N + Ionically modified alpha-PbO porous electrode, method of making and use in electrocatalytic synthesis of sodium borohydride

Abstract

The present invention discloses N + Ion-modified α-PbO porous electrode, preparation method thereof, and application in electrocatalytic synthesis of sodium borohydride. The preparation process of the porous electrode is as follows: β-PbO powder is first ball-milled, and then stirred with a N-containing cationic surfactant solution to form N on the surface of α-PbO. + Modification, mixing with sodium metaborate, conductive powder and paraffin, grinding, tableting, embedding in alumina and sintering, the preparation is completed. + Modification can improve the double electric layer structure of the catalytic electrode surface and promote the reaction of B(OH)4 ‑ At the same time, the modified catalyst surface is easy to form Pb-N-O bonds, which enhances the adsorption of OH and helps activate the reactants on the catalyst surface. + The ion-modified α-PbO porous electrode has high efficiency in the solid-phase electrolysis synthesis of sodium borohydride. The current efficiency of the electroreduction synthesis of sodium borohydride in alkaline sodium metaborate solution can reach above 67.6%.

Description

Technical Field

[0001] The present invention relates to the technical field of green hydrogen production, in particular to N + Ion-modified α-PbO porous electrode, preparation method thereof, and application in electrocatalytic synthesis of sodium borohydride. Background Art

[0002] Sodium borohydride (NaBH4), a member of the hydrogen storage material family, offers significant advantages, including high hydrogen storage density (10.8 wt%), high-purity hydrogen, long-term stable storage, and environmental friendliness. Ideally, 1 mol of sodium borohydride can produce 4 mol of hydrogen, making hydrogen energy a promising prospect. However, despite years of research, the synthesis of sodium borohydride remains challenging. The U.S. Department of Energy (DOE) previously determined that the process was unfeasible due to the high cost of recovering its hydrolysis byproduct, sodium metaborate, and the low efficiency of synthesizing sodium borohydride from sodium metaborate. Further exploration of solutions to these challenges is still needed.

[0003] Although sodium borohydride offers unparalleled advantages as a hydrogen source for fuel cells, industrialization requires a simple and low-cost production process. Furthermore, the byproduct, sodium metaborate, should be recycled to avoid boron contamination. To date, reported methods for recycling sodium borohydride after hydrogen release include chemical reduction, a combination of mechanical and chemical methods, and electrochemical methods, but none have been industrialized. Theoretically, the first two methods require the introduction of a reducing agent to achieve boron recycling, which is not only costly but also requires the disposal of byproducts introduced by the reducing agent. Electrochemical methods, on the other hand, do not require the addition of a reducing agent and achieve boron recycling through an electrical reduction process.

[0004] The main problem in preparing sodium borohydride by electrochemical reduction is that during the electrolysis process, due to the repulsion of like charges and attraction of opposite charges, B(OH)4 - Electromigration to the anode causes B(OH)4 to migrate near the cathode. - The concentration decreases, resulting in B(OH)4 - Reduction to BH4 - It is very difficult, so the current efficiency of synthesizing sodium borohydride is extremely low. How to improve the double layer structure of the electrode surface and alleviate the B(OH)4 - The repulsive effect at the cathode has always been a problem that has troubled many researchers. Therefore, in order to achieve efficient and low-cost large-scale synthesis of sodium borohydride, methods to effectively improve the double layer structure on the cathode surface are of great research value. Summary of the Invention

[0005] Aiming at the technical problems of the obstruction of anion mass transfer on the cathode surface and low reduction efficiency, the present invention aims to provide N +Ion-modified α-PbO porous electrode and its preparation method and application in electrocatalytic synthesis of sodium borohydride. The present invention combines α-PbO with a specific cationic surfactant through a combined process of ball milling, sintering and cationic surfactant modification to form a positive charge layer on the surface of the α-PbO catalyst, change the double electric layer structure of the cathode surface, and promote the electrocatalytic synthesis of B(OH)4 - In the mass transfer process at the cathode, the modified α-PbO catalyst enhances the adsorption of -OH, and Pb-NO bonds are easily formed on the surface, which helps activate the reactants on the catalyst surface and promotes the conversion of the reactants to sodium borohydride.

