can enhance the hydrophilicity and dispersibility of the material, improve the wettability of the electrolyte, increase the catalytic active sites, promote charge transfer, accelerate electrochemical reactions such as oxygen reduction, and optimize the electronic structure and conductivity, which helps to increase the catalytic performance of the catalyst. When it is applied to electrocatalytic H2O2 synthesis, it is expected to improve its synthesis efficiency. However, existing methods often use more cumbersome processes to functionalize graphite-based catalysts or electrodes with oxygen-containing groups. For example, Chinese patent CN118398752 B proposes a method for modifying carbon fibers. This method involves soaking the carbon felt material in a copper nitrate solution, calcining it after soaking, and then using plasma-enhanced chemical vapor deposition to attach carbonyl and carboxyl groups to the surface of the carbon felt. Finally, vapor-phase carbon deposition is performed to oxidize the carboxyl groups to form carbonyl groups. The modification of the carbonyl group improves the hydrophilicity of the carbon felt electrode material and the electrochemical properties of the electrode material. However, the steps of this method are cumbersome, making it difficult to precisely control the synthesis process of the material, and it is difficult to keep the modification sites and modified areas consistent each time. In addition, the process requires high temperature, plasma and other conditions, which limits its large-scale preparation and practical application. In addition, although the carbon felt electrode prepared by this method has good conductivity and hydrophilicity, the patent does not involve the application of this electrode in electrocatalytic H2O2 synthesis, and it is unknown whether this electrode can help improve the yield and selectivity of H2O2. Summary of the Invention

[0004] In response to the above-mentioned problems, the present invention aims to develop a graphite-based cathode with a simple preparation method, suitable for the electrocatalytic preparation of hydrogen peroxide, and with potential for commercial and large-scale application, so as to improve the yield and selectivity of the electrocatalytic synthesis of H2O2.

[0005] To achieve the above objectives, the present invention prepares a graphite-based cathode from a widely available and low-cost graphite material, which is then placed in a mixed solution of oxygen-containing acid and nitric acid for water bath immersion. This method successfully modifies the graphite-based catalyst with oxygen-containing acid groups (sulfonate groups, phosphate groups), greatly improving its hydrophilicity and electrocatalytic hydrogen peroxide production performance, while exhibiting excellent stability.

[0006] The present invention first provides a method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, comprising the following steps:

[0007] (1) Preparation of mixed acid solution: mixed acid solution is prepared by mixing concentrated nitric acid with oxygen-containing acid, wherein the oxygen-containing acid includes sulfuric acid and / or phosphoric acid;

[0008] (2) Post-treatment of mixed acid: the graphite-based cathode is immersed in the mixed acid solution, and then taken out after constant temperature water bath to obtain an oxygen-containing acid radical modified graphite-based cathode;

[0009] (3) Cleaning of electrode: the oxygen-containing acid radical modified graphite-based cathode obtained in step (2) is cleaned with ultrapure water for 3 times and vacuum dried.

[0010] In an embodiment of the present application, in step (1), the sulfuric acid is concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid is 95% to 98.3%, and the phosphoric acid is concentrated phosphoric acid, and the concentration of the concentrated phosphoric acid is 80% to 85%.

[0011] In an embodiment of the present application, in step (1), the concentration of the concentrated nitric acid is 65% to 68%.

[0012] In an embodiment of the present application, in step (1), the volume ratio of the oxygen-containing acid to the concentrated nitric acid is 1:(0.2-5), preferably 3:1 to 1:3, further preferably 3:1 to 1:1, and more preferably 3:1.

[0013] In an embodiment of the present application, in step (2), the graphite-based cathode is prepared by solution dip coating method.

[0014] In an embodiment of the present application, in step (2), the specific steps for preparing the graphite-based cathode by solution dip coating method are as follows:

[0015] S1, first, the graphite-based substrate is sequentially ultrasonically cleaned in ethanol and deionized water for 5-10 min to remove surface organic contaminants and solvent residues, and then dried in an oven at 50-70℃ for 30-60 min for standby;

[0016] S2, in a beaker, active components and binders are added, and then solvents and surfactants are added. First, stirring is performed for 10-30 min to ensure preliminary mixing, and then ultrasonic dispersion is performed for 30-60 min to ensure uniform dispersion of the active components and binders, thereby forming a stable coating solution;

[0017] S3, the pretreated graphite-based substrate in step S1 is slowly immersed in the coating solution obtained in step S2 for 20-40 s to ensure uniform adsorption of the active material on the fiber surface, and then pulled up at a speed of 0.5-1.5 mm / s to obtain a dried graphite-based cathode.

