Monolithic catalyst for hydrogen production through hydrolysis of ammonia borane as well as preparation method and application of monolithic catalyst

Abstract

The invention discloses a monolithic catalyst for hydrogen production through hydrolysis of ammonia borane, and a preparation method and application thereof. The monolithic catalyst comprises a titanium foil substrate; the iron-doped titanium dioxide nano array is formed on the titanium foil substrate, and iron is dispersed in a monatomic form; the iron-doped titanium dioxide nano array is loaded on the substrate, and the platinum nano cluster is loaded on the iron-doped titanium dioxide nano array; and a Pt-O-Fe bond is formed between the platinum nanocluster and the iron-doped titanium dioxide nano array. The monolithic catalyst provided by the invention can efficiently catalyze ammonia borane hydrolysis for hydrogen production at normal temperature, has high conversion efficiency, very high catalytic activity and stability, and is a catalyst with great development prospects.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, specifically relating to an integral catalyst for hydrogen production by hydrolysis of ammonia borane, its preparation method, and its application. Background Technology

[0002] With the increasing severity of the global energy crisis and environmental problems, developing a clean, efficient, and sustainable energy system has become a critical issue that urgently needs to be addressed. Hydrogen energy, with its high energy density (142 MJ / kg) and the clean characteristic that its combustion product is only water, is considered an ideal energy carrier to replace fossil fuels in the future, and has broad application prospects in transportation, energy storage, and other fields. However, the safe storage and controlled release of hydrogen remain the core bottlenecks restricting its large-scale application, and developing efficient hydrogen storage and release technologies is key to the development of the hydrogen energy industry.

[0003] Among various hydrogen storage technologies, solid-state hydrogen storage materials have attracted much attention due to their high safety and high storage density. Ammonia borane, as a typical solid-state hydrogen storage material, boasts an ultra-high theoretical hydrogen storage density of 19.6 wt%, excellent water solubility, and controllable dehydrogenation under mild conditions. Its hydrolysis reaction can release 3 equivalents of hydrogen, making it a hydrogen source carrier with great application potential. However, the hydrolysis reaction of ammonia borane involves multiple intermediate transformations, has a high kinetic energy barrier, and limits the reaction rate, requiring a catalyst to achieve efficient hydrogen release.

[0004] Existing ammonia borane hydrolysis catalysts are mostly in powder form, which suffers from difficulties in separation and recovery, easy agglomeration and loss, and high mass transfer resistance, limiting their practical applications. Monolithic catalysts, with their integrated structure, good mechanical stability, efficient mass / heat transfer characteristics, and ease of separation and recovery, effectively overcome the drawbacks of traditional powder catalysts and show broad application prospects in the field of heterogeneous catalysis. Currently, developing highly efficient monolithic catalysts suitable for the ammonia borane hydrolysis reaction has become one of the research hotspots in this field. However, the advantages of the monolithic structure only solve the macroscopic engineering problems of the catalyst; to achieve high-performance catalysis, the core still lies in the precise control of active sites.

[0005] Existing optimization strategies mainly focus on two aspects: first, reducing the Pt size to sub-nanometer or near-atomic scale to maximize the exposure of active sites; second, achieving thermodynamic equilibrium between reactant activation and intermediate desorption by regulating the electronic structure of Pt through metal-support interactions. However, the high surface energy of sub-nanometer Pt clusters easily induces aggregation, leading to a decline in catalytic activity and making it difficult to balance high activity and stability. The rise of single-atom catalysis has provided a new approach to solving these problems: atomically dispersed transition metals can enhance the catalytic activity of materials by optimizing the electronic environment of active sites. However, the lack of a clear construction strategy between single atoms, noble metal clusters, and supports makes it impossible to effectively regulate the active sites of Pt and achieve efficient catalysis of ammonia borane hydrolysis. Therefore, developing a catalyst design scheme that can precisely regulate the electronic structure of Pt, inhibit Pt aggregation, and reduce Pt loading is key to overcoming the current technological bottlenecks. Summary of the Invention

[0006] In view of this, and addressing the technical challenges of existing Pt-based monolithic catalysts in the hydrolysis of ammonia borane, such as high Pt loading, severe agglomeration, and difficulty in synergistically improving activity and stability, this invention provides a monolithic catalyst for hydrogen production from ammonia borane hydrolysis, its preparation method, and its application. This invention achieves highly efficient and stable catalysis with low Pt loading by constructing a single-atom Fe-doped TiO2 nanoarray support and loading highly dispersed Pt nanoclusters onto it using photodeposition. The Pt-O-Fe bridging bond optimizes the electronic environment of the active sites.