[0006] The technical solution adopted in the present invention is as follows:

[0007] N + The preparation method of the ion-modified α-PbO porous electrode comprises the following steps:

[0008] 1) Place β-PbO powder and stainless steel balls in a ball mill and mill them in a ball mill. The milled product is micron flower-like α-PbO, which is then placed in a solution of N-containing cationic surfactant and stirred. Afterwards, N is filtered to obtain + Ion-modified micronized flower-like α-PbO;

[0009] 2) N + Ion-modified micron flower-shaped α-PbO, sodium metaborate, conductive powder and paraffin are mixed and ground to form a fine powder;

[0010] 3) The powder obtained in step 2) is pressed into an electrode sheet, and alumina is used as an embedding material to embed the electrode sheet in alumina (alumina mainly plays a role in chemical protection and makes the sample evenly heated), and then placed in a muffle furnace for sintering. Finally, the electrode sheet is taken out after cooling in the furnace to obtain N + Ion-modified α-PbO porous electrode.

[0011] Furthermore, the particle size of the β-PbO powder in step 1) is in the range of 100-500 mesh, the diameter of the stainless steel ball is 10-20 mm, and the mass of the stainless steel ball is 4-8 times the mass of the β-PbO powder.

[0012] Furthermore, in step 1), the ball milling time is controlled to be 40-80 hours, and the ball milling speed is 200-500 rpm. The ball milling speed determines the grain size of the sample powder. A long ball milling time can make the sample powder reach a certain mesh size, and the length of the ball milling time can control the uniformity of the powder grains.

[0013] Furthermore, the N-containing cationic surfactant is a mixture of one or more of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and sodium triacetoxyborohydride, preferably dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, or tetradecyltrimethylammonium bromide, and more preferably hexadecyltrimethylammonium bromide.

[0014] Furthermore, the concentration of the N-containing cationic surfactant solution is 5-50 g / L, preferably 10-30 g / L. The selection of the cationic surfactant is the key to whether the sample powder can be successfully loaded.

[0015] Furthermore, the stirring time in step 1) is 6-60 h, preferably 12-24 h.

[0016] Furthermore, in step 2), the sodium metaborate includes at least one of sodium metaborate tetrahydrate, sodium metaborate dihydrate or anhydrous sodium metaborate, and has a particle size range of 300-700 mesh; the conductive powder includes a mixture of one or more of activated carbon, amorphous carbon, silver powder, carbon nanotubes, and conductive graphite powder.

[0017] Further, in step 2), the mass of sodium metaborate powder is N + The conductive powder is 0.3-2.5 times the mass of ion-modified micron flower-shaped α-PbO, preferably 0.5-1 times; + The mass of the ion-modified micron flower-shaped α-PbO is 0.02-0.2 times, preferably 0.05-0.1 times; paraffin is N + The concentration of ions is 0.02-0.2 times, preferably 0.05-0.1 times, of the ion-modified micron flower-shaped α-PbO.

[0018] Furthermore, in step 3), the sintering temperature and holding time are controlled at 100-300° C., preferably 200±20° C., and the holding time is controlled at 1-5 h, preferably 2-3 h.

[0019] The present invention also provides the N + The ion-modified α-PbO porous electrode is used as a cathode for electrocatalytic synthesis of sodium borohydride. The application method is as follows: the cathode chamber and the anode chamber are separated by a cation exchange membrane, and the electrolyte in the anode chamber is 0.1-1 mol·L -1 Sodium hydroxide aqueous solution, the cathode electrolyte contains 0.1-1 mol·L -1 Sodium hydroxide and 0.05-0.5 mol·L -1 A mixed aqueous solution of sodium metaborate tetrahydrate, with the N + The ion-modified α-PbO porous electrode was used as the cathode and the graphite electrode was used as the anode. The current density of the electrolysis process was 5-20 mA cm -2, the electrolyte temperature is room temperature.

[0020] The present invention + Ion-modified α-PbO porous electrode for electroreduction of B(OH)4 - It has a good application in the field. After ball milling, the catalyst forms a large number of dislocations and oxygen vacancies. These defects are B(OH)4 - It provides a large number of reaction sites. The modification of cations makes the catalyst surface positively charged, and anions migrate to N under the action of the electric field. + Modify the micron flower-shaped α-PbO porous electrode to obtain electrons to generate BH4 - , thus the reaction current efficiency is significantly improved.

[0021] The above solution of the present invention has the following beneficial effects:

[0022] 1. The present invention utilizes a special surfactant (such as hexadecyltrimethylammonium bromide) to modify the α-PbO catalyst to form N + Ion-modified micron flower-like α-PbO forms a positive charge layer on the catalyst surface, changes the double electric layer structure on the cathode surface, and helps B(OH)4 - Mass transfer at the cathode.