[0018] In one embodiment of the present invention, the graphite-based substrate in step S1 includes any one of carbon fiber paper (CFP), carbon cloth (CC), and carbon fiber felt (CFF).

[0019] In one embodiment of the present invention, the solvent in step S2 includes any one of ethanol, acetone, and N-methylpyrrolidone.

[0020] In one embodiment of the present invention, the surfactant in step S2 includes any one of Triton X-100, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP).

[0021] In one embodiment of the present invention, the volume ratio of the solvent to the surfactant in step S2 is 50:1 to 100:1.

[0022] In one embodiment of the present invention, the active component in step S2 includes any one or more of carbon fiber, graphite, and carbon black.

[0023] In one embodiment of the present invention, the diameter of the carbon fiber is 5-8 μm, the thickness of the graphite is 10-15 nm, and the particle size of the carbon black is 15-25 nm.

[0024] In one embodiment of the present invention, the binder in step S2 includes any one or more of polytetrafluoroethylene (PTFE), perfluorosulfonic acid polymer (Nafion), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN).

[0025] In one embodiment of the present invention, the mass ratio of the active component to the binder in step S2 is 90-96:4-10.

[0026] In one embodiment of the present invention, the concentration of the active component in the mixed solution (total mass of the slurry) in step S2 is 12 to 30 wt.%.

[0027] In one embodiment of the present invention, the drying in step S3 is firstly natural drying at room temperature for 10 to 30 minutes, and then drying at 60° C. to 80° C. for 30 minutes.

[0028] In one embodiment of the present invention, the time of the constant temperature water bath in step (2) is 2 to 12 hours, preferably 6 to 10 hours, more preferably 7 to 9 hours, and the water bath temperature is 50 to 65°C.

[0029] In one embodiment of the present invention, the vacuum drying time in step (3) is 4 to 8 hours, and the drying temperature is 60 to 80°C.

[0030] The present invention also provides an oxygen-containing acid radical-modified graphite-based cathode prepared according to the above method.

[0031] The present invention also provides an application of an oxygen-containing acid radical-modified graphite-based cathode in the electrocatalytic preparation of hydrogen peroxide.

[0032] In one embodiment of the present invention, the application includes using the above-mentioned graphite-based cathode modified with oxygen-containing acid radicals as the cathode, and using Ag / AgCl and Pt sheets as the reference electrode and counter electrode, respectively, to carry out an electrocatalytic oxygen reduction reaction in a dual-cell electrolytic cell containing an electrolyte solution.

[0033] In one embodiment of the present invention, the electrolyte solution is Na2SO4 or K2SO4 solution.

[0034] In one embodiment of the present invention, the concentration of the electrolyte solution is 0.1 to 0.75 mol / L, preferably 0.5 mol / L.

[0035] In one embodiment of the present invention, the voltage of the electrocatalytic oxygen reduction reaction is -0.2 to -0.6 V vs. Ag / AgCl, preferably -0.4 V vs. Ag / AgCl.

[0036] Beneficial effects:

[0037] 1. The present invention selects an oxygen-containing acid (sulfuric acid or phosphoric acid) and nitric acid to form a mixed acid solution, and uses the mixed acid solution to modify the graphite-based electrode with oxygen-containing acid radicals. The preparation method of the oxygen-containing acid-modified graphite-based electrode is simple, low-cost, does not require harsh conditions such as high temperature, and has great potential for industrial and large-scale production.

[0038] 2. The present invention obtains an oxygen-containing acid-modified graphite-based cathode with better electrochemical performance by optimizing the ratio of oxygen-containing acid to nitric acid, the graphite-based electrode substrate, the time of electrode modification and other parameters. The electrode not only has good electrochemical performance, but also has good hydrophilic properties.

[0039] 3. The graphite-based cathode modified by the acid treatment method prepared by the present invention reduces oxygen to produce hydrogen peroxide, and the yield of hydrogen peroxide exceeds 21.79 mg·cm -2 ·h -1 , which is significantly higher than the yield of oxygen oxidation by unmodified original commercial carbon paper (1.13 mg cm -2 ·h -1 ) increased by nearly 20 times, while the highest selectivity of hydrogen peroxide was as high as 97.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1This is a photograph of commercial carbon paper modified with sulfonic acid groups prepared in the present invention.