[0007] The technical solution adopted is as follows:

[0008] In a first aspect, the present invention provides an integral catalyst for hydrogen production by hydrolysis of ammonia boron, comprising:

[0009] Titanium foil substrate;

[0010] An iron-doped titanium dioxide nanoarray formed on the titanium foil substrate, wherein iron is dispersed in single-atom form; and

[0011] Platinum nanoclusters loaded on the iron-doped titanium dioxide nanoarray;

[0012] Pt-O-Fe bonds are formed between the platinum nanoclusters and the iron-doped titanium dioxide nanoarray.

[0013] The iron-doped titanium dioxide nanoarray is designated as Fe1-TiO2 nanoarray, and the monolithic catalyst is designated as Pt. c / Fe1-TiO2 monolithic catalytic material.

[0014] Furthermore, the iron-doped titanium dioxide nanoarray is a nanotube array. This ordered tubular structure has a large specific surface area, which is beneficial for the dispersion of active components and the mass transfer of reactants.

[0015] Furthermore, the average particle size of the platinum nanoclusters is 1-2 nm. Platinum clusters within this size range have a high proportion of surface-active atoms while remaining stable due to strong interactions with the support.

[0016] In a second aspect, the present invention provides a method for preparing the monolithic catalyst described in the first aspect above, comprising the following steps:

[0017] S1. The cleaned titanium foil is placed in an electrolyte containing iron ions for anodic oxidation, and then annealed to grow an iron-doped titanium dioxide nanoarray in situ on the titanium foil substrate.

[0018] S2. The titanium foil loaded with iron-doped titanium dioxide nanoarray obtained in step S1 is immersed in a solution containing platinum precursor and photodeposited to load platinum nanoclusters onto the iron-doped titanium dioxide nanoarray, thereby obtaining the monolithic catalyst.

[0019] Further, in step S1, the electrolyte is an ethylene glycol solution containing ammonium fluoride, water, and ferric nitrate. The content of ammonium fluoride is 0.5-1 wt%, the content of water is 3.0-5.0 vol%, and the concentration of ferric nitrate is 5-20 mM. Ammonium fluoride provides the necessary fluoride ions for etching to form nanotube structures, and ferric nitrate provides the iron source. By controlling the concentration of iron ions, atomic-level dispersion of iron in the titanium dioxide lattice can be achieved, avoiding the formation of iron oxide clusters.

[0020] Further, in step S1, the anodizing is a multi-step anodizing process, comprising a first-step anodizing and a second-step anodizing. The first-step anodizing is performed at a voltage of 40-60 V for 80-120 min; the second-step anodizing is performed at a voltage of 10-20 V for 10-30 min. This multi-step oxidation process helps improve the morphological order and interfacial bonding strength of the nanotube array. The first-step high-pressure oxidation is used to grow the main nanotube structure, while the second-step low-pressure oxidation helps to peel away the disordered surface layer, exposing more regular tube openings.

[0021] Furthermore, in step S1, the annealing treatment is carried out at a temperature of 450-600 ℃ for 2-5 h, with a heating rate of 1-5 ℃ / min. These annealing conditions can transform amorphous TiO2 into the anatase phase, while simultaneously promoting the entry of iron atoms into the crystal lattice and their stable dispersion.

[0022] Further, in step S2, the platinum precursor is chloroplatinic acid; the solution containing the platinum precursor is a mixture of an aqueous solution of chloroplatinic acid and ethanol, wherein the volume ratio of water, ethanol, and the aqueous solution of chloroplatinic acid in the mixture is 30-40:10-20:1-4. Ethanol can act as a hole sacrificial agent to promote the photoreduction process. Furthermore, by adjusting the amount of chloroplatinic acid, the platinum loading can be controlled, thereby optimizing the catalytic activity.

[0023] Furthermore, in step S2, the light source used for photodeposition has a wavelength below 320 nm and a light intensity of 80-100 μW / cm². 2 The irradiation time is 30-60 minutes. This ultraviolet light can excite TiO2 to generate photogenerated electrons, which will then adsorb the Pt. 4+ Restore to Pt 0 This forms nanoclusters.

