Gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride film electrode and preparation method thereof

Abstract

The application discloses a kind of gold nanoparticle loaded oxygen-doped ultrathin porous boron nitride film electrode and preparation method thereof, the preparation method includes the following steps: according to mass ratio 1:3-6:0.25-0.35, boric acid, urea, oxalic acid is prepared oxygen-doped ultrathin porous boron nitride, then gold nanoparticle is loaded oxygen-doped ultrathin porous boron nitride and coated on conductive substrate to form film electrode.The oxygen-doped ultrathin porous boron nitride film electrode loaded with gold nanoparticles prepared by the application has the advantages of large specific surface area, high electron-hole separation efficiency, fast electron transfer rate, etc., is a new type of film electrode with excellent photoelectric performance, meets the actual production demand, and has wide application prospect in photoelectrochemical field.The preparation method also has the advantages of simple process, easy operation, high preparation efficiency and low cost, and is suitable for large-scale preparation, which is beneficial to industrial application.

Description

Technical Field

[0001] This invention belongs to the field of materials technology and relates to an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles and its preparation method. Background Technology

[0002] Photoelectrochemistry, an emerging field of study derived from electrochemistry, investigates the interaction between semiconductor materials and light. It primarily concerns the conversion of light to electricity and the interconversion of electrical and chemical energy. Photoactive materials absorb photons to generate electron-hole pairs. One type of photogenerated charge carrier is absorbed by the external circuitry of the electrode, while the other participates in a catalytic reaction at the solid-liquid interface between the electrode and the electrolyte, thus forming a circuit and achieving energy transfer, thereby generating an electrical signal. Based on these characteristics, photoelectrochemistry has found wide applications in energy recovery and environmental pollution control.

[0003] High-performance photoelectroactive materials are fundamental to the continued development of photoelectrochemical technology. Hexagonal boron nitride (h-BN), a non-metallic semiconductor, has attracted attention as a promising photoelectroactive material due to its excellent chemical stability and low preparation cost. However, pure h-BN exhibits low photocatalytic activity due to its low quantum yield, and the bulk h-BN prepared under conventional conditions is large, making it difficult to form thin sheets, which is detrimental to the loading and dispersion of other materials. Traditional methods for preparing h-BN thin-film electrodes still suffer from drawbacks such as incomplete electron-hole separation, slow electron transport speed, and recombination due to their small specific surface area. Furthermore, existing porous boron nitride materials are mainly prepared from melamine and boric acid through a hydrothermal reaction followed by calcination. This method cannot incorporate oxygen atoms into the porous boron nitride material, thus retaining the defect of rapid recombination of photogenerated electrons and holes. Furthermore, during the doping of boron nitride materials with oxygen atoms, it was found that even with excessive doping, it was still difficult to effectively increase the photocurrent of the material. Therefore, its application as a photoelectric active material in the field of photoelectrochemistry remains limited. Meanwhile, currently developed porous hexagonal boron nitride materials loaded with gold nanoparticles still suffer from drawbacks such as bulk agglomeration, leading to uneven distribution of gold nanoparticles and thus affecting the material's photoelectric properties. Therefore, obtaining a boron nitride-based photoelectric active material with a large specific surface area, high electron-hole separation efficiency, and fast electron transport rate is of great significance for expanding the widespread application of photoelectrochemical technology in energy recovery and environmental remediation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles with large specific surface area, high electron-hole separation efficiency and fast electron transport rate, and a method for preparing the same.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles includes the following steps:

[0007] S1. Oxygen-doped ultrathin porous boron nitride is prepared using boric acid, urea, and oxalic acid as raw materials; the mass ratio of boric acid, urea, and oxalic acid is 1:3 to 6:0.25 to 0.35.

[0008] S2. Using the oxygen-doped ultrathin porous boron nitride obtained in S1 as a support, oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles was prepared.

[0009] S3. Prepare a dispersion of oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles obtained in S2, and coat it on a conductive substrate to form a gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride thin film electrode.

