Device for biomimetic preparation of gas diffusion electrode for electrosynthesis of hydrogen peroxide and preparation method

Abstract

The invention relates to the technical field of preparation of gas diffusion electrodes, and particularly discloses a device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide and a preparation method.The device for biomimetic preparation of the gas diffusion electrode comprises a reaction tank, an oxygen supplementing tank and a circulating pump, the oxygen supplementing tank is used for continuously supplementing needed oxygen into reaction liquid, and the circulating pump is used for circulating the reaction liquid; the circulating pump is used for enabling the reaction liquid to circularly pass through the oxygenating tank and the reaction tank. The device for biomimetic preparation of the gas diffusion electrode for electro-synthesis of hydrogen peroxide is compact in structure, provides stable dissolved oxygen concentration for dopamine self-polymerization reaction, enables the binding force between the catalyst layer and the gas diffusion layer to be good, and the prepared gas diffusion electrode does not contain a hydrophobic PTFE binding agent, so that low catalytic activity caused by high hydrophobicity of the catalyst layer is avoided, and the service life of the gas diffusion electrode is prolonged. And the stability and the catalytic performance of the gas diffusion electrode are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas diffusion electrode preparation, in particular to a device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide and a preparation method thereof. Background Art

[0002] The gas diffusion electrode consists of a gas diffusion layer and a catalytic layer. The gas diffusion layer consists of a support layer and a microporous layer. The support layer is mostly made of a porous fiber substrate such as carbon paper or carbon cloth, with a thickness of 100-400μm, which plays the role of supporting the microporous layer and stabilizing the electrode structure; the microporous layer usually refers to the carbon powder layer on the base layer, with a thickness of 10-100μm. Its main function is to improve the pore structure of the base layer, reduce the contact resistance between the base layer and the catalytic layer, and allow the reaction gas to quickly pass through the diffusion layer and be evenly distributed to the surface of the catalytic layer for reaction. At the same time, the generated water is discharged in time to prevent the catalytic layer from being flooded.

[0003] When preparing a diffusion layer using a substrate such as carbon paper or carbon cloth, the carbon paper or cloth is first treated with a polytetrafluoroethylene (PTFE) emulsion to render it hydrophobic, and then the microporous layer is applied. The microporous layer's main raw material is carbon powder, which is mixed with the PTFE emulsion to form a slurry. This slurry is then cast or rolled onto the hydrophobicized carbon paper, dried, and baked at 300-400°C. Once the gas diffusion layer is prepared, the catalyst is evenly coated onto the surface of the microporous layer, creating the gas diffusion electrode.

[0004] To ensure good adhesion between the catalyst and the microporous layer, the catalyst is typically mixed with a PTFE emulsion to form a slurry, which is then applied to the microporous layer. Heat treatment is then performed to organically bond the microporous layer to the PTFE in the catalyst layer. However, the addition of the PTFE binder renders the catalyst layer superhydrophobic. When placed in an electrolyte, a gas film forms on the surface of the catalyst layer (i.e., a gas-solid interface), separating the catalyst layer from the electrolyte. A gas diffusion electrode (GDE) achieves optimal catalytic performance when the catalyst layer forms a gas-liquid-solid three-phase interface with the electrolyte. However, this hydrophobic gas-solid interface restricts electron transfer between the catalyst layer and the electrolyte, hindering the achievement of high oxygen reduction current density. Reducing the amount of PTFE used in the catalyst layer can moderately reduce its hydrophobicity and increase its hydrophilicity, but this significantly reduces the adhesion between the catalyst layer and the microporous layer. Hydraulic scouring and gas flow through the GDE can easily cause the catalyst layer to detach, significantly reducing the life of the GDE. Summary of the Invention

[0005] The present invention provides a device and method for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide, which solves the problems of gas diffusion electrodes obtained by existing preparation methods, such as decreased catalytic performance of a catalytic layer due to the use of PTFE emulsion, and easy detachment of the catalytic layer and shortened electrode life due to reduced PTFE emulsion usage.

