Octagonal electrocatalyst and its preparation method and application

Abstract

The present invention relates to an octagonal electrocatalyst and its preparation method and application, belonging to the field of electrocatalysis. The preparation method comprises the following steps: dissolving a bismuth source, a lead source and a structure inducing agent in an alkaline solution, preparing an octagonal electrocatalyst precursor by a hydrothermal method, washing and drying the precursor, and calcining the obtained solid under an inert gas atmosphere to obtain the octagonal electrocatalyst. The corresponding X-ray diffraction spectrum shows that the octagonal electrocatalyst is Bi2O3 and Pb 0.89 Bi 12 O 19.78 The heterojunction structure of the prepared electrocatalyst is beneficial to the electron transfer and adsorption of intermediates in the ozone generation process, and has high application value in the electrochemical anode ozone production reaction. At the same time, the preparation process is simple and the raw materials are cheap. The catalyst has regular morphology and excellent performance, which greatly improves the efficiency of ozone production by electrolysis of water and realizes the application of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to an octagonal electrocatalyst and a preparation method and application thereof. Background Art

[0002] Renewable energy-driven electrochemical water separation has been widely recognized as a promising method to be added to the future energy production mix. As an efficient strategy, water electrolysis to produce ozone has important strategic significance as a replacement for the anodic OER reaction. It has important applications in daily disinfection, air purification, and sewage treatment.

[0003] Currently, in electrochemical reactions, the main method for preparing ozone is low-voltage electrolysis technology, which is mainly based on PEM technology to coat the catalyst on the substrate, complete the electrochemical decomposition of water under low-voltage current conditions, and realize the efficient preparation of ozone on the anode, which has high added value products and efficient bactericidal and disinfecting effects.

[0004] Currently, the main catalysts for producing ozone at the anode in water electrolysis reactions are commercial lead dioxide and platinum. However, lead dioxide is prone to deposition and loss during the electrochemical process, resulting in poor stability and dissolution into aqueous solutions, causing significant toxicity. Platinum, on the other hand, has achieved better results due to its excellent adsorption properties for reaction intermediates, but its high price makes it difficult to expand its application. Heterojunction electrocatalysts, due to their unique structural characteristics, have been widely used in fuel cells, supercapacitors, and other applications. The synergistic effect between the two different components can achieve efficient material application, and the choice of multiple materials also expands the application range of electrocatalysts. Summary of the Invention

[0005] In view of the above problems, the present invention proposes an octagonal electrocatalyst and its preparation method and application. The octagonal electrocatalyst is composed of Bi, Pb and O elements, which are Bi2O3 and Pb 0.89 Bi 12 O 19.78 heterojunction structure.

[0006] The method for preparing the octagonal electrocatalyst comprises the following steps:

[0007] 1) Dissolve the bismuth source, lead source and structure-inducing agent in an alkaline solution and stir at room temperature for 40-60 minutes to obtain a light yellow suspension;

[0008] 2) adding the oxidant solution to the solution obtained in step 1), continuing stirring for 20-30 minutes, and then naturally cooling to room temperature;

[0009] 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 160-200° C. for 8-14 hours. Afterwards, the solution is naturally cooled to room temperature, filtered, washed with deionized water and anhydrous ethanol 3-5 times each, and then vacuum dried at 60-80° C. for 6-8 hours to obtain an octagonal electrocatalyst precursor.

[0010] 4) transferring the octagonal electrocatalyst precursor material obtained in step 3) into a porcelain boat and placing it in a tube furnace, and calcining it at 150-300° C. for 2-4 hours under an inert atmosphere to obtain an octagonal electrocatalyst material;

[0011] Furthermore, the present invention also defines that the bismuth source in step 1) is one of bismuth nitrate and bismuth acetate;

[0012] Furthermore, the present invention further defines that the lead source in step 1) is one of lead nitrate, lead chloride and lead acetate, and the molar ratio of the bismuth source to the lead source is 2-8:1;

[0013] Furthermore, the present invention further defines that in step 1), the structure inducing agent is one of polyvinyl pyrrolidone and hexadecyltrimethylammonium bromide, the molecular weight of polyvinyl pyrrolidone is 1300000, the alkali solution is one of sodium hydroxide solution and potassium hydroxide solution, the concentration of the alkali solution is 3-5 mol / L, the mass ratio of the structure inducing agent to the alkali solution volume is 2.5-2.7:1, the mass unit is mg, and the solution volume is mL;

[0014] Furthermore, the present invention further defines that the oxidant solution used in step 2) is one of sodium hypochlorite, potassium permanganate, and hydrogen peroxide, and the volume ratio of the oxidant solution to the alkali solution is 1:4-9;

[0015] Furthermore, the present invention also defines the inert atmosphere in step 4) as nitrogen, argon and helium, and the heating rate is 3-8°C / min.