[0041] Figure 2 A photograph of a dual-cell electrolysis cell separated by a proton exchange membrane for synthesizing hydrogen peroxide utilized in the present invention.

[0042] Figure 3 This is the XPS graph of the sulfonic acid group-modified carbon paper electrode prepared in Example 2.

[0043] Figure 4 This is the FTIR spectrum of the phosphate-modified carbon paper electrode prepared in Example 14.

[0044] Figure 5 The yield and selectivity of electrocatalytic hydrogen peroxide production of the sulfonic acid group-modified carbon paper electrode prepared in Example 2.

[0045] Figure 6 The yield and selectivity of electrocatalytic hydrogen peroxide production of the phosphate-modified carbon paper electrode prepared in Example 11.

[0046] Figure 7 The content of hydrogen peroxide produced by the sulfonic acid group-modified carbon paper electrode prepared in Examples 1 to 5 during electrocatalysis for 3 hours.

[0047] Figure 8 The content of hydrogen peroxide produced by the phosphate-modified carbon paper electrode prepared in Examples 10 to 15 during electrocatalysis for 3 hours.

[0048] Figure 9 The content of hydrogen peroxide produced by the electrodes with different carbon fiber substrates modified with sulfonic acid groups prepared in Examples 2, 6 and 7 after electrocatalysis for 3 hours.

[0049] Figure 10 The content of hydrogen peroxide produced by the electrodes based on different carbon fiber substrates modified with phosphate groups prepared in Examples 11, 16 and 17 after electrocatalysis for 3 hours.

[0050] Figure 11 This is the It curve of the sulfonic acid group-modified carbon paper electrode prepared in Example 2 after running at a voltage of -0.41Ag / AgCl for 100 h.

[0051] Figure 12 The oxygen reduction activity of the electrodes prepared by treating the carbon paper substrate with a mixture of different types of acids prepared in Example 2 and Comparative Examples 1 to 3 and nitric acid to produce hydrogen peroxide was analyzed.

[0052] Figure 13 The content, yield and selectivity of hydrogen peroxide produced by the sulfonic acid-modified carbon paper electrodes prepared in Examples 2 and 8-9 with different treatment times during electrocatalysis for 3 hours. DETAILED DESCRIPTION

[0053] The application will be further described in conjunction with specific examples and comparative examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. In addition, it should be understood that after reading the content taught by the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims.

[0054] The electrocatalytic activity provided by the application is tested by the following method: the production process of H2O2 is carried out in a customized H-cell equipped with a three-electrode system. Acid-treated commercial carbon paper is used as the working electrode, Ag / AgCl and Pt sheet are used as the reference electrode and the counter electrode, respectively. The concentration of H2O2 is determined by the traditional cerium sulfate titration method, which relies on the reduction of yellow Ce 4+ solution to colorless Ce 3+ solution by H2O2, and the consumed Ce 4+ concentration is quantified by ultraviolet-visible spectrophotometry (peaking at about 319 nm, and the concentration of hydrogen peroxide is calculated according to the peak intensity at this position according to the Lambert-Beer law). (Lu Z, Chen G, Siahrostami S, et al. High-efficiency oxygen reduction to hydrogen peroxide catalysed by oxidized carbon materials [J]. Nature Catalysis, 2018, 1(2): 156-162.).

[0055] Example 1:

[0056] A preparation method of an oxygen-containing acid radical modified graphite-based cathode for electrocatalytic synthesis of hydrogen peroxide, comprising the following steps:

[0057] (1) Preparation of graphite-based electrode by solution coating method: first, carbon paper (YLS-30T, 20x20x0.5mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Subsequently, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant was added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) was sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a speed of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0058] (2) Preparation of mixed acid solution: 10 mL of concentrated sulfuric acid with a mass fraction of 98.3% was mixed with 1 mL of concentrated nitric acid with a mass fraction of 68%;

[0059] (3) Post-mixed acid treatment: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 9 h;

[0060] (4) Post-treatment electrode cleaning: after the water bath, the electrode was cleaned with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a sulfonic acid-modified carbon paper electrode (CFP).

[0061] Example 2:

[0062] The difference between Example 2 and Example 1 is that the volume of concentrated sulfuric acid in step (2) is 3 mL.

