A composite electrocatalyst for the electrochemical synthesis of H2O2 and its preparation method

Abstract

This invention discloses a composite electrocatalyst for the electrochemical synthesis of H2O2 and its preparation method, belonging to the technical field of catalysts and their preparation for the electrochemical synthesis of hydrogen peroxide. This invention solves the problems of low catalyst activity, selectivity, and stability in existing electrochemical H2O2 synthesis processes. This invention uses carbon spheres synthesized hydrothermally from glucose as the carbon source, and employs a eutectic salt of zinc chloride and potassium chloride as both the zinc source and a pore-forming agent. After mixing the carbon spheres and the eutectic salt, a one-step pyrolysis treatment is performed under an inert atmosphere to complete carbonization, ZnO loading, and porous structure construction, resulting in a ZnO / porous carbon composite electrocatalyst. This electrocatalyst exhibits a high H2O2 selectivity of up to 95% under alkaline conditions and a 7.02 mol / g reaction rate at 0.2 V vs RHE. ‑1 h ‑1 The high yield and excellent cycle stability significantly improve the efficiency and practicality of electrochemical synthesis of H2O2.

Description

Technical Field

[0001] This invention relates to a composite electrocatalyst for the electrochemical synthesis of H2O2 and its preparation method, belonging to the technical field of catalysts for the electrochemical synthesis of hydrogen peroxide and their preparation. Background Technology

[0002] Hydrogen peroxide (H₂O₂) is an important chemical, but traditional anthraquinone production methods suffer from high energy consumption and environmental impact. Electrochemical synthesis of H₂O₂ involves a two-electron oxygen reduction reaction (2e⁻¹). - Ortho-hydrogenase (ORR) directly produces H2O2 from oxygen, offering a greener and more sustainable alternative and becoming a research hotspot. The key to this technology lies in developing efficient, highly selective, and stable electrocatalysts to preferentially generate H2O2 and suppress the side reaction that produces water.

[0003] While noble metal catalysts such as palladium (Pd) possess high ORR activity and are often used as benchmarks, their high cost and limited H2O2 selectivity restrict their practical applications, necessitating the development of low-cost alternatives. Non-noble metals (such as Fe, Co, Cu, Zn, etc.) and their compounds (especially metal oxides) and carbon-based materials (such as activated carbon, graphene, etc.) have attracted considerable attention due to their abundant resources, low cost, and tunable properties. Constructing composite catalysts by loading non-noble metal active components onto carbon materials, utilizing the conductivity, high surface area, and stability of carbon, and the catalytic activity of non-noble metals, while optimizing the structure and interface through synergistic effects, has proven to be an effective strategy for improving catalytic activity, selectivity, and stability. Among non-noble metal components, metal oxides (such as zinc oxide ZnO) possess unique electronic structures and surface properties (including defect sites), playing a crucial role in regulating 2e2e2 activity. - It shows potential in ORR selectivity. Meanwhile, porous carbon supports can effectively disperse active components, optimize mass transfer, and potentially improve performance through confinement effects. Therefore, constructing composite catalysts (such as ZnO / porous carbon) by supporting metal oxides on porous carbon supports is considered a highly promising strategy. Summary of the Invention

[0004] To address the problems of low catalyst activity, selectivity, and stability in existing electrochemical synthesis of H2O2 processes, this invention provides a composite electrocatalyst for electrochemical synthesis of H2O2 and its preparation method.

[0005] The technical solution of the present invention:

[0006] One objective of this invention is to provide a method for preparing a composite electrocatalyst, the method comprising the following steps:

[0007] (1) Dissolve glucose in ultrapure water, perform hydrothermal reaction, filter, wash and dry to obtain glucose carbon spheres;

[0008] (2) After the glucose carbon spheres and eutectic salt are mixed evenly, they are placed in a tube furnace for pyrolysis under an inert atmosphere. The product is filtered and washed with deionized water until the pH is 7, and then dried to obtain oxide-supported glucose mesoporous carbon spheres, which are the composite electrocatalysts.

[0009] Further specified, the mass-to-volume ratio of glucose to ultrapure water in (1) is 2.0-6.0g:30-70mL.

[0010] Further specifying, (1) the process of dissolving glucose in ultrapure water is as follows: add glucose to ultrapure water and ultrasonically treat it for 10±5 min at 300W until the solution is clear.

[0011] Further, (1) the hydrothermal reaction temperature is 150-200℃ and the time is 4-8h.

[0012] Further specifying, (1) the washing solution is a mixture of ethanol and water in a volume ratio of 3:1, the washing method is centrifugal washing, and the number of times is 3.

[0013] Further specified, in (1) the drying temperature is 60℃ and the time is 12h.