[0016] Furthermore, a method for preparing an octagonal electrocatalyst of the present invention specifically comprises the following steps:

[0017] 1) Dissolve 0.6–1 g of bismuth source, 83–400 mg of lead source, and 50–70 mg of structure-inducing agent in 20–28 mL of alkaline solution and stir at room temperature for 40–60 minutes to obtain a light yellow suspension.

[0018] 2) Add 3-5 mL of sodium hypochlorite solution to the solution obtained in step 1), continue stirring for 20-30 minutes, and then cool naturally to room temperature;

[0019] 3) The precursor solution obtained in step 2) is transferred to a polytetrafluoroethylene liner and then placed in a hydrothermal autoclave for hydrothermal treatment at 160-200°C for 8-14 hours. The resulting solution is then naturally cooled to room temperature, filtered, washed with deionized water and anhydrous ethanol 3-5 times each, and then vacuum dried at 60-80°C for 6-8 hours to obtain an octagonal electrocatalyst precursor.

[0020] 4) placing 80-95 mg of the octagonal electrocatalyst precursor obtained in step 3) in a porcelain boat and transferring it to a tube furnace, and calcining it at 150-300° C. for 2-4 hours under an inert atmosphere to obtain an octagonal electrocatalyst material;

[0021] Furthermore, the present invention also proposes the use of the octagonal electrocatalyst in the complete water decomposition reaction to produce ozone and hydrogen peroxide.

[0022] Furthermore, the application of the present invention comprises the following steps: controlling the current and voltage by a constant current meter, reacting in a beaker, using saturated potassium sulfate as an electrolyte, dropping the octagonal electrocatalyst on a carbon cloth as a working electrode in the anode chamber, using a platinum sheet as a cathode, and controlling the reaction current at 50 mA / cm -2 , the cell voltage is controlled between 3-10 V, and the electrolysis of water to produce ozone reaction is carried out.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The octagonal electrocatalyst of the present invention can maximize the exposure of active sites by virtue of its unique octagonal structure and unique exposed surface, thereby optimizing the catalytic activity and current efficiency of the material;

[0025] 2) In the octagonal electrocatalyst of the present invention, the interaction between the two metals, bismuth and lead, is beneficial to promoting the reaction kinetics of ozone generation and promoting the formation of ozone;

[0026] 3) In the octagonal electrocatalyst of the present invention, the introduction of the heterojunction is beneficial to promoting the adsorption of reaction intermediates and the timely desorption of products during the electrolysis of water to produce ozone, thereby facilitating the efficient electrochemical synthesis of ozone.

[0027] 4) Compared with traditional electrocatalysts, the octagonal electrocatalyst of the present invention has a heterojunction structure of highly active oxides, a simple preparation process, and low raw material prices. In the electrolysis of water to produce ozone, it has a high selectivity and current efficiency, good stability, and has high application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the scanning electron microscope at 5 μm of the octagonal electrocatalyst prepared in Example 1;

[0029] Figure 2 Schematic diagram of a scanning electron microscope image of the octagonal electrocatalyst prepared in Example 2 at 5 μm;

[0030] Figure 3 Schematic diagram of a scanning electron microscope image of the octagonal electrocatalyst prepared in Example 3 at 5 μm;

[0031] Figure 4 Schematic diagram of a scanning electron microscope image of the octagonal electrocatalyst prepared in Example 4 at 5 μm;

[0032] Figure 5 This is the X-ray diffraction spectrum of the octagonal electrocatalyst prepared in Example 1;

[0033] Figure 6 This is a comparison chart of real-time detection data of ozone concentration generated when the octagonal electrocatalyst prepared in Examples 1-4 is used to electrolyze water to produce ozone. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0035] Example 1: Preparation of an octagonal electrocatalyst, comprising the following steps:

[0036] 1) Dissolve 790 mg of bismuth nitrate, 83 mg of lead nitrate, and 50 mg of polyvinylpyrrolidone in 20 mL of 5 mol / L sodium hydroxide solution. Stir at room temperature for 40 minutes to obtain a light yellow suspension.

