Method for preparing hydrogen peroxide in acidic electrolyte by using bimetallic manganese catalyst

Abstract

The invention relates to a method for preparing hydrogen peroxide in an acidic electrolyte by using a bimetallic manganese catalyst. According to the preparation method, a two-electron oxygen reduction reaction is carried out in an acidic electrolyte in the presence of a bimetallic manganese catalyst to obtain hydrogen peroxide. According to the preparation method of the hydrogen peroxide, electrochemical synthesis of the hydrogen peroxide can be carried out in the acidic electrolyte under the industrial-grade current density, and the activity and durability of the catalyst are good.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical synthesis, specifically relating to a method for preparing hydrogen peroxide in an acidic electrolyte using a bimetallic manganese catalyst. Background Technology

[0002] Hydrogen peroxide (H2O2) is a chemical widely used in public and domestic applications, with an annual production exceeding 5.5 million tons. It serves as an important raw material for medical disinfectants and chemical synthesis, and more importantly, it is a green oxidant in many fields. Currently, the industrial synthesis of H2O2 is mainly carried out through the anthraquinone process, which involves the hydrogenation and oxidation of anthraquinone over a palladium-based catalyst. This method produces H2O2 with a very high concentration (30%–70%), posing risks, especially for residents in central and western China, during storage and transportation. Furthermore, apart from the aerospace industry and special-purpose industrial synthesis, few applications require such high concentrations of hydrogen peroxide. Moreover, anthraquinone is difficult to recover effectively, generating various degradation products in the process, thus requiring continuous replenishment for sustained production, which fails to meet the requirements of green chemistry.

[0003] The production of H₂O₂ via the acidic two-electron oxygen reduction reaction (ORR) is a novel decentralized approach to hydrogen peroxide production. Energy can be derived from renewable sources, and the only byproduct is water. The reaction can proceed under mild operating conditions, and productivity can be controlled simply by varying the applied voltage. Furthermore, hydrogen peroxide is intrinsically more stable and less prone to decomposition under acidic conditions. Therefore, researchers have focused on designing catalysts and reactor configurations to realize this process; however, most catalysts tend to undergo four-electron ORR, and the selectivity and stability of most catalysts are unsatisfactory.

[0004] Single-atom catalysts (SACs) are characterized by high atom utilization and highly tunable electronic structure, and have been widely used in various thermochemical and electrochemical reactions. Recent research has discovered that single-atom catalysts containing transition metals such as iron, cobalt, platinum, and palladium exhibit certain activity and selectivity for acidic two-electron oxygen reduction reactions.

[0005] There have been reports on diatomic catalysts (DACs). For example, Non-Patent Literature 1 discloses a general synthetic method for macrocyclic precursor-mediated diatomic catalysts and studies the performance of Fe-Cu DAC catalysts in the oxygen reduction reaction (ORR). It was found that they unlock an unconventional reaction pathway in the oxygen reduction process, through which the byproduct H2O2 is mainly reduced to H2O instead of ROS.

[0006] References

[0007] Non-patent literature 1: J.Am.Chem.Soc.2023,145,4819-4827. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Single-atom catalysts are generally used at industrial-grade current densities (>200 mA cm⁻¹). 2 The catalyst has insufficient stability (<200h), and a large number of active free radical intermediates are generated during the electrosynthesis of hydrogen peroxide under acidic conditions, which destroys the catalyst structure. Furthermore, it is difficult to achieve both high activity and high stability of the catalyst during the reaction.

[0010] Therefore, there is still an urgent need to develop a method that enables the electrochemical synthesis of hydrogen peroxide in acidic electrolytes at industrial-grade current densities, with good catalyst activity and durability.

[0011] Solution for solving the problem

[0012] To address the aforementioned problems, the inventors conducted long-term and in-depth research and discovered that bimetallic manganese catalysts can electrocatalyze oxygen reduction reactions in acidic electrolysis at industrial-grade current densities to produce hydrogen peroxide, and that the catalysts exhibit good activity and durability, thus completing this invention.

[0013] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0014] [1] A method for preparing hydrogen peroxide, wherein a two-electron oxygen reduction reaction is carried out in an acidic electrolyte in the presence of a bimetallic manganese catalyst to obtain hydrogen peroxide.

[0015] The bimetallic manganese catalyst is obtained by carbonization or loading of a precursor, and the precursor has the structure shown in formula (1).

[0016]

[0017] In equation (1), the distance between the two Mn atoms is... Between; L1-L6 independently represent organic ligands containing heteroatoms as coordinating atoms, wherein the heteroatoms are selected from one or more of N, O, S, and P, and L1-L6 are optionally connected to each other to form a ring structure; X n- Selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO42– The anion.

[0018] [2] According to the preparation method described in [1], wherein L1-L6 are independently selected from phenolic groups, pyridine groups, pyrrole groups, aniline groups, Schiff base groups, porphyrin groups, phthalocyanine groups and their derivative groups.

[0019] [3] According to the preparation method described in [1] or [2], wherein the precursor has the structure shown in formula (2),

[0020]

[0021] Y is selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– ,

[0022] n is 2 or 3

[0023] m represents the quantity of Y, which can be 1, 2, or 3.

[0024] R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group.

[0025] R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms.

[0026] R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms.

[0027] Z represents either O or S.

