Catalyst for hydrogen production through ammonia decomposition and preparation method thereof

Abstract

The invention relates to the technical field of hydrogen production, and particularly discloses an ammonia decomposition hydrogen production catalyst and a preparation method thereof.The ammonia decomposition hydrogen production catalyst comprises a carrier and a ruthenium-based active component loaded on the carrier, the carrier is a charcoal / titanium dioxide composite carrier prepared through a liquid phase deposition method, and the ruthenium-based active component is ruthenium metal. By optimizing the interaction among the components of the composite carrier and the dispersion degree of the active metal, the problems of activity, stability, cost, the dispersion degree of the ruthenium active component and the like are synergistically solved, and the efficiency of hydrogen production through ammonia decomposition is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production technology, and particularly relates to an ammonia decomposition hydrogen production catalyst and its preparation method. Background Technology

[0002] Traditional compressed gaseous hydrogen storage and cryogenic liquid hydrogen storage suffer from high energy consumption, significant safety hazards, or exorbitant costs. Liquid ammonia (NH3), due to its high hydrogen content (17.6 wt%), mature synthesis and storage infrastructure, relatively mild liquefaction conditions, and carbon-free characteristics, is considered a highly promising chemical hydrogen storage medium. On-site, on-demand hydrogen production through the catalytic decomposition of ammonia (NH3 → 1 / 2N2 + 3 / 2H2) can effectively solve the end-use hydrogen storage and transportation challenges. The key to realizing the commercial application of ammonia decomposition hydrogen production technology lies in developing high-performance, highly stable, and cost-effective catalysts.

[0003] Ruthenium-based ammonia decomposition hydrogen production catalysts have attracted widespread attention due to their excellent activity in ammonia decomposition hydrogen production. However, due to their scarcity and high cost, much research has focused on reducing the loading of metallic ruthenium on the catalyst support and improving the atomic utilization rate of ruthenium, such as CN120169355A and CN120550804A. Meanwhile, the type and performance of the catalyst support for ammonia decomposition hydrogen production have a significant impact on its catalytic hydrogen production performance. Higher ammonia decomposition hydrogen production efficiency usually requires the support to have good dispersibility and a high specific surface area to improve the dispersion of the active component. Numerous catalyst supports have been reported for ammonia decomposition to hydrogen production, including carbon materials, magnesium oxide, silicon dioxide, and alumina. Among these, carbon material supports include reduced graphene oxide, carbon nanotubes, activated carbon, and biochar (Lv, L.; Chu, P.; Han, T.; Jiang, Y.; Wang, Z.; Liu, Y.; Dai, H.; Wei, L.; Deng, J. Carbon and Oxygen Double Defects Enhanced Ru-based Catalyst for Ammonia Decomposition. Angew. Chem. Int. Ed. 2025, e202501898.).

[0004] Biochar is a carbon-rich material obtained by pyrolyzing biomass (such as crop straw, sawdust, and nutshells) under oxygen-limited conditions. It has unique advantages as a catalyst support: it is widely available and inexpensive; it is environmentally friendly, utilizing waste biomass resources, which aligns with the concept of sustainable development; and its high specific surface area and well-developed pore structure are beneficial for the dispersion of active components and the mass transfer of reactants / products. However, directly using biochar as a support for ammonia decomposition hydrogen production catalysts, especially for loading the precious metal ruthenium, has significant drawbacks. For example, it lacks high-temperature stability; under the high-temperature reducing atmosphere of ammonia decomposition, biochar itself is prone to pyrolysis, gasification, or graphitization, resulting in poor structural stability and causing support collapse. Simultaneously, active components are prone to agglomeration under high-temperature sintering. Therefore, improving the activity of biochar-based ammonia decomposition hydrogen production catalysts, lowering the catalytic decomposition hydrogen production temperature, and extending catalyst lifetime have been the main research directions for ammonia decomposition hydrogen production catalysts in recent years. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an ammonia decomposition hydrogen production catalyst and its preparation method, which solves the problems of activity, stability, cost and dispersion of ruthenium active component.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an ammonia decomposition hydrogen production catalyst, comprising a support and a ruthenium-based active component supported on the support, wherein the support is a biochar / titanium dioxide composite support prepared by liquid phase deposition, and the ruthenium-based active component is ruthenium metal.