[0063] A method for preparing an oxygen-containing acid group-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, comprising the following steps:

[0064] (1) Preparation of graphite-based electrode by solution coating method: first, the carbon paper (YLS-30T, 20x20x0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0065] (2) Preparation of mixed acid solution: Mix 3 mL of 98.3% concentrated sulfuric acid with 1 mL of 68% concentrated nitric acid;

[0066] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0067] (4) Electrode cleaning after treatment: After the water bath, take it out and wash it with ultrapure water three times. Finally, dry it in a vacuum oven at 60°C for 4 h to obtain a sulfonic acid group-modified carbon paper electrode.

[0068] Example 3

[0069] The difference between Example 3 and Example 1 is that the volume of concentrated sulfuric acid in step (2) is 1 mL.

[0070] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0071] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0072] (2) Preparation of mixed acid solution: Mix 1 mL of 98.3% concentrated sulfuric acid and 1 mL of 68% concentrated nitric acid;

[0073] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0074] (4) Electrode cleaning after treatment: After the water bath, take it out and wash it with ultrapure water three times. Finally, dry it in a vacuum oven at 60°C for 4 h to obtain a sulfonic acid group-modified carbon paper electrode.

[0075] Example 4

[0076] The difference between Example 4 and Example 1 is that the volume of concentrated sulfuric acid in step (2) is 1 mL, and the volume of concentrated nitric acid is 3 mL.

[0077] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0078] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Then, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant were added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) were sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a speed of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0079] (2) Preparation of mixed acid solution: 1 mL of concentrated sulfuric acid with a mass fraction of 98.3% was mixed with 3 mL of concentrated nitric acid with a mass fraction of 68%;

[0080] (3) Post-mixed acid treatment: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 9 h;

[0081] (4) Post-treatment electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a sulfonic acid group modified carbon paper electrode.

[0082] Example 5

[0083] The difference between Example 5 and Example 1 is that in step (2), the volume of concentrated sulfuric acid is 1 mL and the volume of concentrated nitric acid is 6 mL.

[0084] A method for preparing an oxygen-containing acid group modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, comprising the following steps:

[0085] (1) Preparation of graphite-based electrode by solution coating method: first, the carbon paper (YLS-30T, 20x20x0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0086] (2) Preparation of mixed acid solution: Mix 1 mL of 98.3% concentrated sulfuric acid with 6 mL of 68% concentrated nitric acid;

[0087] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0088] (4) Electrode cleaning after treatment: After the water bath, take it out and wash it with ultrapure water three times. Finally, dry it in a vacuum oven at 60°C for 4 h to obtain a sulfonic acid group-modified carbon paper electrode.

[0089] Example 6

[0090] The difference between Example 6 and Example 2 is that the substrate of the graphite-based cathode used is carbon cloth (W1S1011, 20×20×0.5mm 3 ).

[0091] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0092] (1) Preparation of graphite-based electrodes by solution coating: First, carbon cloth (W1S1011, 20×20×0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0093] (2) Preparation of mixed acid solution: Mix 3 mL of 98.3% concentrated sulfuric acid with 1 mL of 68% concentrated nitric acid;

[0094] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0095] (4) Electrode cleaning after treatment: After the water bath is finished, the electrode is taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60°C for 4 h to obtain a sulfonic acid group-modified carbon cloth electrode (CC).

[0096] Example 7

[0097] The difference between Example 7 and Example 2 is that the substrate of the graphite-based cathode used is carbon fiber felt (GraphiteFelt, 20×20×0.5mm 3 ).

[0098] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0099] (1) Preparation of graphite-based electrodes by solution coating: First, carbon fiber felt (Graphite Felt, 20×20×0.5mm 3) for pretreatment to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0100] (2) Preparation of mixed acid solution: Mix 3 mL of 98.3% concentrated sulfuric acid with 1 mL of 68% concentrated nitric acid;

[0101] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0102] (4) Electrode cleaning after treatment: After the water bath is finished, the electrode is taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a sulfonic acid group-modified carbon cloth electrode (CFF).

[0103] Example 8

[0104] The difference between Example 8 and Example 2 is that the water bath time in step (3) is 6 hours.