[0028] [4] According to the preparation method described in [1] or [2], wherein the precursor has the structure shown in formula (3),

[0029]

[0030] Among them, A is independently selected from NO3. – Cl – ,Br – OAc – ClO4 – OH – CH3O– HOCH2CH2O – or SO4 2– .

[0031] [5] According to the preparation method described in [1] or [2], the bimetallic manganese catalyst is obtained by carbonization of the precursor, wherein the carbonization is carried out by mixing the precursor with zinc nitrate and 2-methylimidazole and calcining.

[0032] [6] According to the preparation method described in [1] or [2], the bimetallic manganese catalyst is obtained by loading the precursor, and the loading is carried out by mixing the precursor with the support and loading the precursor onto the support; preferably, the support is a carbon-based support, preferably selected from one or more of Norit, Ketjen Black, Vulcan, Black Pearl, acetylene black, carbon nanotubes, graphene, carbon nitride (g-C3N4), nitrogen-doped carbon, molybdenum carbide, and iron carbide.

[0033] [7] According to the preparation method described in [1] or [2], the pH of the acidic electrolyte is 0 to 3; preferably, the acidic electrolyte is an aqueous solution of perchloric acid, an aqueous solution of hydrochloric acid or an aqueous solution of sulfuric acid, and the concentration is preferably 0.001 to 1 mol / L.

[0034] [8] According to the preparation method described in [1] or [2], wherein the two-electron oxygen reduction reaction is carried out in an electrolytic cell, the electrolytic cell comprising an electrode assembly, the electrode assembly comprising a cathode and an anode, the cathode comprising a cathode current collector, a binder and the bimetallic manganese catalyst; based on the surface area of ​​the cathode current collector, the loading of the bimetallic manganese catalyst is preferably 0.1 to 1 mg cm⁻¹. -2 .

[0035] [9] According to the preparation method described in [6], the bimetallic manganese catalyst is coated on the cathode current collector, the cathode current collector is made of carbon material or metal material, the carbon material is graphite or carbon paper, and the metal material is one or more selected from platinum, gold, copper, stainless steel and aluminum; the anode includes an anode current collector, the anode current collector is made of metal material, and the metal material is one or more selected from platinum, gold, copper, stainless steel and aluminum.

[0036]

[10] According to the preparation method described in [1] or [2], wherein the two-electron oxygen reduction reaction is carried out at a current density of 200 mA cm-2 or higher, and the selectivity of hydrogen peroxide is 80% or higher.

[0037] The effects of the invention

[0038] The method for preparing hydrogen peroxide of the present invention enables the electrochemical synthesis of hydrogen peroxide in an acidic electrolyte at an industrial-grade current density, and the catalyst exhibits good activity and durability. Attached Figure Description

[0039] Figure 1 (a) is a transmission electron microscope (TEM) image of catalyst A obtained in synthesis example 1;

[0040] Figure 1 (b) is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of catalyst A obtained in synthesis example 1;

[0041] Figure 1 (c) is the energy dispersive X-ray spectrum of catalyst A obtained in synthesis example 1;

[0042] Figure 2 The test results obtained using the rotating ring disk electrode in Example 1-1;

[0043] Figure 3 The results are from the free radical yield test in Examples 1-2;

[0044] Figure 4 The results of electron paramagnetic resonance measurements in Examples 1-3;

[0045] Figure 5 The results are the stability test results of the gas diffusion electrodes in Examples 1-4. Detailed Implementation

[0046] The present invention will now be described in detail. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0047] In this instruction manual, "room temperature" refers to a temperature range of 20 to 30°C, such as 25°C.

[0048] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0049] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0050] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0051] In this specification, the terms "optionally" or "optionally" are used to indicate the use or non-use of certain substances, components, procedures, application conditions, etc.

[0052] All unit names used in this manual are international standard unit names, and unless otherwise stated, the "%" used refers to weight or mass percentage content.

[0053] In this specification, references to "preferred embodiments," "implementation methods," etc., mean that a specific element (e.g., feature, structure, property, and / or characteristic) related to that embodiment is included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Furthermore, it should be understood that the elements may be combined in any suitable manner in various embodiments.

[0054] One object of the present invention is to provide a method for preparing hydrogen peroxide, wherein a two-electron oxygen reduction reaction is carried out in an acidic electrolyte in the presence of a bimetallic manganese catalyst to obtain hydrogen peroxide.

[0055] The preparation method of the present invention will be described in detail below.

[0056] <Catalyst>

[0057] The bimetallic manganese catalyst used in this invention is obtained by carbonization or loading of a precursor, the precursor having the structure shown in formula (1).

[0058]

[0059] In equation (1), the distance between the two Mn atoms is... Between; L1-L6 independently represent organic ligands containing heteroatoms as coordinating atoms, wherein the heteroatoms are selected from one or more of N, O, S, and P, and L1-L6 are optionally connected to each other to form a ring structure; X n- Selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– The anion.

[0060] For example, in at least a portion of the group pairs consisting of L1 and L2, L1 and L3, L3 and L5, L5 and L6, L2 and L4, and L4 and L6, the two groups in each pair are connected to form a ring structure. Preferably, the two groups in all the above-mentioned group pairs are connected to form a ring structure.

[0061] Preferably, L1-L6 are independently selected from phenolic groups, pyridine groups, pyrrole groups, aniline groups, Schiff base groups, porphyrin groups, phthalocyanine groups, and their derivative groups.