[0010] A further improvement to the above preparation method is that, in step S1, oxygen-doped ultrathin porous boron nitride is prepared using a ternary copolymerization method, comprising the following steps:

[0011] S1-1. Dissolve boric acid, urea and oxalic acid in water to obtain a mixed solution;

[0012] S1-2. Heat the mixed solution obtained in S1-1 until the water evaporates to obtain mixed crystals.

[0013] S1-3. The mixed crystal obtained in S1-2 is calcined to obtain oxygen-doped ultrathin porous boron nitride.

[0014] In a further improvement to the above preparation method, in step S1-1, the mass ratio of boric acid, urea, and oxalic acid is 1:3 to 6:0.3.

[0015] In a further improvement to the above preparation method, in step S1-2, the heating is performed to 60°C to 80°C.

[0016] In a further improvement to the above preparation method, in steps S1-3, the calcination is carried out at a temperature of 800℃ to 1000℃; and the calcination time is 3h to 7h.

[0017] A further improvement to the above preparation method is that, in step S2, oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles is prepared by photochemical reduction, including the following steps:

[0018] S2-1. Disperse the oxygen-doped ultrathin porous boron nitride obtained in S1 in a methanol / water mixed solution to obtain an oxygen-doped ultrathin porous boron nitride dispersion.

[0019] S2-2. The oxygen-doped ultrathin porous boron nitride dispersion obtained in S2-1 is mixed with chloroauric acid solution, stirred, and subjected to photocatalytic reduction reaction to obtain oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles.

[0020] In a further improvement to the above preparation method, in step S2-1, the mass-to-volume ratio of the oxygen-doped ultrathin porous boron nitride to the methanol / water mixed solution is 4 mg to 6 mg: 1 m6; the methanol / water mixed solution is prepared by mixing methanol and ultrapure water; and the volume ratio of methanol to ultrapure water is 1 to 2: 10.

[0021] In a further improvement to the above preparation method, in step S2-2, the volume ratio of the chloroauric acid solution to the oxygen-doped ultrathin porous boron nitride dispersion is 0.001–0.1:1; the chloroauric acid solution is prepared by mixing chloroauric acid and ultrapure water; the mass-volume ratio of chloroauric acid to ultrapure water is 1 g: 60 m6–120 m6; the stirring time is 0.5 h–1.5 h; and the photocatalytic reduction reaction time is 0.5 h–1.5 h.

[0022] In a further improvement to the above preparation method, step S3 specifically comprises:

[0023] S3-1. Mix the oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles obtained in S2 with a perfluorosulfonic acid / ethanol mixed solution and sonicate to obtain a dispersion.

[0024] S3-2. The dispersion obtained in S3-1 is drop-coated onto the surface of a conductive substrate to form a wet film;

[0025] S3-3. Anneal the wet film obtained in S3-2 to obtain an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles.

[0026] The above preparation method is further improved by including the following process in step S3: repeating the operations in steps S3-2 to S3-3 3 to 5 times until the thickness of the oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles reaches the preset value.

[0027] In a further improvement to the above preparation method, in step S3-1, the mass-to-volume ratio of the oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles to the perfluorosulfonic acid / ethanol mixed solution is 2 mg to 10 mg: 1 m6; the perfluorosulfonic acid / ethanol mixed solution is prepared by mixing perfluorosulfonic acid and ethanol; the volume ratio of perfluorosulfonic acid to ethanol is 0.1 to 1:10; the frequency of the ultrasound is 5 kHz to 10 kHz, and the ultrasound time is 30 min to 60 min.

[0028] In a further improvement to the above preparation method, in step S3-2, the conductive substrate is tin dioxide transparent conductive glass; the conductive substrate also includes the following pretreatment before use: the conductive substrate is washed with acetone, ethanol and water 1 to 3 times in sequence, with each washing time being 5 minutes; the amount of the dispersion is 50 μ6 to 150 μ6 of electrode liquid per square centimeter of conductive substrate surface.

