A combined electrode and a method for simultaneous electrochemical synthesis of H2O2 using the same electrode.

Abstract

This invention provides a combined electrode and a method for simultaneous electrochemical synthesis of H2O2 using it. The combined electrode includes an anode and a cathode. The anode is made of polyvinylidene fluoride-modified carbon fiber paper, and the cathode is made of polytetrafluoroethylene / carbon black-modified carbon cloth. This combined electrode is used for simultaneous electrochemical synthesis of H2O2. This invention couples 2e-WOR and 2e-ORR to construct a simultaneous electrochemical synthesis technology between the anode and cathode, which significantly increases the current efficiency while greatly improving the synthesis rate and concentration of H2O2, greatly reducing the cost of electrochemical H2O2 synthesis, and holds promise for direct application in advanced oxidation systems such as electro-Fenton.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, and particularly relates to a combined electrode and a method for simultaneous electrochemical synthesis of H2O2 using it. Background Technology

[0002] H2O2 is one of the most important basic chemicals in modern chemical engineering, sustainable energy conversion / storage, and environmental remediation, playing a vital role in production and daily life. Statistics show that the global annual demand for H2O2 exceeds 3 million tons. Currently, the main methods for synthesizing H2O2 include the anthraquinone process, direct hydrogen-oxygen synthesis, photocatalytic synthesis, and electrochemical synthesis. The anthraquinone process is the most mature H2O2 production method: currently, 90% of global H2O2 production uses the anthraquinone process, with product concentrations as high as 70 wt.%. However, the anthraquinone process is energy-intensive, involves cumbersome separation and purification steps, generates large amounts of waste, and requires complex large-scale infrastructure. Furthermore, due to safety concerns regarding the transportation and storage of H2O2, decentralized production is highly attractive. The direct hydrogen-oxygen synthesis method is an important decentralized H2O2 production method, but it typically requires the use of noble metal-based catalysts (Pd, Au, etc.), and the direct use of high-concentration H2 and O2 poses potential safety risks, limiting its large-scale practical application. Photocatalytic synthesis can utilize solar energy to synthesize H2O2, but common photocatalysts generally suffer from problems such as severe photocorrosion, high electron-hole recombination rate, slow reaction kinetics, and narrow absorption wavelength range.

[0003] Electrochemical synthesis of H2O2 is a promising decentralized production method with significant advantages such as simple equipment, controllable production scale, and mild process conditions. Furthermore, it uses electricity as the energy source and H2O and O2 as raw materials, making the production process green and environmentally friendly. Electrochemical synthesis of H2O2 can occur through two pathways: the two-electron reduction reaction of O2 at the cathode (2e-ORR, Equations 1 and 2) and the two-electron oxidation reaction of H2O at the anode (2e-WOR, Equation 3). Figure 1(As shown). Since the potential for synthesizing H2O2 via 2e-WOR is higher than that of the side reaction of H2O oxidation to O2 at the anode (Equation 4), it is thermodynamically less advantageous. Therefore, most current research on the electrochemical synthesis of H2O2 focuses on 2e-ORR. The electrochemical synthesis of H2O2 based on 2e-ORR was first reported by Berl in the 1930s, subsequently improved by Dow Chemical and Huron Technologies, and commercialized in 1991. However, the Dow-Huron process requires a strongly alkaline environment, the equipment is prone to corrosion, and alkaline H2O2 often requires acid neutralization in practical applications. Furthermore, this process uses ceramic membranes to separate the anode and cathode, resulting in high resistance and energy consumption. On the other hand, anodic 2e-WOR electrosynthesis of H2O2 does not require additional power to provide a saturated dissolved oxygen environment, making it more energy-efficient than cathode 2e-ORR. Moreover, recent studies have found that some metal oxides and carbon-based catalysts exhibit high 2e-WOR selectivity, providing opportunities for the electrochemical synthesis of H2O2 via 2e-WOR. However, currently, the current efficiency of electrochemical synthesis of H2O2 is generally not high, whether based on cathode 2e-ORR or anode 2e-WOR.

