A catalyst for the electrochemical preparation of hydrogen peroxide, its preparation method and application

Abstract

This invention discloses a catalyst for the electrochemical preparation of hydrogen peroxide, its preparation method, and its application, belonging to the field of electrochemical hydrogen peroxide preparation. The preparation method includes the following steps: (1) dissolving a transition metal salt in an organic solvent to obtain a transition metal salt solution; (2) sequentially adding PAN and thiophene to the transition metal salt solution and stirring to obtain a precursor solution; (3) electrospinning the precursor solution to obtain a catalyst precursor; (4) pre-oxidizing the catalyst precursor; and (5) calcining the catalyst precursor treated in step (4) to obtain the catalyst. The catalyst prepared by this method has good mechanical properties and excellent catalytic performance, and exhibits good performance when applied to fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical preparation of hydrogen peroxide, specifically relating to a catalyst for electrochemical preparation of hydrogen peroxide, its preparation method, and its application. Background Technology

[0002] Electrochemical two-electron oxygen reduction (2e - The ORR (Organic Oxygen Reduction) pathway enables continuous, decentralized production of H2O2 under mild conditions. This technology not only effectively avoids problems related to H2O2 storage and transportation but also achieves efficient utilization of renewable energy, making it a promising H2O2 preparation process for the future. In the 1930s, Berl et al. first reported the synthesis of H2O2 using electrochemical oxygen reduction. With continuous research development, the emergence of electro-Fenton technology has to some extent overcome the limitations of H2O2 preparation under alkaline systems. In recent years, the electrochemical two-electron oxygen reduction (ORR) system for H2O2 preparation has gradually developed into an emerging field and shows broad application prospects.

[0003] To date, various high-performance electrocatalysts have been successfully developed, mainly including noble metal-based catalysts, carbon-based catalysts, single-atom catalysts, and molecular catalysts. However, the scarcity of noble metal resources and the environmental pollution caused by transition metals limit their practical application. In contrast, carbon-based materials have been widely used in 2e electrocatalysts in recent years due to their advantages such as low cost, abundant reserves, and easily tunable surface structure. - In the research on ORR production of H2O2, it has a broader application prospect in the electrocatalytic synthesis of H2O2.

[0004] Di-Jia Liu et al. used cobalt-containing or cobalt-zinc-containing zeolite imidazole ester frameworks (ZIFs) as precursors, thermally activated them, introduced Pt, then reduced crude amine in situ and annealed at high temperature under ammonia (NH3) to obtain the final catalyst. However, the catalytic performance was poor, with a selectivity of around 50%. Vojislav R. Stamenkovic's team prepared a platinum-nickel (Pt-Ni) bimetallic nanocatalyst by transforming the precursor PtNi3 polyhedron into PtNi3 with a three-dimensional nanoframework structure and then heat-treating it. This catalyst had better selectivity, but the raw material metal Pt was expensive, resulting in high costs.

[0005] In summary, there is currently a lack of catalysts in this field that possess high electrical conductivity, thermal stability, and oxidation resistance. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a catalyst for the electrochemical preparation of hydrogen peroxide, its preparation method, and its application, solving the technical problems of low selectivity and high cost in the electrochemical synthesis of hydrogen peroxide in the prior art. The catalyst of this invention for the electrochemical preparation of hydrogen peroxide has a simple preparation method, stable electrolysis effect, high hydrogen peroxide selectivity, and long service life.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, comprising the following steps:

[0009] (1) Dissolve the transition metal salt in an organic solvent to obtain a transition metal salt solution;

[0010] (2) Polyacrylonitrile (PAN) and thiophene were added sequentially to the transition metal salt solution and stirred to obtain the precursor solution;

[0011] (3) Electrospinning the precursor solution to obtain the catalyst precursor;

[0012] (4) Pre-oxidize the catalyst precursor;

[0013] (5) The catalyst precursor treated in step (4) is calcined to obtain the catalyst.

[0014] Preferably, the catalyst is used after being ground, washed, and dried.

[0015] Furthermore, the washing process involves washing with deionized water for 0.5-2 hours; the drying process is carried out at a temperature of 60-70°C for 12-24 hours.

[0016] The S-doped Ni-NC nanowires prepared by the method of this invention have a diameter of 7-11 nm and exhibit excellent mechanical properties. The PAN polymer, uniformly dispersed within the fiber membrane, exposes the maximum specific surface area, maximizing the adsorption of transition metal salts and thiophene while minimizing their loss. Furthermore, the nanofiber membrane prepared from the polymerized PAN nanowires can effectively share applied stress, thereby improving the membrane's mechanical strength.

