Neodymium-doped titanium dioxide loaded platinum nanoparticle composite catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of catalyst preparation, in particular to a neodymium-doped titanium dioxide loaded platinum nanoparticle composite catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving an organic titanium salt and a soluble neodymium salt in ethanol to obtain a mixed solution; mixing the ethanol dispersion liquid of the SiO2 spheres, the mixed solution and ammonia water, and carrying out hydrothermal reaction to obtain Nd-SiO2 (at) TiO2 core-shell spheres; etching SiO2 in the Nd-SiO2 (at) TiO2 core-shell sphere by adopting a sodium hydroxide solution to obtain a neodymium-doped titanium dioxide hollow sphere; and dropwise adding a sodium borohydride solution into an aqueous solution of the neodymium-doped titanium dioxide hollow spheres and a soluble platinum salt, and carrying out a reduction reaction to obtain the neodymium-doped titanium dioxide loaded platinum nanoparticle composite catalyst. The preparation method provided by the invention not only improves the photocatalytic efficiency and electro-catalytic reaction activity of the neodymium-doped titanium dioxide loaded platinum nanoparticle composite catalyst, but also enhances the long-term stability and durability of the neodymium-doped titanium dioxide loaded platinum nanoparticle composite catalyst.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry technology, and particularly to a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Titanium dioxide is regarded as a typical material for photocatalysis, having excellent photocatalytic activity, chemical stability, easy doping modification, and non-toxicity. However, in photocatalytic and electrocatalytic reactions, especially under visible light conditions, the catalytic efficiency of traditional titanium dioxide catalysts is relatively low. This phenomenon is mainly attributed to the wide bandgap characteristic of titanium dioxide, which limits its effective catalytic action only under ultraviolet light. In addition, titanium dioxide also faces the challenge of a relatively high electron-hole recombination rate, which further weakens the efficiency of the catalytic reaction.

[0003] Although the catalytic reaction efficiency can be improved by doping titanium dioxide or supporting noble metal nanoparticles (such as Pt), the prior art still has the following problems: when supporting Pt nanoparticles, the binding force between the Pt nanoparticles and titanium dioxide is relatively weak, which makes the Pt nanoparticles prone to falling off or aggregating during the catalytic process. The falling off and aggregation of Pt nanoparticles not only damage the long-term stability of the catalyst, but also lead to a significant reduction in the active sites on the catalyst surface, thereby reducing the catalytic effect. The aggregation of Pt nanoparticles not only reduces the active sites of the reaction, but also affects the selectivity of the catalytic reaction, thereby reducing the overall efficiency of the catalyst. In particular, the existing TiO2 supported Pt catalyst has a problem of high photogenerated carrier recombination rate, resulting in low photoelectric conversion efficiency, which limits the application of the TiO2 supported Pt catalyst in the field of photoelectrocatalysis. In addition, the poor electrical conductivity of traditional titanium dioxide catalysts limits their application in electrocatalytic reactions. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, its preparation method and application. The present invention uses an organic titanium salt, a soluble neodymium salt and SiO2 spheres as raw materials, and through the hard template method combined with the sol-gel technology, Nd-SiO2@TiO2 core-shell spheres are obtained; then the Nd-SiO2@TiO2 core-shell spheres are etched to obtain neodymium-doped titanium dioxide hollow spheres; finally, platinum nanoparticles are supported on the neodymium-doped titanium dioxide hollow spheres through a reduction reaction, and a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst is successfully obtained. Through neodymium doping and oxygen vacancy regulation, the present invention successfully introduces additional energy levels into titanium dioxide, thereby reducing the band gap energy and significantly improving the separation efficiency of photogenerated electron-hole pairs, thus greatly enhancing its photoelectrocatalytic activity. It not only overcomes the problems of low catalytic efficiency of traditional titanium dioxide catalysts under visible light, high electron-hole recombination rate, and easy shedding or aggregation of Pt particles, but also enhances its long-term stability and durability.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The first object of the present invention is to provide a preparation method of a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, comprising the following steps:

[0007] S1. Dissolve an organic titanium salt and a soluble neodymium salt in ethanol to obtain a mixed solution.

[0008] S2. Mix an ethanol dispersion of SiO2 spheres, the mixed solution and ammonia water, and carry out a hydrothermal reaction to obtain Nd-TiO2@SiO2 core-shell spheres.

