A cationic compound modified carbon material for electro-synthesis of hydrogen peroxide, a solid-state cationic layer modified carbon electrode, and a preparation method and application thereof

Abstract

The application belongs to the technical field of electrochemical catalysis and hydrogen peroxide preparation, and particularly relates to a cationic compound modified carbon material for electro-synthesis of hydrogen peroxide, a solid-state cationic layer modified carbon electrode and a preparation method and application thereof. The carbon material is assembled by a carbon carrier with oxygen-containing groups or defects and a cationic surfactant or ionomer through intermolecular electrostatic assembly. The carbon electrode is composed of a catalytic carbon layer and a cationic polymer layer, the carbon catalytic layer can use the above-mentioned material or unmodified commercial carbon black, and the solid-state cationic layer is an ionomer containing a positive charge group. By constructing a cationic modified acidic charged catalytic interface, the proton transfer and OOH adsorption strength are regulated, and the O-O bond rupture under high current density is inhibited, so that the industrial-grade current density (up to 1.125 A cm ‑2 ) is realized in high-salt or seawater to efficiently synthesize H2O2, the Faraday efficiency is 80%~100, the stable operation time is 40~200 hours, the production cost is as low as 0.68~1.2 dollars / kg, no noble metal is needed, and the method has industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis and hydrogen peroxide preparation technology, specifically involving a cation-modified carbon material and a solid cation-layer modified carbon electrode for the electrosynthesis of hydrogen peroxide, as well as their preparation method and application. By controlling the acidic charged interface through cation modification, hydrogen peroxide can be electrosynthesized in seawater or high-salt wastewater at industrial-grade current density. Technical Background

[0002] Hydrogen peroxide (H₂O₂) is an environmentally friendly strong oxidant widely used in disinfection, wastewater treatment, and lithium battery recycling. Currently, the anthraquinone process is the main industrial method for producing H₂O₂. This method is energy-intensive, generates hazardous waste, and relies on centralized plants and complex storage and transportation facilities. The electrochemical two-electron oxygen reduction reaction (2e⁻² ... - ORR (Organic Oxygen Resin) can directly synthesize H2O2 using water and oxygen at room temperature and pressure, and is a highly promising decentralized, in-situ production technology. However, existing 2e - The ORR system still faces many prominent problems: (1) High performance 2e - ORR electrosynthesis of H2O2 is highly dependent on high concentrations of alkaline solution (such as KOH), but H2O2 is easily decomposed under alkaline conditions, making product separation and purification difficult, and KOH is costly and difficult to recover; (2) H2O2 still has good stability at temperatures up to 90°C under acidic conditions, but acidic 2e - ORR catalyst materials mostly rely on precious metals, and their catalytic activity and selectivity are significantly lower than those of alkaline systems; (3) Although using seawater or high-salt wastewater as an electrolyte can avoid additional electrolyte costs, the pH increase near the cathode under high current density will lead to Ca 2+ / Mg 2+ Precipitation, clogging of electrodes; (4) At industrial-grade current densities, enrichment of hydrogen ions at the electrochemical interface will enhance interaction with 2e - ORR intermediates The binding of the OOH intermediate leads to the breaking of the OO bond, thereby significantly reducing the selectivity of H2O2. Therefore, developing an H2O2 electrosynthesis technology that can achieve high current density, high selectivity, and long-term stability in acidic, high-salt, or seawater media has important application prospects. Summary of the Invention

[0003] This invention aims to solve the existing 2e - ORR electrosynthesis of H2O2 technology faces technical challenges such as low current density, poor selectivity, and easy precipitation of calcium and magnesium in acidic or seawater media.

[0004] According to a first aspect of the present invention, a cationic compound-modified carbon material for the electrosynthesis of hydrogen peroxide is provided, comprising a carbon support and a cationic modifier assembled on the surface of the carbon support by electrostatic interaction, wherein the adsorption amount is 1% to 10% of the mass of the carbon material;

[0005] The carbon support is a carbon material that has undergone oxidation, thermal reduction, or defect treatment. The carbon material is selected from at least one of the following: oxidized single-walled carbon nanotubes, oxidized multi-walled carbon nanotubes, oxidized graphene, oxidized carbon black, defective single-walled carbon nanotubes, defective multi-walled carbon nanotubes, defective graphene, defective carbon black, porous carbon, and biomass-derived carbon. The cationic modifier is a cationic surfactant or a cationic ionomer.

[0006] Based on the above technical solution, the cationic surfactant is a polymer having a hydrophobic tail with a C8~C22 alkyl group and a hydrophilic head with a quaternary ammonium salt, a pyridinium salt, or an imidazolium salt. The general formula of the quaternary ammonium salt is R1R2R3R4N. + X - R1, R2, R3, and R4 are independently selected from at least one of methyl and C8-C22 straight-chain alkyl groups, X - The halide ion is Cl. - or Br - ; The general formula for the pyridinium salt is [Py-R]. + X - Where Py is a pyridine ring (C5H5N), R is selected from at least one of methyl and C8-C22 straight-chain alkyl groups, and X - For Cl - or Br - ; The general formula of the imidazolium salt is [R1ImR2]. + X - Where Im is an imidazole ring (C3H4N2), R1 and R2 are independently selected from at least one of methyl and C8-C22 straight-chain alkyl groups, X - For Cl - or Br - .

