A composite electrode material for electrocatalytic water oxidation to synthesize hydrogen peroxide, a preparation method and applications

Abstract

This invention belongs to the field of electrochemical catalytic materials technology, and relates to a composite electrode material, its preparation method, and its application for the electrocatalytic oxidation of water to synthesize hydrogen peroxide. Addressing the problems of insufficient activity and selectivity of existing catalysts and the easy decomposition of products, this invention employs a self-supporting carbon substrate and a polytetrafluoroethylene (PTFE) coating on its surface, constructing a composite electrode through spraying and heat treatment. The composite electrode is used for the synthesis of hydrogen peroxide in an electrolyte containing carbonates and phosphates; it achieves a maximum Faraday efficiency of 89.0% and a maximum formation rate of [missing information].

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalytic materials technology, specifically to a poly(perfluoroethylene propylene) modified carbon-based composite electrode material, its preparation method, and its application in the synthesis of hydrogen peroxide via the two-electron water oxidation pathway. Background Technology

[0002] Hydrogen peroxide (H2O2), as a highly efficient and environmentally friendly green oxidant, decomposes only into water and oxygen, conforming to the principles of green chemistry. Therefore, it has wide applications in chemical synthesis, wastewater treatment, pulp bleaching, and semiconductor cleaning. In recent years, the application potential of H2O2 in the energy sector (such as fuel cells) has also attracted increasing attention. Therefore, developing efficient and low-cost H2O2 synthesis and catalytic technologies is of great significance for achieving sustainable development.

[0003] Currently, the industrial production of H2O2 mainly relies on the anthraquinone process, which suffers from problems such as complex processes, environmental pollution, and storage and transportation safety risks. In contrast, electrochemical synthesis of H2O2, due to its advantages such as mild reaction conditions, the ability to achieve distributed production, and environmental friendliness, is gradually becoming a research hotspot. In the electrochemical synthesis pathway, the two-electron oxygen reduction (… ) and two-electron water oxidation ( These are two main technical routes. Among them, During the cathode synthesis of hydrogen peroxide, the process constantly faces competing reactions for the further reduction of the product to water. This necessitates controlling the catalyst and potential within a narrow "selectivity window," increasing the complexity of system regulation. In contrast, The pathway uses water as a raw material, fundamentally avoiding dependence on external oxygen supply. This not only greatly simplifies the system structure but also makes distributed, on-demand hydrogen peroxide synthesis possible.

[0004] In recent years, in response to Catalyst research has primarily focused on some metal oxides and carbon-based materials. Previous studies have attempted to modify the surface of carbon-based electrodes with polymers, such as using PVDF to coat carbon fiber paper to improve the selectivity of hydrogen peroxide formation. However, these techniques still suffer from unsatisfactory Faradaic efficiency and formation rate of hydrogen peroxide. Therefore, it remains necessary to develop new polymer-modified carbon-based composite electrode systems to improve the Faradaic efficiency and formation rate in the two-electron water oxidation process for hydrogen peroxide synthesis. Summary of the Invention

[0005] This invention provides a poly(perfluoroethylene propylene) modified carbon-based composite electrode material, its preparation method, and its application in the water oxidation synthesis of hydrogen peroxide. The inventors discovered that after spraying and heat treatment, poly(perfluoroethylene propylene) can stably bond to the surface of a self-supporting carbon substrate and influence the electrode interface properties. Furthermore, in an electrolyte containing both carbonates and phosphates, the FEP-modified carbon-based composite electrode achieves high hydrogen peroxide generation performance during two-electron water oxidation synthesis. Experimental results show that by adjusting the FEP loading, annealing temperature, and electrolyte composition, the composite electrode, under different optimized conditions, achieves a Faraday efficiency of up to 89.0% and a hydrogen peroxide generation rate of up to [missing value]. Compared to unmodified carbon cloth, at an FEP loading of... Within the specified range, the FEP / CC composite electrode exhibits higher Faradaic efficiency and hydrogen peroxide generation rate. Compared to using 2MK2CO3 electrolyte alone, the hydrogen peroxide concentration and Faradaic efficiency are both higher in the 2MK2CO3 + 0.1MK3PO4 mixed electrolyte system. These results indicate that this invention does not simply replace other polymers with FEP, but rather achieves improved performance in water oxidation for hydrogen peroxide synthesis through the synergistic regulation of FEP modification, heat treatment conditions, and mixed electrolyte composition.