[0105] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0106] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Subsequently, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant was added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) was sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a speed of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0107] (2) Preparation of mixed acid solution: 3 mL of concentrated sulfuric acid with a mass fraction of 98.3% was mixed with 1 mL of concentrated nitric acid with a mass fraction of 68%;

[0108] (3) Post-mixed acid treatment: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 6 h;

[0109] (4) Post-treatment electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a sulfonic acid group modified carbon cloth electrode (CFP).

[0110] Example 9:

[0111] The difference between Example 9 and Example 2 is that the water bath time in step (3) is 12 h.

[0112] A method for preparing an oxygen-containing acid group modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, comprising the following steps:

[0113] (1) Preparation of graphite-based electrode by solution coating method: first, the carbon paper (YLS-30T, 20x20x0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0114] (2) Preparation of mixed acid solution: Mix 3 mL of 98.3% concentrated sulfuric acid with 1 mL of 68% concentrated nitric acid;

[0115] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 12 h;

[0116] (4) Electrode cleaning after treatment: After the water bath is finished, the electrode is taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60°C for 4 h to obtain a sulfonic acid group-modified carbon cloth electrode (CFP).

[0117] Example 10

[0118] The difference between Example 10 and Example 1 is that in step (2), 10 mL of concentrated phosphoric acid with a mass fraction of 85% is used instead of concentrated sulfuric acid.

[0119] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0120] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Subsequently, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant was added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) was sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a speed of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0121] (2) Preparation of mixed acid solution: 10 mL of 85% concentrated phosphoric acid was mixed with 1 mL of 68% concentrated nitric acid;

[0122] (3) Mixed acid post-processing: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 9 h;

[0123] (4) Post-processing electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphoric acid-based modified carbon cloth electrode (CFP).

[0124] Example 11

[0125] The difference between Example 11 and Example 10 is that the amount of concentrated phosphoric acid added is 3 mL.

[0126] A method for preparing an oxygen-containing acid group modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, comprising the following steps:

[0127] (1) Solution coating method to prepare graphite-based electrode: first, the carbon paper (YLS-30T, 20x20x0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0128] (2) Preparation of mixed acid solution: Mix 3 mL of 85% concentrated phosphoric acid with 1 mL of 68% concentrated nitric acid;

[0129] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0130] (4) Electrode cleaning after treatment: After the water bath, the electrode was taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphate-modified carbon cloth electrode (CFP).

[0131] Example 12

[0132] The difference between Example 12 and Example 10 is that the amount of concentrated phosphoric acid added is 1 mL.

[0133] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0134] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Subsequently, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant was added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) was sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a rate of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0135] (2) Preparation of mixed acid solution: 1 mL of 85% concentrated phosphoric acid and 1 mL of 68% concentrated nitric acid were mixed;

[0136] (3) Mixed acid post-treatment: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 9 h;

[0137] (4) Post-treatment electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphoric acid-modified carbon cloth electrode (CFP).

[0138] Example 13

[0139] Example 13 differs from Example 10 in that the amount of concentrated phosphoric acid added is 1 mL and the amount of concentrated nitric acid added is 3 mL. A method for preparing an oxygen-containing acid group-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis includes the following steps:

[0140] (1) Preparation of graphite-based electrode by solution coating method: first, the carbon paper (YLS-30T, 20x20x0.5mm 3) was performed to ensure its surface clean and conducive to coating adhesion. The carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Subsequently, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant was added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) was sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a rate of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0141] (2) Preparation of mixed acid solution: 1 mL of 85% concentrated phosphoric acid was mixed with 3 mL of 68% concentrated nitric acid;

[0142] (3) Mixed acid post-processing: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 9 h;

[0143] (4) Post-processing electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphoric acid group modified carbon cloth electrode (CFP).

[0144] Example 15

[0145] Example 15 differs from Example 10 in that the amount of concentrated phosphoric acid added is 1 mL and the amount of concentrated nitric acid added is 6 mL. A method for preparing an oxygen-containing acid group modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis includes the following steps:

[0146] (1) Preparation of graphite-based electrode by solution coating method: First, the carbon paper (YLS-30T, 20x20x0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0147] (2) Preparation of mixed acid solution: Mix 1 mL of 85% concentrated phosphoric acid with 6 mL of 68% concentrated nitric acid;

[0148] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0149] (4) Electrode cleaning after treatment: After the water bath, the electrode was taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphate-modified carbon cloth electrode (CFP).