[0009] Using ethanol as the solvent is mainly due to its good solubility, reaction stability and compatibility with the surface of SiO2, which can ensure the uniform formation of Nd-TiO2@SiO2 core-shell spheres. Through experimental verification, other solvents such as methanol, acetone, and tetrahydrofuran are prone to cause morphological defects or non-uniform coating of Nd-TiO2@SiO2 core-shell spheres. Therefore, ethanol is the key solvent of the present invention.

[0010] Among them, during the hydrothermal reaction process, an organic titanium salt such as a typical organic titanium precursor Ti(OBu)4 undergoes a hydrolysis reaction in the presence of water or ammonia water to generate Ti(OH)4, and Ti(OH)4 continues to undergo a condensation reaction to form TiO2 nanoparticles; while ammonia water releases OH in the system - to promote the hydrolysis of Ti(OBu)4 and at the same time adjust the pH value, which helps to uniformly coat the SiO2 spheres. At the same time, after the soluble neodymium salt is dissolved in ethanol, Nd 3+ is uniformly distributed in the solution and partially substitutes Ti during the hydrothermal process 4+Enter the lattice of TiO2 nanoparticles to form Nd-doped TiO2. 3+ The radius (0.0983nm) is smaller than that of Ti 4+ The radius (0.0605nm) is large, so Nd 3 + Doping can easily cause lattice distortion of TiO2 nanoparticles, forming oxygen vacancies, thereby improving the photocatalytic activity of Nd-doped titanium dioxide-loaded platinum nanoparticle composite catalysts.

[0011] In addition, the surface of SiO2 spheres carries a large number of hydroxyl groups, namely Si-OH. Under hydrothermal conditions, SiO2 interacts with TiO2 nanoparticles, promoting the uniform coating of TiO2 on the surface of SiO2 spheres through hydrogen bonding or electrostatic adsorption, and further forming a stable SiO2@TiO2 core-shell structure, which is further crystallized after calcination.

[0012] S3, using sodium hydroxide solution to etch SiO2 in the Nd-TiO2@SiO2 core-shell sphere to obtain neodymium-doped titanium dioxide hollow spheres.

[0013] S4, adding sodium borohydride solution to the aqueous solution of neodymium-doped titanium dioxide hollow spheres and soluble platinum salt to carry out a reduction reaction. During the reduction reaction, sodium borohydride hydrolyzes to produce BH4 - Ions and hydrogen anions or active hydrogen reduce platinum ions to platinum nanoparticles, and are loaded on the surface of neodymium-doped titanium dioxide hollow spheres through electrostatic adsorption, oxygen vacancies and the interaction of surface functional groups to obtain a neodymium-doped titanium dioxide-loaded platinum nanoparticle composite catalyst.

[0014] Among them, if the method of adding NaBH4 all at once is adopted, the following problems will arise: First, the strong reducing property of NaBH4 causes its reaction rate with platinum ions to be extremely high. Local high concentration conditions can easily cause violent reactions and generate large-sized platinum agglomerates, which affect the catalytic activity of the neodymium-doped titanium dioxide-loaded platinum nanoparticle composite catalyst. Second, a large amount of H2 is generated during the reaction of NaBH4 and platinum salts. The instantaneous release of H2 causes severe disturbances in the reaction system, resulting in uneven distribution of platinum nanoparticles, thereby reducing the catalytic activity of the neodymium-doped titanium dioxide-loaded platinum nanoparticle composite catalyst. Third, the NaBH4 solution is strongly alkaline, while the soluble platinum salt solution is acidic. When the two are mixed, the violent acid-base neutralization reaction causes the pH value of the system to change rapidly, destroying the suitable conditions for the reduction reaction, resulting in incomplete reduction of platinum ions and causing Pt 4+ and Pt 2+ The coexistence of these two species hinders the formation of high-purity Pt nanoparticles, and the deposition of by-products such as NaBO2 affects the surface properties of the Nd-doped titanium dioxide-supported platinum nanoparticle composite catalyst.

[0015] Preferably, the mass ratio of neodymium-doped titanium dioxide hollow spheres, soluble platinum salt and sodium borohydride is 1.3 - 1.5:1:0.1 - 0.2.

[0016] Preferably, the mass-volume ratio of SiO2 spheres, organic titanium salt and soluble neodymium salt is 0.12 g - 0.18 g:1.8 mL - 2.2 mL:0.01 g - 0.02 g; more preferably, the mass-volume ratio of SiO2 spheres, organic titanium salt and soluble neodymium salt is 0.15 g:2 mL:11.8 g.