[0006] The present invention adopts the following technical solution: a device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide, comprising: Reaction tank, used for compounding the catalyst in the reaction liquid with the gas diffusion layer; Oxygen supply tank, used to continuously supply the required oxygen to the reaction solution; A circulation pump, used to circulate the reaction liquid through the oxygen supply tank and the reaction tank; A gas-liquid separator and a dissolved oxygen meter are provided between the reaction tank and the oxygen supplement tank, and the oxygen supplement tank is connected to an oxygen source.

[0007] Furthermore, the reaction tank has a reaction tank liquid inlet and a reaction tank liquid outlet, and the oxygenation tank has an oxygenation tank liquid inlet and an oxygenation tank liquid outlet. The reaction tank liquid outlet is connected to the oxygenation tank liquid inlet, and the oxygenation tank liquid outlet is connected to the reaction tank liquid inlet.

[0008] Furthermore, the oxygen source in the oxygen supplementation tank is connected to the oxygen supplementation tank through a gas flow meter and a microporous aerator.

[0009] Furthermore, a stirring device is provided in the oxygen supplementation tank.

[0010] Furthermore, the reaction cell includes a liquid storage frame body and a bottom plate. The liquid storage frame body includes a first sealing gasket and a second sealing gasket arranged above and below, and the gas diffusion layer is placed between the first sealing gasket and the second sealing gasket.

[0011] A method for preparing a biomimetic gas diffusion electrode for electrosynthesis of hydrogen peroxide comprises the following steps: (1) Place the gas diffusion layer in the reaction tank, connect the reaction tank to the oxygen supply tank, and turn on the oxygen source; (2) Mix the catalyst, dopamine, and buffer solution at a ratio of 1 mg:0.2 mg:2 mL, ultrasonicate in an ice-water bath, and place the reaction solution in an oxygenation tank. (3) introducing oxygen into the reaction solution in step (2); (4) The reaction liquid passes through the gas-liquid separator and circulates through the reaction tank. After the circulatory reaction for 2 hours, dopamine and catalyst are added to the reaction liquid; (5) After the reaction is terminated, the gas diffusion layer is removed, rinsed, and dried to obtain a gas diffusion electrode.

[0012] Furthermore, the buffer solution is tris(hydroxymethyl)aminomethane hydrochloride solution, and the pH of the buffer solution is 8.5.

[0013] Furthermore, the gas diffusion electrode includes a gas diffusion layer and a catalytic layer, and the catalytic layer is bonded to the surface of the gas diffusion layer through dopamine self-polymerization.

[0014] Furthermore, the catalyst loading on the gas diffusion electrode is 200-500 μg / cm 2 , the thickness of the catalytic layer is 10-50 μm.

[0015] Dopamine can well simulate the mucin components secreted by marine organisms such as mussels, and produce a polydopamine layer with permanent adhesion properties on the solid surface through self-polymerization reaction. Polydopamine is highly hydrophilic.

[0016] Beneficial effects of the present invention: 1. The biomimetic preparation of the gas diffusion electrode for electrosynthesis of hydrogen peroxide in the present invention connects the oxygen supply tank to the reaction tank through a circulation pump. The oxygen supply tank is connected to an oxygen source, so that the dopamine self-polymerization reaction in the reaction solution is combined with the gas diffusion layer in a stable dissolved oxygen concentration.

[0017] 2. The present invention utilizes the super-strong adhesion properties generated by the self-polymerization reaction of dopamine to adhere the catalyst to the gas diffusion layer to prepare a gas diffusion electrode. The catalyst has good bonding strength with the gas diffusion layer, and the prepared gas diffusion electrode does not contain a hydrophobic PTFE binder, thereby avoiding the high hydrophobicity of the catalyst affecting the reaction between the catalyst and the electrolyte, thereby improving the catalytic effect of the gas diffusion electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of the processing device for the gas diffusion electrode of the present invention.

[0019] Figure 2 It is a schematic structural diagram of the reaction cell in the processing device structure of the gas diffusion electrode of the present invention.

[0020] Figure 3 It is a structural exploded view of the reaction tank of the present invention.