[0023] 2. N prepared by the present invention + Ion-modified micron flower-shaped α-PbO porous electrodes, using ball milling technology and special surfactant modification, can increase the Zeta potential of the catalyst surface ( Figure 2 The adsorption of anions is enhanced.

[0024] 3. N prepared by the present invention + There are a large number of Pb-NO bonds on the surface of the ion-modified micron flower-shaped α-PbO porous electrode, indicating that it is suitable for B(OH)4 - (OH) - The adsorption and desorption effect of ions contributes to the activation and conversion of reactants on the electrode surface.

[0025] 4. N prepared by the present invention + Ion-modified micronized flower-like α-PbO porous electrodes for electroreduction of B(OH)4 - It has significant advantages, and the current efficiency of synthesizing sodium borohydride reaches 67.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart for preparing the α-PbO porous electrode in Example 1 of the present invention.

[0027] Figure 2Zeta potential diagrams of commercial β-PbO, ball-milled α-PbO, and electrodes treated with different surfactants.

[0028] Figure 3 N prepared in Example 1 of the present invention + Concentration and current efficiency of sodium borohydride electrosynthesis on ion-modified micron flower-like α-PbO porous electrodes;

[0029] Figure 4 The concentration and current efficiency of the electrosynthesized sodium borohydride electrode prepared for commercially purchased β-PbO. DETAILED DESCRIPTION

[0030] 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.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0032] In the embodiment of the present invention, the embedding material is alumina balls with a diameter of 1 mm. The current efficiency is calculated using the following formula:

[0033] Where η is the current efficiency, m is the actual current product mass, I is the electrolysis current, t is the electrolysis time, and k is the electrochemical equivalent. The electrochemical equivalent of synthesized sodium borohydride is 0.177 g / Ah.

[0034] Example 1

[0035] (1) 20 g of β-PbO powder was placed in a ball mill, and then 120 g of stainless steel balls were added to give a ball-to-powder ratio of 6:1. The sample was ground in a ball mill at 300 rpm for 60 h to obtain micron-shaped α-PbO. It was then placed in a cationic surfactant hexadecyltrimethylammonium bromide solution (0.5 g of cationic surfactant dissolved in 50 ml of water) and stirred for 24 h. N was obtained by filtration. + Ion-modified micron flower-like α-PbO, denoted as CTAB-α-PbO.

[0036] (2) 12g of N + Ion-modified micron flower-like α-PbO, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder and 1 g of paraffin wax are continuously ground to form fine powder and mixed.

[0037] (3) The powder obtained in step (2) was pressed into an electrode sheet under a pressure of 70 MPa, and then buried under alumina balls (i.e., 1 mm alumina balls were used as embedding material, and the upper and lower surfaces of the electrode sheet were covered with alumina balls, which is the same in the following embodiments). It was sintered at 200°C in a muffle furnace and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet was taken out to obtain N + Ion modified micron flower-shaped α-PbO porous electrode. The specific process is as follows Figure 1 shown.

[0038] The N prepared in Example 1 + The ion-modified micron flower-shaped α-PbO porous electrode was used as the cathode and the graphite electrode as the anode. The electrolysis process was carried out in an electrolytic cell equipped with a cation exchange membrane. The CEM-II cation exchange membrane separated the cathode chamber from the anode chamber. The solution in the anode chamber was 0.5 mol·L -1 Sodium hydroxide solution, the solution in the cathode chamber is 0.5 mol·L -1 Sodium hydroxide and 0.2 mol·L -1 Sodium metaborate tetrahydrate mixed solution. The electrolysis process is at 10mA·cm -2 The electrolyte temperature was maintained at 25±1℃. The results of the changes in sodium borohydride concentration and current efficiency with electrolysis time were shown in Table 1. Figure 3 The experimental results show that the current efficiency can reach up to 67.6% within 2 hours of electrolysis, and the concentration of sodium borohydride produced during 2 hours of electrolysis is as high as 8.1×10 -3 mol·L -1 .

[0039] The present invention combines α-PbO with a special cationic surfactant to form an electrode with unique catalytic function. + The ion-modified micron flower-shaped α-PbO porous electrode has excellent performance in the electrocatalytic reduction of sodium metaborate, can significantly improve the current efficiency, and makes the recovery of sodium metaborate more convenient. This method is more environmentally friendly and energy-saving, and has good application prospects.