[0017] Preferably, the conditions of the hydrothermal reaction are: stirring and reacting at 55°C - 65°C for 2 h - 4 h.

[0018] Preferably, the conditions of the reduction reaction are: stirring and reacting at 10°C - 30°C for 1 h - 3 h.

[0019] Preferably, the concentration of the sodium hydroxide solution is 1 mol / L - 2 mol / L. When the concentration of the sodium hydroxide solution is too low, less than 1 mol / L, the dissolution rate of SiO2 is slow, the etching is insufficient, and it is easy to cause an incomplete hollow sphere structure; when the concentration of the sodium hydroxide solution is too high, more than 1 mol / L, TiO2 will also be etched, affecting the morphology and stability of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst; more preferably 1.5 mol / L, which can effectively remove the SiO2 template while avoiding excessive corrosion of the TiO2 shell layer.

[0020] Preferably, the conditions of the etching are: heating at 70°C - 90°C for 4 h - 6 h.

[0021] Preferably, the organic titanium salt is selected from tetrabutyl titanate, isopropyl titanate or tetraethyl titanate.

[0022] Preferably, the soluble neodymium salt is selected from neodymium acetate, neodymium nitrate or neodymium chloride.

[0023] Preferably, the soluble platinum salt is selected from chloroplatinic acid, potassium chloroplatinate or platinum nitrate.

[0024] The second object of the present invention is to provide a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst prepared by the above preparation method.

[0025] Preferably, in the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, the neodymium-doped titanium dioxide hollow spheres exhibit a hierarchical structure composed of nanoparticles.

[0026] The third object of the present invention is to provide the application of the above neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst in the preparation of a photocatalyst.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The present invention provides a method for preparing a composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles. An organic titanium salt and a soluble neodymium salt are dissolved in ethanol to obtain a mixed solution. An ethanol dispersion of SiO2 spheres, the mixed solution, and ammonia water are mixed and subjected to a hydrothermal reaction. During the hydrothermal reaction, while TiO2 nanoparticles are formed, Nd 3+ partially substitutes for Ti 4+ and enters the lattice of the TiO2 nanoparticles to form Nd-doped TiO2, and the SiO2 spheres are coated to obtain Nd-TiO2@SiO2 core-shell spheres. The SiO2 in the Nd-TiO2@SiO2 core-shell spheres is etched with a sodium hydroxide solution to obtain neodymium-doped titanium dioxide hollow spheres. The neodymium-doped titanium dioxide hollow spheres are mixed with an aqueous solution of a soluble platinum salt, and then a sodium borohydride solution is added dropwise for a reduction reaction. The soluble platinum salt is reduced to platinum nanoparticles and loaded on the surface of the neodymium-doped titanium dioxide hollow spheres to obtain a composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles.

[0029] Through the strategies of neodymium doping and the introduction of oxygen vacancies, the present invention optimizes the electronic structure of titanium dioxide, significantly enhances its electrical conductivity and photocatalytic activity, and effectively inhibits the recombination phenomenon of electrons and holes. In addition, by optimizing the loading process of Pt nanoparticles, the present invention ensures that the Pt nanoparticles can be uniformly and stably loaded on the surface of the neodymium-doped titanium dioxide hollow spheres and significantly enhances the interfacial binding force between Pt and titanium dioxide. The preparation method of the present invention not only effectively avoids the agglomeration problem of Pt nanoparticles, but also greatly increases the density of active sites of the composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles, thereby significantly improving the catalytic effect and long-term stability of the composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles.

[0030] 2. Compared with the traditional titanium dioxide catalyst, the composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles of the present invention exhibits significantly improved catalytic efficiency under visible light irradiation. This excellent performance is attributed to the doping of neodymium element and the loading of platinum nanoparticles. Specifically, during the preparation of the composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles, the introduction of neodymium element doping can not only reduce the size of the neodymium-doped titanium dioxide hollow spheres to the nanoscale, but also induce lattice distortion to form a high concentration of oxygen vacancy defects, while narrowing the band gap energy level. The oxygen vacancy defects, as electron donor centers, not only significantly enhance the carrier mobility of titanium dioxide, but also expand the light absorption threshold through the defect energy level transition mechanism, thereby significantly improving the light capture ability of the composite catalyst of neodymium-doped titanium dioxide loaded with platinum nanoparticles.