[0008] In some embodiments, the biochar / titanium dioxide composite carrier is obtained by mixing nitrogen-doped biochar with a mixture of boric acid and ammonium fluorotitanate solution, depositing the mixture in the liquid phase under magnetic stirring, filtering, drying, and then calcining.

[0009] In some embodiments, the nitrogen-doped biochar is prepared by the following method:

[0010] Crush the banyan leaves and mix with L-cysteine;

[0011] Nitrogen gas is introduced, and the temperature is raised to the first preset temperature under the nitrogen atmosphere and held, then cooled to room temperature;

[0012] Add hydroxide, then purge with nitrogen gas, heat to the second preset temperature under nitrogen atmosphere and hold, then cool to room temperature;

[0013] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0014] In another aspect, the present invention provides a method for preparing an ammonia decomposition hydrogen production catalyst, comprising:

[0015] (1) Preparation of nitrogen-doped biochar;

[0016] (2) The nitrogen-doped biochar was mixed with a mixture of boric acid and ammonium fluorotitanate solution, and liquid phase deposition was carried out under magnetic stirring. After filtration and drying, the mixture was calcined to obtain biochar / titanium dioxide composite carriers with liquid phase deposition time.

[0017] (3) The biochar / titanium dioxide composite support is mixed with ruthenium chloride in water, then heated until the water is completely evaporated, dried and then nitrogen gas is introduced. The temperature is raised under the nitrogen atmosphere to obtain a biochar / titanium dioxide supported ruthenium ammonia decomposition hydrogen production catalyst.

[0018] In some embodiments, in step (1), the nitrogen-doped biochar is prepared by the following method:

[0019] Crush the banyan leaves and mix with L-cysteine;

[0020] Nitrogen gas is introduced, and the temperature is raised to the first preset temperature under the nitrogen atmosphere and held, then cooled to room temperature;

[0021] Add hydroxide, then purge with nitrogen gas, heat to the second preset temperature under nitrogen atmosphere and hold, then cool to room temperature;

[0022] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0023] In some embodiments, in step (1), the nitrogen-doped biochar is prepared by the following method:

[0024] Wash, dry, crush, and sieve the banyan leaves, then add L-cysteine ​​and grind.

[0025] Nitrogen gas was introduced, and the temperature was increased to 300-400°C at a rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The product was then cooled to room temperature.

[0026] The product and hydroxide are mixed and ground according to the preset carbon-alkali ratio and then placed in a tube furnace. Nitrogen gas is then introduced and heated to 600-700°C at a heating rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The temperature is then cooled to room temperature.

[0027] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0028] In some embodiments, in step (1), the mass ratio of the banyan leaves to L-cysteine ​​is 1:0.1 to 1:2, and the carbon-base ratio is 1:1.1 to 1:2.0;

[0029] The hydroxide is KOH;

[0030] The nitrogen gas is introduced over a period of 10 to 70 minutes.

[0031] The heat preservation time is 1 to 4 hours.

[0032] In some embodiments, in step (2), the mixture of boric acid and ammonium fluorotitanate solution comprises 50-200 mL of 0.1-0.5 mol / L ammonium fluorotitanate solution and 100-250 mL of 0.4-1 mol / L boric acid solution;

[0033] The nitrogen-doped biochar has a mass of 0.3–1 g;

[0034] The liquid phase deposition time under the magnetic stirring condition is 10–90 min;

[0035] The calcination temperature is 250–350°C, and the calcination time is 30–90 min.