[0007] Based on the above technical solution, the cationic modifier is selected from at least one of hexadecyltrimethylammonium bromide, octyltrimethylammonium bromide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, polyarylene quinine (Quin), XA9, and imidazolyl functionalized polymer (Fum).

[0008] Based on the above technical solution, the cationic ionomer refers to a polymer chain with positively charged groups covalently bonded to it. These positively charged groups are usually composed of counterions (such as chloride ions, Cl- ions, etc.). - bromide ions, Br - , sulfate, SO4² - These are a class of polymeric electrolytes that maintain charge balance. These compounds are characterized by a hydrophobic backbone and ionic groups. The hydrophobic backbone refers to one or more of polyolefins, polystyrene, and poly(p-phenylene), while the positively charged groups refer to one or more of quaternary ammonium salts, pyridinium, and imidazodium; preferably, one or more of imidazodium-functionalized polymers, quaternary ammonium poly(N-methyl-piperidine-co-p-terphenyl), quaternized polystyrene, and polyaromatic quinine compounds.

[0009] Based on the above technical solution, the cationic ionomer is a polymer with positively charged groups, preferably an imidazolium functionalized polymer, a quaternary ammonium poly(N-methyl-piperidine-co-p-terphenyl), a quaternized polystyrene, or a polyaromatic quinine compound.

[0010] Based on the above technical solution, the oxidation specifically involves: using 100-1000 mL of nitric acid with a concentration of 20-70 wt% to oxidize 1-100 g of carbon material, and then refluxing at 80-140℃ for 3-14 hours to obtain oxidized carbon material.

[0011] Based on the above technical solution, the heat reduction treatment specifically involves placing the carbon material in a muffle furnace and heat-treating it at 400~500℃ for 1~5 hours.

[0012] Based on the above technical solution, the defect treatment specifically involves placing the carbon material under a hydrogen gas atmosphere with a concentration of 2-10% and heat-treating it at 600-1000°C for 1-5 hours.

[0013] According to a second aspect of the present invention, a method for preparing a cationic compound-modified carbon material for the electrosynthesis of hydrogen peroxide is provided, comprising the following steps: Step 1: Disperse the carbon support in an aqueous nitric acid solution, reflux for oxidation, wash and dry to obtain carbon oxide support; Step 2: Disperse the carbon oxide support obtained in Step 1 and the cationic modifier in water at a mass ratio of 1:0.01-0.1, assemble with ultrasonic assistance, filter, wash and dry to obtain the cationic compound modified carbon material.

[0014] According to a third aspect of the present invention, a method for preparing a cationic compound-modified carbon catalytic gas diffusion electrode using a cationic compound-modified carbon material is provided, comprising the following steps: A cationic compound-modified carbon material and a Nafion membrane solution were dispersed in a solvent as a binder, and ultrasonically mixed to form a mixed ink. 200–25000 μL of this mixed ink was then coated onto one side of a hydrophobic carbon fiber-based carbon paper, covering an area of ​​4–500 cm². 2 (The other side is the diffusion layer), dry at 25~40℃ for 5~30 min to obtain a carbon catalytic gas diffusion electrode modified with cationic compounds.

[0015] Based on the above technical solution, the mass ratio of the cationic compound-modified carbon material to the Nafion membrane solution is 20:50~150; The solvent is a mixture of an organic alcohol and water, wherein the organic alcohol is selected from at least one of isopropanol and ethanol.

[0016] Based on the above technical solution, the ratio of cationic compound modified carbon material to solvent in the mixed ink is 20~20000 mg: 2~2000 mL, and the ratio of organic alcohol to water in the solvent is 200~600 μL: 1800~1400 μL.

[0017] According to a fourth aspect of the present invention, a solid cation-modified carbon catalytic gas diffusion electrode prepared by modifying carbon materials with cationic compounds or by using unmodified commercial carbon black is provided. The solid cation-modified carbon catalytic gas diffusion electrode comprises hydrophobic carbon fiber-based carbon paper, a carbon catalytic layer, and a cation-modified layer covering the surface of the carbon catalytic layer. The carbon catalytic layer is loaded on one side of the carbon paper, and the solid cation-modified layer covers the surface of the carbon catalytic layer, wherein the loading amount of the carbon catalytic layer is 0.05~2 mg cm⁻¹. -2 .

[0018] According to a fifth aspect of the present invention, a method for preparing a solid cation-modified carbon catalytic gas diffusion electrode using a cation compound-modified carbon material is provided, comprising the following steps: Step 1: Disperse the cationic compound-modified carbon material or unmodified carbon material with cationic polymer solution A as a binder in a solvent, and sonicate to form a mixed ink. Coat 200-25000 μL of the mixed ink onto one side of hydrophobic carbon fiber-based carbon paper, covering an area of ​​4-500 cm². 2 (The other side is a diffusion layer), drying forms a carbon catalytic layer; Step 2: Coat the surface of the carbon catalyst layer with 5-30 μL of a 5wt% cationic ionomer solution B, and dry to form a cationic modification layer, thereby obtaining the solid cationic layer modified carbon catalytic gas diffusion electrode.