[0029] In a further improvement to the above preparation method, in step S3-3, the annealing treatment is carried out at 150℃ to 250℃; and the annealing time is 5 min to 15 min.

[0030] As a general technical concept, the present invention also provides an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles, which is prepared by the above-described preparation method.

[0031] The above-mentioned oxygen-doped ultrathin porous boron nitride film electrode loaded with gold nanoparticles is further improved in that the oxygen-doped ultrathin porous boron nitride film electrode loaded with gold nanoparticles uses a conductive substrate as a carrier, and the surface of the carrier is loaded with an oxygen-doped ultrathin porous boron nitride film loaded with gold nanoparticles.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] (1) To address the shortcomings of existing boron nitride-based photoelectric active materials, such as small specific surface area, high electron-hole recombination rate, poor electron transport efficiency, and consequently low photocurrent, this invention creatively proposes a method for preparing oxygen-doped ultrathin porous boron nitride thin film electrodes loaded with gold nanoparticles. Using boric acid, urea, and oxalic acid as raw materials, oxygen-doped ultrathin porous boron nitride is prepared by a ternary copolymerization method. Specifically, boric acid, urea, and oxalic acid are dissolved in water at a mass ratio of 1:3 to 6:0.25 to 0.35 and heated... Moisture is removed to obtain mixed crystals, which are then calcined to achieve both ultrathin porous boron nitride and oxygen doping. The precise addition of oxalic acid allows for precise control of the oxygen doping amount. During the mixed crystallization process, the oxalic acid ensures thorough mixing with other precursors, facilitating deeper oxygen doping. Optimizing the amount of oxalic acid can optimize the oxygen doping level. Experimental data shows that excessively high or low oxalic acid dosages lead to decreased electrode performance. Furthermore, the nitrogen content is altered by doping with inorganic oxygen. The band structure of boron nitride significantly increases its specific surface area, making electron-hole separation more efficient, improving photocurrent signal, reducing resistance, and increasing sensitivity, resulting in excellent photoelectric performance. Based on this, this invention utilizes a photochemical reduction method to prepare oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles. Specifically, an oxygen-doped ultrathin porous boron nitride dispersion is mixed with a chloroauric acid solution and stirred. A photocatalytic reduction reaction generates gold nanoparticles, which are then loaded onto the oxygen-doped ultrathin porous boron nitride to form gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride. The introduction of gold nanoparticles brings a plasma effect to the composite material, improving catalytic and photoelectric performance, and providing a foundation for subsequent applications. Finally, the oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles is coated onto a conductive substrate, resulting in a gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride thin-film electrode with a large specific surface area, high electron-hole separation efficiency, and fast electron transport rate. This is a novel thin-film electrode with excellent photoelectric performance, meeting practical production needs and showing broad application prospects in the field of photoelectrochemistry.

[0034] (2) The preparation method of the present invention has the advantages of simple process, convenient operation, high preparation efficiency and low cost, and is suitable for large-scale preparation and industrial application.

[0035] (3) In the preparation method of the present invention, other solvents besides water cannot be used to prepare a mixed solution of boric acid, urea and oxalic acid. This is because other solutions (such as organic solvents) may react with the raw materials, destroy the material structure, or introduce impurity elements. Attached Figure Description

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0037] Figure 1 These are TEM images of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention and hexagonal boron nitride (h-BN) prepared in Comparative Example 1.

[0038] Figure 2 The images show the adsorption isotherm and pore size distribution of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention and hexagonal boron nitride (h-BN) prepared in Comparative Example 1.

[0039] Figure 3 The X-ray photoelectron spectra of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention and hexagonal boron nitride (h-BN) prepared in Comparative Example 1 are shown.

[0040] Figure 4 The photocurrent response diagrams are of the oxygen-doped ultrathin porous boron nitride thin film electrode (Au / O-BN thin film electrode) loaded with gold nanoparticles prepared in Example 1 of the present invention and the boron nitride thin film electrode (h-BN thin film electrode) prepared in Comparative Example 1.