[0021] Figure numerals: reaction tank 1, oxygenation tank 2, oxygen source 3, gas flow meter 4, microporous aerator 5, stirrer 6, gas-liquid separator 7, dissolved oxygen meter 8, circulation pump 9, oxygenation tank liquid outlet 10, reaction tank liquid inlet 11, reaction tank liquid outlet 12, oxygenation tank liquid inlet 13, bottom plate 14, first sealing gasket 15, gas diffusion layer 16, second sealing gasket 17, liquid storage plate frame 18. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0023] Example 1: Figure 1-Figure 3As shown, a device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide includes a reaction cell 1, an oxygenation cell 2 and a circulation pump 9. The liquid outlet 10 of the oxygenation cell is connected to the liquid inlet 11 of the reaction cell, and the liquid outlet 12 of the reaction cell is connected to the liquid inlet 13 of the oxygenation cell. The reaction cell 1 and the oxygenation cell 2 are connected to the circulation pump 9 to enable the reaction liquid to circulate between the reaction cell 1 and the oxygenation cell 2.

[0024] The oxygen supply tank 2 is connected to an oxygen source 3, which controls the amount of gas entering the oxygen supply tank through a gas flow meter 4. The gas entering the oxygen supply tank passes through a microporous aerator 5 to form tiny bubbles and enter the reaction liquid, thereby increasing the residence time of oxygen in the reaction liquid and the dissolved oxygen concentration.

[0025] A gas-liquid separator 7 and a dissolved oxygen meter 8 are sequentially provided between the liquid outlet 10 of the oxygen supply tank and the liquid inlet 11 of the reaction tank. The dissolved oxygen meter 8 is used to measure the concentration of dissolved oxygen in the reaction liquid. The gas flow meter on the oxygen source can be dynamically adjusted to control the flow rate of oxygen according to the measurement data of the dissolved oxygen meter 8.

[0026] The reaction tank 1 includes a liquid storage plate frame 18 and a bottom plate 14. A first sealing gasket 15 and a second sealing gasket 17 are provided on the liquid storage plate frame 18. The first sealing gasket 15 is a solid sealing gasket, and the second sealing gasket 17 is hollow in the center. The gas diffusion layer 16 is provided between the first sealing gasket 15 and the second sealing gasket 17.

[0027] Example 2: A method for preparing a biomimetic gas diffusion electrode for electrosynthesis of hydrogen peroxide, comprising the following steps: (1) Place the gas diffusion layer 16 with the microporous layer facing upward between the first gasket 15 and the second gasket 17, and then connect the various components of the processing device in sequence with pipelines; (2) The catalyst was mixed with dopamine and buffer solution in the ratio of 1 mg catalyst: 2 mL buffer solution: 0.2 mg dopamine. The buffer solution was tris-HCl solution with a pH of 8.5. The catalyst used was carbon black oxidized with concentrated nitric acid. The mixture was placed in an ice-water bath and ultrasonicated for 10 min to uniformly disperse the catalyst and dopamine. Low-temperature ultrasonication can temporarily suspend the self-polymerization reaction of dopamine. (3) Transfer the ultrasonic reaction liquid to the oxygen supply tank 2, turn on the oxygen source 3, which can be an air pump, adjust the gas flow meter 4 to control the oxygen flow rate to 0.25 L / min, and introduce oxygen into the reaction liquid. Turn on the stirrer 6 and adjust the magnetic stirring speed to 1000 r / min; (4) The reaction liquid rich in bubbles in the oxygenation tank 2 is subjected to gas-liquid separation by the gas-liquid separator 7. The debubbled reaction liquid flows out from the oxygenation tank outlet 10, passes through the dissolved oxygen meter 8, and then enters the reaction tank 1 from the reaction tank liquid inlet 11. The reaction liquid in the reaction tank 1 flows out from the reaction tank liquid outlet 12 under the suction action of the circulation pump 9, and then returns to the oxygenation tank through the circulation pump 9 and the oxygenation tank liquid inlet 13; (5) After 2 h of reaction, dopamine and catalyst were added to the oxygenation tank. The added dopamine mass was 20% of the original catalyst mass. Dopamine was added twice in total until the reaction terminated. (6) The gas diffusion layer coated with the catalytic layer is taken out from the reaction cell 1, rinsed with deionized water and dried to obtain a gas diffusion electrode.