[0017] Further, in step (1), the molar concentration of the transition metal in the transition metal salt solution is 0.10-0.15 mol / L, and the transition metal salt is a nickel salt, sodium salt, or zinc salt; the organic solvent is a strongly polar aprotic organic solvent; the method of dissolving to obtain the transition metal salt solution includes ultrasound, with an ultrasound power of 50-300W and an ultrasound time of 0.3-1h.

[0018] Preferably, the transition metal salt is a nickel salt, and more preferably nickel acetate.

[0019] Preferably, the strongly polar aprotic organic solvent includes N,N-dimethylformamide (DMF).

[0020] Furthermore, the nickel salt is at least one of nickel nitrate and nickel acetate; the sodium salt is at least one of sodium chloride and sodium nitrate; and the zinc salt is at least one of zinc acetate and zinc chloride.

[0021] Further, in step (2), the ratio of transition metal, PAN and thiophene in the precursor solution is 1:20-30:42-84 (m(g):m(g):v(mL)); the polymerization amount of PAN ranges from 100,000 to 1,500,000; the stirring method is magnetic stirring, the stirring power is 50-100W, and the stirring time is 1-12h.

[0022] Furthermore, in step (3), the voltage of the electrospinning is 10-22kV, the temperature is 20-40℃, the humidity is 20-50%rh, and the injection rate is 4-6mL / h.

[0023] Further, in step (4), the pre-oxidation conditions are 150-220℃ for 20-40h; in step (5), the calcination temperature is 700-1000℃, and the heating rate is 3-8℃ / min. -1 Under a nitrogen atmosphere, calcine for 1-4 hours.

[0024] In a second aspect, the present invention provides a catalyst for the electrochemical preparation of hydrogen peroxide, wherein the catalyst is an S-doped MNC network structure nanowire, wherein M represents a transition metal element;

[0025] Furthermore, the transition metal element is Ni, Na, or Zn.

[0026] Thirdly, the present invention provides the application of the catalyst in the electrocatalytic synthesis of H2O2.

[0027] Fourthly, the present invention provides a fuel cell including the catalyst described above.

[0028] Beneficial effects:

[0029] (1) The catalyst provided by the present invention is an S-doped Ni-NC nanowire network structure. S is doped into the M (metal)-NC structure. Unlike traditional doping, the present invention performs S doping and MNC structure synthesis simultaneously to form a nanowire structure. This doping will enable the nanowire to construct an auxiliary network structure that helps proton conduction, resulting in a significant improvement in both proton conductivity and mechanical strength of the nanowire.

[0030] (2) In the preparation method of the present invention, PAN, thiophene, and Ni salt in a highly polymerized state are formed into nanofibers by electrospinning, which can expose the largest specific surface area and maximize the adsorption and anchoring of Ni salt and thiophene, which is beneficial to reducing the subsequent loss of Ni and S. At the same time, PAN in a highly polymerized state can fully share the applied stress and improve the mechanical strength. S in the fiber can enhance the selectivity of oxygen reduction catalysis through S action, and increase the hydrogen peroxide selectivity. Due to the high conductivity, low metal salt loss rate, and high hydrogen peroxide selectivity of the nanofibers of the present invention, the assembled battery has better performance and lifespan.

[0031] (3) Nanofibers prepared by electrospinning PAN have been widely used as catalyst supports for fuel cells due to their ultra-high specific surface area, good chemical resistance, conductivity, and mechanical properties. Although the nanofibers obtained by spinning have many advantages, such as good mechanical strength, they are greatly affected by external conditions and their performance is easily altered, leading to a decrease in hydrogen peroxide selectivity, which affects catalytic activity and thus battery life. Therefore, from a long-term perspective, we need to further optimize the process to improve the hydrogen peroxide selectivity and further improve the battery's operating efficiency and lifespan. Attached Figure Description

[0032] Figure 1 The images are scanning electron microscope (SEM) images of the fiber filaments prepared in Example 1(a), Comparative Example 1(b), and Comparative Example 2(c) of the present invention.

[0033] Figure 2 Images obtained from testing the catalysts prepared in Examples 1(a), 2(b), and 3(c) of this invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0035] Example 1

[0036] The catalyst was prepared using polyacrylonitrile (PAN), thiophene, and nickel acetate as raw materials according to the following steps:

[0037] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0038] Step 2: Add 3g of polyacrylonitrile (PAN, polymerization amount 1.5 million) and 10mL of thiophene to the nickel acetate solution in sequence, and stir magnetically for 4h (stirring power of 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0039] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at a high temperature of 200°C for 20 hours to pre-oxidize the catalyst precursor.