[0041] Figure 5 Impedance diagrams are shown for the oxygen-doped ultrathin porous boron nitride thin film electrode (Au / O-BN thin film electrode) loaded with gold nanoparticles prepared in Example 1 of this invention and the boron nitride thin film electrode (h-BN thin film electrode) prepared in Comparative Example 1.

[0042] Figure 6 The photocurrent response diagrams are for the p-BNO thin film electrode (p-BNO) prepared in Comparative Example 2 and the O-BN thin film electrodes (O-BN-1, O-BN-2, O-BN-3, O-BN-4, O-BN-5) prepared in Comparative Example 3. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0044] Unless otherwise specified, all materials and instruments used in the following embodiments are commercially available. The processes and equipment used are conventional, and all data obtained are averages from at least three repeated experiments.

[0045] Example 1:

[0046] A method for preparing an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles includes the following steps:

[0047] S1. Oxygen-doped ultrathin porous boron nitride was prepared using boric acid, urea, and oxalic acid as raw materials, specifically as follows:

[0048] S1-1. Take 10g of boric acid, 45g of urea and 3g of oxalic acid and dissolve them in 100ml of water to obtain a mixed solution.

[0049] S1-2. Heat the mixed solution obtained in step S1-1 to 60℃~80℃ (can be controlled at 70℃) to evaporate the water and obtain mixed crystals.

[0050] S1-3. The mixed crystal obtained in step S1-2 is placed in a tube furnace and heated to 900℃ for 5 hours. After natural cooling, the block is taken out and ground to obtain oxygen-doped ultrathin porous boron nitride, denoted as O-BN.

[0051] S2. Using the oxygen-doped ultrathin porous boron nitride obtained in step S1 as a support, prepare oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles, specifically:

[0052] S2-1. Disperse 50 mg of oxygen-doped ultrathin porous boron nitride in 50 m6 of methanol / water mixed solution (the mixed solution is prepared by mixing methanol and ultrapure water, wherein the volume ratio of methanol to ultrapure water is 1.5:10) to obtain an oxygen-doped ultrathin porous boron nitride dispersion, denoted as O-BN dispersion.

[0053] S2-2. The O-BN dispersion obtained in S2-1 is mixed with 2.5 m6 of chloroauric acid solution (the chloroauric acid solution is prepared by mixing chloroauric acid and ultrapure water, wherein the mass-volume ratio of chloroauric acid and ultrapure water is 1 g: 100 m6), stirred for 1 h, and photocatalytic reduction reaction is carried out for 1 h to obtain oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles, denoted as Au / O-BN.

[0054] S3. Prepare the Au / O-BN obtained in step S2 into a dispersion, coat it onto the pretreated tin dioxide conductive glass (the size of the conductive glass is 1cm×2cm), and after annealing, obtain the Au / O-BN thin film electrode.

[0055] S3-1. Disperse 4 mg of Au / O-BN obtained in step S2 in 1 m6 of a perfluorosulfonic acid / ethanol mixed solution (the mixed solution is prepared by mixing perfluorosulfonic acid and ethanol, wherein the volume ratio of perfluorosulfonic acid and ethanol is 0.5:10), and sonicate at 8 kHz for 45 min to obtain a dispersion.

[0056] S3-2. The tin dioxide transparent conductive glass is washed twice each with acetone, ethanol and water, with each wash lasting 5 minutes. 200 μL of the dispersion obtained in step S3-1 is dropped onto the pretreated tin dioxide transparent conductive glass to obtain a wet film.

[0057] S3-3. Anneal the wet film obtained in step S3-2 at 200℃ for 10 minutes.

[0058] Repeat the operations (drop coating and baking) in S3-2 to S3-3 three times to obtain an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles, denoted as Au / O-BN thin film electrode.