[0036] In some embodiments, in step (3), 0.1-1 g of the biochar / titanium dioxide composite carrier is mixed with 0.05-0.6 g of ruthenium chloride in water, and the mixture is ultrasonically treated for 10-50 min;

[0037] Heating in a water bath at 40–60°C for 3–8 hours, then continuing to heat and stir at 85–95°C until all the water has evaporated;

[0038] Collect the solid sample after evaporation and dry it;

[0039] After introducing nitrogen gas for 10–30 min, the temperature is increased to 600–800 °C at a rate of 5–15 °C / min under nitrogen atmosphere and held for 1–2 h to finally obtain a ruthenium-supported biochar / titanium dioxide catalyst for ammonia decomposition and hydrogen production.

[0040] The beneficial effects of this invention are:

[0041] This invention provides a ruthenium-supported ruthenium biochar / titanium dioxide catalyst for ammonia decomposition and its preparation method. Using nitrogen-doped biochar as a support, a biochar / titanium dioxide composite support is first prepared by growing titanium dioxide nanoparticles on the biochar using liquid-phase deposition. Then, the active components are loaded onto the biochar / titanium dioxide composite support using a conventional impregnation process. By optimizing the interactions between the components of the composite support and the dispersion of the active metal, the efficiency of ammonia decomposition for hydrogen production is significantly improved. Details are as follows:

[0042] (1) This invention prepares nitrogen-doped biochar by modifying banyan leaves with L-cysteine. Compared with other biochar materials, this biochar has a richer pore structure, thus having a larger specific surface area and abundant surface functional groups. It is also inexpensive and has a wide range of raw material sources.

[0043] (2) Compared with other carrier materials, titanium dioxide nanoparticles grown by liquid phase deposition have good dispersibility on biochar, and the porous structure of biochar provides more growth sites for titanium dioxide, preventing it from agglomerating and obtaining a high-performance biochar / titanium dioxide composite carrier.

[0044] (3) The ruthenium-supported biochar / titanium dioxide ammonia decomposition hydrogen production catalyst prepared in this invention has a high degree of ruthenium dispersion on its surface. Compared with the ruthenium / biochar ammonia decomposition hydrogen production catalyst, the synergistic effect between ruthenium and the biochar / titanium dioxide composite support promotes the conversion rate of ammonia decomposition hydrogen production. When preparing the composite support, the ammonia decomposition hydrogen production catalyst has an ammonia conversion rate of 97.52% at 650°C. Attached Figure Description

[0045] Figure 1 These are XRD patterns of different ammonia decomposition hydrogen production catalysts prepared in the embodiments and comparative examples of the present invention.

[0046] Figure 2 These are SEM and EDS mapping images of different ammonia decomposition hydrogen production catalysts prepared in the embodiments and comparative examples of the present invention. Specifically, a1-a3 are SEM images of LKBC, a4-a5 are EDS mapping images of LKBC; b1-a3 are SEM images of Ru / LKBC, b4-b6 are EDS mapping images of Ru / LKBC; c1-c3 are SEM images of Ru / LKBCT20, c4-c7 are EDS mapping images of Ru / LKBCT20; d1-d3 are SEM images of Ru / LKBCT40, d4-d7 are EDS mapping images of Ru / LKBCT40; e1-e3 are SEM images of Ru / LKBCT60, e4-e7 are EDS mapping images of Ru / LKBCT40.

[0047] Figure 3 This is a TEM image of the ammonia decomposition hydrogen production catalyst prepared in Example 1 of this invention.

[0048] Figure 4 This is a graph showing the ammonia conversion rate of different ammonia decomposition hydrogen production catalysts prepared in the embodiments and comparative examples of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0050] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0051] In a first aspect, the present invention provides an ammonia decomposition hydrogen production catalyst, comprising a support and a ruthenium-based active component supported on the support, wherein the support is a biochar / titanium dioxide composite support prepared by liquid phase deposition, and the ruthenium-based active component is ruthenium metal.

[0052] Biochar, used as a support for ammonia decomposition catalysts for hydrogen production, especially for loading the precious metal ruthenium, has significant drawbacks. For example, it suffers from insufficient high-temperature stability. Under the high-temperature reducing atmosphere of ammonia decomposition, biochar itself is prone to pyrolysis, gasification, or graphitization, resulting in poor structural stability and support collapse. Furthermore, the active components are prone to agglomeration under high-temperature sintering. This invention prepares a biochar / titanium dioxide composite support via liquid-phase deposition, optimizing the interactions between the composite support components and the dispersion of the active metal to load the precious metal ruthenium. This improves the problems of insufficient stability and agglomeration under high-temperature conditions, thereby significantly enhancing the efficiency of ammonia decomposition for hydrogen production.