[0062] In one embodiment, the precursor has the structure shown in formula (2).

[0063]

[0064] Wherein, Y is an anion, which can be selected from NO3. – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– Preferred from NO3 – Cl – ,Br – ClO4 – CH3O – HOCH2CH2O – More preferably Cl – Y – It can be axially coordinated at the center of a metal atom.

[0065] n can be 2 or 3, preferably 2.

[0066] m represents the quantity of Y, which can be 1, 2, or 3, preferably 2.

[0067] R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group. Preferably, R2 represents H.

[0068] R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms, preferably from H, C1-C6 alkyl, and more preferably from methyl or ethyl.

[0069] R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms, preferably propylene or 1,2-phenylene, and more preferably propylene.

[0070] Z can be O (oxygen atom) or S (sulfur atom), preferably O.

[0071] In one embodiment, the precursor has the structure shown in formula (3).

[0072]

[0073] Among them, A is independently selected from NO3. – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– The two A's can be the same or different.

[0074] Preferably, the manganese content in the bimetallic manganese catalyst is 0.1-5 wt%, more preferably 0.5-3 wt%, more preferably 0.5-1.5 wt%, and also, for example, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, etc.

[0075] In one implementation and scheme, the bimetallic manganese catalyst is obtained by carbonization of a precursor.

[0076] On one hand, the carbonization is carried out by mixing the precursor with zinc nitrate and 2-methylimidazole and then calcining it. Zinc nitrate and 2-methylimidazole can coordinate to form a ZIF-8 MOF framework, which encapsulates the precursor, thus preventing metal sites from agglomerating after calcination.

[0077] More specifically, the precursor is dissolved in water with zinc nitrate and optionally a surfactant to obtain solution A, which is then mixed with an aqueous solution of 2-methylimidazole. The resulting mixture is stirred at room temperature for a period of time and then subjected to solid-liquid separation. Optionally, the obtained solid is washed and dried, followed by calcination.

[0078] The stirring time is preferably 6 to 24 hours, more preferably 8 to 20 hours; solid-liquid separation is performed, for example, by centrifugation and / or filtration; washing is performed, for example, using an alcohol solvent, preferably methanol, and the number of washings is preferably 1 to 10 times, more preferably 2 to 8 times, and even more preferably 3 to 7 times; drying is preferably performed under vacuum conditions at a drying temperature of 70 to 100°C; calcination is preferably performed in an inert gas (e.g., nitrogen, argon), the calcination temperature is preferably 700 to 1100°C, more preferably 800 to 1000°C, and the calcination time is preferably 1 to 6 hours, more preferably 1.5 to 4 hours.

[0079] Preferably, in solution A, the concentration of zinc nitrate is 1–5 mol / L, more preferably 2–4 mol / L; the concentration of the precursor is 0.002–0.01 mol / L, more preferably 0.004–0.008 mol / L; and the concentration of the surfactant is 0.001–0.005 mol / L, more preferably 0.002–0.004 mol / L.

[0080] Preferably, the molar ratio of the precursor, zinc nitrate and 2-methylimidazole in the mixture is 1:(10-30):(500-1500), more preferably 1:(15-25):(800-1200).

[0081] Preferably, the concentration of 2-methylimidazole in the aqueous solution is 0.5–1 mol / L, more preferably 0.6–0.9 mol / L, and even more preferably 0.7–0.85 mol / L.

[0082] On the other hand, the carbonization can also be performed by loading the precursor onto a solid support and calcining it. The solid support is preferably a carbon-based support, more preferably one or more selected from Norit, Ketjen Black, Vulcan, Black Pearl, acetylene black, carbon nanotubes, graphene, carbon nitride (g-C3N4), nitrogen-doped carbon, molybdenum carbide, and iron carbide. The mass ratio of the precursor to the solid support is 1:(5-50), preferably 1:(10-40), and more preferably 1:(15-35).

[0083] The calcination is preferably carried out in an inert gas (e.g., nitrogen or argon), the calcination temperature is preferably 700–1100°C, more preferably 800–1000°C, and the calcination time is preferably 1–6 hours, more preferably 1.5–4 hours.

[0084] The present invention does not impose any particular limitations on the method of loading the precursor onto a solid carrier, and it can be carried out by conventional methods.

[0085] In one embodiment, the bimetallic manganese catalyst is obtained by loading the precursor. The loading is performed by mixing the precursor with a support and loading the precursor onto the support.

[0086] The present invention does not particularly limit the method for loading the precursor onto the carrier, and it can be carried out by conventional methods. For example, the precursor solution can be mixed with the dispersion of the carrier and stirred for a period of time, followed by solid-liquid separation, and the resulting solid can be dried.

[0087] The solvent contained in the precursor solution and the carrier dispersion can be a mixed solvent of alcohol and water, and the volume ratio of alcohol to water can be 1:(0.8 to 1.2), for example, a mixed solvent of methanol:water = 1:1.

[0088] Preferably, stirring is carried out at room temperature for 1 to 5 hours, more preferably 1.5 to 3 hours; solid-liquid separation is carried out, for example, by centrifugation and / or filtration; drying is preferably carried out under vacuum conditions at a temperature of 70 to 100°C.