[0059] Comparative Example 1:

[0060] A method for preparing a boron nitride thin film electrode without gold nanoparticle loading and oxygen doping includes the following steps:

[0061] Take 10g of boric acid and 45g of urea and dissolve them in 100ml of water to obtain a mixed solution; heat the mixed solution to evaporate the water and obtain mixed crystals; place the mixed crystals in a tube furnace and heat to 900℃ for 5h. After natural cooling, take out the block and grind it to obtain hexagonal boron nitride, denoted as h-BN.

[0062] The tin dioxide transparent conductive glass was washed twice each with acetone, ethanol, and water. 4 mg of step h-BN was dissolved in 1 mL of a perfluorosulfonic acid / ethanol (0.5:10) mixture and sonicated at 8 kHz for 45 min to obtain a dispersion. 200 μL of the dispersion was drop-coated onto the pretreated tin dioxide transparent conductive glass to obtain a wet film. The wet film was annealed at 200 °C for 10 min. The drop-coating and baking steps were repeated three times to obtain a boron nitride thin film electrode, denoted as the h-BN thin film electrode.

[0063] Comparative Example 2:

[0064] A method for preparing oxygen-doped porous boron nitride thin film electrodes using melamine and boric acid as raw materials includes the following steps:

[0065] 37.2 g of boric acid and 25.2 g of melamine were mixed and dissolved in 100 mL of water to obtain a mixed solution. The mixed solution was kept at 90 °C for 3 h and then cooled at room temperature to obtain a white precursor. The precursor was then dried at 60 °C for 12 h and finally heated at 1100 °C for 4 h under a flowing nitrogen atmosphere to obtain oxygen-doped porous boron nitride.

[0066] The tin dioxide transparent conductive glass was washed twice each with acetone, ethanol, and water. 4 mg of p-BNO was dissolved in 1 m³ of a perfluorosulfonic acid / ethanol (0.5:10) mixture and sonicated at 8 kHz for 45 min to obtain a dispersion. 200 μL of the dispersion was drop-coated onto the pretreated tin dioxide transparent conductive glass to obtain a wet film. The wet film was annealed at 200 °C for 10 min. The drop-coating and baking steps were repeated three times to obtain the p-BNO thin film electrode, denoted as p-BNO.

[0067] Comparative Example 3:

[0068] Fabrication of oxygen-doped boron nitride thin film electrodes prepared using oxalic acid of varying masses

[0069] Each time, 10g of boric acid and 45g of urea were mixed with 1g, 2g, 4g, and 5g of oxalic acid respectively and dissolved in 100ml of water to obtain a mixed solution. The mixed solution was heated to evaporate the water and obtain mixed crystals. The mixed crystals were placed in a tube furnace and heated to 900℃ for 5 hours. After natural cooling, the block was taken out and ground to obtain hexagonal boron nitride with different oxygen doping amounts, which were denoted as A1, A2, A4, and A5 respectively.

[0070] The tin dioxide transparent conductive glass was washed twice each with acetone, ethanol, and water. For each wash, 4 mg of hexagonal boron nitride (A1, A2, A4, A5) with different oxygen doping levels was dissolved in 1 mL of a perfluorosulfonic acid / ethanol (0.5:10) mixture, and the solution was sonicated at 8 kHz for 45 min to obtain a dispersion. 200 μL of the dispersion was drop-coated onto the pretreated tin dioxide transparent conductive glass to obtain a wet film. The wet film was annealed at 200 °C for 10 min. The drop-coating and baking steps were repeated three times to obtain O-BN thin film electrodes, which were subsequently designated O-BN-1, O-BN-2, O-BN-4, and O-BN-5.

[0071] Following the preparation method in Comparative Example 3, the oxygen-doped ultrathin porous boron nitride (O-BN) prepared in Example 1 was used to fabricate an O-BN thin film electrode, denoted as O-BN-3.