[0150] Example 16

[0151] The difference between Example 16 and Example 11 is that the substrate of the graphite-based cathode used is carbon cloth (W1S1011, 20×20×0.5 mm 3 ).

[0152] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0153] (1) Preparation of graphite-based electrodes by solution coating: First, carbon cloth (W1S1011, 20×20×0.5mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0154] (2) Preparation of mixed acid solution: Mix 3 mL of 85% concentrated phosphoric acid and 1 mL of 68% concentrated nitric acid;

[0155] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0156] (4) Electrode cleaning after treatment: After the water bath, the electrode was taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphate-modified carbon cloth electrode (CC).

[0157] Example 17

[0158] The difference between Example 16 and Example 11 is that the substrate of the graphite-based cathode used is carbon fiber felt (Graphite Felt, 20×20×0.5 mm 3 ).

[0159] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0160] (1) Preparation of graphite-based electrodes by solution coating: First, carbon fiber felt (Graphite Felt, 20×20×0.5mm 3) for pretreatment to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL of ethanol and 20mL of deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL of acetone and 0.16mL of Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg of carbon black (EC 600JD) and 0.04mL of PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0161] (2) Preparation of mixed acid solution: Mix 3 mL of 85% concentrated phosphoric acid and 1 mL of 68% concentrated nitric acid;

[0162] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 9 h;

[0163] (4) Electrode cleaning after treatment: After the water bath, the electrode was taken out and washed with ultrapure water three times, and finally dried in a vacuum oven at 60 °C for 4 h to obtain a phosphate-modified carbon cloth electrode (CFF).

[0164] Comparative Example 1

[0165] The difference between Comparative Example 1 and Example 2 is that step (2) does not contain concentrated sulfuric acid.

[0166] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0167] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0168] (2) Preparation of acid solution: 4 mL of 68% concentrated nitric acid;

[0169] (3) Acid post-treatment: immerse the graphite-based cathode in a nitric acid solution and keep it in a constant temperature water bath at 60 °C for 6 h;

[0170] (4) Electrode cleaning after treatment: After the water bath, take it out and wash it with ultrapure water three times, and finally dry it in a vacuum oven at 60°C for 4 h.

[0171] Comparative Example 2

[0172] The difference between Comparative Example 2 and Example 2 is that in step (2), 3 mL of 30% by mass hydrogen peroxide is used instead of concentrated sulfuric acid.

[0173] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0174] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) to ensure that its surface is clean and conducive to coating adhesion. The carbon paper was ultrasonically cleaned in 20mL ethanol and 20mL deionized water for 5 minutes respectively to remove surface organic pollutants and solvent residues, and then dried in a 60°C oven for 30 minutes for use. Subsequently, 8mL acetone and 0.16mL Triton X-100 surfactant were added to the beaker and stirred for 10 minutes to ensure preliminary uniform mixing. Next, 1mg carbon black (EC-600JD) and 0.04mL PTFE (4wt.%) were added in sequence and ultrasonically dispersed for 30 minutes to ensure that the active components, surfactants, and binders were evenly dispersed to form a stable coating solution. Subsequently, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30s and then pulled at 1mm / s. After coating, the sample was first dried naturally at room temperature for 10 minutes, and then dried in a vacuum oven at 60°C for 30 minutes to enhance the adhesion of the coating to prepare a graphite-based cathode.

[0175] (2) Preparation of mixed acid solution: Mix 3 mL of 30% hydrogen peroxide with 1 mL of 68% concentrated nitric acid;

[0176] (3) Mixed acid post-treatment: immerse the graphite-based cathode in a mixed acid solution and keep it in a constant temperature water bath at 60 °C for 6 h;

[0177] (4) Electrode cleaning after treatment: After the water bath, take it out and wash it with ultrapure water three times, and finally dry it in a vacuum oven at 60°C for 4 h.

[0178] Comparative Example 3

[0179] The difference between Comparative Example 3 and Example 2 is that in step (2), 3 mL of hydrochloric acid with a mass fraction of 36% is used instead of concentrated sulfuric acid.