[0014] Further specifying, (2) the crystalline salt is composed of zinc chloride and potassium chloride in a molar ratio of 1:1.

[0015] Further specifying, in (2), the mass ratio of glucose carbon spheres to eutectic salt is 1:2-4.

[0016] Further, in (2), the pyrolysis treatment temperature is 700-900℃ and the time is 4-8h.

[0017] Further, the heating rate of the pyrolysis treatment in (2) is 3-5℃ / min.

[0018] Further specified, in (2), the inert atmosphere is nitrogen, and the nitrogen flow rate is 30-50 mL / min.

[0019] The second objective of this invention is to provide a composite electrocatalyst prepared by the above method.

[0020] The third objective of this invention is to provide an application of the above-mentioned composite electrocatalyst, specifically for the preparation of cathode materials for the electrochemical synthesis of H2O2.

[0021] The fourth objective of this invention is to provide a method for preparing a cathode material for electrochemical synthesis of H2O2. Specifically, the above-mentioned composite electrocatalyst, deionized water, anhydrous ethanol and Nafion solution are mixed evenly, then drop-coated onto a hydrophobic substrate and dried to obtain the cathode material.

[0022] Further specifying, the mass-volume ratio of the composite electrocatalyst, deionized water, anhydrous ethanol, and Nafion solution is 3-10 mg: 300-1000 μL: 150-500 μL: 50-200 μL, wherein the mass concentration of the Nafion solution is 5%.

[0023] Further specifying, the hydrophobic substrate is hydrophobic carbon paper, hydrophobic carbon cloth, or a gas diffusion layer.

[0024] The fifth objective of this invention is to provide a method for electrochemically synthesizing H2O2. This method employs a three-electrode system, with an H-type electrolytic cell. Under alkaline electrolyte conditions, the aforementioned cathode material is used as the working electrode, a mercury / mercury oxide electrode as the reference electrode, and a carbon rod as the auxiliary electrode. Electrolysis is carried out under a constant voltage of 0.2V (relative to the reversible hydrogen electrode, RHE).

[0025] Beneficial effects:

[0026] This invention utilizes carbon spheres synthesized hydrothermally from glucose as the carbon source, and a eutectic salt of zinc chloride and potassium chloride as both the zinc source and a pore-forming agent. By mixing the carbon spheres and the eutectic salt, a one-step pyrolysis process is performed under an inert atmosphere to complete carbonization, ZnO loading, and porous structure construction, resulting in a ZnO / porous carbon composite electrocatalyst. This electrocatalyst exhibits a high H₂O₂ selectivity of up to 95% under alkaline conditions and a 7.02 mol / g e⁻¹ at 0.2 V vs RHE. -1 The high yield and excellent cycling stability of h-1 significantly improve the efficiency and practicality of electrochemical synthesis of H2O2, demonstrating outstanding catalytic performance. Attached Figure Description

[0027] Figure 1 SEM image of the cathode material for electrochemical synthesis of H2O2 prepared in Example 1;

[0028] Figure 2 The nitrogen adsorption-desorption curve of ZnO@MCS-800 prepared in Example 1 is shown.

[0029] Figure 3 A comparison of the BET specific surface areas of ZnO@MCS-800 and CS prepared in Example 1 and MCS-800 prepared in Comparative Example 1;

[0030] Figure 4 X-ray diffraction patterns of ZnO@MCS-800 and CS prepared in Example 1 and MCS-800 prepared in Comparative Example 1;

[0031] Figure 5 These are the CV curves of ZnO@MCS-800 prepared in Example 1 under different atmospheres;

[0032] Figure 6 Comparison of electron transfer number and H2O2 selectivity between ZnO@MCS-800 prepared in Example 1 and MCS-800 prepared in Comparative Example 1;

[0033] Figure 7 This is a comparison of the hydrogen peroxide yield of ZnO@MCS-800 prepared in Example 1 and MCS-800 prepared in Comparative Example 1 in an H electrolysis cell;

[0034] Figure 8 This is a graph showing the yield change of ZnO@MCS-800 prepared in Example 1 after ten cycles in an H electrolytic cell. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0039] Example 1

[0040] Step 1, Preparation of glucose carbon spheres:

[0041] 5.4 g of analytical grade glucose was poured into 60 ml of ultrapure water (resistivity 18.2 MΩ·cm) and ultrasonicated at 300 W for 20 min in a 40 kHz ultrasonic cleaner until the glucose was completely dissolved in the ultrapure water and the solution was clear. The solution was then transferred to a 100 ml high-pressure reactor lined with polytetrafluoroethylene (40-60% filling). The reactor was then placed in a forced-air drying oven and heated to 190 °C at a rate of 5 °C / min. The mixture was hydrothermally reacted at 190 °C for 5 h and allowed to cool naturally to room temperature. The sample was then filtered through a 0.22 μm nylon filter membrane. The resulting sample was washed by centrifugation with a 3:1 volume ratio of ethanol and water (7000 rpm × 3 times) and vacuum dried at 60 °C for 12 h to obtain brown monodisperse carbon spheres, which were named CS.