[0089] Preferably, the carrier is a carbon-based carrier, and is preferably selected from one or more of Norit, Ketjen Black, Vulcan, Black Pearl, acetylene black, carbon nanotubes, graphene, carbon nitride (g-C3N4), nitrogen-doped carbon, molybdenum carbide, and iron carbide.

[0090] Preferably, the mass ratio of the precursor to the carrier is (1-30):100, more preferably (5-20):100.

[0091] <Acidic Electrolytes>

[0092] In the preparation method of the present invention, the two-electron oxygen reduction reaction is carried out in an acidic electrolyte.

[0093] Preferably, the pH of the acidic electrolyte is 0 to 3, more preferably 0.5 to 2.5, more preferably 1 to 2, for example 1.5.

[0094] Preferably, the acidic electrolyte is an aqueous solution of an acid, such as an aqueous solution of perchloric acid, hydrochloric acid, or sulfuric acid. More preferably, the concentration of the acid is 0.001–1 mol / L, for example, 0.005–0.8 mol / L, 0.01–0.6 mol / L, 0.05–0.5 mol / L, or 0.10–0.3 mol / L.

[0095] Electrolytic Cell

[0096] In one embodiment, in the preparation method of the present invention, the two-electron oxygen reduction reaction is carried out in an electrolytic cell, the electrolytic cell including an electrode assembly including a cathode and an anode, the cathode including a cathode current collector, a binder and the bimetallic manganese catalyst.

[0097] In one embodiment, the bimetallic manganese catalyst is coated onto the cathode current collector. The present invention does not particularly limit the method of coating the bimetallic manganese catalyst onto the cathode current collector. For example, the bimetallic manganese catalyst, binder, and solvent (e.g., isopropanol) can be mixed to obtain a catalyst ink, which is then coated onto the cathode current collector and dried.

[0098] Adhesives serve to bind the catalysts together and, preferably, also act as proton conductors. Examples of adhesives include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. In particular, adhesives can be perfluorinated resins, such as commercially available Nafion (D520, wt%, Alfa Aesar).

[0099] Preferably, based on the surface area of ​​the cathode current collector, the loading of the bimetallic manganese catalyst on the cathode is 0.1–1 mg / cm². -2 Preferably, it is 0.2–0.8 mg cm. -2 More preferably 0.4–0.6 mg cm -2 For example, 0.5mg cm -2 .

[0100] Preferably, the cathode current collector is made of carbon material or metal material, wherein the carbon material is graphite or carbon paper, and the metal material is one or more selected from platinum, gold, copper, stainless steel, and aluminum.

[0101] In one embodiment, the anode includes an anode current collector and optionally includes an IrO2 layer, said IrO2 layer being sprayed or in-situ grown on the surface of the anode current collector. Preferably, the IrO2 loading is 1–2 mg / cm² based on the surface area of ​​the anode current collector. -2 Preferably, it is 1.2–1.8 mg cm. -2 More preferably 1.4–1.6 mg cm -2 For example, 1.5mg cm -2 The anode current collector is made of a metallic material, which is selected from one or more of platinum, gold, copper, stainless steel, and aluminum.

[0102] Specifically, the electrode assembly can be a gas diffusion electrode or a membrane electrode. The catalyst can be coated (e.g., sprayed) onto the cathode current collector, or it can be directly coated (e.g., sprayed) onto the membrane and then bonded to the cathode current collector (e.g., by hot pressing).

[0103] The present invention does not impose any particular restrictions on the specific structure of the electrolytic cell, which can have any known suitable structure.

[0104] In one embodiment, the electrolytic cell includes a container for containing electrolyte, an electrode assembly, a diaphragm, and a power source. The diaphragm divides the container into an anode chamber and a cathode chamber, with the anode and cathode of the electrode assembly located in the anode chamber and cathode chamber, respectively. The electrolytic cell may optionally have a separate oxygen inlet. Oxygen may have a separate flow path or may be introduced in a gas-liquid two-phase flow mixed with a liquid.

[0105] In one embodiment, the electrolytic cell is a gas diffusion flow cell. Specifically, the gas diffusion flow cell includes a porous hydrophobic gas diffusion layer (GDL), a cathode chamber, an anode chamber, and an ion exchange membrane. This structure retains the excellent mass transfer efficiency of a flow-type electrolytic cell, thus enabling the achievement of high current densities. In the electrolytic cell, the gas diffusion layer (GDL) typically provides gas diffusion channels and serves as a medium for gas distribution, ensuring uniform gas distribution and efficient transport during electrolysis. The main functions of high-performance GDL materials include gas transport, drainage, support, electrical conductivity, and thermal conductivity. These functions collectively promote the electrolytic reaction and improve the efficiency of the electrolysis process.

[0106] <Electrolysis Conditions>

[0107] In the preparation method of this invention, the two-electron oxygen reduction reaction can be carried out at industrial-grade current densities. For example, it can be carried out at 200 mA cm⁻¹. 2 The test is performed at the above current density, preferably at 210 mA cm⁻¹. 2 Above, 220mA cm 2 Above, 230mA cm 2 Above, 240mA cm 2 Above, 250mA cm 2 Above, 260mA cm 2 Above, 270mA cm 2 Above, 280mA cm 2 Above, 290mA cm 2 Above, 300mA cm 2 above.

[0108] In the preparation method of this invention, the two-electron oxygen reduction reaction can be carried out at 0 to -1.2V. RHE The electrolysis is carried out within a certain potential range. The cell voltage of the entire electrolytic cell is between 2 and 4V, which is suitable for industrial needs.