[0180] A method for preparing an oxoacid-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis comprises the following steps:

[0181] (1) Preparation of graphite-based electrodes by solution coating: First, carbon paper (YLS-30T, 20×20×0.5 mm 3) Pretreatment was performed to ensure its surface clean and conducive to coating adhesion. Carbon paper was sequentially cleaned in 20 mL ethanol and 20 mL deionized water for 5 min each by ultrasonic, to remove surface organic contaminants and solvent residues, and then dried in a 60 °C oven for 30 min for standby. Then, 8 mL of acetone, 0.16 mL of Triton X-100 surfactant were added in a beaker, stirred for 10 min to ensure initial mixing uniformity. Next, 1 mg of carbon black (EC-600JD), 0.04 mL of PTFE (4 wt.%) were sequentially added and ultrasonically dispersed for 30 min to ensure uniform dispersion of active components, surfactants, and binders, forming a stable coating solution. Then, the pretreated carbon paper substrate was slowly immersed in the coating solution for 30 s, and then pulled out at a rate of 1 mm / s. After coating, the sample was naturally dried at room temperature for 10 min, and then dried in a vacuum oven at 60 °C for 30 min to enhance the adhesion of the coating, to prepare a graphite-based cathode.

[0182] (2) Preparation of mixed acid solution: 3 mL of 36% hydrochloric acid and 1 mL of 68% concentrated nitric acid were mixed;

[0183] (3) Post-mixed acid treatment: the graphite-based cathode was immersed in the mixed acid solution and kept in a constant temperature water bath at 60 °C for 6 h;

[0184] (4) Post-treatment electrode cleaning: after the water bath, the electrode was washed with ultrapure water for 3 times, and finally dried in a vacuum oven at 60 °C for 4 h.

[0185] Application example:

[0186] A method for electrocatalytic synthesis of hydrogen peroxide based on oxygen-containing acid group modified graphite-based cathode, comprising the following steps:

[0187] In a double-cell electrolytic cell separated by a proton exchange membrane as shown in Figure 2 , the oxygen-containing acid group modified graphite-based cathode was used as the cathode, Ag / AgCl and Pt sheet were used as the reference electrode and the counter electrode respectively, and 0.5 M sodium sulfate was used as the electrolyte solution. The synthesis of H2O2 from oxygen was carried out under the condition of voltage -0.41 Ag / AgCl.

[0188] Results analysis

[0189] Figure 3 and Figure 4 XPS and FTIR spectra of the sulfonate-modified carbon paper cathode and the phosphate-modified carbon paper cathode prepared in Example 2 and Example 11 respectively, proving that the sulfonic groups and phosphate groups are successfully modified on the surface of the graphite-based electrode.

[0190] Figure 5 and Figure 6The electrocatalytic hydrogen peroxide production and selectivity of the sulfonate-modified carbon paper cathode and phosphate-modified carbon paper cathode prepared in Example 2 and Example 11 respectively. Figure 5 As can be seen from the figure, the sulfonate-modified carbon paper electrode produces up to 120 mM of H2O2 after the catalytic reaction, with a H2O2 selectivity of over 85%. The phosphate-modified carbon paper electrode, on the other hand, produces up to 90 mM of H2O2 after the catalytic reaction, with a H2O2 selectivity of over 80%.

[0191] Figure 7 The content of hydrogen peroxide produced by electrocatalysis of sulfonic acid group modified carbon paper electrode for 3h under different ratios of sulfuric acid and nitric acid prepared in Examples 1 to 5. Figure 7 It can be seen that as the ratio of sulfuric acid and nitric acid decreases, the yield and selectivity of H2O2 both show a trend of first increasing and then decreasing. When the ratio of the two is 3:1, the prepared sulfonic acid group-modified carbon paper electrode has the highest selectivity and yield for oxygen reduction to produce hydrogen peroxide. Figure 8 The content of hydrogen peroxide produced by the phosphate-modified carbon paper electrode under different ratios of phosphoric acid and nitric acid in 3 hours of electrocatalysis is given. The production and selectivity of H2O2 also show a trend of first increasing and then decreasing with the decrease of the proportion of phosphoric acid.

[0192] Effect of carbon fiber substrate on the content of hydrogen peroxide produced by sulfonic acid group-modified graphite-based electrode electrocatalysis for 3h Figure 9 (sulfonic acid group) and 10 (phosphoric acid group). It can be seen from the figure that the production of hydrogen peroxide is the highest when carbon paper is used as the substrate.

[0193] The electrochemical performance of the sulfonic acid group-modified carbon paper electrode was tested. Figure 11 The results showed that Example 2 operated at a voltage of -0.41Ag / AgCl for 100 hours. Throughout the test, the current was stable, demonstrating the strong stability of the catalyst.