[0040] Comparative Example 1

[0041] (1) 20 g of β-PbO powder was placed in a ball mill, followed by the addition of 120 g of stainless steel balls. The sample was milled in a ball mill at 300 rpm for 60 h to obtain micron-flower-like α-PbO, denoted as α-PbO. The only difference from step (1) of Example 1 was that the micron-flower-like α-PbO was not stirred with the specific cationic surfactant, cetyltrimethylammonium bromide.

[0042] (2) 12 g of micron flower-shaped α-PbO that has not been treated with hexadecyltrimethylammonium bromide, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder, and 1 g of paraffin wax are continuously ground into fine powder and mixed.

[0043] (3) The powder obtained in step (2) is compressed into an electrode sheet under a pressure of 70 MPa, and then buried under an alumina ball. It is sintered at 200°C in a muffle furnace and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a micron flower-shaped α-PbO porous electrode.

[0044] The electrolysis experiment of Control Example 1 was the same as that of Example 1, except that the cathode was replaced with the micron flower-shaped α-PbO porous electrode of Control Example 1. Other conditions remained unchanged. Finally, under the same current density and electrolysis time, the current efficiency within 2 h of electrolysis was as high as 15%, and the concentration of sodium borohydride produced after 2 h of electrolysis was 1.2×10 -3 mol L -1 .

[0045] Comparison of the experimental results of Example 1 of the present invention and Comparative Example 1 shows that the N + Ion-modified micro-flower-like α-PbO porous electrodes significantly improved the current efficiency.

[0046] Example 2

[0047] (1) 20 g of β-PbO powder was placed in a ball mill, and then 120 g of stainless steel balls were added. The sample was ground in a ball mill at 300 rpm for 60 h to obtain micron-shaped α-PbO. Then, it was placed in a solution of a cationic surfactant tetradecyltrimethylammonium bromide (0.5 g of cationic surfactant dissolved in 50 ml of water) and stirred for 24 h. N was obtained by filtration. + Ion-modified micron flower-like α-PbO, denoted as TTAB-α-PbO.

[0048] (2) 12g of N + Ion-modified micron flower-like α-PbO, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder and 1 g of paraffin wax are continuously ground to form fine powder and mixed.

[0049] (3) The powder obtained in step (2) is pressed into an electrode sheet under a pressure of 70 MPa, coated with an alumina ball, sintered at 200°C in a muffle furnace, and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a porous electrode.

[0050] The electrolysis experiment of Example 2 was the same as that of Example 1, except that the cathode was replaced with the porous electrode of Example 2, and the other conditions remained unchanged. In Example 2, different types of N-cationic surfactants were used. The electrolysis results were as follows: the current efficiency within 2 h of electrolysis was 51% at most, and the concentration of sodium borohydride produced within 2 h of electrolysis was 5.8×10 -3 mol·L -1 .

[0051] Example 3

[0052] (1) 20 g of β-PbO powder was placed in a ball mill, and then 120 g of stainless steel balls were added. The sample was ground in a ball mill at 300 rpm for 60 h to obtain micron-shaped α-PbO. The sample was then placed in a cationic surfactant dodecyltrimethylammonium bromide solution (0.5 g of cationic surfactant dissolved in 50 ml of water) and stirred for 24 h. N was obtained by filtration. + Ion-modified micron flower-like α-PbO, denoted as DTAB-α-PbO.

[0053] (2) 12 g of micron flower-shaped α-PbO treated with dodecyltrimethylammonium bromide, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder, and 1 g of paraffin wax were continuously ground into fine powder and mixed.

[0054] (3) The powder obtained in step (2) is pressed into an electrode sheet under a pressure of 70 MPa, coated with an alumina ball, sintered at 200°C in a muffle furnace, and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a porous electrode.

[0055] The electrolysis experiment of Example 3 was the same as that of Example 1, except that the cathode was replaced with the porous electrode of Example 3, and the other conditions remained unchanged. Example 3 used a different type of N cationic surfactant. The electrolysis results were: the current efficiency within 2 hours of electrolysis was as high as 46%, and the concentration of sodium borohydride produced within 2 hours of electrolysis reached 5.2×10 -3 mol·L -1 .

[0056] Example 4

[0057] (1) 20g of β-PbO powder was placed in a ball mill, and then 120g of stainless steel balls were added. The sample was ground in a ball mill at 300rpm for 60h to obtain micron flower-like α-PbO. Then it was placed in a cationic surfactant hexadecyltrimethylammonium bromide solution (0.5g of cationic surfactant was dissolved in 50ml of water) and stirred for 24h. N was obtained by filtration. + Ion-modified micro-flower-like α-PbO.