[0006] The technical solution of this invention:

[0007] A composite electrode material for the electrocatalytic oxidation of water to synthesize hydrogen peroxide, the composite electrode material comprising a self-supporting carbon substrate and a polytetrafluoroethylene propylene coating bonded to its surface.

[0008] Furthermore, the self-supporting carbon substrate is one of carbon cloth, carbon paper, carbon sheet, or carbon felt.

[0009] Furthermore, the loading rate of the polytetrafluoroethylene propylene coating is Preferred .

[0010] A method for preparing a composite electrode material for the electrocatalytic oxidation of water to synthesize hydrogen peroxide, comprising the following steps:

[0011] S1: Pretreatment of the self-supporting carbon substrate;

[0012] S2: Spray the poly(perfluoroethylene propylene) dispersion onto the surface of the pretreated self-supporting carbon substrate;

[0013] S3: After drying, repeat step S2 to control the load of the polytetrafluoroethylene propylene coating;

[0014] S4: Anneal the sprayed material under an inert atmosphere to obtain the composite electrode material.

[0015] Further, in step S1, the pretreatment includes: cutting the self-supporting carbon substrate, ultrasonically cleaning it in acetone, isopropanol, ethanol and deionized water in sequence, and then drying it.

[0016] Further, in step S2, the mass percentage concentration of the poly(perfluoroethylene) propylene dispersion is 0.1% to 50%, preferably 5%.

[0017] Furthermore, in step S3, the drying temperature is 60°C to 100°C, and the drying time is 1 hour to 3 hours.

[0018] Further, in step S4, the annealing temperature is 300°C to 500°C, preferably 400°C. The annealing time is 0.5 hours to 5 hours, preferably 0.5 hours.

[0019] Application of a composite electrode material for the electrocatalytic oxidation of water to synthesize hydrogen peroxide: The composite electrode material is used as the working electrode to perform constant potential electrolysis in an electrolyte containing both carbonate and phosphate, thereby achieving the oxidation of water to hydrogen peroxide using two electrons.

[0020] Furthermore, in the electrolyte, the concentration of carbonate is 0.1M to 5M, and the concentration of phosphate is 0.01M to 2M. Preferably, the concentration of carbonate is 2M and the concentration of phosphate is 0.1M.

[0021] The beneficial effects of this invention are: compared with unmodified carbon cloth electrodes, at an FEP loading of... Within the specified range, the composite electrode modified with FEP achieves higher Faraday efficiency and hydrogen peroxide formation rate under the same test conditions. Experimental results show that, by adjusting the FEP loading, annealing temperature, and electrolyte composition, the composite electrode, when synthesizing hydrogen peroxide through two-electron water oxidation in an electrolyte containing carbonates and phosphates, achieves a maximum Faraday efficiency of 89.0% and a maximum formation rate of [missing value] under different optimized conditions. . Attached Figure Description

[0022] Figure 1 A schematic diagram of the possible reaction mechanism of this invention. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0024] Unless otherwise specified, the raw materials used in the embodiments of this invention were all purchased through commercial channels.

[0025] The performance of this invention was tested under constant potential conditions using the Shanghai Chenhua CHI760E electrochemical workstation.

[0026] Example 1

[0027] This embodiment provides a method for preparing a poly(fluoroethylene propylene) (FEP) modified carbon cloth (CC) composite electrode and its application in the electrocatalytic oxidation of water to synthesize hydrogen peroxide (H2O2).