[0024] Thirdly, the present invention provides an application of the monolithic catalyst described in the first aspect above in the catalytic hydrolysis of ammonia borane to produce hydrogen.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) In this invention, iron-doped TiO2 nanoarrays are grown in situ on the surface of titanium foil by anodic oxidation, which achieves high dispersion of iron in the form of single atoms. Subsequently, Pt nanoclusters are loaded by photodeposition. By utilizing the formation of Pt-O-Fe bridging bonds, Pt clusters are not only effectively anchored and their aggregation and loss during the reaction process are suppressed, but the electronic structure of Pt active sites is also optimized, thereby improving intrinsic catalytic activity.

[0027] (2) The present invention Pt c A method for preparing monolithic Fe1-TiO2 catalytic materials includes a two-step anodic oxidation process to prepare Fe atom-doped TiO2 nanotube arrays, followed by photodeposition to load Pt clusters and tightly connect them to a support, ultimately obtaining highly dispersed sub-nanometer Pt cluster catalytic materials on the surface of the TiO2 nanoarrays. The Pt prepared by this method... c The monolithic Pt / TiO2 catalyst can withstand the erosion of reaction fluids, effectively solving the problems of easy loss and difficult separation and recovery of traditional powder catalysts. Simultaneously, the stable Pt-O-Fe bridging bonds optimize the active site environment for the ammonia borane hydrolysis reaction. At low Pt loadings, it exhibits superior hydrogen production performance from ammonia borane hydrolysis compared to traditional Pt / TiO2 catalysts and commercial Pt / C catalysts. This synthesis method has both promising application prospects and socio-economic benefits.

[0028] In summary, the catalyst prepared by this invention uses Ti foil as a substrate and contains Fe... 3+TiO2 nanoarrays were formed on the surface of the Pt nanoparticles in the electrolyte by anodic oxidation, and then Pt nanoclusters were prepared by photodeposition to obtain Pt nanoclusters with highly dispersed Pt clusters. c / Fe1-TiO2 monolithic catalyst. The catalytic material prepared using this method can withstand the erosion of the reaction fluid, effectively solving the problem of difficult separation and recovery of traditional powder catalysts. Simultaneously, the stable Pt-O-Fe bridging bonds not only inhibit Pt aggregation and loss but also optimize the electronic environment of the active sites. This catalyst can efficiently catalyze the hydrolysis of ammonia borane to produce hydrogen at room temperature, exhibiting high conversion efficiency, high catalytic activity, and high stability, making it a catalyst with great development potential. Attached Figure Description

[0029] Figure 1 Pt prepared in Example 1 of this invention c SEM image of the Fe1-TiO2 monolithic catalytic material.

[0030] Figure 2 Pt prepared in Example 1 of this invention c TEM and particle size distribution of the Fe1-TiO2 monolithic catalytic material.

[0031] Figure 3 Pt prepared in Example 1 of this invention c Cyclic catalytic activity test diagram of / Fe1-TiO2 monolithic catalytic material.

[0032] Figure 4 The XRD patterns of different catalytic materials prepared in Example 1 and Comparative Examples 1-3 of this invention are shown.

[0033] Figure 5 XPS spectra (Pt 4f) of the catalytic materials prepared in Example 1 and Comparative Example 1 of this invention.

[0034] Figure 6 This is a comparison chart of the hydrogen production conversion efficiency of ammonia borane hydrolysis of different comparative materials prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0035] Figure 7 This is a comparison chart of the hydrogen production conversion efficiency of ammonia borane hydrolysis in materials prepared with different amounts of Pt and Fe added in Examples 2-6 of this invention; wherein... Figure 7 a represents the effect of different Fe addition amounts. Figure 7 b represents the effect of different amounts of Pt added. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials are available from open commercial sources.

[0038] Example 1

[0039] A type of Pt c The preparation method of Fe1-TiO2 monolithic catalytic material includes the following steps:

[0040] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0041] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0042] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2 nanotube array.

[0043] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 2 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol for 10 min with stirring, and then dried to obtain Pt. c / Fe1-TiO2 monolithic catalytic material.