[0031] In addition, by optimizing the dropping method of sodium borohydride, the stepwise reduction of platinum ions is achieved, avoiding the agglomeration phenomenon caused by local concentration overload. Utilizing the oxygen vacancies, surface hydroxyl groups, and electrostatic adsorption effects generated by neodymium doping, platinum nanoparticles are uniformly anchored on the surface of TiO2 hollow spheres, forming a strong interfacial binding force to ensure long-term catalytic stability.

[0032] 3. The neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst of the present invention has excellent catalytic activity, especially showing remarkable catalytic activity in the methanol oxidation reaction. In addition, the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst of the present invention has anti-poisoning ability, and the mass activity is still as high as 65% after 400 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 SEM images of OV-Nd-THS and OV-Nd-THS / Pt prepared in Example 1, where (a) is OV-Nd-THS and (b) is OV-Nd-THS / Pt.

[0034] Figure 2 Performance test result graphs of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst prepared in Example 1 under light and dark conditions, where (a) is the CV curve graph, (b) is the activity bar graph, (c) is the Nyquist graph, (d) is the anodic polarization curve, (e) is the photo-responsive current curve, and (f) is the performance comparison graph of OV-Nd-TiO2 / Pt of the present invention with other existing platinum-based catalysts. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Next, the technical solutions of the present invention will be clearly and completely described in combination with the data in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0036] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods. Among them, commercial platinum-carbon, that is, JM Pt / C catalyst, is purchased from Johnson Matthey Company.

[0037] In the prior art, although researchers have explored various methods to improve the performance of titanium dioxide catalysts, such as adjusting preparation process parameters, trying different doping elements, and optimizing the loading strategy of noble metal nanoparticles, these methods often have difficulty in simultaneously solving the problems of easy shedding or aggregation of noble metal nanoparticles, high recombination rate of photo-generated carriers, and poor conductivity.

[0038] In view of the problems existing in the above prior art, the present invention provides a method for preparing a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, comprising the following steps: dissolving an organic titanium salt and a soluble neodymium salt in ethanol to obtain a mixed solution; mixing an ethanol dispersion of SiO2 spheres, the mixed solution, and ammonia water, and performing a hydrothermal reaction. During the hydrothermal reaction, while TiO2 nanoparticles are formed, part of Nd 3+ substitutes Ti 4+ in the lattice of the TiO2 nanoparticles to form Nd-doped TiO2, and coating the SiO2 spheres to obtain Nd-TiO2@SiO2 core-shell spheres; etching the SiO2 in the Nd-TiO2@SiO2 core-shell spheres with a sodium hydroxide solution to obtain neodymium-doped titanium dioxide hollow spheres; mixing the neodymium-doped titanium dioxide hollow spheres with an aqueous solution of a soluble platinum salt, and then dropping a sodium borohydride solution to perform a reduction reaction, reducing the soluble platinum salt to platinum nanoparticles and loading them on the surface of the neodymium-doped titanium dioxide hollow spheres to obtain a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst.

[0039] In view of the problems of high recombination rate of photo-generated carriers and poor conductivity in the prior art, the present invention, by introducing neodymium element doping, can not only reduce the size of the neodymium-doped titanium dioxide hollow spheres to the nanoscale, but also form high-concentration oxygen vacancy defects by inducing lattice distortion, while realizing the narrowing of the band gap energy level. The oxygen vacancy defects, as electron donor centers, not only significantly enhance the carrier mobility of titanium dioxide, but also expand the light absorption threshold through the defect energy level transition mechanism, effectively suppressing the recombination phenomenon of electrons and holes, thereby significantly improving the light capture ability and photoelectric conversion efficiency of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, and overcoming the problems of high recombination rate of photo-generated carriers and poor conductivity of the traditional TiO2 supported Pt catalyst.

[0040] In addition, the neodymium-doped titanium dioxide hollow sphere structure not only provides a larger specific surface area and more reactive sites, but also optimizes the contact efficiency between the reactants and the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, thereby further enhancing the catalytic performance.