[0028] Example 3: The gas diffusion electrode prepared by Example 1 and Example 2 includes a gas diffusion layer and a catalyst layer. The catalyst layer is attached to the surface of the gas diffusion layer by dopamine. The thickness of the catalyst layer is 10 μm. The catalyst loading in the gas diffusion electrode is 200 μg / cm 2 .

[0029] Example 4: A gas diffusion electrode prepared in Example 2 by adjusting the gas flow meter 4 to control the oxygen flow rate to 0.5 L / min comprises a gas diffusion layer and a catalyst layer. The catalyst layer is attached to the surface of the gas diffusion layer via dopamine. The thickness of the catalyst layer is 50 μm. The catalyst loading in the gas diffusion electrode is 500 μg / cm 2 .

Claims

1. A device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide, characterized by: include A reaction tank (1) for combining the catalyst in the reaction liquid with the gas diffusion layer; An oxygen supply tank (2) is used to continuously supply the required oxygen to the reaction solution; a circulation pump (9) for circulating the reaction liquid through the oxygenation tank (2) and the reaction tank (1); A gas-liquid separator (7) and a dissolved oxygen meter (8) are provided between the reaction tank (1) and the oxygen supply tank (2), and an oxygen source (3) is connected to the oxygen supply tank (2).

2. The device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 1, characterized in that: The reaction pool (1) is provided with a reaction pool liquid inlet (11) and a reaction pool liquid outlet (10), and the oxygenation pool (2) is provided with an oxygenation pool liquid inlet (13) and an oxygenation pool liquid outlet (10), the reaction pool liquid outlet (12) is connected to the oxygenation pool liquid inlet (13), and the oxygenation pool liquid outlet (10) is connected to the reaction pool liquid inlet (11).

3. The device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 2, characterized in that: The oxygen source (3) in the oxygen supplementation tank is connected to the oxygen supplementation tank (2) via a gas flow meter (4) and a microporous aerator (5).

4. The device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 3, characterized in that: A stirring device (6) is provided in the oxygen supplementation tank.

5. The device for biomimetic preparation of a gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 1, characterized in that: The reaction cell (1) comprises a liquid storage frame body (18) and a bottom plate (14); the liquid storage frame body (18) comprises a first sealing gasket (15) and a second sealing gasket (17) arranged above and below; and a gas diffusion layer (16) is disposed between the first sealing gasket (15) and the second sealing gasket (17).

6. A method for preparing a gas diffusion electrode for electrosynthesis of hydrogen peroxide using the device according to any one of claims 1 to 5, characterized in that: The steps include: (1) placing the gas diffusion layer (16) in the reaction cell (1), connecting the reaction cell (1) to the oxygen supply cell (2), and turning on the oxygen source (3); (2) Mix the catalyst, dopamine, and buffer solution at a ratio of 1 mg:0.2 mg:2 mL, then sonicate in an ice-water bath. Place the reaction solution in an oxygenation tank (2). (3) introducing oxygen into the reaction solution in step (2) and controlling the oxygen flow rate to be 0.25-0.5 L / min; (4) The reaction liquid passes through the gas-liquid separator (7) and then circulates through the reaction tank (1). After 2 hours of circulatory reaction, dopamine is added to the reaction liquid. The mass of the added dopamine is 20% of the mass of the original catalyst. Dopamine is added twice in total and the reaction is terminated. (5) After the reaction is terminated, the gas diffusion layer (16) is removed, rinsed, and dried to obtain a gas diffusion electrode.

7. The method for preparing a biomimetic gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 6, characterized in that: The buffer solution is tris (hydroxymethyl)aminomethane hydrochloride solution, and the pH value of the buffer solution is 8.

5.

8. The method for preparing a biomimetic gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 6, characterized in that: The gas diffusion electrode comprises a gas diffusion layer, a catalyst layer is arranged on the gas diffusion layer, and the catalyst layer is bonded to the surface of the gas diffusion layer by self-polymerization of dopamine.

9. The method for preparing a biomimetic gas diffusion electrode for electrosynthesis of hydrogen peroxide according to claim 8, characterized in that: The catalyst loading on the gas diffusion electrode is 200-500 μg / cm 2 , the thickness of the catalytic layer is 10-50 μm.

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