[0053] In some embodiments, the mass fraction of the loading of the ruthenium-based active component is 10-40%, preferably 10-35%, specifically 10%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, and is not limited thereto. More preferably, the mass fraction of the loading of the ruthenium-based active component is 15-30%.

[0054] In some embodiments, the biochar / titanium dioxide composite carrier is obtained by mixing nitrogen-doped biochar with a mixture of boric acid and ammonium fluorotitanate solution, depositing the mixture in the liquid phase under magnetic stirring, filtering, drying, and then calcining.

[0055] Preferably, the nitrogen-doped biochar is mixed with a mixture of boric acid and ammonium fluorotitanate solution, and liquid-phase deposition is performed under magnetic stirring. After filtration, drying, and calcination, biochar / titanium dioxide composite carriers with different liquid-phase deposition times are obtained. The mixture of boric acid and ammonium fluorotitanate solution comprises 50-200 mL of 0.1-0.5 mol / L ammonium fluorotitanate solution and 100-250 mL of 0.4-1 mol / L boric acid solution; the mass of the nitrogen-doped biochar is 0.3-1 g; the liquid-phase deposition time under magnetic stirring is 10-90 min; and the calcination temperature is 250-350℃, and the calcination time is 30-90 min.

[0056] In some embodiments, the nitrogen-doped biochar is prepared by the following method:

[0057] Crush the banyan leaves and mix with L-cysteine;

[0058] Nitrogen gas is introduced, and the temperature is raised to the first preset temperature under the nitrogen atmosphere and held, then cooled to room temperature;

[0059] Add hydroxide, then purge with nitrogen gas, heat to the second preset temperature under nitrogen atmosphere and hold, then cool to room temperature;

[0060] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0061] Preferably, the nitrogen-doped biochar is prepared by the following method:

[0062] Wash, dry, crush, and sieve the banyan leaves, then add L-cysteine ​​and grind.

[0063] Nitrogen gas was introduced, and the temperature was increased to 300-400°C at a rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The product was then cooled to room temperature.

[0064] The product and hydroxide are mixed and ground according to the preset carbon-alkali ratio and then placed in a tube furnace. Nitrogen gas is then introduced and heated to 600-700°C at a heating rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The temperature is then cooled to room temperature.

[0065] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0066] In some embodiments, the mass ratio of banyan leaves to L-cysteine ​​is 1:0.1 to 1:2, and the carbon-base ratio is 1:1.1 to 1:2.0; the hydroxide is KOH; the nitrogen gas is introduced for 10 to 70 minutes; and the heat preservation time is 1 to 4 hours.

[0067] This invention utilizes nitrogen-doped biochar prepared from banyan leaves, which is inexpensive, has a large specific surface area, a high degree of graphitization, and a rich porous structure with abundant surface functional groups. Titanium dioxide is then loaded onto this biochar using liquid-phase deposition to obtain a biochar / titanium dioxide composite support. This optimizes the interactions between the components of the composite support and the dispersion of the active metal, allowing for the loading of the noble metal ruthenium. This improves the ruthenium's instability at high temperatures and its tendency to agglomerate, thereby significantly enhancing the efficiency of ammonia decomposition for hydrogen production. This catalyst exhibits excellent catalytic activity for ammonia decomposition for hydrogen production, achieving a conversion rate of 97.52% at 650℃, comprehensively addressing issues related to activity, stability, cost, and the dispersion of the ruthenium active component.

[0068] In another aspect, the present invention provides a method for preparing an ammonia decomposition hydrogen production catalyst, comprising:

[0069] (1) Preparation of nitrogen-doped biochar;

[0070] (2) The nitrogen-doped biochar was mixed with a mixture of boric acid and ammonium fluorotitanate solution, and liquid phase deposition was carried out under magnetic stirring. After filtration and drying, the mixture was calcined to obtain biochar / titanium dioxide composite carriers with liquid phase deposition time.