[0041] Aiming at the problem that noble metal nanoparticles are prone to fall off or aggregate in the prior art, the present invention realizes the gradual reduction of platinum ions by optimizing the dropping method of sodium borohydride, avoiding the agglomeration phenomenon caused by local concentration overload. Utilizing the oxygen vacancies, surface hydroxyl groups and electrostatic adsorption effects generated by neodymium doping, platinum nanoparticles are uniformly anchored on the surface of neodymium-doped TiO2 hollow spheres, forming a strong interfacial binding force, which not only strengthens the fixation of neodymium-doped titanium dioxide hollow spheres on Pt nanoparticles, but also optimizes the local charge density of Pt nanoparticles, thereby ensuring its long-term catalytic stability.

[0042] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will specifically describe the technical solution of the present invention in detail with reference to specific embodiments:

[0043] Example 1

[0044] A preparation method of a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst includes the following steps:

[0045] S1. Disperse 0.15 g of SiO2 spheres in 50 mL of ethanol by ultrasonic treatment to obtain an ethanol dispersion of SiO2 spheres; at the same time, dissolve 2 mL of tetrabutyl titanate and 11.8 mg of neodymium acetate in 50 mL of ethanol, and perform ultrasonic stirring for 0.5 h to obtain a mixed solution.

[0046] S2. Add the mixed solution and 0.75 mL of ammonia water to the ethanol dispersion of SiO2 spheres together, then stir vigorously at 60 °C for 3 h. After the reaction, perform centrifugation and washing with ethanol, and dry in air at 40 °C to obtain Nd-SiO2@TiO2 core-shell spheres.

[0047] S3. Prepare a 40 mL, 1.5 mol / L sodium hydroxide solution, add the Nd-SiO2@TiO2 core-shell spheres to the sodium hydroxide solution and stir for 30 min, then heat at 80 °C for 5 h. After heating, naturally cool to room temperature, centrifuge and wash several times with distilled water to obtain neodymium-doped titanium dioxide hollow spheres, denoted as OV-Nd-THS.

[0048] S4. Dissolve 10 mg of neodymium-doped titanium dioxide hollow spheres in 2 mL of water, add 2 mL of 8 mmol / L chloroplatinic acid solution under stirring, and continue stirring for 1.5 h; then, slowly drop 1 mL of 30 mmol / L sodium borohydride solution into the system at a rate of 0.5 mL / min, and continue stirring at 40 °C for 1.5 h. After the reaction, wash three times with deionized water and ethanol respectively, and after drying, obtain a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, denoted as OV-Nd-THS / Pt.

[0049] Example 2

[0050] Preparation method of neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, comprising the following steps:

[0051] S1. Disperse 0.12 g of SiO2 spheres in 50 mL of ethanol by ultrasonic treatment to obtain an ethanol dispersion of SiO2 spheres; meanwhile, dissolve 1.8 mL of tetrabutyl titanate and 10 mg of neodymium acetate in 50 mL of ethanol, and perform ultrasonic stirring for 0.5 h to obtain a mixed solution.

[0052] S2. Add the mixed solution and 0.75 mL of ammonia water into the ethanol dispersion of SiO2 spheres together, then stir vigorously at 60 °C for 3 h. After the reaction, perform centrifugation and washing with ethanol, and dry in air at 10 °C to obtain Nd-SiO2@TiO2 core-shell spheres.

[0053] S3. Prepare 40 mL of 1.5 mol / L sodium hydroxide solution, add the Nd-SiO2@TiO2 core-shell spheres into the sodium hydroxide solution and stir for 30 min, then heat at 80 °C for 5 h. After heating, cool naturally to room temperature, centrifuge and wash several times with distilled water to obtain neodymium-doped titanium dioxide hollow spheres, denoted as OV-Nd-THS.

[0054] S4. Dissolve 10 mg of neodymium-doped titanium dioxide hollow spheres in 2 mL of water, add 2 mL of 8 mmol / L chloroplatinic acid solution under stirring, and continue stirring for 1.5 h; then, slowly dropwise add 1 mL of 30 mmol / L sodium borohydride solution into the system at a rate of 0.5 mL / min, continue stirring at 10 °C for 1.5 h. After the reaction, wash three times with deionized water and ethanol respectively, and after drying treatment, obtain neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, denoted as OV-Nd-THS / Pt.

[0055] Example 3

[0056] Preparation method of neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, comprising the following steps:

[0057] S1. Disperse 0.18 g of SiO2 spheres in 50 mL of ethanol by ultrasonic treatment to obtain an ethanol dispersion of SiO2 spheres; meanwhile, dissolve 2.2 mL of tetrabutyl titanate and 20 mg of neodymium acetate in 50 mL of ethanol, and perform ultrasonic stirring for 0.5 h to obtain a mixed solution.