[0109] In this instruction manual, "V" RHE "" indicates the potential relative to the reversible hydrogen electrode. It should be noted that, except for the cell voltage of the electrolytic cell, all descriptions of voltage in this specification are relative to the reversible hydrogen electrode.

[0110] In the preparation method of the present invention, the selectivity of hydrogen peroxide is 80% or more, preferably 85% or more.

[0111] The stable operating time of the preparation method of the present invention is 80 hours or more, preferably 100 hours or more, more preferably 150 hours or more, such as 200 hours or more, 250 hours or more, 300 hours or more, 350 hours or more, 400 hours or more, 450 hours or more, etc. "Stable operation" means that the voltage variation does not exceed 200mV.

[0112] In the preparation method of the present invention, the Faraday efficiency of hydrogen peroxide is 60% or more, preferably 65% ​​or more, for example 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, 96% or more, 97% or more, 98% or more, etc.

[0113] The present invention also relates accordingly to the use of the catalysts described above for the preparation of hydrogen peroxide.

[0114] Example

[0115] The following specific embodiments further illustrate the present invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by this invention.

[0116] Synthesis example 1

[0117] (1-1) Precursor Mn2(C 24 H 26 Preparation of N4O2)(Cl)2:

[0118] 1,3-Diaminopropane (0.151 mL, 1.8 mmol) in 1 mL of methanol and 2,6-diformyl-4-methylphenol (0.294 g, 1.8 mmol) in 9 mL of methanol were sequentially added to a methanol solution of MnCl₂·4H₂O (0.335 g, 0.19 M, 9 mL). After reflux for 15 minutes, a yellow solid precipitated from the solution. The solid was filtered and washed with boiling methanol to give yellow crystals (0.220 g, yield 42%, based on MnCl₂·4H₂O).

[0119] The structure of the precursor is shown below:

[0120]

[0121] (1-2) Preparation of Mn2-NC catalyst with Mn element content of 1wt%:

[0122] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol), Mn2 (C 24 H 26N4O2)(Cl)2 (0.010 g, 0.15 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foam-rich solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL), and the resulting solution was labeled as solution B. Solution A was added dropwise to solution B under sonication, and the mixture was stirred at room temperature for 12 hours. The resulting orange powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and subsequently calcined at 900 °C under a N2 atmosphere for 2 hours to obtain a black powder, which was the 1 wt% Mn2-NC catalyst, denoted as catalyst A.

[0123] Synthesis example 2

[0124] Mn2-NC catalyst with a loading of 2 wt%:

[0125] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol) and the precursor Mn2 (C) obtained in the examples were used. 24 H 26 N4O2)(Cl)2 (0.020 g, 0.15 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foam-rich solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL), and the resulting solution was labeled as solution B. Solution A was added dropwise to solution B under sonication, and the resulting mixture was stirred at ambient temperature for 12 hours. The orange powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and subsequently calcined at 900 °C under a N2 atmosphere for 2 hours to obtain a black powder, which was the 2 wt% Mn2-NC catalyst, denoted as catalyst B.

[0126] Synthesis example 3

[0127] (1) Mn2 complex precursor C 30 H 44 Preparation of Cl2Mn2N6O2

[0128] At 0 °C, a solution of 98% terephthalaldehyde (0.9973 g, 7.44 mmol) in MeCN (80 mL) was added dropwise to a solution of 1-[bis(2-aminoethyl)amino]-2-propanol (1.0937 g, 7.44 mmol) in MeCN (80 mL). The mixture was stirred for 4 hours to allow the condensation of 1-[bis(2-aminoethyl)amino]-2-propanol with terephthalaldehyde to give Schiff base L, the structure of which is shown below.

[0129]

[0130] An aqueous solution of Schiff base L (0.0512 g, 0.10 mmol) was added dropwise to an aqueous solution (2 mL) containing MnCl2·4H2O (0.0341 g, 0.20 mmol). The pH was adjusted to 8.0 with 1 M NaOH, and the filtered solution was slowly evaporated at 20 °C for several days to obtain colorless rod-shaped crystals, which were the Mn2 complex precursor C. 30 H 44 Cl2Mn2N6O2 has the following structure.

[0131]

[0132] (2) Preparation of supported catalyst Mn2-C3N4:

[0133] Weigh 10 mg of Mn2 complex precursor and dissolve it in 10 mL of methanol-water solution with a volume ratio of 1 / 2. Then, take 100 mg of C3N4 and disperse it in another 10 mL of methanol-water solution with a volume ratio of 1 / 2. Finally, add the Mn2 complex precursor solution to the C3N4 dispersion (total 20 mL), stir for 2 hours, centrifuge and dry to obtain the supported catalyst Mn2-C3N4, denoted as catalyst C.

[0134] Comparative Synthesis Example 1

[0135] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol), manganese chloride tetrahydrate (0.010 g, 0.15 mmol), and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foamy solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL) and labeled as solution B. Solution A was added dropwise to solution B under sonication, and the resulting mixture was stirred at ambient temperature for 12 hours. The resulting orange powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and then heated at 900°C. N2 The material was calcined for 2 hours under a certain atmosphere to obtain a single-atom Mn material, denoted as catalyst D.