[0004] pH>11.6: O2+ H2O + 2e-→ HO2-+ OH-Eo=0.06 V vs. RHE, (1);

[0005] pH<11.6: O2 + 2H+ + 2e-→ H2O2 Eo=0.7 V vs. RHE, (2);

[0006] 2H2O → H2O2 + 2H++ 2e-Eo=1.76 V vs. RHE, (3);

[0007] 2H2O→O2+4H++4e-Eo=1.23V vs.RHE, (4);

[0008] Furthermore, H2O2 is a commonly used oxidant in advanced oxidation processes such as electro-Fenton. However, the concentration of H2O2 synthesized by unipolar electrochemical synthesis is currently low (generally between 0.14% and 8%), which would lead to insufficient oxidation capacity and low current efficiency if used directly in the electro-Fenton system. Summary of the Invention

[0009] In view of this, in order to solve the problems and defects of the existing technology, the present invention provides a combined electrode and a method for simultaneous electrochemical synthesis of H2O2 using it. The method couples 2e-WOR and 2e-ORR to construct a simultaneous electrochemical synthesis technology of anode and cathode, in order to multiply the current efficiency, while increasing the synthesis rate and concentration of H2O2 and reducing the cost of electrochemical synthesis of H2O2. This technology is expected to be directly used in advanced oxidation systems such as electro-Fenton.

[0010] To achieve the above technical objectives, the technical solution adopted in this application is as follows:

[0011] In a first aspect, the present invention provides a combined electrode comprising an anode and a cathode, wherein the anode is made of polyvinylidene fluoride (PVDF) modified carbon fiber paper (CFP) material, and the cathode is made of polytetrafluoroethylene (PTFE) / carbon black (CB) modified carbon cloth (CC) material.

[0012] Furthermore, the preparation method of the polyvinylidene fluoride modified carbon fiber paper material includes: preparing a polyvinylidene fluoride solution, uniformly coating the solution onto the surface of carbon fiber paper, and finally drying it to obtain the final product.

[0013] Furthermore, the mass-volume percentage concentration of the polyvinylidene fluoride solution is 5-15%.

[0014] Preferably, the polyvinylidene fluoride solution has a mass-volume percentage concentration of 15%.

[0015] Optionally, the solvent of the polyvinylidene fluoride solution is at least one of N-methylpyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, triethyl phosphate, and dimethyl sulfoxide.

[0016] Preferably, the solvent for the polyvinylidene fluoride solution is N-methylpyrrolidone (NMP).

[0017] Furthermore, the carbon fiber paper of the anode is pretreated before modification. The pretreatment includes cutting the carbon fiber paper into small pieces of 1×2cm, ultrasonically cleaning it in 0.5M NaOH, 0.5M H2SO4, ethanol and deionized water for 20-30 minutes in sequence, and then drying it.

[0018] Furthermore, the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material includes:

[0019] Prepare a polytetrafluoroethylene dispersion, and then immerse the carbon cloth in the polytetrafluoroethylene dispersion for a period of time to perform hydrophobic treatment;

[0020] The hydrophobic treated carbon cloth is dried and then annealed.

[0021] Polytetrafluoroethylene, carbon black, and deionized water are mixed evenly in a certain proportion. The evenly mixed slurry is then coated evenly on the surface of the annealed carbon cloth and dried.

[0022] Furthermore, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the mass concentration of the polytetrafluoroethylene dispersion is 1-3%, and the dispersing agent is deionized water.

[0023] Furthermore, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the hydrophobic treatment time is controlled at 10-20 min.

[0024] Furthermore, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the control parameters for the annealing treatment are: temperature 300-400℃, time 30-40min.

[0025] Preferably, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the control parameters for annealing treatment are: temperature 350±1℃, time 30±1min.