[0072] Performance testing:

[0073] Figure 1 These are TEM images of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention and hexagonal boron nitride (h-BN) prepared in Comparative Example 1. Figure 1 In the diagram, a represents h-BN, and b represents Au / O-BN. From... Figure 1 As can be seen in (a), the h-BN prepared in Comparative Example 1 is blocky with a smooth surface, while Figure 1In (b), the Au / O-BN prepared in Example 1 of the present invention exhibits uniform nanopores and a distinct nanolayer structure, with a larger specific surface area compared to h-BN, indicating that Au / O-BN can promote the effective transfer of electrons and inhibit the recombination of electrons and holes.

[0074] Figure 2 The images show the adsorption isotherm and pore size distribution of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention and hexagonal boron nitride (h-BN) prepared in Comparative Example 1. Figure 1 In the diagram, a is the adsorption isotherm curve, and b is the pore size distribution diagram. Figure 2 As can be seen from point a, the specific surface area analysis results show that h-BN is 11.2 m². 2 / g, Au / O-BN is 202.5m 2 / g. From Figure 2 As shown in b, the pore size distribution of Au / O-BN in this invention is around 50 nm. This indicates that Au / O-BN has a larger specific surface area and a more pronounced mesoporous structure compared to h-BN.

[0075] Figure 3 The images show the X-ray photoelectron spectra of oxygen-doped ultrathin porous boron nitride (Au / O-BN) loaded with gold nanoparticles prepared in Example 1 of this invention, and hexagonal boron nitride (h-BN) prepared in Comparative Example 1. Figure 3 It can be clearly seen that Au / O-BN contains characteristic peaks of Au 4f, B 1s, C 1s, N 1s, and O 1s. In contrast, h-BN lacks the characteristic peaks of Au 4f and O 1s, indicating that gold nanoparticles were successfully loaded and oxygen was successfully doped in the Au / O-BN material.

[0076] Figure 4 The images show the photocurrent response of the oxygen-doped ultrathin porous boron nitride thin film electrode (Au / O-BN thin film electrode) loaded with gold nanoparticles prepared in Example 1 of this invention, and the boron nitride thin film electrode (h-BN thin film electrode) prepared in Comparative Example 1. Figure 4 It can be seen that the photocurrent density of the Au / O-BN thin film electrode prepared by this invention is 1519 nA / cm. 2 The photocurrent density of the h-BN thin film electrode prepared in Comparative Example 1 was 791 nA / cm. 2 As can be seen, compared with the h-BN thin film electrode in Comparative Example 1, the photocurrent density of the Au / O-BN thin film electrode prepared in Example 1 of the present invention is significantly enhanced, about twice that of the h-BN thin film electrode.

[0077] Figure 5Impedance maps are shown for the oxygen-doped ultrathin porous boron nitride thin film electrode (Au / O-BN thin film electrode) loaded with gold nanoparticles prepared in Example 1 of this invention, and the boron nitride thin film electrode (h-BN thin film electrode) prepared in Comparative Example 1. Compared with the h-BN thin film electrode in Comparative Example 1, the impedance of the Au / O-BN thin film electrode prepared in Example 1 of this invention is significantly reduced. Impedance reflects the strength of resistance; under a certain voltage, the smaller the resistance, the larger the current. Figure 4 and Figure 5 The conclusions are mutually supportive.