[0058] S2. Add the mixed solution and 0.75 mL of ammonia water into the ethanol dispersion of SiO2 spheres. Then, stir the mixture vigorously at 60 °C for 3 h. After the reaction, perform centrifugation and washing with ethanol, and dry in air at 20 °C to obtain Nd-SiO2@TiO2 core-shell spheres.

[0059] S3. Prepare 40 mL of 1.5 mol / L sodium hydroxide solution. Add the Nd-SiO2@TiO2 core-shell spheres into the sodium hydroxide solution and stir for 30 min. Then, heat at 80 °C for 5 h. After heating, cool naturally to room temperature, centrifuge, and wash several times with distilled water to obtain neodymium-doped titanium dioxide hollow spheres, denoted as OV-Nd-THS.

[0060] S4. Dissolve 10 mg of neodymium-doped titanium dioxide hollow spheres in 2 mL of water. Add 2 mL of 8 mmol / L chloroplatinic acid solution under stirring, and continue stirring for 1.5 h. Then, slowly dropwise add 1.17 mL of 30 mmol / L sodium borohydride solution into the system at a rate of 0.75 mL / min, and continue stirring at 20 °C for 1.5 h. After the reaction, wash three times with deionized water and ethanol respectively, and after drying, obtain a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, denoted as OV-Nd-THS / Pt.

[0061] Example 4

[0062] A preparation method of a neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst, comprising the following steps:

[0063] S1. Disperse 0.15 g of SiO2 spheres in 50 mL of ethanol by ultrasonic treatment to obtain an ethanol dispersion of SiO2 spheres. At the same time, dissolve 2 mL of tetrabutyl titanate and 11.8 mg of neodymium acetate in 50 mL of ethanol, and perform ultrasonic stirring for 0.5 h to obtain a mixed solution.

[0064] S2. Add the mixed solution and 0.75 mL of ammonia water into the ethanol dispersion of SiO2 spheres. Then, stir the mixture vigorously at 60 °C for 3 h. After the reaction, perform centrifugation and washing with ethanol, and dry in air at 30 °C to obtain Nd-SiO2@TiO2 core-shell spheres.

[0065] S3. Prepare 40 mL of 1.5 mol / L sodium hydroxide solution. Add the Nd-SiO2@TiO2 core-shell spheres into the sodium hydroxide solution and stir for 30 min. Then, heat at 80 °C for 5 h. After heating, cool naturally to room temperature, centrifuge, and wash several times with distilled water to obtain neodymium-doped titanium dioxide hollow spheres, denoted as OV-Nd-THS.

[0066] S4. Dissolve 8.67 mg of neodymium-doped titanium dioxide hollow spheres in 2 mL of water. Add 2 mL of 8 mmol / L chloroplatinic acid solution under stirring, and continue stirring for 1.5 h. Subsequently, slowly dropwise add 0.58 mL of 30 mmol / L sodium borohydride solution into the system at a rate of 1 mL / min, and continue stirring for 1.5 h at 30 °C. After the reaction is completed, wash three times with deionized water and ethanol respectively, and after drying treatment, obtain neodymium-doped titanium dioxide supported platinum nanoparticles composite catalyst, denoted as OV-Nd-THS / Pt.

[0067] Comparative Example 1

[0068] A preparation method of titanium dioxide supported platinum nanoparticles composite catalyst, comprising the following steps:

[0069] S1. Disperse 0.15 g of SiO2 spheres in 50 mL of ethanol by ultrasonic treatment to obtain an ethanol dispersion of SiO2 spheres; at the same time, dissolve 2 mL of tetrabutyl titanate in 50 mL of ethanol and perform ultrasonic stirring for 0.5 h to obtain a mixed solution.

[0070] S2. Add the mixed solution and 0.75 mL of ammonia water into the ethanol dispersion of SiO2 spheres together, and then vigorously stir and react at 60 °C for 3 h. After the reaction is completed, perform centrifugation treatment and washing with ethanol, and dry in air at 40 °C to obtain SiO2@TiO2 core-shell spheres.

[0071] S3. Prepare 40 mL of 1.5 mol / L sodium hydroxide solution, add the SiO2@TiO2 core-shell spheres into the sodium hydroxide solution and stir for 30 min, and then heat at 80 °C for 5 h. After heating, naturally cool to room temperature, centrifuge and wash several times with distilled water to obtain neodymium-doped titanium dioxide hollow spheres, denoted as OV-THS.