[0040] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1 Under a nitrogen atmosphere, the temperature was raised to the set temperature and held for 2 hours. Then, the temperature was lowered to room temperature in the furnace to obtain the S-doped Ni-NC nanowire catalyst.

[0041] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0042] Example 2

[0043] The catalyst was prepared using polyacrylonitrile (PAN), thiophene, and nickel acetate as raw materials according to the following steps:

[0044] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0045] Step 2: Add 3g of polyacrylonitrile (PAN, polymerization amount 1.5 million) and 5mL of thiophene to the nickel acetate solution in sequence, and stir magnetically for 4h (stirring power of 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0046] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at a high temperature of 200°C for 20 hours to pre-oxidize the catalyst precursor.

[0047] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1Under a nitrogen atmosphere, the temperature was raised to the set temperature and held for 2 hours. Then, the temperature was lowered to room temperature in the furnace to obtain the S-doped Ni-NC nanowire catalyst.

[0048] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, comprising the following steps:

[0051] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0052] Step 2: Add 3g of polyacrylonitrile (PAN, polymerization amount 1.5 million) to the nickel acetate solution and stir magnetically for 4h (stirring power is 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0053] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at a high temperature of 200°C for 20 hours to pre-oxidize the catalyst precursor.

[0054] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1 Under a nitrogen atmosphere, the temperature is raised to the set temperature and maintained for 2 hours. Then, the temperature is lowered to room temperature in the furnace to obtain the catalyst.

[0055] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0056] Comparative Example 2

[0057] This comparative example provides a method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, comprising the following steps:

[0058] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0059] Step 2: Add 3g of polyethylene oxide (PEO, polymerization amount 100,000) and 10mL of thiophene to the nickel acetate solution in sequence, and stir magnetically for 4h (stirring power is 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0060] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at a high temperature of 200°C for 20 hours to pre-oxidize the catalyst precursor.

[0061] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1 Under a nitrogen atmosphere, the temperature is raised to the set temperature and maintained for 2 hours. Then, the temperature is lowered to room temperature in the furnace to obtain the catalyst.

[0062] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, comprising the following steps:

[0065] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0066] Step 2: Add 3g of polyacrylonitrile (PAN, polymerization amount 1.5 million) and 10mL of thiophene to the nickel acetate solution in sequence, and stir magnetically for 4h (stirring power of 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0067] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at a high temperature of 280°C for 20 hours to pre-oxidize the catalyst precursor.

[0068] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1 Under a nitrogen atmosphere, the temperature is raised to the set temperature and maintained for 2 hours. Then, the temperature is lowered to room temperature in the furnace to obtain the catalyst.

[0069] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0070] Comparative Example 4

[0071] This comparative example provides a method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, comprising the following steps:

[0072] Step 1: Weigh 0.5g of nickel acetate and dissolve it in 20mL of DMF. Sonicate at 50W for 1h to obtain a nickel acetate solution.

[0073] Step 2: Add 3g of polyacrylonitrile (PAN, polymerization amount 1.5 million) and 10mL of thiophene to the nickel acetate solution in sequence, and stir magnetically for 4h (stirring power of 50W). When the solution is stable and uniform, start electrospinning. The spinning voltage is 10kV, the temperature is controlled at 25℃, the humidity is 30%rh, and the injection rate is 6mL / h, thus obtaining the catalyst precursor.

[0074] Step 3: Place the catalyst precursor obtained by spinning in a petri dish and dry it in a muffle furnace at 120°C for 20 hours to pre-oxidize the catalyst precursor.

[0075] Step 4: Calcine the pre-oxidized catalyst precursor in a tube furnace, heating it from room temperature to 1000℃ at a rate of 5℃ / min. -1 Under a nitrogen atmosphere, the temperature is raised to the set temperature and maintained for 2 hours. Then, the temperature is lowered to room temperature in the furnace to obtain the catalyst.

[0076] The obtained catalyst was transferred to a mortar and carefully ground into powder. It was then washed with deionized water for 2 hours. The resulting solid was dried in an oven at 60°C for 12 hours before use.