[0042] Step 2, Preparation of composite electrocatalyst:

[0043] Take 300 mg of the glucose carbon spheres obtained in step 1 above and grind and mix them with 900 mg of eutectic salt (the eutectic salt consists of 575 mg of zinc chloride and 325 mg of potassium chloride). After mixing evenly, pour the mixture into 10 ml of ultrapure water, stir magnetically for 1 h, and then dry it in a forced-air drying oven. Place the dried mixture in a tube furnace for pyrolysis treatment for 4 h at a pyrolysis temperature of 800 °C, a heating rate of 3 °C / min, and a nitrogen flow rate of 30 mL / min. After pyrolysis, allow the temperature inside the tube furnace to cool naturally to room temperature, remove the sample, and then filter and wash it with deionized water until the pH is 7. Finally, dry the sample to obtain the glucose mesoporous carbon spheres supported by metal oxide, which is the composite electrocatalyst, named ZnO@MCS-800.

[0044] Step 3, Preparation of cathode material for electrochemical synthesis of H2O2:

[0045] Take 3 mg ZnO@MCS-800, add 300 μL of deionized water, 150 μL of anhydrous ethanol and 50 μL of 5% Nafion solution, sonicate for 30 min and then drop onto a hydrophobic carbon cloth substrate and dry to form a catalyst cathode material.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that the ZnO@MCS-800 obtained in step 2 was treated with 3 mol / L hydrochloric acid for 1 hour to remove ZnO, resulting in a porous carbon electrocatalyst without ZnO support, which was named MCS-800. The remaining process steps and parameter settings are the same as in Example 1.

[0048] Example of effect

[0049] (1) The morphology of the electrode prepared in Example 1 was observed using a Hitachi S-4800 scanning electron microscope, and the resulting scanning electron microscope images are shown below. Figure 1As shown. By Figure 1 It can be seen that the prepared ZnO@MCS-800 has a uniform morphology and is spherical, with a particle size distribution between 200-400 nm.

[0050] (2) The nitrogen (N2) adsorption-desorption isotherm of ZnO@MCS-800 prepared in Example 1 was measured using a Bestech high-performance surface area and micropore analyzer. The obtained BET curve is shown below. Figure 2 As shown, by Figure 2 It can be seen that the prepared ZnO@MCS-800 exhibits a type IV nitrogen adsorption-desorption curve characteristic of mesoporous structures. Further comparisons of the BET specific surface areas of ZnO@MCS-800 and CS prepared in Example 1, and MCS-800 prepared in Comparative Example 1, are shown below. Figure 3 As shown in the figure, compared with CS and MCS-800, ZnO@MCS-800 has the largest BET specific surface area of ​​1003.79㎡ / g, which is beneficial to improving the exposure of active sites of the catalyst and the mass transfer efficiency of reactants.

[0051] (3) The phase composition of ZnO@MCS-800 and CS prepared in Example 1 and MCS-800 prepared in Comparative Example 1 were analyzed by X-ray diffraction (XRD). The diffraction patterns obtained are shown in the attached figure. Figure 4 As shown in the figure. The analysis results show that CS mainly exhibits an amorphous carbon structure, while ZnO@MCS-800 clearly shows the characteristic diffraction peaks of zinc oxide (ZnO), proving that ZnO was successfully loaded and maintained its crystal phase structure, providing an active catalytic component for the composite electrocatalyst.

[0052] (4) The hydrogen evolution performance and oxygen reduction reaction (ORR) activity of the ZnO@MCS-800 prepared in Example 1 were detected using a rotating ring-disk electrode (RDE) method in 0.1M KOH electrolyte on an electrochemical workstation (CHI760E). The ZnO@MCS-800 prepared in Example 1 was used as the working electrode, the hydrogen reduction electrode was used as the reference electrode, and the auxiliary electrode was a 1×1 cm electrode. 2 A glassy carbon electrode was used. The test conditions were a scan rate of 5 mV·s. -1 Cyclic voltammetry (CV) tests were performed under oxygen and nitrogen saturation conditions, with a potential range of -0.1V to 1.1V (relative to the reversible hydrogen electrode, RHE). The test results are as follows: Figure 5 As shown, under oxygen-saturated conditions, the ZnO / porous carbon composite electrocatalyst exhibits a significant reduction peak, demonstrating excellent oxygen reduction activity; however, under nitrogen-saturated conditions, there is no significant reduction peak, proving that the reduction reaction mainly originates from the participation of oxygen.