[0044] Figure 1 For this embodiment, Pt c SEM image of the monolithic Fe1-TiO2 catalytic material. The image shows that the TiO2 host material is a tubular nanoarray with diameters ranging from 91 nm to 133 nm, serving as an ideal scaffold for supporting highly dispersed active sites. The rough surface and uniformly distributed small particles can be attributed to Pt nanoclusters. No obvious nanoparticle aggregation was observed.

[0045] Figure 2 For this embodiment, Pt c TEM image of the monolithic Fe1-TiO2 catalytic material. The image clearly shows Pt nanoclusters uniformly loaded on the surface of the TiO2 nanoarray material. Based on the particle size distribution diagram in the inset, the average size of the Pt nanoclusters is 1.44 nm.

[0046] Figure 3 For this embodiment, Pt c Cyclic stability test results of the Fe1-TiO2 monolithic catalytic material for hydrogen production. Figure 3 As can be seen from this, after six photocatalytic hydrogen production cycle experiments, Pt c The catalytic hydrogen production activity of the Fe1-TiO2 monolithic catalytic material did not show a significant decrease, indicating that the Pt prepared in this invention... c The Fe1-TiO2 monolithic catalyst exhibits excellent cycle stability in the catalytic ammonia-borane hydrogen production application.

[0047] Comparative Example 1

[0048] This comparative example provides a Pt C The TiO2 monolithic catalyst is prepared in a manner similar to that in Example 1, except that ferric nitrate hydrate is not added to the electrolyte in step (2). The specific steps are as follows:

[0049] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0050] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride and 3.0 vol% deionized water. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0051] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h.

[0052] (4) Immerse the sample in a mixture of 78 mL deionized water, 20 mL ethanol, and 2 mL chloroplatinic acid hydrate aqueous solution (concentration 1 mg / mL). Stir at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, irradiate both sides of the sample for 30 min each using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface is 15 cm, and the light intensity is calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol for 10 min with stirring, and then dried to obtain Pt. c / TiO2 nanotube array catalyst.

[0053] Tests showed that its ammonia borane hydrolysis conversion efficiency reached 405 mol. H2 / mol Pt / min.

[0054] Comparative Example 2

[0055] This comparative example provides a Fe1-TiO2 monolithic material, the preparation method of which is basically the same as that of Example 1, except that step (4) of photodeposition loading Pt is not performed. The specific steps are as follows:

[0056] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0057] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0058] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2.

[0059] Comparative Example 3

[0060] This comparative example provides a monolithic TiO2 material, the preparation method of which is basically the same as that of Example 1, except that ferric nitrate hydrate is not added to the electrolyte in step (2), and photodeposition in step (4) is not performed. The specific steps are as follows:

[0061] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0062] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride and 3.0 vol% deionized water. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0063] (3) The sample after reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h. The catalyst synthesized by this method was named TiO2.

[0064] Tests showed that its ammonia borane hydrolysis conversion efficiency was zero.

[0065] Figure 4 The XRD patterns are for Example 1 and Comparative Examples 1-3. All diffraction peaks correspond to anatase TiO2 (JCPDS: 21-1272), indicating that the introduction of Fe and Pt species did not alter the crystal structure of the titanium TiO2 nanoarray support. No characteristic peaks of metallic Fe or metallic Pt were detected, further confirming their low loading and high dispersibility.

[0066] Figure 5 XPS plots for Example 1 and Comparative Example 1. The high-resolution Pt 4f plot shows that at Pt... c / Fe1-TiO2 and Pt c In both TiO2 and platinum materials, platinum is mainly Pt. 0 and Pt δ+ Mixed valence states exist. With Pt c Compared to TiO2, the Pt 4f peak shifts slightly towards lower binding energies, indicating an increase in the electron density of the Pt clusters. This confirms the existence of electronic interactions between Pt and Fe, forming Pt-O-Fe bonds.

[0067] Figure 6The graphs show the catalytic hydrogen production performance of Example 1 and Comparative Examples 1-3. It can be seen that the catalytic hydrogen production performance of pure TiO2 is zero. After photodeposition of Pt clusters, Pt... c The catalytic hydrogen production performance of the TiO2 catalyst was significantly enhanced, reaching 405 mol / L. H2 / mol Pt / min. When Fe is deposited on TiO2, the catalytic hydrogen production performance of Fe1-TiO2 is essentially zero. However, when Pt clusters are photodeposited, Pt... c The Fe1-TiO2 catalyst exhibited the best hydrogen production performance, reaching 803 mol / L. H2 / mol Pt / min.