[0136] Comparative Synthesis Example 2

[0137] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol) and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foam-rich solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL) and labeled as solution B. Solution A was added dropwise to solution B under sonication, and the resulting mixture was stirred at ambient temperature for 12 hours. The white powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and subsequently calcined at 900 °C under a N2 atmosphere for 2 hours to obtain a metal-free nitrogen-doped carbon material, denoted as catalyst E.

[0138] Comparative Synthesis Example 3

[0139] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol), cobalt nitrate hexahydrate (0.010 g, 0.15 mmol), and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foam-rich solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL) and labeled as solution B. Solution A was added dropwise to solution B under sonication, and the resulting mixture was stirred at ambient temperature for 12 hours. The resulting orange powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and subsequently calcined at 900 °C under a N2 atmosphere for 2 hours to obtain a Co single-atom material, denoted as catalyst F.

[0140] Comparative Synthesis Example 4

[0141] Zinc nitrate hexahydrate (0.84 g, 2.8 mmol), ferric nitrate nonahydrate (0.010 g, 0.15 mmol), and hexadecyltrimethylammonium bromide (CTAB, 0.028 g, 0.077 mmol) were dissolved in deionized water (28 mL) and then sonicated to form a foam-rich solution, which was labeled as solution A. 2-Methylimidazole (12.712 g, 150 mmol) was dissolved in deionized water (196 mL) and labeled as solution B. Solution A was added dropwise to solution B under sonication, and the resulting mixture was stirred at ambient temperature for 12 hours. The resulting orange powder was then collected by centrifugation, washed five times with methanol, dried under vacuum overnight, and subsequently calcined at 900 °C under a N2 atmosphere for 2 hours to obtain a single-atom Fe material, denoted as catalyst G.

[0142] Catalyst evaluation

[0143] Transmission electron microscopy (TEM) images of catalyst A obtained in synthesis example 1 were taken using a Hitachi H-7650B microscope at 80 kV, as shown below. Figure 1 As shown in (a).

[0144] High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of catalyst A were obtained using a FEI-Titan Cubed Themis G2 300 microscope at 300 kV, as shown below. Figure 1 As shown in (b).

[0145] Energy dispersive X-ray spectroscopy (EDS) of catalyst A was obtained using a FEI-Themis Z-type microscope at a voltage of 300 kV. Figure 1 As shown in (c).

[0146] Depend on Figure 1 As can be seen, the transmission electron microscope (TEM) images show that Mn2-NC is cubic in shape, with a particle diameter between 70-100 nm, and no obvious nanoparticles were observed, proving that there is no aggregation of metal sites. High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) images show many pairs of Mn atoms, with the distance between the two Mn atoms being... Between. Energy-dispersive X-ray spectroscopy (EDS) plots show the uniform distribution of C, N, O, and Mn elements throughout Mn2-NC.

[0147] Example 1-1 and Comparative Examples 1-1 and 2-1

[0148] Hydrogen peroxide was synthesized by oxygen reduction reaction using a rotating ring disk electrode and catalyst A (Example 1-1) obtained in Synthesis Example 1 above, and catalyst D (Comparative Example 1-1) and catalyst E (Comparative Example 2-1) obtained in Comparative Synthesis Examples 1 and 2, respectively, according to the method described below, and the performance of the catalysts was evaluated.

[0149] The oxygen reduction reaction was carried out in a three-chamber glass electrochemical cell using a Pine rotating disk electrode assembly and a Biologic VSP-300 potentiostat. A rotating disk electrode (RRDE, E6R2, PINE Research Instrumentation) was used as the working electrode, while a platinum wire (99.997% metal-based, Alfa Aesar) and a silver / silver chloride electrode (RE-1CP, ALSI) were used as the counter and reference electrodes, respectively. The oxygen reduction reaction and all measurements were performed at room temperature in 0.1 M HClO4 electrolyte (prepared with 70% HClO4 from Sigma-Aldrich). Ultrapure water (18.2 MΩcm, MilliQ) was used throughout the testing process. The reference electrode was calibrated against a reversible hydrogen electrode before each measurement.

[0150] 2 mg of catalyst and 10 μL of 5% Nafion (D520, 5 wt%, Alfa Aesar) solution were dispersed in 990 μL of isopropanol, and then sonicated for one hour to achieve uniform dispersion, thus obtaining a homogeneous dispersion, i.e., catalyst ink. Then, 3 μL of the obtained catalyst ink was carefully drop-cast onto a polished RRDE surface and dried in air to obtain 25 μg cm⁻¹. -2 Catalyst loading.

[0151] Before the oxygen reduction reaction, the atmosphere is first heated to 0.05 to 1.2 V. RHE Continuous cyclic voltammetry (CV) measurements were performed on the platinum ring electrode of the RRDE until a stable CV curve was obtained. Background current was then collected on the disk electrode between 1.05 and 0.05 V RHE at a scan rate of 20 mV s. -1 .

[0152] Next, linear sweep voltammetry (LSV) was used in an oxygen-saturated 0.1M HClO4 solution from 1.05 to 0.05 V. RHE The ORR catalytic activity of the catalyst was measured. Simultaneously, H₂O₂ generated by the disk electrode was detected on a platinum ring electrode, with the platinum ring electrode potential fixed at 1.2V. RHE All current densities were manually corrected to eliminate ohmic iR drop. The H2O2 collection efficiency (N) of the RRDE electrode was 38%, and the H2O2 selectivity (%) was calculated based on the disk current (Idisk) and ring current (Iring).