[0037] 2) Add 3 mL of sodium hypochlorite solution to the solution obtained in step 1) and continue stirring for 20 minutes;

[0038] 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 160° C. for 8 hours. After cooling the solution to room temperature, the solution was filtered, washed with deionized water and anhydrous ethanol three times each, and then vacuum dried at 60° C. for 6 hours to obtain an octagonal electrocatalyst precursor.

[0039] 4) transferring 100 mg of the octagonal electrocatalyst precursor material obtained in step 3) to a porcelain boat and placing it in a tube furnace. The temperature was raised to 150° C. at a rate of 3° C. / min under a nitrogen atmosphere and calcined for 2 hours to obtain an octagonal electrocatalyst material.

[0040] The scanning electron microscope diagram of the octagonal electrocatalyst obtained in Example 1 at 5 μm is shown in FIG. Figure 1As shown, it can be seen that the prepared catalyst has a good octagonal morphology, and the unique crystal face is conducive to maximizing the exposure of active sites, which can better promote the generation of ozone and hydrogen peroxide; the X-ray diffraction spectrum of the octagonal electrocatalyst obtained in Example 1 is shown as Figure 5 As shown in the PDF card, the octagonal electrocatalyst has two obvious characteristic peaks, corresponding to Bi2O3 and Pb 0.89 Bi 12 O 19.78 , which shows that it is a unique heterojunction structure, Pb 0.89 Bi 12 O 19.78 The introduction of is beneficial to the precipitation of lattice oxygen during the electrochemical ozone production at the anode, while the presence of the heterojunction is beneficial to the transfer of electrons and the adsorption of active species during the ozone generation process, thereby facilitating the generation of more ozone.

[0041] The octagonal electrocatalyst of Example 1 is used for the electrolysis of water to produce ozone:

[0042] Weigh 10 mg of the prepared octagonal electrocatalyst powder and mix it with 1000 μL of ethanol and 200 μL of a 5% Nafion solution. Ultrasonic treatment is then performed for 30 minutes to completely disperse the catalyst in the mixture of ethanol and Nafion solution, resulting in a uniform catalyst slurry. A carbon cloth is cut into approximately 3 cm × 2 cm pieces, and the catalyst slurry is evenly drop-coated onto the cloth. After drying, it serves as the working electrode (i.e., the octagonal electrocatalyst is coated on the carbon cloth as the working electrode).

[0043] The current and voltage of the reaction were controlled by a constant current meter. An H-type electrolytic cell was used as the reaction vessel. In the anode chamber, the octagonal electrocatalyst prepared above was coated on carbon cloth as the working electrode. In the cathode chamber, a platinum sheet was used as the counter electrode, and the electrolyte was a saturated potassium sulfate solution. An ozone detector was connected to the outlet of one end of the H-type electrolytic cell to monitor the amount of ozone generated in real time, objectively reflecting the catalytic performance of the catalyst. During the entire electrocatalytic ozone production process, the reaction current was controlled at 50 mA / cm -2 The cell voltage is controlled between 3-10 V, the reaction time is 150 minutes, and the relationship between the concentration of ozone produced by the electrolytic water catalytic reaction and the reaction time is as follows: Figure 6 shown.

[0044] Example 2: Preparation of an octagonal electrocatalyst, comprising the following steps:

[0045] 1) Dissolve 269 mg of bismuth acetate, 139 mg of lead chloride, and 60 mg of cetyltrimethylammonium bromide in 23 mL of 4 mol / L potassium hydroxide solution. Stir at room temperature for 50 minutes to obtain a light yellow suspension.

[0046] 2) Add 3 mL of potassium permanganate solution to the solution obtained in step 1) and continue stirring for 30 min;

[0047] 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 180° C. for 10 hours. After naturally cooling the solution to room temperature, the solution was filtered and washed with deionized water and anhydrous ethanol five times each, and then vacuum dried at 80° C. for 8 hours to obtain an octagonal electrocatalyst precursor.