[0026] Furthermore, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the mass ratio of polytetrafluoroethylene to carbon black is 0.2 to 1:1.

[0027] Furthermore, an appropriate amount of anhydrous ethanol is added to the slurry.

[0028] Furthermore, in the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the control parameters of the drying process are: vacuum 100-133 Pa, temperature 60-80℃, and drying time not less than 10h.

[0029] Furthermore, the carbon cloth of the cathode undergoes pretreatment before modification. This pretreatment includes cutting the carbon cloth into small pieces of 3.5×4.5cm, ultrasonically cleaning it in 0.5M NaOH, 0.5M H2SO4, ethanol, and deionized water for 20-30 minutes in sequence, and then drying it.

[0030] Furthermore, the drying control parameters during the pretreatment of carbon fiber or carbon cloth are: vacuum 100-133 Pa, temperature 70-80℃, and drying time not less than 10 hours.

[0031] Secondly, the present invention provides the application of the above-mentioned combined electrode in electro-oxidation catalytic reactions.

[0032] Thirdly, the present invention provides a method for the electrochemical synthesis of H2O2 by water oxidation, which uses the above-mentioned combined electrode, wherein the anode and cathode of the combined electrode are located in the anode chamber and the cathode chamber respectively, and the anode chamber and the cathode chamber are separated by a separator membrane, and the anode chamber and the cathode chamber are respectively loaded with anode electrolyte and cathode electrolyte, and the anode and cathode are simultaneously electrolyzed in the anode electrolyte and the cathode electrolyte to prepare H2O2.

[0033] Furthermore, the separating membrane is a proton exchange membrane.

[0034] Furthermore, the anolyte is a 1-2M K2CO3 solution.

[0035] Furthermore, the cathode electrolyte is a 0.2–0.5 M Na₂SO₄ solution.

[0036] Furthermore, the current density during the electrolysis process is 100–250 mA / cm². -2 Preferably 150 mAcm -2 .

[0037] This invention develops a combined electrode in which the anode and cathode materials are PVDF-modified CFP and PTFE / CB-modified CC, respectively. Using this electrode material as an electrode for the electro-oxidation catalytic preparation of H2O2 can significantly improve the current efficiency while greatly increasing the synthesis rate and concentration of H2O2, greatly reducing the cost of electrochemical synthesis of H2O2, and is expected to be directly used in advanced oxidation systems such as electro-Fenton. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the electrolysis device used in Embodiment 2 of the present invention.

[0039] Figure 2 This illustrates the effect of different current densities on the selectivity of simultaneous electrosynthesis of H2O2 at the anode and cathode in Example 2 of the present invention.

[0040] Figure 3 This is a curve showing the change in the amount of H2O2 synthesized simultaneously at the anode and cathode in Example 3 of the present invention over time. Detailed Implementation

[0041] The proton exchange membrane used in this embodiment of the invention is Nafion 117.

[0042] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These descriptions are for illustrative purposes only and are not intended to limit the scope of the invention.

[0044] Example 1

[0045] This embodiment provides a combined electrode, which includes an anode and a cathode. The anode is made of PVDF-modified CFP material, and the cathode is made of PTFE / CB-modified CC material.

[0046] The specific preparation method of PVDF-modified CFP material is as follows:

[0047] (1) CFP is cut into small pieces of 1×2cm and ultrasonically cleaned in 0.5M NaOH, 0.5M H2SO4, ethanol and deionized water for 30 minutes respectively. Then it is dried overnight in a vacuum oven at 80℃ with a vacuum of 100~133Pa.

[0048] (2) Weigh 0.5g of PVDF and dissolve it completely in 3.24mL of NMP to prepare a concentration of 15%. Coat the CFP surface obtained in step (1) with the solution and then dry it overnight in a vacuum oven at a vacuum of 100-133Pa and a temperature of 80℃ to obtain 15% PVDF-CFP electrode material.