[0072] S4. Dissolve 10 mg of neodymium-doped titanium dioxide hollow spheres in 2 mL of water. Add 2 mL of 8 mmol / L chloroplatinic acid solution under stirring, and continue stirring for 1.5 h. Subsequently, slowly dropwise add 1 mL of 30 mmol / L sodium borohydride solution into the system at a rate of 0.5 mL / min, and continue stirring for 1.5 h at 40 °C. After the reaction is completed, wash three times with deionized water and ethanol respectively, and after drying treatment, obtain neodymium-doped titanium dioxide supported platinum nanoparticles composite catalyst, denoted as OV-THS / Pt.

[0073] Figure 1The display of the broken sphere image presented shows the formation process of neodymium-doped titanium dioxide hollow spheres. Its rough surface structure indicates that the neodymium-doped titanium dioxide hollow spheres exhibit a hierarchical structure composed of nanoparticles. Due to the aggregation characteristics of titanium dioxide nanoparticles, it inevitably leads to the collapse of the porous hollow sphere structure, and then leads to the generation of a large number of nanoparticle particles.

[0074] This hollow spherical morphology has the following advantages: First, the high specific surface area property. The structure of the neodymium-doped titanium dioxide hollow spheres has a large external surface area and internal surface area, enabling it to provide more reactive sites. Second, the neodymium-doped titanium dioxide hollow spheres have a low volume density and good surface permeability, which can shorten the mass and charge transfer paths. Third, the porous structure of the neodymium-doped titanium dioxide hollow spheres significantly enhances its light trapping ability. The multiple reflections of ultraviolet light inside the neodymium-doped titanium dioxide hollow spheres contribute to improving the photoelectrocatalytic performance of the neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst.

[0075] The electrocatalytic performance of the neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst prepared in Example 1 of the present invention in the methanol oxidation reaction (MOR) in a 0.5 mol / L KOH solution containing 1 mol / L of CH3OH was evaluated.

[0076] 5 mg of the OV-Nd-THS / Pt powder of Example 1 and 5 mg of the OV-THS / Pt powder of Comparative Example 1 were respectively dispersed in 1 mL of an aqueous solution containing 8 μL of Nafion and ultrasonically stirred for 30 minutes. Then, 5 μL of the dispersion was evenly coated on a carbon cloth that had been flame-treated and had an active area of 1 cm 2 and dried at 60 °C to obtain working electrodes, denoted as OV-Nd-TiO2 / Pt and OV-TiO2 / Pt respectively.

[0077] Using OV-Nd-TiO2 / Pt, OV-TiO2 / Pt, and JM-Pt / C as working electrodes, a mercury / mercuric oxide electrode as a reference electrode, and a platinum wire as a counter electrode, one end of the working electrode, reference electrode, and counter electrode was placed in a quartz electrolytic cell, and the other ends were commonly electrically connected to a CHI750b electrochemical workstation for electrocatalytic and photoelectrocatalytic oxidation detection.

[0078] The detection conditions were as follows: A 300 W xenon lamp (PLS-SXE300, Perfect Light, China) equipped with an AM 1.5G filter was used to simulate sunlight irradiation conditions with a light intensity of 100 mW / cm 2 for the light irradiation experiment; the light irradiation condition was briefly recorded as illuminated.

[0079] By Figure 2From (a) and (b) in [reference], the peak current density of OV-Nd-TiO2 / Pt is 2686 mA / mg, which is 1.3 times that of OV-THS / Pt (2032 mA / mg) and 3.9 times that of JM / Pt / C (696 mA / mg), respectively. Under simulated sunlight irradiation conditions, the peak current density of OV-Nd-TiO2 / Pt further reaches 5252 mA / mg, significantly higher than that of OV-THS / Pt (3918 mA / mg) and JM / Pt / C (1277 mA / mg).

[0080] It can be obtained from Figure 2 in (c) that the impedance arc radius of OV-Nd-TiO2 / Pt is much smaller than that of OV-TiO2 / Pt and JM Pt / C. Especially under illumination, the Rct value of OV-Nd-TiO2 / Pt decreases significantly, indicating a faster and more efficient charge transfer ability between the electrolyte and the OV-Nd-TiO2 / Pt electrode.