[0019] The cationic ionomer solution A and cationic ionomer solution B are polymers having a hydrophobic tail with a C8-C22 alkyl group, a hydrophilic head with a quaternary ammonium salt, a pyridinium salt, or an imidazolium salt, preferably at least one of imidazolium functionalized polymers, quaternized polystyrene, quaternary ammonium poly(N-methyl-piperidine-co--terphenyl), and polyaromatic quinine compounds. The cationic polymer solution A and cationic ionomer solution B may be the same or different.

[0020] Based on the above technical solution, the mass ratio of the carbon material to the cationic polymer solution A is 20:50~150.

[0021] The solvent is selected from a mixture of alcohol and water, preferably at least one of isopropanol and ethanol.

[0022] Based on the above technical solution, the ratio of catalyst to solvent in the mixed ink is 20~20000 mg: 2~2000 mL, and the ratio of organic solvent to water in the solvent is 200~600 μL: 1800~1400 μL.

[0023] According to a sixth aspect of the present invention, an apparatus for electrosynthesizing H2O2 is provided, comprising a two-chamber or three-chamber electrolytic cell, wherein the cathode is a cation-modified carbon catalytic gas diffusion electrode or a solid cation-layer modified carbon catalytic gas diffusion electrode, the anode is a platinum electrode or an iridium-tantalum-titanium composite oxide, an acidic high-salt electrolyte or seawater is introduced into the cathode chamber, an acidic electrolyte is introduced into the anode chamber, oxygen or air is introduced into the side of the cathode chamber, and the cathode chamber and the anode chamber are separated by a proton exchange membrane.

[0024] According to a sixth aspect of the present invention, a method for synthesizing hydrogen peroxide is provided, wherein the synthesis of H2O2 is carried out using an apparatus for electrosynthesis of H2O2, specifically, the synthesis of H2O2 is performed in a constant current mode with a current density of 50~1125 mA cm⁻¹. -2 The cathode electrolyte is an acidified high-salt solution or acidified seawater with a pH of 0.8–2.0, the anolyte is 0.1–1 M H₂SO₄, and the oxygen flow rate is 10–100 mL / min. -1 The acidified high-salt solution with pH 0.8-2.0 is an acidic salt solution composed of 0.1-0.5 Mn2SO4 and 0.05-0.1 MH2SO4, wherein M2SO4 is selected from at least one of Li2SO4, Na2SO4, K2SO4, Rb2SO4, Cs2SO4, and (NH4)2SO4, and the cathode electrolyte flow rate is 10-300 mL / h. -1 .

[0025] Catalytic mechanism: Cation-modified carbon electrodes or solid cation-modified carbon electrodes are used for two-electron oxygen reduction reactions in acidic media. The modification with cation compounds can change the binding properties between the catalytic site and the reactants / intermediates, as well as regulate the hydrogen bond network of water at the catalytic interface, thereby changing the oxygen hydrogenation mode and promoting H2O2 generation. The solid cation-modified layer can form a quasi-solid double layer on the surface of the catalytic layer, inhibiting the transfer of protons to the catalytic site, thereby inhibiting the breaking of OO bonds under high current conditions and improving the H2O2 selectivity.

[0026] Beneficial effects (1) This invention constructs a unique acidic charged interface on the surface of a carbon catalyst through cation modification. The cation head groups polarize the water molecules at the interface through electrostatic interaction, thereby regulating proton transfer and effectively controlling the flow of protons. The adsorption strength of OOH intermediates; the solid cation layer modified on the carbon electrode surface can form a unique semi-solid double layer, which inhibits the transfer of hydrogen ions to the catalytic interface, thereby inhibiting the breaking of OO bonds under high current conditions and significantly improving the current efficiency of H2O2 production.

[0027] (2) The catalyst of this invention, in an acidic high-salt electrolyte, at 500 mA cm⁻¹ -2 Lower Faraday efficiency > 90%, with a maximum achievable 1.125 A cm⁻¹. -2 It achieves industrial-grade current density and yields far superior results compared to unmodified carbon catalysts.

[0028] (3) This invention is the first to apply a cation modification strategy to the direct electrosynthesis of H2O2 from seawater, inhibiting Ca2+ by acidification (pH 0.8~1.6). 2+ / Mg 2+ Precipitation, at 500 mA cm -2 Lower Faraday efficiency > 90%, stable operation for more than 40 hours.

[0029] (4) Technical and economic analysis shows that the production cost of H2O2 using seawater as electrolyte is about US$0.77 / kg, which is economically competitive compared with the market price (US$1.14 / kg).

[0030] (5) The catalyst of the present invention is simple to prepare, low in cost, does not depend on precious metals, and is easy to scale up for production.