[0078] Figure 6 The images show the photocurrent response of the p-BNO thin film electrode (p-BNO) prepared in Comparative Example 2 and the O-BN thin film electrodes (O-BN-1, O-BN-2, O-BN-3, O-BN-4, O-BN-5) prepared in Comparative Example 3. Figure 5 It can be seen that the photocurrent density of the p-BNO thin film electrode (p-BNO) prepared in Comparative Example 2 is 998 nA / cm. 2 The photocurrent densities of the O-BN thin film electrodes (O-BN-1, O-BN-2, O-BN-3, O-BN-4, and O-BN-5) prepared in Comparative Example 3 were 805 nA / cm², respectively. 2 610nA / cm 2 1097 nA / cm 2 512nA / cm 2 469 nA / cm 2 Comparison shows that, compared with oxygen-doped porous boron nitride prepared by conventional methods, the oxygen-doped ultrathin porous boron nitride prepared by the method of this invention can significantly improve the photocurrent response performance of thin film electrodes, giving them higher photocurrent density and photocatalytic activity. In particular, when the mass ratio of boric acid, urea, and oxalic acid is 1:3–6:0.25–0.35, the Au / O-BN thin film electrode prepared by oxygen-doped ultrathin porous boron nitride exhibits superior photocatalytic activity. This is because when the amount of oxalic acid is low, the amount of oxygen atoms doped is low, making it difficult to reduce the recombination rate of photogenerated electron-hole pairs, resulting in poor photocatalytic activity. Although increasing the amount of oxalic acid can increase the amount of oxygen atoms doped, thereby reducing the interlayer distance of boron nitride and significantly reducing the recombination rate of photogenerated electron-hole pairs, which is beneficial to improving photocurrent density and photocatalytic activity, when the amount of oxalic acid is excessive, the excessive amount of doped oxygen atoms will cause an increase in the disorder of the boron nitride polymerization structure, leading to a decrease in the effective charge transport in boron nitride, i.e., a slow electron transport rate, which in turn results in a still poor photocurrent density and difficulty in effectively improving photocatalytic activity.

[0079] As shown in the above results, the preparation method of this invention uses boric acid, urea, and oxalic acid as raw materials and employs a ternary copolymerization method to prepare oxygen-doped ultrathin porous boron nitride. Specifically, the method involves dissolving boric acid, urea, and oxalic acid in water at a mass ratio of 1:3 to 6:0.25 to 0.35, removing the water by heating to obtain a mixed crystal, and then calcining the mixed crystal. This process achieves both ultrathin porous boron nitride and oxygen doping. The precise addition of oxalic acid effectively controls the amount of oxygen doping, allowing for thorough mixing with other precursors during the mixed crystallization process, which facilitates deeper oxygen doping. Optimizing the amount of oxalic acid optimizes the oxygen doping amount. Experimental data shows that excessively high or low oxalic acid dosages lead to decreased electrode performance. Furthermore, the doping of inorganic oxygen alters the band structure of boron nitride, significantly increasing its specific surface area, making electron-hole separation more effective, and improving the photocurrent signal. This invention reduces resistance, improves sensitivity, and exhibits excellent photoelectric properties. Based on this, the invention utilizes a photochemical reduction method to prepare oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles. Specifically, an oxygen-doped ultrathin porous boron nitride dispersion is mixed with a chloroauric acid solution and stirred. A photocatalytic reduction reaction generates gold nanoparticles, which are then loaded onto the oxygen-doped ultrathin porous boron nitride to form a gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride. The introduction of gold nanoparticles brings a plasma effect to the composite material, improving its catalytic and photoelectric properties, and providing a foundation for future applications. Finally, the gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride is coated onto a conductive substrate to obtain a gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride thin-film electrode with a large specific surface area, high electron-hole separation efficiency, and fast electron transport rate. This is a novel thin-film electrode with excellent performance, meeting practical production needs and showing broad application prospects in the field of photoelectrochemistry.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above. Therefore, any simple modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention's technical solutions shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles, characterized in that, Includes the following steps: S1. Using boric acid, urea, and oxalic acid as raw materials, oxygen-doped ultrathin porous boron nitride is prepared by ternary copolymerization, including the following steps: S1-1. Dissolve boric acid, urea, and oxalic acid in water to obtain a mixed solution; the mass ratio of boric acid, urea, and oxalic acid is 1:3 to 6:0.25 to 0.

35. S1-2. Heat the mixed solution obtained in S1-1 until the water evaporates to obtain mixed crystals; S1-3. The mixed crystal obtained in S1-2 is calcined to obtain oxygen-doped ultrathin porous boron nitride. S2. Using the oxygen-doped ultrathin porous boron nitride obtained in S1 as a support, oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles was prepared. S3. Prepare a dispersion of oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles obtained in S2, and coat it on a conductive substrate to form a gold nanoparticle-loaded oxygen-doped ultrathin porous boron nitride thin film electrode.