[0048] 4) 80 mg of the octagonal electrocatalyst precursor obtained in step 3) was placed in a porcelain boat and transferred to a tube furnace. The temperature was raised to 200°C at a rate of 5°C / min under an argon atmosphere and calcined for 4 hours to obtain an octagonal electrocatalyst material. The scanning electron microscopy diagram of the octagonal electrocatalyst obtained in Example 2 at 5 μm is shown in FIG. Figure 2 As shown, the prepared catalyst has a good octagonal morphology and is a triangular pyramidal bismuth-lead bimetallic oxide.

[0049] The octagonal electrocatalyst of Example 2 is used for the electrolysis of water to produce ozone:

[0050] In the process of preparing the electrode anode using the catalyst prepared in Example 2, the catalyst in Example 1 was replaced with the catalyst prepared in Example 2 of equal mass. The remaining operating conditions were the same as those in the experimental process of preparing ozone by electrolysis of water in Example 1. The relationship between the concentration of ozone generated by the electrolysis of water catalysis and the reaction time is shown in FIG. Figure 6 shown.

[0051] Example 3: Preparation of an octagonal electrocatalyst, comprising the following steps:

[0052] 1) Dissolve 790 mg of bismuth nitrate, 325 mg of lead acetate, and 70 mg of polyvinylpyrrolidone in 26 mL of 3 mol / L sodium hydroxide solution. Stir at room temperature for 60 minutes to obtain a light yellow suspension.

[0053] 2) adding hydrogen peroxide solution to the solution obtained in step 1) and continuing stirring for 30 minutes;

[0054] 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 200° C. for 12 hours. Afterwards, the solution was naturally cooled to room temperature, filtered, washed with deionized water and anhydrous ethanol three times each, and then vacuum dried at 60° C. for 8 hours to obtain an octagonal electrocatalyst precursor.

[0055] 4) 95 mg of the octagonal electrocatalyst precursor material obtained in step 3) was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 200°C at a rate of 5°C / min under a nitrogen atmosphere and calcined for 4 hours to obtain an octagonal electrocatalyst material. The scanning electron microscopy diagram of the octagonal electrocatalyst obtained in Example 3 at 5 μm is shown as follows: Figure 3 As shown, the prepared catalyst has a good octagonal morphology and is a triangular pyramidal bismuth-lead bimetallic oxide.

[0056] The octagonal electrocatalyst of Example 3 is used for the electrolysis of water to produce ozone:

[0057] In the process of preparing the electrode anode using the catalyst prepared in Example 3, the catalyst of Example 1 was replaced with the catalyst prepared in Example 3 of equal mass. The remaining operating conditions were the same as those in the experimental process of preparing ozone by electrolysis of water in Example 1. The relationship between the concentration of ozone generated by the electrolysis of water catalysis and the reaction time is shown in FIG. Figure 6 shown.

[0058] Example 4: Preparation of an octagonal electrocatalyst, comprising the following steps:

[0059] 1) Dissolve 807 mg of bismuth acetate, 278 mg of lead chloride, and 150 mg of cetyltrimethylammonium bromide in 28 mL of sodium hydroxide solution and stir at room temperature for 60 minutes to obtain a light yellow suspension.

[0060] 2) Add 3 mL of sodium hypochlorite solution to the solution obtained in step 1) and continue stirring for 30 min;

[0061] 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 180° C. for 12 hours. Afterwards, the solution was naturally cooled to room temperature, filtered, washed with deionized water and anhydrous ethanol three times each, and then vacuum dried at 60° C. for 8 hours to obtain an octagonal electrocatalyst precursor.

[0062] 4) 100 mg of the octagonal electrocatalyst precursor material obtained in step 3) was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 300°C at 8°C / min under an argon atmosphere and calcined for 2 hours to obtain an octagonal electrocatalyst material. The scanning electron microscopy diagram of the octagonal electrocatalyst obtained in Example 4 at 5 μm is shown as follows: Figure 4 As shown, it can be seen that the prepared catalyst has a good octagonal morphology.

[0063] The octagonal electrocatalyst of Example 4 is used for the electrolysis of water to produce ozone:

[0064] In the process of preparing the electrode anode using the catalyst prepared in Example 1, the catalyst of Example 1 was replaced with the catalyst prepared in Example 4 of equal mass. The remaining operating conditions were the same as those in the experimental process of preparing ozone by electrolysis of water in Example 1. The relationship between the concentration of ozone generated by the electrolysis of water catalysis and the reaction time is shown in FIG. Figure 6 shown.