[0031] (6) The cation-modified carbon material provided by the present invention can directly use seawater or industrial high-salt wastewater as electrolyte to achieve low-cost, high-efficiency and long-life in-situ electrosynthesis of hydrogen peroxide. It can be used in the fields of seawater aquaculture disinfection, ship ballast water treatment, near-shore pollution remediation, and advanced oxidation pretreatment of industrial wastewater, and has good industrialization prospects. Attached Figure Description

[0032] Figure 1The diagram shows the preparation process and characterization of the cation-modified carbon catalyst in Example 1 (a: Schematic diagram of the preparation process, b: FT-IR spectra of OCNT, CTAB, and OCNT-CTAB, c: High-resolution XPS of OCNT and OCNT-CTAB). s and N 1 s Spectrum, d~e: Schematic diagram of electrostatic and hydrophobic interactions between CTAB molecules and the OCNT surface in an aqueous environment, where white spheres represent H atoms, gray spheres represent C atoms, red spheres represent O atoms, and blue spheres represent N atoms. Figure 2 Performance evaluation of acidic H2O2 electrosynthesis using cation-modified carbon catalytic electrodes (a: comparison of acidic H2O2 electrosynthesis performance of OCNT-CTAB catalyst, unmodified OCNT catalyst, and unsupported catalyst-supported gas diffusion electrode carbon substrate CP; b: performance of acidic H2O2 electrosynthesis using several quaternary ammonium salt cation-modified OCNT catalysts; c: performance of acidic H2O2 electrosynthesis using an electrode prepared by physical mixing of CTAB and OCNT). Figure 3 Performance evaluation of H2O2 electrosynthesis in acidic high-salt electrolytes and seawater (a: OCNT-CTAB catalyst at 300 mA cm⁻¹) -2 At current density and unmodified OCNT catalyst at 200 mA cm⁻¹ -2 Stability test comparison at current density, b: Performance evaluation of H2O2 electrosynthesis with the cathode electrolyte replaced by acidified Na2SO4, c: H2O2 Faradaic efficiency and current-voltage curves using OCNT-CTAB cathode and commercial IrTaTi or Pt anode, d: Performance evaluation of H2O2 electrosynthesis using acidified seawater as cathode electrolyte). Figure 4 To assess the performance of acidic H2O2 electrosynthesis using a carbon black electrode modified with a solid cation layer. Detailed Implementation

[0033] To make the objectives and technical solutions of this invention clearer, the following embodiments are provided for further explanation. However, the scope of protection of this invention is not limited to these embodiments; the embodiments are merely for illustrative purposes. Those skilled in the art should understand that any changes or equivalent substitutions that do not depart from the concept of this invention are included within the scope of protection of this invention.

[0034] Unless otherwise specified, all reagents and raw materials used in this invention are obtained through purchase. The Faraday efficiency measured in the embodiments of this invention is the average of three repeated measurements; the error bar represents the standard deviation; and the battery voltage is the average of two or three measurements.

[0035] Example 1: Preparation of cationic modified carbon catalyst according to Figure 1 The preparation process shown in a is carried out, specifically, 1g of single-walled carbon nanotubes (SWCNTs, with an inner diameter of 0.8~1.6nm, an outer diameter <2nm, a length of 1~2 / 5~20μL, a single-walled nanotube content >95%, and a specific surface area of ​​300~400 m²) are taken. 2 / g, density is 0.14g / cm³ 2 Carbon oxide nanotubes (OCNTs) were dispersed in 150 mL of 27 wt% nitric acid, refluxed at 140 °C for 5 hours, cooled, filtered, washed with water until neutral, and dried under vacuum at 60 °C. 100 mg of OCNTs and 0.03 mmol of cetyltrimethylammonium bromide (CTAB) were separately dispersed in 50 mL of deionized water and sonicated for 30 minutes to ensure thorough dispersion. The two solutions were then mixed and sonicated for 30 minutes, filtered, washed with water, and dried at 60 °C to obtain the OCNT-CTAB catalyst, i.e., the cationic modified carbon catalyst (quaternary ammonium salt adsorption capacity of 1-2 wt%). The FT-IR spectra of OCNTs, CTAB, and OCNT-CTAB are shown in [Figure number missing]. Figure 1 b, High-resolution XPS O1 of OCNT and OCNT-CTAB s and N1 s The spectrum shown in 1c confirms the successful loading of CTAB onto OCNT; a schematic diagram of the electrostatic and hydrophobic interactions between CTAB molecules and the OCNT surface in an aqueous environment is shown in [reference needed]. Figure 1 d~ Figure 1 e; The hexadecyltrimethylammonium bromide (CTAB) was replaced with octyltrimethylammonium bromide (OTAB, added in an amount of 0.03 mmol), and the remaining steps were the same as those for the preparation of the OCNT-CTAB catalyst, thus obtaining the OCNT-OTAB catalyst; The hexadecyltrimethylammonium bromide (CTAB) was replaced with dodecyltrimethylammonium bromide (CTAB, added in an amount of 0.03 mmol), and the remaining steps were the same as those for the preparation of the OCNT-CTAB catalyst, to obtain the OCNT-DTAB catalyst; The hexadecyltrimethylammonium bromide (CTAB) was replaced with octadecyltrimethylammonium bromide (STAB, added in an amount of 0.03 mmol), and the remaining steps were the same as those for the preparation of the OCNT-CTAB catalyst, to obtain the OCNT-STAB catalyst.