[0068] Example 2

[0069] This embodiment provides a Pt c The preparation method of the Fe1-TiO2 monolithic catalytic material is basically the same as that in Example 1, except that the concentration of ferric nitrate hydrate in the electrolyte in step (2) is changed to 2.5 mM. The specific steps are as follows:

[0070] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0071] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 2.5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0072] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2 nanotube array.

[0073] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 2 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol for 10 min with stirring, and then dried to obtain Pt. c / Fe1-TiO2 monolithic catalytic material.

[0074] Tests showed that the catalyst synthesized by this method achieved a catalytic conversion efficiency of 674 mol / L for the hydrolysis of ammonia borane. H2 / mol Pt / min, results are shown Figure 7 a.

[0075] Example 3

[0076] This embodiment provides a Pt c The preparation method of the Fe1-TiO2 monolithic catalytic material is basically the same as that in Example 1, except that the concentration of ferric nitrate hydrate in the electrolyte in step (2) is changed to 10 mM. The specific steps are as follows:

[0077] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0078] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 10 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0079] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2 nanotube array.

[0080] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 2 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol for 10 min with stirring, and then dried to obtain Pt. c / Fe1-TiO2 monolithic catalytic material.

[0081] Tests showed that the catalyst synthesized by this method achieved a catalytic conversion efficiency of 621 mol / L for the hydrolysis of ammonia borane. H2 / mol Pt / min, results are shown Figure 7 a.

[0082] Figure 7 Figure a shows a comparison of the conversion efficiencies of Examples 2-3. The figure shows that the conversion efficiencies at ferric nitrate hydrate concentrations of 2.5 mM and 10 mM are lower than those at a concentration of 5 mM, indicating that the conversion efficiency is significantly dependent on the concentration of ferric nitrate hydrate.

[0083] Example 4

[0084] This embodiment provides a Pt c The preparation method of the Fe1-TiO2 monolithic catalytic material is basically the same as that in Example 1, except that in step (4), 2 mL of chloroplatinic acid aqueous solution is replaced with 1 mL. The specific steps are as follows:

[0085] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0086] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0087] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2 nanotube array.

[0088] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 1 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol with stirring for 10 min each time, and then dried to obtain the catalyst. The results are shown in [Figure number missing]. Figure 7 b.

[0089] Example 5

[0090] This embodiment provides a Pt c The preparation method of the Fe1-TiO2 monolithic catalytic material is basically the same as that in Example 1, except that in step (4), 2 mL of chloroplatinic acid aqueous solution is replaced with 3 mL. The specific steps are as follows:

[0091] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0092] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0093] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2.

[0094] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 3 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol with stirring for 10 min each time, and then dried to obtain the catalyst. The results are shown in [Figure number missing]. Figure 7 b.

[0095] Example 6

[0096] This embodiment provides a Pt c The preparation method of the Fe1-TiO2 monolithic catalytic material is basically the same as that in Example 1, except that in step (4), 2 mL of chloroplatinic acid aqueous solution is replaced with 4 mL. The specific steps are as follows:

[0097] (1) The titanium foil was prepared on a titanium foil substrate (thickness 0.5 mm, size 1 cm × 4 cm) by a two-step anodizing method. Before anodizing, the Ti foil was ultrasonically cleaned for 30 min each in anhydrous ethanol, acetone and deionized water.

[0098] (2) The oxidation process uses a two-electrode system, with titanium foil as the anode and a 1 cm × 1 cm Pt sheet as the cathode (electrode spacing 3 cm). The electrolyte is an ethylene glycol solution containing 0.5 wt% ammonium fluoride, 3.0 vol% deionized water and 5 mM ferric nitrate hydrate. The first step of anodic oxidation is carried out at 60 V for 110 min, followed immediately by the second step of oxidation: the reaction is carried out at 20 V for 10 min, and the temperature is maintained at 25 ℃ throughout the process.

[0099] (3) The sample after the reaction was rinsed with deionized water, dried in air at 150 °C, and then annealed in air at a heating rate of 5 °C / min to 450 °C for 2 h to finally obtain Fe1-TiO2.