[0028] 1. Electrode preparation:

[0029] a. Carbon cloth pretreatment: Cut the carbon cloth into 1cm×3cm sheets, place them in acetone, isopropanol, ethanol and deionized water in sequence, and ultrasonically clean them for 30 minutes each, then dry them for later use.

[0030] b. FEP dispersion spraying: Prepare a 5% FEP dispersion and spray it evenly onto the surface of the pretreated carbon cloth.

[0031] c. Repeated spraying and drying: Drying is performed after each spraying. The repeated spraying process is used to control the load of FEP on the carbon cloth. The sample was then placed in a 100°C oven and dried for 2 hours.

[0032] d. Heat treatment: The above materials are placed in a tube furnace and annealed at 400°C for 0.5 h under argon atmosphere protection to obtain the FEP / CC composite electrode.

[0033] 2. Electrochemical performance testing:

[0034] A three-electrode system was used for testing: the prepared FEP / CC electrode was used as the working electrode, and the area of ​​the working electrode after packaging was 0.6 cm². 2 A platinum sheet was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. A Nafion 117 proton exchange membrane was used to separate the anode and cathode chambers. The electrolyte was a 20 mL aqueous solution containing 2 Mk₂CO₃ and 0.1 Mk₃PO₄. Electrolysis was carried out at a constant potential of 2.75 V (relative to the reversible hydrogen electrode, vs. RHE) at ambient temperature and pressure.

[0035] Test results show that the electrode achieves a Faraday efficiency of 81.3% in synthesizing H2O2 under the stated conditions, with a formation rate of [missing information]. .

[0036] Example 2

[0037] The difference between this embodiment and Embodiment 1 is that the loading amount of FEP on the carbon cloth is adjusted by controlling the number of spraying operations. Other preparation steps and testing conditions are the same as in Example 1.

[0038] The evaluation was conducted under the same electrochemical testing system and conditions. The test results show that the Faraday efficiency of this electrode for synthesizing H₂O₂ is 87.6%, and the formation rate is [missing information]. .

[0039] Example 3

[0040] The difference between this embodiment and Embodiment 1 is that the loading amount of FEP on the carbon cloth is adjusted by controlling the number of spraying operations. Other preparation steps and testing conditions are the same as in Example 1.

[0041] The evaluation was conducted under the same electrochemical testing system and conditions. The test results show that the Faraday efficiency of this electrode for synthesizing H₂O₂ is 89.0%, and the formation rate is [missing information]. .

[0042] Example 4

[0043] The difference between this embodiment and Embodiment 1 is that the loading amount of FEP on the carbon cloth is adjusted by controlling the number of spraying operations. Other preparation steps and testing conditions are the same as in Example 1.

[0044] The evaluation was conducted under the same electrochemical testing system and conditions. The test results show that the electrode achieves a Faraday efficiency of 85.7% in synthesizing H₂O₂ under these conditions, with a formation rate of [missing information]. .

[0045] Example 5

[0046] The difference between this embodiment and Example 4 is that the concentration of K3PO4 in the electrolyte is kept constant at 0.1M, and the concentration of K2CO3 is kept constant at 3M. Other preparation steps and testing conditions are the same as in Example 6. Test results show that the Faraday efficiency of this electrode in synthesizing H2O2 is 86.8%, and the generation rate is... .

[0047] Example 6

[0048] The difference between this embodiment and Example 4 is that the concentration of K3PO4 in the electrolyte is kept constant at 0.1M, and the concentration of K2CO3 is kept constant at 5M. Other preparation steps and testing conditions are the same as in Example 6. Test results show that the Faraday efficiency of this electrode in synthesizing H2O2 is 87.2%, and the generation rate is... .

[0049] To further illustrate the influence of different electrolyte systems on the hydrogen peroxide generation performance of the composite electrode of the present invention, a single salt electrolyte system is set as a comparative example, and a carbonate / phosphate mixed electrolyte system is set as an example for comparison, so as to examine the differences between the mixed electrolyte system and the single salt system.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 4 is that the electrolyte is saturated K2SO4, while the other preparation steps and test conditions are the same as in Example 4. Test results show that in the control electrolyte system without carbonates and phosphates, the electrode's Faraday efficiency is 1.4%, and the H2O2 concentration is 0.04 mM.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 4 is that the electrolyte is 2.1 M KH2PO4, while the other preparation steps and test conditions are the same as in Example 4. Test results show that in a single phosphate electrolyte system, the electrode's Faraday efficiency is 1.7%, and the H2O2 concentration is 0.05 mM.