[0049] The specific preparation method of PTFE / CB modified CC material is as follows:

[0050] 1) Cut CC into small pieces of 3.5×4.5cm, and ultrasonically clean them in 0.5M NaOH, 0.5M H2SO4, ethanol and deionized water for 30 minutes in sequence. Then dry them overnight in a vacuum oven at 80℃ with a vacuum of 100~133Pa.

[0051] 2) Immerse the CC obtained in step 1) in 2wt% PTFE-water dispersion, stir for 10 min, take it out and place it in a vacuum oven to dry overnight under a vacuum of 100-133 Pa and a temperature of 80℃ to obtain PTFE hydrophobic treated carbon cloth (PTFE-CC).

[0052] 3) Place the PTFE-CC obtained in step 2) in a muffle furnace and anneal at 350°C for 30 minutes. After annealing, remove it for later use.

[0053] 4) Mix 0.2 mL of 60 wt% PTFE-aqueous dispersion with 0.3 g of carbon black (CB) (where the density of the PTFE-aqueous dispersion is 1.5 g / mL and the mass ratio of PTFE to carbon black is 0.6:1), add 1 mL of anhydrous ethanol, and then stir for 6 h to ensure the slurry is uniformly mixed. Then coat the uniformly mixed slurry onto the PTFE-CC surface obtained in step 4) to prepare a PTFE / CB-coated CC electrode (PTFE / CB-CC).

[0054] Example 2

[0055] This embodiment examines a method for the electrochemical synthesis of H2O2 from water oxidation using the combined electrode obtained in Example 1. The electrolysis apparatus is as follows: Figure 1 As shown, the specific operation is as follows:

[0056] PVDF-CFP was used as the anode, PTFE / CB-CC as the cathode, 1M K2CO3 solution as the anolyte, and 0.2M Na2SO4 solution as the catholyte. A proton exchange membrane (Nafion 117) was used as the separator between the cathode and anode chambers. Electrolysis was terminated when the electrolysis time reached 10 minutes.

[0057] Determination of H2O2 concentration: After the reaction, take 0.5 mL of electrolyte from both the cathode and anode chambers, add 0.5 mL of 3M H2SO4 to each chamber for acidification, and then add 0.5 mL of 0.05M potassium titanium oxalate solution to each chamber. After standing for 10 min, measure the absorbance of each electrolyte and calculate the H2O2 concentration according to the standard curve. The 2e-WOR selectivity is determined by the ratio of the generated H2O2 content to the theoretical value.

[0058] Selectivity = 2 × F × the sum of H2O2 produced by cathode and anode electrolysis / Q × 100%, where F represents the Faraday constant and Q represents the total amount of electricity involved in the reaction.

[0059] The above methods were investigated using different current densities (20, 100, 150, 200, 250 mA / cm²). 2 The selectivity of H2O2 synthesis. Results are as follows: Figure 2 As shown, this indicates that when the current density is 150 mA / cm² 2 At that time, the simultaneous electrochemical synthesis of H2O2 at the anode and cathode exhibited the highest selectivity, reaching ~150%. Meanwhile, Figure 2 It also shows that at this current density, the combined electrode in this case has a higher current efficiency than a single cathode (2e-ORR) or anode (2e-WOR), approximately three times that of a single anode and 1.5 times that of a single cathode, significantly increasing the synthesis rate and concentration of H2O2 while multiplying the current efficiency.

[0060] Example 3

[0061] In this embodiment, the combined electrode obtained in Example 1 was used to perform water oxidation electrosynthesis of H2O2 to investigate the change in H2O2 production over time. The specific method is as follows:

[0062] PVDF-CFP was used as the anode, PTFE / CB-CC as the cathode, 1M K2CO3 solution as the anolyte, 0.2M Na2SO4 solution as the catholyte, and a proton exchange membrane (Nafion 117) as the separator between the cathode and anode chambers. The current density used was 150mA, and the reaction was terminated after 12 hours.