[0153] Test results are as follows Figure 2 As shown. By Figure 2 It can be seen that catalyst A used in Examples 1-1 exhibits excellent catalytic activity, maintaining over 85% hydrogen peroxide selectivity over a wide potential range of 0.2-0.6V in the rotating ring electrode test, and achieving a hydrogen peroxide partial current density of 2.3 mA cm⁻¹ at an overpotential of 0.1V. -2 Its performance is among the best reported in the literature. Furthermore, compared to catalysts D and E used in Comparative Examples 1-1 and 2-1 respectively, catalyst A used in Example 1-1, as a catalyst for the electrosynthesis of hydrogen peroxide under acidic conditions, exhibits a lower overpotential for the oxygen reduction reaction, higher selectivity for hydrogen peroxide, and good electrocatalytic performance.

[0154] Examples 1-2 and Comparative Examples 1-2, 3-2 and 4-2

[0155] Hydrogen peroxide was synthesized by oxygen reduction reaction using catalysts A, D, F, and G respectively, and the yield of free radicals was determined.

[0156] The working electrode is coated with 0.2 mg cm -2 The rotating disk electrode (RDE) of the catalyst was pre-activated in a N2-saturated 0.1M HClO4 electrolyte by 100 cycles of CV at 100 mV / s between 0.05 and 1.05 VRHE. It was then immersed in 40 mL of oxygen-saturated 0.1M HClO4 electrolyte (containing 0.005 mM 2,2'-azidobis(3-ethylbenzothiazoline-6-sulfonate ammonium salt) (ABTS)). A reversible hydrogen reference electrode and a platinum counter electrode (99.99%, Gaoss Union) were separated from the working electrode by a Nafion membrane (Nafion N117, DuPont). Subsequently, it curves were recorded using a CHI 760 electrochemical workstation, with the potential controlled at 0.3 V. RHE The rotation speed is 1600 rpm.

[0157] Reactive oxygen species (ROS) detection: During the oxygen reduction reaction, the electrolyte was continuously circulated between the electrochemical cell and the UV-Vis cuvette using a peristaltic pump at a flow rate of 0.1 mL / s. The electrolyte in the cuvette was analyzed by UV-Vis spectroscopy every 5 minutes. The level of ROS species was monitored in real time based on the absorbance change at a wavelength of 417 nm. The results are as follows: Figure 3 As shown.

[0158] Examples 1-3 and Comparative Examples 1-3, 3-3 and 4-3

[0159] Hydrogen peroxide was synthesized by oxygen reduction reaction using catalysts A, D, F, and G respectively, and electron paramagnetic resonance (EPR) measurements were performed.

[0160] Electron paramagnetic resonance measurements were performed on a JEOL FA-200EPR spectrometer. Instrument parameters were as follows: microwave power = 4mW; modulation frequency = 100kHz; modulation amplitude = 1.00G; time constant = 0.1 seconds. Four scans were performed to provide high resolution. All measurements were conducted at room temperature.

[0161] The catalyst (2 mg) was sonicated in 0.1 M HClO4 solution (0.5 mL) for one hour to achieve uniform dispersion, yielding catalyst ink. Then, 5,5-dimethyl-1-pyrrololine N-oxide (DMPO, >98%, Energy Chemicals) and H2O2 were added sequentially to the catalyst ink (0.5 mL) to achieve concentrations of 0.4 M and 0.6 wt%, respectively. After 5 minutes, the solution was filtered (syringe filter, 0.22 μm) to separate the catalyst powder from the liquid. The resulting liquid was immediately transferred to a capillary with an outer diameter of 1 mm, and electron paramagnetic resonance (EPR) measurements were performed to detect free radical signals in the capillary. The results are as follows: Figure 4 As shown.

[0162] Depend on Figure 3 and Figure 4 It can be seen that the free radical yield of catalyst A is significantly lower than that of catalysts D, F and G, which indicates that catalyst A has excellent stability.

[0163] Examples 1-4, 2-4, 3-4 and Comparative Examples 1-4, 2-4

[0164] Hydrogen peroxide was synthesized by oxygen reduction reaction using catalysts A, B, D, and E respectively, and the results were tested.

[0165] Oxygen reduction reaction in a flow cell: 5 mg of catalyst, 990 μL of isopropanol, and 10 μL of 5 wt% Nafion suspension were mixed and sonicated for at least one hour to obtain catalyst ink. The catalyst ink was then sprayed onto carbon paper until the catalyst loading reached 0.5 mg / cm³. -2 After drying in a vacuum for 12 hours, a 1.5×1.5cm sample was taken. 2 A catalyst-supported carbon paper was assembled as a cathode in a gas diffusion flow cell. IrO2-coated carbon paper (catalyst loading 1.0 mg cm⁻¹) was used for the experiment. -2 Titanium foam containing Ag and AgCl (saturated) was used as the counter and reference electrodes. The working and reference regions were separated by a Nafion 117 film. The actual working area of ​​the cell was 1 cm². 2 O2 (99.995% purity) was used as the cathode reactant and injected into the battery at a flow rate of 40 sccm. The flow rate was pre-calibrated using an Agilent ADM flow meter before each measurement. The electrolyte (0.1M HClO4, 100 mL) was circulated in two separate compartments, and the electrolyte flow rate was set to 20 mL / min using a peristaltic pump (Kamoer). -1 First at -10mA cm -2Catalyst activation was performed by running the circuit for 300 seconds. A constant current electrolysis experiment was then conducted to evaluate the stability of H₂O₂ electrosynthesis at a fixed current density. All potentials were manually IR-corrected after electrolysis. The test results are as follows: Figure 5 As shown in Table 1.