[0065] Figure 1-4 The morphology of the catalysts under different conditions is shown in the figure, and it is found that all of them are octagonal in shape, which shows the reliability of the method. Electrocatalysts with specific regular morphology can be prepared by this method. Figure 5 The X-ray diffraction spectrum of the electrocatalyst prepared in Example 1 shows that it has two different lattice structures, corresponding to Bi2O3 and Pb 0.89 Bi 12 O 19.78 , indicating a unique heterojunction structure. Figure 6 The ozone yields obtained from the catalysts prepared in Examples 1-4 and a conventional commercial PbO2 catalyst during water electrolysis are shown. PbO2 is widely used for water electrolysis to produce ozone due to its high overpotential and high yield. It can be seen that the different catalysts prepared all have high ozone yields, outperforming conventional commercial catalysts. The contents described in this specification are merely an enumeration of the various forms of implementation of the inventive concept, and the scope of protection of the present invention should not be construed as being limited to the specific forms described in the examples.

Claims

1. An octagonal electrocatalyst, characterized in that The octagonal electrocatalyst is composed of Bi, Pb and O elements. 0.89 Bi 12 O 19.78 heterojunction structure.

2. A method for preparing the octagonal electrocatalyst according to claim 1, characterized in that The steps include: 1) Dissolve the bismuth source, lead source and structure-inducing agent in an alkaline solution and stir at room temperature for 40-60 minutes to obtain a light yellow suspension; 2) adding an oxidant to the solution obtained in step 1), continuing stirring for 20-30 minutes, and then cooling naturally to room temperature; 3) transferring the precursor solution obtained in step 2) into a polytetrafluoroethylene liner, placing the solution in a hydrothermal autoclave, and subjecting the solution to hydrothermal treatment at 160-200° C. for 8-14 hours. Afterwards, the solution is naturally cooled to room temperature, filtered, washed with deionized water and anhydrous ethanol 3-5 times each, and then vacuum dried at 60-80° C. for 6-8 hours to obtain an octagonal electrocatalyst precursor. 4) The octagonal electrocatalyst precursor material obtained in step 3) is placed in a porcelain boat and placed in a tube furnace, and calcined at 150-300° C. for 2-4 hours under an inert atmosphere to obtain an octagonal electrocatalyst material.

3. The method for preparing an octagonal electrocatalyst according to claim 2, characterized in that The bismuth source in step 1) is one of bismuth nitrate and bismuth acetate, the lead source is one of lead nitrate, lead chloride and lead acetate, and the molar ratio of the bismuth source to the lead source is 2-8:

1.

4. The method for preparing an octagonal electrocatalyst according to claim 2, characterized in that The structure inducing agent in step 1) is polyvinyl pyrrolidone or hexadecyltrimethylammonium bromide, the alkaline solution is one of sodium hydroxide solution and potassium hydroxide solution, the concentration of the alkaline solution is 3-5 mol / L, the mass ratio of the structure inducing agent to the alkaline solution volume is 2.5-2.7:1, the mass unit is mg, and the solution volume is mL.

5. The method for preparing an octagonal electrocatalyst according to claim 2, characterized in that In step 2), the oxidant solution used is one of sodium hypochlorite, potassium permanganate, and hydrogen peroxide, and the volume ratio of the oxidant solution to the alkali solution is 1:4-9.

6. The method for preparing an octagonal electrocatalyst according to claim 2, characterized in that The inert atmosphere in step 4) is nitrogen, argon and helium, and the heating rate is 3-8 °C / min.

7. An octagonal electrocatalyst prepared according to the method according to any one of claims 2 to 6.

8. Use of the octagonal electrocatalyst according to claim 7 in the electrolysis of water to produce ozone.

9. Use of the octagonal electrocatalyst according to claim 8 in the electrolysis of water to produce ozone, characterized in that The following steps are involved: The current and voltage were controlled by a constant current meter. The reaction was carried out in a beaker. Saturated potassium sulfate was used as the electrolyte. The catalyst slurry formed by mixing the octagonal electrocatalyst with 900 μL of ethanol and 100 μL of Nafion solution was drop-coated on a carbon cloth as the working electrode in the anode chamber. A platinum sheet was used as the cathode. The reaction current was controlled at 50 mA / cm -2 , the cell voltage is controlled between 3-10 V, and the electrolysis of water to produce ozone reaction is carried out.

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