[0063] Determination of H2O2 concentration: After the reaction, take 0.5 mL of electrolyte from both the cathode and anode chambers, add 0.5 mL of 3M H2SO4 to each chamber for acidification, and then add 0.5 mL of 0.05M potassium titanium oxalate solution to each chamber. After standing for 10 min, measure the absorbance of each electrolyte and calculate the H2O2 concentration according to the standard curve. The 2e-WOR selectivity is determined by the ratio of the generated H2O2 content to the theoretical value.

[0064] Selectivity = 2 × F × the sum of H2O2 produced by cathode and anode electrolysis / Q × 100%, where F represents the Faraday constant and Q represents the total amount of electricity involved in the reaction.

[0065] The results are as follows Figure 3 As shown, this anode-cathode synchronous device can stably synthesize H2O2, with a total H2O2 synthesized in 12 hours reaching ~4.4 mmol, demonstrating good prospects for practical application.

[0066] In summary, the combined electrode material of the present invention, when used as an electrode for the electro-oxidative catalytic preparation of H2O2, significantly improves the current efficiency while greatly increasing the synthesis rate and concentration of H2O2, greatly reducing the cost of electrochemical synthesis of H2O2, and is expected to be directly used in advanced oxidation systems such as electro-Fenton.

[0067] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A composite electrode, characterized in that: The combined electrode includes an anode and a cathode. The anode is made of polyvinylidene fluoride modified carbon fiber paper material, and the cathode is made of polytetrafluoroethylene and carbon black modified carbon cloth material. The preparation method of the polyvinylidene fluoride modified carbon fiber paper material includes: preparing a polyvinylidene fluoride solution, uniformly coating the solution onto the surface of carbon fiber paper, and finally drying it to obtain the final product; The preparation method of the polytetrafluoroethylene and carbon black modified carbon cloth material includes: Prepare a polytetrafluoroethylene dispersion, and then immerse the carbon cloth in the polytetrafluoroethylene dispersion for a period of time to perform hydrophobic treatment; The hydrophobic treated carbon cloth is dried and then annealed. Polytetrafluoroethylene, carbon black, and deionized water are mixed evenly in a certain proportion. The evenly mixed slurry is then coated evenly on the surface of the annealed carbon cloth and dried. The mass ratio of polytetrafluoroethylene to carbon black is 0.6:

1.

2. The combined electrode according to claim 1, characterized in that: The polyvinylidene fluoride solution has a mass-volume percentage concentration of 5-15%.

3. A combined electrode according to claim 1 or 2, characterized in that: The solvent for the polyvinylidene fluoride solution is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, triethyl phosphate, and dimethyl sulfoxide.

4. A combined electrode according to claim 1, characterized in that: In the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the mass concentration of the polytetrafluoroethylene dispersion is 1-3%, and the dispersing agent is deionized water.

5. A combined electrode according to claim 1, characterized in that: In the preparation method of the polytetrafluoroethylene / carbon black modified carbon cloth material, the control parameters for annealing treatment are: temperature 300~400℃, time 30~40min.

6. The application of the combined electrode according to any one of claims 1 to 5 in electro-oxidation catalytic reactions.

7. A method for the electrosynthesis of H2O2 by water oxidation, characterized in that: The electrode is a combination electrode as described in any one of claims 1 to 5, wherein the anode and cathode of the combination electrode are located in the anode chamber and the cathode chamber, respectively, and the anode chamber and the cathode chamber are separated by a separator membrane. The anode chamber and the cathode chamber are respectively loaded with anode electrolyte and cathode electrolyte, and the anode and cathode are simultaneously electrolyzed in the anode electrolyte and the cathode electrolyte to prepare H2O2.

8. The method for water oxidation electrosynthesis of H2O2 according to claim 7, characterized in that: The current density during the electrolysis process is 100–250 mA / cm². -2 .

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