[0036] Example 2: Preparation of a carbon catalytic gas diffusion electrode modified with a cationic compound Take 20 mg of OCNT-CTAB catalyst, add 1.6 mL of deionized water, 0.4 mL of isopropanol, and 100 μL of 5 wt% Nafion solution (perfluorosulfonic acid resin solution), and ultrasonically disperse for 60 minutes to form catalyst ink. Coat 200 μL of the ink evenly onto hydrophobic carbon fiber paper (4 cm²). 2 The thickness is 0.21±0.01mm, and the resistivity is <23mΩcm. 2 A cationic compound-modified carbon catalytic gas diffusion electrode (OCNT-CTAB electrode) was obtained by drying the electrode at room temperature or 40°C for 5 to 30 minutes on a substrate with a gas resistance >20 mmH2O and a bending radius >15 cm (purchased from Shanghai Hesen Electric Co., Ltd., model HCP120). The electrode had a catalyst loading of approximately 0.5 mg / cm³. -2 .

[0037] The OCNT-CTAB catalyst was replaced with the OCNT-OTAB catalyst, and the remaining steps were the same as those for the preparation of the OCNT-CTAB electrode, to obtain the OCNT-OTAB electrode. The OCNT-CTAB catalyst was replaced with the OCNT-DTAB catalyst, and the remaining steps were the same as those for the preparation of the OCNT-CTAB electrode, to obtain the OCNT-DTAB electrode. The OCNT-CTAB catalyst was replaced with the OCNT-STAB catalyst, and the remaining steps were the same as those for the preparation of the OCNT-CTAB electrode, to obtain the OCNT-STAB electrode.

[0038] Example 3: Preparation of a solid cation layer modified gas diffusion carbon electrode 150 μL of XA9 solution (1.25 g Sustainion® XA-9 dissolved in 30 mL of ethanol to form a 5 wt% solution), 5 mg carbon black (CB), 250 μL of isopropanol, and 750 μL of deionized water were mixed and then sonicated until uniformly dispersed to obtain a catalyst ink mixture. 50 μL of the catalyst ink mixture was uniformly coated onto the surface of carbon paper to prepare a cationic XA9-modified carbon black gas diffusion carbon electrode (XA9 / CB). Subsequently, 50 μL of polyarylene quinine solution (5 wt%, solvent being DMSO and isopropanol in a 1:1 volume ratio) was dissolved in 4 mL of deionized water to prepare a polyarylene quinine solution. Take 800 μL of the diluted polyarylene quinine solution and apply it in 50 μL increments to the surface of the XA9 / CB electrode. Finally, heat the solution to 40 °C and evaporate it to form a solid polyarylene quinine cationic membrane, thus obtaining a polyarylene quinine cationic layer modified gas diffusion carbon electrode (Quin / XA9 / CB).

[0039] Replace the XA9 solution with a 10 wt% imidazolium functionalized polymer solution (Fum, 150 μL, solvent: ethanol), a 5 wt% polyarylene quinine solution (Quin, 150 μL, solvent: DMSO and isopropanol in a 1:1 volume ratio), or a 5 wt% Nafion membrane solution (150 μL). The remaining steps are the same as for the XA9 solution, to obtain Quin and Fum co-modified (Quin / Fum / CB) or Quin-modified gas diffusion carbon electrode (Quin / Quin / CB) or Quin and Nafion co-modified (Quin / Nafion / CB), respectively.

[0040] The polyarylene quinine cation membrane was replaced with 5 wt% XA9 solution (10 μL) or 10 wt% imidazolium functionalized polymer solution (Fum, 10 μL, solvent: ethanol) to obtain XA9 modified (XA9 / XA9 / CB) and gas diffusion carbon electrode co-modified with Fum and XA9 (Fum / XA9 / CB).

[0041] Test Example 1: Acidic Electrosynthesis of H2O2 The cation-modified carbon catalyst (OCNT-CTAB catalyst) prepared in Example 1 was used as the cathode for the electrosynthesis of H2O2. A two-chamber electrolytic cell was used, with a Pt electrode as the anode. The cathode solution was a salt solution of potassium sulfate and sulfuric acid (0.3M K2SO4 + 0.1M H2SO4, pH≈1.4), and the anolyte was 0.5M H2SO4. The oxygen flow rate was 30 mL / min. -1 Cathodic liquid flow rate 100 mL / h -1 At current densities of 25~500 mA cm⁻¹ -2 Electrolysis was performed below, and the test results are shown in [the table]. Figure 2 a; The results show that in the range of 25~500 mA cm -2 Constant current electrolysis was used, and the Faraday efficiency of H2O2 was measured to be 90%~100%.