2. The preparation method according to claim 1, characterized in that, In S1-1, the mass ratio of boric acid, urea and oxalic acid is 1:3 to 6:0.3; In step S1-2, the heating is to a temperature of 60°C to 80°C; In steps S1-3, the calcination is carried out at a temperature of 800 ℃ to 1000 ℃; the calcination time is 3 h to 7 h.

3. The preparation method according to claim 1 or 2, characterized in that, In step S2, oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles is prepared using a photochemical reduction method, including the following steps: S2-1. Disperse the oxygen-doped ultrathin porous boron nitride obtained in S1 in a methanol / water mixed solution to obtain an oxygen-doped ultrathin porous boron nitride dispersion. S2-2. The oxygen-doped ultrathin porous boron nitride dispersion obtained in S2-1 is mixed with chloroauric acid solution, stirred, and subjected to photocatalytic reduction reaction to obtain oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles.

4. The preparation method according to claim 3, characterized in that, In S2-1, the mass-to-volume ratio of the oxygen-doped ultrathin porous boron nitride to the methanol / water mixed solution is 4 mg to 6 mg: 1 mL; the methanol / water mixed solution is prepared by mixing methanol and ultrapure water; the volume ratio of methanol to ultrapure water is 1 to 2:

10. In step S2-2, the volume ratio of the chloroauric acid solution to the oxygen-doped ultrathin porous boron nitride dispersion is 0.001–0.1:1; the chloroauric acid solution is prepared by mixing chloroauric acid and ultrapure water; the mass-volume ratio of chloroauric acid to ultrapure water is 1 g: 60 mL–120 mL; the stirring time is 0.5 h–1.5 h; and the photocatalytic reduction reaction time is 0.5 h–1.5 h.

5. The preparation method according to claim 1 or 2, characterized in that, Specifically, S3 is: S3-1. Mix the oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles obtained in S2 with a perfluorosulfonic acid / ethanol mixed solution and sonicate to obtain a dispersion. S3-2. The dispersion obtained in S3-1 is drop-coated onto the surface of a conductive substrate to form a wet film; S3-3. Anneal the wet film obtained in S3-2 to obtain an oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles.

6. The preparation method according to claim 5, characterized in that, S3 further includes the following process: repeating the operations in S3-2 to S3-3 3 to 5 times until the thickness of the oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles reaches the preset value.

7. The preparation method according to claim 6, characterized in that, In step S3-1, the mass-to-volume ratio of the oxygen-doped ultrathin porous boron nitride loaded with gold nanoparticles to the perfluorosulfonic acid / ethanol mixed solution is 2 mg to 10 mg: 1 mL; the perfluorosulfonic acid / ethanol mixed solution is prepared by mixing perfluorosulfonic acid and ethanol; the volume ratio of perfluorosulfonic acid to ethanol is 0.1 to 1:10; the frequency of the ultrasound is 5 kHz to 10 kHz, and the ultrasound time is 30 min to 60 min. In step S3-2, the conductive substrate is tin dioxide transparent conductive glass; the conductive substrate also includes the following pretreatment before use: the conductive substrate is washed with acetone, ethanol and water 1 to 3 times in sequence, and the time for each wash is 5 minutes; the amount of the dispersion is 50 µL to 150 µL of electrode liquid per square centimeter of conductive substrate surface. In step S3-3, the annealing process is performed at 150°C to 250°C; the annealing time is 5 min to 15 min.

8. An oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles, characterized in that, It is prepared by any one of claims 1 to 7.

9. The oxygen-doped ultrathin porous boron nitride thin film electrode loaded with gold nanoparticles according to claim 8, characterized in that, The oxygen-doped ultrathin porous boron nitride film electrode loaded with gold nanoparticles uses a conductive substrate as a carrier, and the surface of the carrier is loaded with an oxygen-doped ultrathin porous boron nitride film loaded with gold nanoparticles.

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