[0081] It can be seen from Figure 2 in (d) that the initial oxidation potential of OV-Nd-TiO2 / Pt under light irradiation has a significant negative shift, indicating that using OV-Nd-THS as the carrier of Pt can significantly improve the kinetic performance of MOR.

[0082] To verify the charge separation ability of the three materials, the photocurrent response was measured by turning on and off every 50 s. It can be obtained from Figure 2 in (e) that the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst of the present invention has a photocurrent response ability. When visible light is turned on, the photocurrent increase effect of OV-Nd-TiO2 / Pt is the most significant, while it drops when the light is turned off, indicating that the doping of Nd effectively improves the photocurrent response ability and promotes the charge separation of the photocatalyst.

[0083] The charge transfer characteristics at the electrolyte-electrode interface during the methanol oxidation reaction were studied by electrochemical impedance spectroscopy at -0.25 V potential. Generally, the diameter of the semicircle reflects the magnitude of the charge transfer resistance. A lower DSA value means more efficient interfacial charge transport, and at the same time, it also indicates that photo-generated electron-hole pairs can be separated more quickly, thus significantly improving the overall efficiency of the reaction.

[0084] It can be obtained from Figure 2It can be obtained from (f) in that, compared with Pt@NiO-TiO2, Pt / Fe-TiO2, Pt / Bi2WO6 / La2-Ti2O7, Pt / BiOBr, Pt-MXene-TiO2, Ce-MoO3 / Pt, UV-Pt@TONR / GN, Pt / TiO2 / G-PV and Pt / GNs / TiO2 in the prior art, the catalytic performance of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst of the present invention in an alkaline electrolyte is significantly improved, and it is one of the highest photocatalytic activities for methanol oxidation among photocatalysts so far.

[0085] It should be noted that when the present invention involves a numerical range, it should be understood that any one of the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods adopted are the same as those in the embodiments, in order to prevent redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

Claims

1. Preparation method of a composite catalyst of platinum nanoparticles supported on neodymium-doped titanium dioxide, characterized in that, It includes the following steps: Dissolve an organic titanium salt and a soluble neodymium salt in ethanol to obtain a mixed solution; Mix the ethanol dispersion of SiO2 spheres, the mixed solution and ammonia water, and carry out a hydrothermal reaction. During the hydrothermal reaction, while TiO2 nanoparticles are formed, Nd 3+ partially substitutes for Ti 4+ enters the lattice of TiO2 nanoparticles to form Nd-doped TiO2, and coats the SiO2 spheres to obtain Nd-TiO2@SiO2 core-shell spheres; Etch SiO2 in the Nd-TiO2@SiO2 core-shell spheres with a sodium hydroxide solution to obtain neodymium-doped titanium dioxide hollow spheres; Mix the neodymium-doped titanium dioxide hollow spheres with an aqueous solution of a soluble platinum salt, then dropwise add a sodium borohydride solution to carry out a reduction reaction. The soluble platinum salt is reduced to platinum nanoparticles and loaded on the surface of the neodymium-doped titanium dioxide hollow spheres to obtain a neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst.

2. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The mass ratio of the neodymium-doped titanium dioxide hollow spheres, the soluble platinum salt to the sodium borohydride is 1.3 - 1.5:1:0.1 - 0.

2.

3. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The mass-volume ratio of the SiO2 spheres, the organic titanium salt to the soluble neodymium salt is 0.12 g - 0.18 g:1.8 mL - 2.2 mL:0.01 g - 0.02 g.

4. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The conditions for the hydrothermal reaction are: stirring and reacting at 55°C - 65°C for 2 h - 4 h.

5. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The conditions for the reduction reaction are: reacting at 10°C - 30°C for 1 h - 3 h.

6. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The organic titanium salt is selected from tetrabutyl titanate, isopropyl titanate or tetraethyl titanate.

7. The preparation method of the neodymium-doped titanium dioxide supported platinum nanoparticle composite catalyst according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 1 mol / L - 2 mol / L.

8. A neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst prepared by the preparation method according to any one of claims 1 - 7.

9. The neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst according to claim 8, wherein In the neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst, the neodymium-doped titanium dioxide hollow spheres exhibit a hierarchical structure composed of nanoparticles.

10. An application of the neodymium-doped titanium dioxide-supported platinum nanoparticle composite catalyst according to claim 8 in the preparation of a photocatalyst.

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