[0042] Test Example 2: Stability Test of Acidic Electrosynthesis of H2O2 The difference from Test Example 1 is that a current density of 300 mA cm⁻¹ was applied. -2 It ran continuously for 200 hours. The test results are shown below. Figure 3 a, at 300 mA cm -2 During a 200-hour operation, the Faraday efficiency remained above 90%, while 1 wt% H2O2 solution was generated.

[0043] Test Example 3: Acidic electrosynthesis of H2O2 from acidic Na2SO4 cathode solution The method differed from Test Example 1 in that the salt solution prepared with potassium sulfate and sulfuric acid (0.3M K₂SO₄ + 0.1M H₂SO₄, pH≈1.4) was replaced with a salt solution prepared with sodium sulfate and sulfuric acid (0.3M Na₂SO₄ + 0.1M H₂SO₄). The catholyte flow rate was 20.7 mL / h. -1 The applied current density is 300 mA cm⁻¹ -2 The test results are shown below. Figure 3 b, at 300 mA cm -2 After running for 4 hours, the Faraday efficiency remained above 90%, while producing 1000 mM H2O2 solution.

[0044] Test Example 4: Performance of Carbon Catalysts Modified with Different Quaternary Ammonium Salt Cationic Compounds The OCNT-CTAB, OCNT-OTAB, OCNT-DTAB, and OCNT-STAB catalysts prepared in Example 1 were used for acidic electrosynthesis of hydrogen peroxide. The test conditions differed from those in Example 1 in that the OCNT-CTAB cathode was replaced with an OCNT-OTAB electrode, an OCNT-DTAB electrode, or an OCNT-OTAB electrode. The catholyte was a salt solution of potassium sulfate and sulfuric acid (0.3 M K₂SO₄ + 0.1 M H₂SO₄, pH ≈ 1.4), the anolyte was 0.5 M H₂SO₄, and the oxygen flow rate was 30 mL / min. -1 Cathodic liquid flow rate 100 mL / h -1 At current densities of 25~500 mA cm⁻¹ -2 Electrolysis was performed below; test results are shown in [link to test results]. Figure 2 b. The results show that the OCNT-OTAB electrode, OCNT-DTAB electrode, and OCNT-OTAB electrode can all achieve high current density electrosynthesis of H2O2 under acidic conditions, in the range of 25–250 mA cm⁻¹. -2 Under these conditions, the Faraday efficiency of H2O2 remains above 90% in the range of 250–500 mAcm⁻¹. -2 Under certain conditions, the Faraday efficiency of H2O2 is over 80%.

[0045] Test Example 5: Electrosynthesis of H2O2 using an IrTaTi anode The test conditions differed from those in Test Example 1 in that the platinum anode was replaced with a commercial IrTaTi electrode. The catholyte was a salt solution of potassium sulfate and sulfuric acid (0.3 M K₂SO₄ + 0.1 M H₂SO₄, pH ≈ 1.4), the anolyte was 0.5 M H₂SO₄, and the oxygen flow rate was 30 mL / min. -1 Cathodic liquid flow rate 100 mL / h -1 At current densities of 250~11250 mA cm⁻¹-2 Electrolysis was performed below; the H2O2 Faraday efficiency and current-voltage curves using the OCNT-CTAB cathode and commercial IrTaTi anode are shown in [reference needed]. Figure 3 c. It was found that using an IrTaTi anode significantly reduced the voltage, achieving 1.125 A cm⁻¹. -2 The current density of H2O2 is 82% and the Faraday efficiency is 82%.

[0046] Test Example 6: Electrosynthesis of H2O2 in Seawater Seawater from the Yellow Sea (Dalian) was used as the catholyte. After filtration, concentrated sulfuric acid was added to adjust the pH to 0.8–1.6. The test conditions differed from those in Example 1 in that the salt solution prepared with potassium sulfate and sulfuric acid (0.3 M K₂SO₄ + 0.1 M H₂SO₄, pH ≈ 1.4) was replaced with acidified seawater. The cathode was the OCNT-CTAB electrode prepared in Example 2, the anode was a Pt electrode, the anolyte was 0.5 M H₂SO₄, and the oxygen flow rate was 30 mL / min. -1 Cathodic liquid flow rate 100 mL / h -1 At current densities of 50~500 mA cm⁻¹ -2 Electrolysis was then performed. Test results are shown below. Figure 3 d. It was found that under pH conditions of 0.8 and 1.2, the Faraday efficiency of H2O2 increased with increasing current density. At 500 mA cm⁻¹ -2 Under pH conditions of 0.8–1.6, the H2O2 Faradaic efficiency is 80–90%, while in unacidified pristine seawater, the H2O2 Faradaic efficiency is 70%, and precipitate forms on the electrode surface; at 350 mA cm⁻¹ -2 No precipitate was formed after 40 hours of operation at pH 0.8, and the electrode surface remained clean. The estimated production costs of electrosynthesized H2O2 for Test Examples 1, 2, and 5 are $1.2, $0.68, and $0.77 / kg, respectively.