[0053] Furthermore, using ZnO@MCS-800 prepared in Example 1 and MCS-800 prepared in Comparative Example 1 as working electrodes, respectively, the two-electron oxygen reduction reaction (ORR) activities of both were characterized using the aforementioned electrochemical workstation. The electron transfer number and H2O2 selectivity comparison curves were obtained by calculating the obtained disk-ring currents. The results are as follows: Figure 6 As shown in the figure, the selectivity of MCS-800 for hydrogen peroxide formation is only 70-80%, while the selectivity of ZnO@MCS-800 is significantly improved, reaching over 90%, and the electron transfer number is close to the ideal two-electron process. This indicates that the ZnO@MCS-800 prepared in Example 1 can efficiently and selectively promote the formation of hydrogen peroxide (2e). - The oxygen reduction reaction produces high-purity hydrogen peroxide.

[0054] (5) Hydrogen peroxide production performance was tested using an electrochemical workstation (CHI760E). The specific tests employed a three-electrode system, with an H-type electrolytic cell in 0.1M KOH electrolyte. The catalyst cathode materials prepared in Example 1 and Comparative Example 1 were used as the working electrodes, respectively; a mercury / mercury oxide electrode was used as the reference electrode, and a carbon rod as the auxiliary electrode. Electrolysis was performed under a constant voltage condition of 0.2V (relative to the reversible hydrogen electrode, RHE). The experimental results are as follows: Figure 7 As shown, under the same conditions, the cathode material prepared in Example 1 exhibited a higher hydrogen peroxide yield, reaching 7.02 mol g. -1 The high yield of h-1 and its Faraday efficiency exceeding 90% significantly improve the electrochemical synthesis efficiency of hydrogen peroxide.

[0055] (6) Electrode stability was tested using an electrochemical workstation (CHI760E). A three-electrode system was employed, with an H-type electrolytic cell in 0.1M KOH electrolyte. The catalyst cathode material prepared in Example 1 was used as the working electrode, a mercury / mercury oxide electrode as the reference electrode, and a carbon rod as the counter electrode. Constant voltage testing was conducted at 0.2V (relative to the reversible hydrogen electrode), and the cyclic test results are as follows: Figure 8 As shown in the figure, after 10 cycles of electrolysis, each lasting 1 hour, the average yield reached 6.88 mol g. -1 h-1 exhibits Faraday efficiencies of over 80%, and its performance does not show significant degradation after 10 cycles, demonstrating excellent cycling stability.

[0056] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a composite electrocatalyst, characterized in that, include: (1) Dissolve glucose in ultrapure water, perform hydrothermal reaction, filter, wash, and dry to obtain glucose carbon spheres; (2) After the glucose carbon spheres and eutectic salt are mixed evenly, they are placed in a tube furnace for pyrolysis under an inert atmosphere. The product is filtered and washed with deionized water until the pH is 7, and then dried to obtain zinc oxide-supported glucose mesoporous carbon spheres, which are the composite electrocatalysts. Among them, (2) the crystalline salt is composed of zinc chloride and potassium chloride in a molar ratio of 1:

1.

2. The preparation method according to claim 1, characterized in that, (1) The mass-volume ratio of glucose to ultrapure water is 2.0-6.0g:30-70mL.

3. The preparation method according to claim 1, characterized in that, (1) The hydrothermal reaction temperature is 150-200℃ and the time is 4-8h.

4. The preparation method according to claim 1, characterized in that, (2) The mass ratio of glucose carbon spheres to eutectic salt is 1:2-4.

5. The preparation method according to claim 1, characterized in that, (2) The pyrolysis treatment temperature is 700-900℃ and the time is 4-8h.

6. A composite electrocatalyst prepared by the method according to any one of claims 1 to 5.

7. An application of the composite electrocatalyst according to claim 6, characterized in that, Preparation of cathode materials for electrochemical synthesis of H2O2.

8. A method for preparing a cathode material for the electrochemical synthesis of H2O2, characterized in that, After uniformly mixing the composite electrocatalyst described in claim 6, deionized water, anhydrous ethanol, and Nafion solution, the mixture is drop-coated onto a hydrophobic substrate and dried to obtain the cathode material.

9. A method for electrochemically synthesizing H2O2, characterized in that, A three-electrode system is adopted, with the electrolytic cell being an H-type battery. Under alkaline electrolyte conditions, the cathode material prepared by the method described in claim 8 is used as the working electrode, the mercury / mercury oxide electrode is used as the reference electrode, and the carbon rod is used as the auxiliary electrode. Electrolysis is carried out under a constant voltage of 0.2 V.

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