[0058] (2) 12g of N + Ion-modified micron flower-like α-PbO, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder and 1 g of paraffin wax are continuously ground to form fine powder and mixed.

[0059] (3) The powder obtained in step (2) is pressed into an electrode sheet under a pressure of 70 MPa, coated with an alumina ball, sintered at 300°C in a muffle furnace, and maintained at this temperature for 4 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a porous electrode.

[0060] The electrolysis experiment of Example 4 is the same as that of Example 1, except that the cathode is replaced by the porous electrode of Example 4, and the other conditions remain unchanged. Example 4 changes the control of calcination temperature and holding time, and conducts electrolysis experiments. The current efficiency within 2 hours of electrolysis is the highest 13.2%, and the concentration of sodium borohydride produced after 2 hours of electrolysis is as low as 1.0×10 -3 mol·L -1 .

[0061] Comparing the experimental results of Example 4 with those of Example 1, it can be seen that the control of calcination temperature and holding time also has a great influence on the electrocatalytic performance of the final porous electrode.

[0062] Example 5

[0063] (1) 20g of β-PbO powder was placed in a ball mill, and then 120g of stainless steel balls were added. The sample was ground in a Mitr ball mill at 300rpm for 60h to obtain micron-shaped α-PbO. Then it was placed in a solution of sodium triacetoxyborohydride, a cationic surfactant (0.5g of cationic surfactant dissolved in 50ml of water), stirred for 24h, and filtered to obtain N + Ion-modified micron flower-like α-PbO, denoted as STAB-α-PbO.

[0064] (2) 12 g of a catalyst treated with sodium triacetoxyborohydride, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder, and 1 g of paraffin wax were continuously ground to form fine powder, which was then mixed.

[0065] (3) The powder obtained in step (2) is pressed into an electrode sheet under a pressure of 70 MPa, coated with an alumina ball, sintered at 200°C in a muffle furnace, and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a porous electrode.

[0066] The electrolysis experiment of Example 5 was the same as that of Example 1, except that the cathode was replaced with the porous electrode of Example 5, and the other conditions remained unchanged. In Example 5, the N cationic surfactant was replaced with another type of cationic surfactant, and the electrolysis experiment was carried out. The current efficiency within 2 hours of electrolysis was as high as 18.6%, and the concentration of sodium borohydride produced during the 2-hour electrolysis was as low as 1.6×10 -3 mol·L -1 .

[0067] Example 6

[0068] (1) 20 g of commercial β-PbO powder was placed in a cationic surfactant hexadecyltrimethylammonium bromide solution (0.5 g of cationic surfactant was dissolved in 50 ml of water) and stirred for 24 h. The N + Ion-modified β-PbO.

[0069] (2) 12g of N + Ion-modified β-PbO, 6 g of sodium metaborate tetrahydrate, 1 g of conductive graphite powder and 1 g of paraffin wax are continuously ground to form fine powder and mixed.

[0070] (3) The powder obtained in step (2) is pressed into an electrode sheet under a pressure of 70 MPa, coated with an alumina ball, sintered at 200°C in a muffle furnace, and maintained at this temperature for 2 hours. After cooling in the furnace, the electrode sheet is taken out to obtain a porous electrode.

[0071] The electrolysis experiment of Example 6 is the same as that of Example 1, except that the cathode is replaced by the porous electrode of Example 6, and the other conditions remain unchanged. In Example 6, the α-PbO obtained by ball milling is replaced by commercial β-PbO, and the electrolysis experiment is carried out. The results of the changes in the sodium borohydride concentration and current efficiency produced by different electrolysis times are shown in Figure 4 The experimental results show that the maximum current efficiency is 0.5% within 2 hours of electrolysis, and the concentration of sodium borohydride produced during 2 hours of electrolysis is as low as 0.1×10 - 3 mol·L -1 .

[0072] Through 6 examples and 1 control experiment, it can be clearly seen that the specific micron flower-shaped α-PbO is combined with the cationic surfactant hexadecyltrimethylammonium bromide to form N + Ion-modified micro-flower-like α-PbO can play a significant role in specific catalytic reduction reactions.