[0047] Test Example 7: Performance of a solid cation layer modified carbon catalytic gas diffusion electrode Solid-state cation-modified gas diffusion carbon electrodes (Quin / XA9 / CB, Quin / Fum / CB, Quin / Quin / CB, and Quin / Nafion / CB) prepared in Example 3 were used as cathode electrodes, with IrTaTi electrodes as anodes. The catholyte was a salt solution of potassium sulfate and sulfuric acid (0.3 M K₂SO₄ + 0.1 M H₂SO₄, pH ≈ 1.4), and the anolyte was 0.5 M H₂SO₄. The oxygen flow rate was 20 mL / min. -1 The catholyte flow rate is 110 mL / h. -1 Left and right. See test results. Figure 4When using a polyarylene quinine cation membrane modified onto the carbon catalytic electrode surface, and employing XA9, Quin9, and Fum as catalyst binders for CB, compared to Nafion, the measured Faraday efficiency for H2O2 at the same current density was higher. Simultaneously, using polyarylene quinine cation-modified CB catalyst and a polyarylene quinine cation membrane-modified electrode surface, at 500 mA cm⁻¹... -2 Constant current electrolysis was used, and the measured Faraday efficiency of H2O2 was 94%.

[0048] Comparative Example 1 H2O2 was electrosynthesized using an unmodified OCNT catalyst under the same conditions as in Test Example 1, at 200 mA cm⁻¹. -2 Electrode flooding occurred; see detailed test results. Figure 2 a. The Faraday efficiency drops to 44%, accompanied by H2 production. The OCNT / CTAB electrode was prepared by adding CTAB to OCNT ink and then coating it onto loaded carbon paper with loadings of 14, 28, and 55 µg cm⁻¹. - ².

[0049] Comparative Example 2 Electrodes were prepared using a physical mixture of OCNT and CTAB (directly mixing CTAB and OCNT instead of electrostatic assembly; the ratio of CTAB, OCNT, and binder was the same as in Example 1). Specific test results are shown below. Figure 2 c, at 100 mA cm -2 and 300mA cm -2 The lower Faraday efficiencies were 50% and 10%, respectively, which are far lower than the 90% of the electrostatically assembled samples.

[0050] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A cationic compound-modified carbon material for the electrosynthesis of hydrogen peroxide, characterized in that, It consists of a carbon support and a cationic modifier assembled on the surface of the carbon support through electrostatic interaction, with an adsorption capacity of 1% to 10% of the mass of the carbon material; The carbon support is a carbon material that has undergone oxidation or defect treatment. The carbon material is selected from at least one of the following: oxidized single-walled carbon nanotubes, oxidized multi-walled carbon nanotubes, oxidized graphene, oxidized carbon black, defective single-walled carbon nanotubes, defective multi-walled carbon nanotubes, defective graphene, defective carbon black, porous carbon, and biomass-derived carbon. The cationic modifier is a cationic surfactant or a cationic ionomer.

2. The cationic compound-modified carbon material according to claim 1, characterized in that, The cationic surfactant is a polymer having a hydrophobic tail with a C8-C22 alkyl group, or a hydrophilic head with a quaternary ammonium salt, a pyridinium salt, or an imidazolium salt. The general formula of the quaternary ammonium salt is R1R2R3R4N. + X - R1, R2, R3, and R4 are independently selected from at least one of methyl and C8-C22 straight-chain alkyl groups, X - The halide ion is Cl. - or Br - ; The general formula for the pyridinium salt is [Py-R]. + X - Where Py is a pyridine ring, R is selected from at least one of methyl and C8-C22 straight-chain alkyl groups, and X - For Cl - or Br - ; The general formula of the imidazolium salt is [R1ImR2]. + X - Where Im is an imidazole ring, R1 and R2 are independently selected from at least one of methyl and C8-C22 straight-chain alkyl groups, and X - For Cl - or Br - ; The cationic ionomer is a polymer with positively charged groups, preferably an imidazolium functionalized polymer, a quaternary ammonium poly(N-methyl-piperidine-co-p-terphenyl), a quaternized polystyrene, or a polyaromatic quinine compound.

3. The cationic compound-modified carbon material according to claim 1, characterized in that, The oxidation process specifically involves: oxidizing 1-100 g of carbon material with 100-1000 mL of nitric acid with a concentration of 20-70 wt%, and refluxing at 80-140°C for 3-14 hours to obtain the oxidized carbon material; The defect treatment specifically involves: placing the carbon material in a muffle furnace and heat-treating it at 400-500°C for 1-5 hours; or placing the carbon material in a hydrogen atmosphere with a concentration of 2-10% and heat-treating it at 600-1000°C for 1-5 hours.

4. A method for preparing a cationic compound-modified carbon material according to claim 1, characterized in that, Includes the following steps: Step 1: Disperse the carbon support in an aqueous nitric acid solution, reflux for oxidation, wash and dry to obtain carbon oxide support; Step 2: Disperse the carbon oxide support obtained in Step 1 and the cationic modifier in water at a mass ratio of 1:0.01-0.1, assemble with ultrasonic assistance, filter, wash and dry to obtain the cationic compound modified carbon material.