[0054] Comparative Example 3

[0055] The difference between this comparative example and Example 4 is that the electrolyte is 2.1M K2HPO4, while the other preparation steps and test conditions are the same as in Example 4. Test results show that in a single phosphate electrolyte system, the electrode's Faraday efficiency is 2.8%, and the H2O2 concentration is 0.09 mM.

[0056] Comparative Example 4

[0057] The difference between this comparative example and Example 4 is that the electrolyte is 2.1mM M3PO4, while the other preparation steps and test conditions are the same as in Example 4. Test results show that in a single phosphate electrolyte system, the electrode's Faraday efficiency is 3.4%, and the H2O2 concentration is 0.11mM.

[0058] Comparative Example 5

[0059] The difference between this comparative example and Example 4 is that the electrolyte is 2.1 Mk₂CO₃, while the other preparation steps and test conditions are the same as in Example 4. Test results show that in a single carbonate electrolyte system, the Faraday efficiency of the electrode is 46.7%, and the H₂O₂ concentration is 1.45 mM.

[0060] Comparative Example 6

[0061] The difference between this comparative example and Example 1 is that the carbon cloth was pretreated, dried and annealed according to the electrode preparation method in Example 1, and FEP was not sprayed. The resulting blank carbon cloth (CC) was directly used as the working electrode.

[0062] Other preparation steps and testing conditions were the same as in Example 1. Test results showed that the Faraday efficiency of H2O2 synthesis from blank carbon cloth was 21.5%, and the generation rate was... The results from Examples 1 to 3 show that the effect of FEP modification on the two-electron water oxidation synthesis of hydrogen peroxide is related to its loading. When the FEP loading is... At that time, the FEP / CC composite electrode exhibited higher Faradaic efficiency and hydrogen peroxide generation rate than the blank carbon cloth. This indicates that, within the aforementioned loading range, FEP modification can improve the electrode's performance in the two-electron water oxidation to hydrogen peroxide synthesis.

[0063] Comparative Example 7

[0064] The difference between this comparative example and Example 4 is that the FEP dispersion was replaced with a PVDF solution with the same polymer loading, and the electrolyte was 2.1 Mk2CO3. All other test conditions were the same as in Example 4. Test results show that in an electrolyte system containing only carbonate, the Faraday efficiency for H2O2 synthesis by the electrode is 40%, and the formation rate is [missing information]. .

[0065] Comparative Example 8

[0066] The difference between this comparative example and Example 4 is that, except for replacing the FEP dispersion with a PVDF solution with the same polymer loading, the preparation of PVDF / CC is the same as in Example 4, except that the spraying, drying, annealing, and testing conditions are identical. Test results show that in a mixed electrolyte system where carbonates and phosphates coexist, the Faraday efficiency for H2O2 synthesis by the electrode is 67%, and the generation rate is... .

[0067] In summary, the experimental results of Comparative Examples 7-8 show that the PVDF / CC electrode exhibits low Faraday efficiency and H2O2 formation rate in a single carbonate electrolyte, which improves under a mixed carbonate and phosphate electrolyte system, but still falls short of the performance of the FEP / CC electrode. This further illustrates that the synergistic effect of the combination of carbonate and phosphate in the electrolyte and the electrode material is crucial for enhancing H2O2 formation. The poly(fluoroethylene propylene) modified self-supporting carbon-based composite electrode and its preparation method provided by this invention, combined with appropriate FEP loading, annealing conditions, and a mixed electrolyte system, can significantly improve H2O2 formation performance. Under different optimized conditions, the Faraday efficiency reaches a maximum of 89.0%, and the formation rate reaches a maximum of [missing information - likely a specific value]. This fully demonstrates the innovation and superiority of the present invention in terms of material modification and electrolyte matching.