[0194] Figure 12 The results show the yield and selectivity of hydrogen peroxide produced over 3 hours using carbon paper electrodes treated with a mixture of different acids and nitric acid (data sets 1, 2, 3, and 4 correspond to Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively). The graph shows that the carbon paper electrode treated with a mixture of phosphoric acid and nitric acid produced the best hydrogen peroxide, more than doubling the yield of hydrogen peroxide produced by the carbon paper electrode treated with nitric acid alone.

[0195] Figure 13 The yield and selectivity of hydrogen peroxide produced over a 3-hour electrocatalytic reaction using a sulfonic acid-modified carbon paper electrode with different treatment times are shown. As can be seen from the figure, hydrogen peroxide production increases significantly as treatment time increases from 6 to 9 hours, but decreases sharply as treatment time continues to increase.

[0196] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing an oxygen-containing acid radical-modified graphite-based cathode for electrocatalytic hydrogen peroxide synthesis, characterized in that: The following steps are involved: (1) Preparation of a mixed acid solution: Mix an oxygen-containing acid with concentrated nitric acid to prepare a mixed acid solution, wherein the oxygen-containing acid includes sulfuric acid and / or phosphoric acid; (2) Mixed acid post-treatment: immersing the graphite-based cathode in a mixed acid solution and taking it out after a constant temperature water bath to obtain an oxygen-containing acid radical-modified graphite-based cathode; (3) Electrode cleaning: The graphite-based cathode modified with oxygen-containing acid radicals obtained in step (2) was cleaned three times with ultrapure water and vacuum dried.

2. The preparation method according to claim 1, characterized in that In step (1), the sulfuric acid is concentrated sulfuric acid with a concentration of 95% to 98.3%, the phosphoric acid is concentrated phosphoric acid with a concentration of 80% to 85%, and the concentrated nitric acid has a concentration of 65% to 68%.

3. The preparation method according to claim 1, characterized in that In step (1), the volume ratio of the oxygen-containing acid to concentrated nitric acid is 1:0.2-5.

4. The preparation method according to claim 1, characterized in that In step (2), the graphite-based cathode is prepared by solution dipping method, and the specific steps are as follows: S1. First, ultrasonically clean the graphite substrate in ethanol and deionized water for 5 to 10 minutes respectively to remove surface organic pollutants and solvent residues, and then dry it in an oven at 50 to 70°C for 30 to 60 minutes before use; S2. Add the active ingredient and binder to a beaker, followed by the solvent and surfactant. Stir for 10 to 30 minutes to ensure initial uniform mixing to obtain a mixed solution. Then, ultrasonically disperse for 30 to 60 minutes to ensure uniform dispersion of the active ingredient and binder to form a stable coating solution. S3. Slowly immerse the graphite-based substrate pretreated in step S1 into the coating solution obtained in step S2 for 20 to 40 seconds to ensure that the active material is evenly adsorbed on the fiber surface, and then pull it at a speed of 0.5 to 1.5 mm / s and dry it to obtain a graphite-based cathode.

5. The preparation method according to claim 4, characterized in that The graphite-based substrate described in step S1 includes any one of carbon fiber paper, carbon cloth, and carbon fiber felt.

6. The preparation method according to claim 4, characterized in that The solvent described in step S2 includes any one of ethanol, acetone, and N-methylpyrrolidone, and the surfactant includes any one of Triton X-100, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone. The volume ratio of the solvent and the surfactant in step S2 is 50:1 to 100:

1.

7. The preparation method according to claim 4, characterized in that The active component in step S2 includes any one or more of carbon fiber, graphite, and carbon black, and the binder includes any one or more of polytetrafluoroethylene, perfluorosulfonic acid polymer, polyvinylidene fluoride, and polyacrylonitrile. The mass ratio of the active component to the binder is 90-96:4-10, and the mass concentration of the active component in the mixed solution is 12-30%.

8. The preparation method according to claim 1, characterized in that The time of the constant temperature water bath in step (2) is 2 to 12 hours, the time of the vacuum drying in step (3) is 4 to 8 hours, and the drying temperature is 60 to 80°C.

9. An oxygen-containing acid radical-modified graphite-based cathode prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the graphite-based cathode modified with oxygen-containing acid radicals according to claim 9 in the electrocatalytic preparation of hydrogen peroxide.

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