5. A method for preparing a cationic compound-modified carbon catalytic gas diffusion electrode using the cationic compound modified carbon material according to claim 1, characterized in that, Includes the following steps: A cationic compound-modified carbon material and a Nafion membrane solution were dispersed in a solvent as a binder, and ultrasonically mixed to form a mixed ink. 200–25000 μL of this mixed ink was then coated onto one side of a hydrophobic carbon fiber-based carbon paper, covering an area of ​​4–500 cm². 2 Dry at 25~40℃ for 4~30 min to obtain a carbon catalytic gas diffusion electrode modified with a cationic compound; The mass ratio of the cationic compound-modified carbon material to the Nafion membrane solution is 20:50~150; The solvent is a mixture of an organic alcohol and water, wherein the organic alcohol is selected from at least one of isopropanol and ethanol. The ratio of cationic compound-modified carbon material to solvent in the mixed ink is 20~20000 mg: 2~2000 mL, and the ratio of organic solvent to water in the solvent is 200~600 μL: 1800~1400 μL.

6. A solid cationic layer-modified carbon catalytic gas diffusion electrode prepared using the cationic compound of claim 1 to modify carbon materials or unmodified commercial carbon black materials, characterized in that, The solid-state cation-modified carbon catalytic gas diffusion electrode consists of hydrophobic carbon fiber-based carbon paper, a carbon catalytic layer, and a cation-modified layer covering the surface of the carbon catalytic layer. The carbon catalytic layer is loaded on one side of the carbon paper, and the solid-state cation-modified layer covers the surface of the carbon catalytic layer. The loading amount of the carbon catalytic layer is 0.05~2 mg cm⁻¹. -2 .

7. A method for preparing a solid cation layer modified carbon catalytic gas diffusion electrode as described in claim 6, characterized in that, Includes the following steps: Step 1: Disperse the cationic compound-modified carbon material or unmodified carbon material with cationic polymer solution A as a binder in a solvent, and sonicate to form a mixed ink. Coat 200-25000 μL of the mixed ink onto one side of hydrophobic carbon fiber-based carbon paper, covering an area of ​​4-500 cm². 2 Drying forms a carbon catalyst layer; Step 2: Coat the surface of the carbon catalyst layer with 5-30 μL of a 5wt% cationic ionomer solution B, and dry to form a cationic modification layer, thereby obtaining the solid cationic layer modified carbon catalytic gas diffusion electrode.

8. The preparation method according to claim 7, characterized in that, The cationic polymers in the cationic ionomer solutions A and B are polymers with hydrophobic tails of C8-C22 alkyl groups, or hydrophilic heads of quaternary ammonium salts, pyridinium salts, or imidazolium salts. Preferably, they are at least one of imidazolium functionalized polymers, quaternized polystyrene, quaternary ammonium poly(N-methyl-piperidine-co-p-terphenyl), or polyaromatic quinine compounds. The cationic polymer solutions A and B may be the same or different. The mass ratio of the carbon material to the cationic polymer solution A is 20:50~150; The solvent is a mixture of an organic alcohol and water, wherein the organic alcohol is selected from at least one of isopropanol and ethanol; The catalyst to solvent ratio in the mixed ink is 20~20000 mg: 2~2000 mL, and the organic solvent to water ratio in the solvent is 200~600 μL: 1800~1400 μL.

9. An apparatus for the electrosynthesis of H2O2, characterized in that, The device includes a two-chamber or three-chamber electrolytic cell. The cathode is a carbon catalytic gas diffusion electrode modified with a cationic compound prepared by the method of claim 5 or a carbon catalytic gas diffusion electrode modified with a solid cationic layer as described in claim 6. The anode is a platinum electrode or an iridium-tantalum-titanium composite oxide. The cathode chamber is circulated with an acidic high-salt electrolyte or seawater, the anode chamber is circulated with an acidic electrolyte, oxygen or air is circulated through the side of the cathode chamber, and the cathode chamber and the anode chamber are separated by a proton exchange membrane.

10. A method for synthesizing hydrogen peroxide, characterized in that, The synthesis of H2O2 using the apparatus described in claim 9 is specifically carried out in a constant current mode with a current density of 50~1125 mA cm⁻¹. -2 The cathode electrolyte is an acidified high-salt solution or acidified seawater with a pH of 0.8–2.0, the anolyte is 0.1–1 M H₂SO₄, and the oxygen flow rate is 10–100 mL / min. -1 The acidified high-salt solution with pH 0.8-2.0 is an acidic salt solution composed of 0.1-0.5 M M2SO4 and 0.05-0.1 M H2SO4, wherein M2SO4 is selected from at least one of Li2SO4, Na2SO4, K2SO4, Rb2SO4, Cs2SO4, and (NH4)2SO4, and the cathode electrolyte flow rate is 10-300 mL / h. -1 .

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