[0073] In addition, the Zeta potential comparison results of commercial β-PbO, α-PbO obtained in Comparative Example 1, CTAB-α-PbO obtained in Example 1, TTAB-α-PbO obtained in Example 2, DTAB-α-PbO obtained in Example 3, and STAB-α-PbO obtained in Example 5 are shown in FIG. Figure 2 The N prepared by the present invention + Ion-modified micron flower-shaped α-PbO porous electrodes, using ball milling technology and special surfactant modification, can increase the Zeta potential of the catalyst surface ( Figure 2 The modified catalyst increases the Zeta potential on the surface of the catalyst, enhancing anion adsorption and promoting the activation and conversion of reactants on the electrode surface, significantly improving electrocatalytic activity.

[0074] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. N + The preparation method of ion-modified α-PbO porous electrode is characterized in that The following steps are involved: 1) Place β-PbO powder and stainless steel balls in a ball mill and mill them in a ball mill. The milled product is micron flower-like α-PbO, which is then placed in a solution of N-containing cationic surfactant and stirred. Afterwards, N is filtered to obtain + Ion-modified micron flower-shaped α-PbO; the N-containing cationic surfactant is a mixture of one or more of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and tetradecyltrimethylammonium bromide; 2) N + Ion-modified micron flower-shaped α-PbO, sodium metaborate, conductive powder and paraffin are mixed and ground to form a fine powder; 3) The powder obtained in step 2) is pressed into an electrode sheet, and alumina is used as an embedding material. The electrode sheet is embedded in alumina and sintered in a muffle furnace. Finally, the electrode sheet is taken out after cooling in the furnace to obtain N + Ion-modified α-PbO porous electrode; In step 3), the sintering temperature and holding time are controlled at 100-300°C, and the holding time is controlled at 1-5 h.

2. N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that The particle size of the β-PbO powder in step 1) is in the range of 100-500 mesh, the diameter of the stainless steel ball is 10-20 mm, and the mass of the stainless steel ball is 4-8 times the mass of the β-PbO powder.

3. The N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 1), the ball milling time is controlled at 40-80 h, and the ball milling rate is controlled at 200-500 rpm.

4. The N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 1), the concentration of the N-containing cationic surfactant solution is 5-50 g / L; and the stirring time in step 1) is 6-60 h.

5. N according to claim 4 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 1), the concentration of the N-containing cationic surfactant solution is 10-30 g / L; and the stirring time in step 1) is 12-24 h.

6. The N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 2), the sodium metaborate includes at least one of sodium metaborate tetrahydrate, sodium metaborate dihydrate or anhydrous sodium metaborate, and has a particle size range of 300-700 mesh; the conductive powder includes a mixture of one or more of activated carbon, amorphous carbon, silver powder, carbon nanotubes, and conductive graphite powder.

7. The N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 2), the mass of sodium metaborate powder is N + The mass of ion-modified micron flower-shaped α-PbO is 0.3-2.5 times; the conductive powder is N + The mass of ion-modified micron flower-shaped α-PbO is 0.02-0.2 times; paraffin is N + The ion-modified micron flower-like α-PbO is 0.02-0.2 times.

8. The N according to claim 7 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 2), the mass of sodium metaborate powder is N + The mass of ion-modified micron flower-shaped α-PbO is 0.5-1 times; the conductive powder is N + The mass of ion-modified micron flower-shaped α-PbO is 0.05-0.1 times; paraffin is N + The ion-modified micron flower-like α-PbO is 0.05-0.1 times.

9. The N according to claim 1 + The preparation method of ion-modified α-PbO porous electrode is characterized in that In step 3), the sintering temperature and holding time are controlled at 200±20°C and 2-3h.

10. N prepared by the method according to any one of claims 1 to 9 + Ion-modified α-PbO porous electrode.

11. The N according to claim 10 + Application of ion-modified α-PbO porous electrode as cathode for electrocatalytic synthesis of sodium borohydride.

12. The use according to claim 11, characterized in that The cathode chamber and the anode chamber are separated by a cation exchange membrane, and the electrolyte in the anode chamber is 0.1-1 mol·L -1 Sodium hydroxide aqueous solution, the cathode electrolyte contains 0.1-1 mol·L -1 Sodium hydroxide and 0.05-0.5 mol·L -1 A mixed aqueous solution of sodium metaborate tetrahydrate, with the N + The ion-modified α-PbO porous electrode was used as the cathode and the graphite electrode was used as the anode. The current density of the electrolysis process was 5-20 mA·cm -2 , the electrolyte temperature is room temperature.

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