[0166] Table 1

[0167]

[0168] Depend on Figure 5 It can be seen that catalyst A has excellent stability and can operate for a long time at industrial current density in PEM gas diffusion electrode, showing potential for industrial application.

[0169] As shown in Table 1, the methods of the present invention using catalysts A, B, and C exhibit longer stable operating times and higher average Faradaic efficiency for hydrogen peroxide. Specifically, compared to Example 3, Examples 1 and 2 using catalysts A and B show even longer stable operating times and higher Faradaic efficiency for hydrogen peroxide, making them suitable for practical applications. The supported catalyst C used in Example 3 exhibits reduced structural stability due to the lack of high-temperature calcination, but its performance is still significantly superior to the single-atom Mn catalyst D and the metal-free catalyst E used in Comparative Examples 1 and 2.

[0170] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0171] Industrial availability

[0172] The preparation method of the present invention can be widely used in the industrial preparation of hydrogen peroxide.

Claims

1. A method for preparing hydrogen peroxide, characterized in that, In an acidic electrolyte, in the presence of a bimetallic manganese catalyst, a two-electron oxygen reduction reaction occurs to produce hydrogen peroxide. The bimetallic manganese catalyst is obtained by carbonization or loading of a precursor, and the precursor has the structure shown in formula (1). In equation (1), the distance between the two Mn atoms is... Between; L1-L6 independently represent organic ligands containing heteroatoms as coordinating atoms, wherein the heteroatoms are selected from one or more of N, O, S, and P, and L1-L6 are optionally connected to each other to form a ring structure; X n- Selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– The anion.

2. The preparation method according to claim 1, characterized in that, L1-L6 are independently selected from phenolic groups, pyridine groups, pyrrole groups, aniline groups, Schiff base groups, porphyrin groups, phthalocyanine groups, and their derivative groups.

3. The preparation method according to claim 1 or 2, characterized in that, The precursor has the structure shown in formula (2). Y is selected from NO3 – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– , n is 2 or 3 m represents the quantity of Y, which can be 1, 2, or 3. R2 is independently selected from H, a hydrocarbon group, a halogen, a hydroxyl group, or a carboxyl group, or R2 is fused with R1 or R1' to form a ring structure, wherein the hydrocarbon group is a C1-C6 alkyl group, preferably a C1-C4 alkyl group. R3 is independently selected from H, halogen, hydroxyl, nitro, carboxyl, and alkyl, alkoxy, and alkoxyalkyl groups having 1 to 6 carbon atoms. R1 and R1' are independently selected from alkylene groups having 2 to 4 carbon atoms or arylene groups having 6 to 20 carbon atoms. Z represents either O or S.

4. The preparation method according to claim 1 or 2, characterized in that, The precursor has the structure shown in formula (3). Among them, A is independently selected from NO3. – Cl – ,Br – OAc – ClO4 – OH – CH3O – HOCH2CH2O – or SO4 2– .

5. The preparation method according to claim 1 or 2, characterized in that, The bimetallic manganese catalyst is obtained by carbonizing the precursor, which is carried out by mixing the precursor with zinc nitrate and 2-methylimidazole and then calcining it.

6. The preparation method according to claim 1 or 2, characterized in that, The bimetallic manganese catalyst is obtained by loading the precursor, which is carried out by mixing the precursor with a support and loading the precursor onto the support; preferably, the support is a carbon-based support, preferably one or more selected from Norit, Ketjen Black, Vulcan, Black Pearl, acetylene black, carbon nanotubes, graphene, carbon nitride (g-C3N4), nitrogen-doped carbon, molybdenum carbide, and iron carbide.

7. The preparation method according to claim 1 or 2, characterized in that, The pH of the acidic electrolyte is 0 to 3; preferably, the acidic electrolyte is an aqueous solution of perchloric acid, hydrochloric acid, or sulfuric acid, and the concentration is preferably 0.001 to 1 mol / L.

8. The preparation method according to claim 1 or 2, characterized in that, The two-electron oxygen reduction reaction is carried out in an electrolytic cell, which includes an electrode assembly comprising a cathode and an anode. The cathode comprises a cathode current collector, a binder, and the bimetallic manganese catalyst. Based on the surface area of ​​the cathode current collector, the loading of the bimetallic manganese catalyst is preferably 0.1–1 mg cm⁻¹. -2 .

9. The preparation method according to claim 8, characterized in that, The bimetallic manganese catalyst is coated on the cathode current collector, which is made of carbon material or metal material. The carbon material is graphite or carbon paper, and the metal material is selected from one or more of platinum, gold, copper, stainless steel, and aluminum. The anode includes an anode current collector, which is made of metal material, selected from one or more of platinum, gold, copper, stainless steel, and aluminum.

10. The preparation method according to claim 1 or 2, characterized in that, The two-electron oxygen reduction reaction occurs at 200 mA / cm². -2 At the above current densities, the selectivity for hydrogen peroxide is over 80%.

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