[0100] (4) The Fe1-TiO2 nanotube array was immersed in a mixture of 78 mL deionized water, 20 mL ethanol, and 4 mL chloroplatinic acid hydrate aqueous solution (the concentration of the chloroplatinic acid hydrate aqueous solution was 1 mg / mL). The mixture was stirred at 1000 rpm for 3 h at 25 °C to ensure sufficient adsorption of the precursor. Subsequently, the sample was irradiated on both sides for 30 min using a light source equipped with a 320 nm cutoff filter. The distance between the light source and the substrate surface was 15 cm, and the light intensity was calibrated to 80 μW / cm² using an optical power meter. 2 After irradiation, the sample was washed sequentially in deionized water and ethanol with stirring for 10 min each time, and then dried to obtain the catalyst. The results are shown in [Figure number missing]. Figure 7 b.

[0101] Figure 7 b is a comparison graph of the conversion efficiency of Examples 4-6. The graph shows that when the volume of the chloroplatinic acid hydrate aqueous solution is 1 mL, the conversion efficiency is 598 mol / L due to insufficient active sites. H2 / mol Pt / min. However, when the volume of the chloroplatinic acid hydrate aqueous solution was 3 mL and 4 mL, the conversion efficiency was also lower than that when 2 mL of chloroplatinic acid hydrate aqueous solution was added. This indicates that the conversion efficiency exhibits a volcano-like distribution with respect to the concentration of chloroplatinic acid hydrate.

[0102] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A monolithic catalyst for hydrogen production from ammonia boron hydrolysis, characterized in that, include: Titanium foil substrate; An iron-doped titanium dioxide nanoarray is formed on the titanium foil substrate, wherein the iron is dispersed in the form of single atoms; as well as Platinum nanoclusters loaded on the iron-doped titanium dioxide nanoarray; Pt-O-Fe bonds are formed between the platinum nanoclusters and the iron-doped titanium dioxide nanoarray.

2. The monolithic catalyst according to claim 1, characterized in that, The iron-doped titanium dioxide nanoarray is a nanotube array.

3. The monolithic catalyst according to claim 1 or 2, characterized in that, The average particle size of the platinum nanoclusters is 1-2 nm.

4. A method for preparing the monolithic catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: S1. The cleaned titanium foil is placed in an electrolyte containing iron ions for anodic oxidation, and then annealed to grow an iron-doped titanium dioxide nanoarray in situ on the titanium foil substrate. S2. The titanium foil loaded with iron-doped titanium dioxide nanoarray obtained in step S1 is immersed in a solution containing platinum precursor and photodeposited to load platinum nanoclusters onto the iron-doped titanium dioxide nanoarray, thereby obtaining the monolithic catalyst.

5. The preparation method according to claim 4, characterized in that, In step S1, the electrolyte is an ethylene glycol solution containing ammonium fluoride, water and ferric nitrate; the content of ammonium fluoride is 0.5-1 wt%, the content of water is 3.0-5.0 vol%, and the concentration of ferric nitrate is 5-20 mM.

6. The preparation method according to claim 4, characterized in that, In step S1, the anodizing is a multi-step anodizing process, which includes a first-step anodizing and a second-step anodizing. The voltage of the first-step anodizing is 40-60 V and the time is 80-120 min; the voltage of the second-step anodizing is 10-20 V and the time is 10-30 min.

7. The preparation method according to claim 4, characterized in that, In step S1, the annealing treatment is carried out at a temperature of 450-600 ℃ for 2-5 h, and the heating rate is 1-5 ℃ / min.

8. The preparation method according to claim 4, characterized in that, In step S2, the platinum precursor is chloroplatinic acid; the solution containing the platinum precursor is a mixture of an aqueous solution of chloroplatinic acid and ethanol; in the mixture, the volume ratio of water, ethanol and aqueous solution of chloroplatinic acid is 30-40:10-20:1-4.

9. The preparation method according to claim 4, characterized in that, In step S2, the light source used for photodeposition has a wavelength below 320 nm and a light intensity of 80-100 μW / cm². 2 The irradiation time is 30-60 minutes.

10. The use of the monolithic catalyst according to any one of claims 1-3 in the catalytic hydrolysis of ammonia borane to produce hydrogen.

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