[0077] The catalyst obtained above was washed with deionized water. 10 mg of the catalyst was added to 100 μL of 5 wt% Nafion and 60 mL of anhydrous ethanol (isopropanol). After ultrasonic mixing, 10 μL was injected using a microsyringe and coated onto a rotating ring electrode (the catalyst loading on the ring electrode was 0.02472 mg / cm³). 2 Ensure even coating without any seepage or leakage. Purge the electrolyte with gas for half an hour to saturate it. Turn on the workstation and rotate it at approximately 1600 r / min to begin RRDE (Rotating Ring Electrode) testing. Process the obtained data. The hydrogen peroxide selectivity of the catalysts in Examples 1-2 and Comparative Examples 1-4 is calculated and compared; the results are shown in Table 1.

[0078] Table 1. Hydrogen peroxide selectivity of the catalysts prepared in Examples 1-2 and Comparative Examples 1-4

[0079]

[0080] Table 1 shows that Example 1 and Comparative Example 1 represent doped and undoped thiophene, respectively. Since thiophene itself can undergo redox reactions, the catalyst selectivity increases under alkaline conditions. Example 1 and Comparative Example 2 used different raw materials to prepare the catalyst. The fiber yarn produced by PAN spinning is stable and has a good structure. Pre-oxidation and calcination can retain N, Ni, S, etc. to the greatest extent and reduce loss. Meanwhile, adding nickel acetate / thiophene to the precursor and calcining it causes the catalyst to form a porous structure, increasing the active sites and improving the hydrogen peroxide selectivity. Comparative Examples 2 and 4 demonstrate that excessively high or low temperatures affect the oxidation effect. Too low a temperature leads to incomplete oxidation, affecting catalyst performance, while too high a temperature leads to over-oxidation, affecting experimental results.

[0081] By comparison Figure 1 and Figure 2 Analysis revealed that, among them Figure 1 The spinning effect of PAN was obvious, with clear lines. However, when PAN was replaced with PEO, the spinning lines became noticeably chaotic and unclear. This suggests the possibility of uneven raw material distribution, which could affect subsequent catalyst preparation. Changing the temperature, altering the molecular weight of PAN, or adding other substances can all change the catalyst's performance. RRDE testing showed a significant change in the catalyst's hydrogen peroxide selectivity.

[0082] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a catalyst for the electrochemical preparation of hydrogen peroxide, characterized in that, Includes the following steps: (1) Dissolve the transition metal salt in an organic solvent to obtain a transition metal salt solution; the transition metal salt is a nickel salt; (2) PAN and thiophene are added sequentially to the transition metal salt solution and stirred to obtain a precursor solution; the ratio of the transition metal, PAN and thiophene in the precursor solution is 1g:20g-30g:42mL-84mL. (3) Electrospinning the precursor solution to obtain the catalyst precursor; (4) Pre-oxidize the catalyst precursor; (5) Calcining the catalyst precursor treated in step (4) to obtain the catalyst; In step (4), the pre-oxidation conditions are 150-220 ℃ for 20-40 h; in step (5), the calcination temperature is 700-1000 ℃, the heating rate is 3-8 ℃ / min, and the calcination is carried out in a nitrogen atmosphere for 1-4 h.

2. The preparation method according to claim 1, characterized in that, The catalyst is used after being ground, washed, and dried; the drying temperature is 60-70 ℃ and the time is 12-24 h.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar concentration of the transition metal in the transition metal salt solution is 0.10-0.15 mol / L; the organic solvent is a strongly polar aprotic organic solvent; the method of dissolving to obtain the transition metal salt solution includes ultrasound, with an ultrasound power of 50-300 W and an ultrasound time of 0.3-1 h.

4. The preparation method according to claim 3, characterized in that, The nickel salt is at least one of nickel nitrate and nickel acetate.

5. The preparation method according to claim 1, characterized in that, In step (2), the polymerization amount of PAN ranges from 100,000 to 1,500,000; the stirring method is magnetic stirring, the stirring power is 50-100 W, and the stirring time is 1-12 h.

6. The preparation method according to claim 1, characterized in that, In step (3), the voltage of electrospinning is 10-22 kV, the temperature is 20-40 ℃, the humidity is 20-50 %rh, and the injection rate is 4-6 mL / h.

7. The catalyst prepared by the method according to any one of claims 1-6, characterized in that, The catalyst is an S-doped MNC network nanowire, where M represents a transition metal element.

8. The application of the catalyst according to claim 7 in the electrocatalytic synthesis of H2O2.

9. A fuel cell, characterized in that, Includes the catalyst as described in claim 7.

Images