[0068] One possible explanation for its mechanism of action is that, after heat treatment, FEP forms a fluorine-containing interface structure on the carbon substrate surface, which may alter the local reaction microenvironment on the electrode surface. Simultaneously, the co-existence of carbonates and phosphates may affect the generation of hydrogen peroxide and subsequent reaction behavior. It should be noted that existing technologies do not provide a clear mechanism for the combined action of FEP-modified self-supporting carbon-based anodes and carbonate / phosphate mixed electrolytes in the two-electron water oxidation process to synthesize hydrogen peroxide. The results of the embodiments and comparative examples of this invention demonstrate that higher Faraday efficiency or hydrogen peroxide generation performance can be obtained under the above-mentioned technical combination, but this invention is not limited to the above theoretical explanation.

[0069] The above embodiments are only used to illustrate the technical content of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art based on the technical concept disclosed in the present invention, as long as they do not depart from the scope defined by the claims of the present invention, should fall within the scope of protection of the present invention.

[0070] Based on the experimental results, Figure 1 A possible reaction mechanism is presented. In this explanation, after heat treatment, FEP can form a fluorine-containing interface layer on the carbon cloth surface, which may affect the local reaction microenvironment on the electrode surface; carbonate ions may participate in the intermediate formation process, and phosphate ions may affect the subsequent reaction behavior of the generated H2O2. This invention is not limited to this mechanism explanation.

Claims

1. A composite electrode material for the electrocatalytic oxidation of water to synthesize hydrogen peroxide, characterized in that, The composite electrode material comprises a self-supporting carbon substrate and a polytetrafluoroethylene propylene coating bonded to its surface.

2. The composite electrode material for electrocatalytic water oxidation to hydrogen peroxide synthesis according to claim 1, characterized in that, The self-supporting carbon substrate is one of the following: carbon cloth, carbon paper, carbon sheet, or carbon felt.

3. The composite electrode material for electrocatalytic water oxidation to hydrogen peroxide synthesis according to claim 1, characterized in that, The loading capacity of the poly(fluoroethylene propylene) coating is .

4. A method for preparing a composite electrode material for electrocatalytic water oxidation to hydrogen peroxide as described in any one of claims 1-3, characterized in that, The steps are as follows: S1: Pretreatment of the self-supporting carbon substrate; S2: Spray the poly(perfluoroethylene propylene) dispersion onto the surface of the pretreated self-supporting carbon substrate; S3: After drying, repeat step S2 to control the load of the polytetrafluoroethylene propylene coating; S4: Anneal the sprayed material under an inert atmosphere to obtain the composite electrode material.

5. The preparation method according to claim 4, characterized in that, In step S1, the pretreatment includes: cutting the self-supporting carbon substrate, ultrasonically cleaning it in acetone, isopropanol, ethanol and deionized water in sequence, and then drying it.

6. The preparation method according to claim 4, characterized in that, In step S2, the mass percentage concentration of the poly(fluoroethylene propylene) dispersion is 0.1% to 50%.

7. The preparation method according to claim 4, characterized in that, In step S3, the drying temperature is 60℃ to 100℃, and the drying time is 1h to 3h.

8. The preparation method according to claim 4, characterized in that, In step S4, the annealing temperature is 300°C to 500°C; the annealing time is 0.5 hours to 5 hours.

9. The application of the composite electrode material for the electrocatalytic oxidation of water to synthesize hydrogen peroxide as described in any one of claims 1-3, characterized in that, Using composite electrode materials as working electrodes, constant potential electrolysis is performed in an electrolyte containing both carbonates and phosphates to achieve the synthesis of hydrogen peroxide through the oxidation of water with two electrons.

10. The application according to claim 9, characterized in that, The electrolyte contains carbonates at a concentration of 0.1 M to 5 M and phosphates at a concentration of 0.01 M to 2 M.

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