[0071] (3) The biochar / titanium dioxide composite support is mixed with ruthenium chloride in water, then heated until the water is completely evaporated, dried and then nitrogen gas is introduced. The temperature is raised under the nitrogen atmosphere to obtain a biochar / titanium dioxide supported ruthenium ammonia decomposition hydrogen production catalyst.

[0072] In some embodiments, in step (1), the nitrogen-doped biochar is prepared by the following method:

[0073] Crush the banyan leaves and mix with L-cysteine;

[0074] Nitrogen gas is introduced, and the temperature is raised to the first preset temperature under the nitrogen atmosphere and held, then cooled to room temperature;

[0075] Add hydroxide, then purge with nitrogen gas, heat to the second preset temperature under nitrogen atmosphere and hold, then cool to room temperature;

[0076] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0077] In some embodiments, in step (1), the nitrogen-doped biochar is prepared by the following method:

[0078] Wash, dry, crush, and sieve the banyan leaves, then add L-cysteine ​​and grind.

[0079] Nitrogen gas was introduced, and the temperature was increased to 300-400°C at a rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The product was then cooled to room temperature.

[0080] The product and hydroxide are mixed and ground according to the preset carbon-alkali ratio and then placed in a tube furnace. Nitrogen gas is then introduced and heated to 600-700°C at a heating rate of 5-15°C / min under nitrogen atmosphere and held at that temperature. The temperature is then cooled to room temperature.

[0081] The biochar is obtained by acid washing, filtration and water washing, and then drying.

[0082] In some embodiments, in step (1), the mass ratio of the banyan leaves to L-cysteine ​​is 1:0.1 to 1:2, and the carbon-base ratio is 1:1.1 to 1:2.0;

[0083] The hydroxide is KOH;

[0084] The nitrogen gas is introduced over a period of 10 to 70 minutes.

[0085] The heat preservation time is 1 to 4 hours.

[0086] In some embodiments, in step (2), the mixture of boric acid and ammonium fluorotitanate solution comprises 50-200 mL of 0.1-0.5 mol / L ammonium fluorotitanate solution and 100-250 mL of 0.4-1 mol / L boric acid solution;

[0087] The nitrogen-doped biochar has a mass of 0.3–1 g;

[0088] The liquid phase deposition time under the magnetic stirring condition is 10–90 min;

[0089] The calcination temperature is 250–350°C, and the calcination time is 30–90 min.

[0090] In some embodiments, in step (3), 0.1-1 g of the biochar / titanium dioxide composite carrier is mixed with 0.05-0.6 g of ruthenium chloride in water, and the mixture is ultrasonically treated for 10-50 min;

[0091] Heating in a water bath at 40–60°C for 3–8 hours, then continuing to heat and stir at 85–95°C until all the water has evaporated;

[0092] Collect the solid sample after evaporation and dry it;

[0093] After introducing nitrogen gas for 10–30 min, the temperature is increased to 600–800 °C at a rate of 5–15 °C / min under nitrogen atmosphere and held for 1–2 h to finally obtain a ruthenium-supported biochar / titanium dioxide catalyst for ammonia decomposition and hydrogen production.

[0094] This invention first prepares nitrogen-doped biochar using waste banyan leaves as biomass feedstock and added nitrogen source L-cysteine ​​via a two-step pyrolysis method. Then, titanium dioxide is loaded onto the biochar using liquid-phase deposition to obtain a biochar / titanium dioxide composite support. Further, ruthenium is loaded using a conventional impregnation process to obtain a biochar / titanium dioxide-supported ruthenium ammonia decomposition hydrogen production catalyst. This improves upon the catalyst's instability at high temperatures and its tendency to agglomerate, thereby significantly enhancing the efficiency of ammonia decomposition hydrogen production. This catalyst exhibits excellent catalytic activity for ammonia decomposition hydrogen production, achieving a conversion rate of 97.52% at 650℃, comprehensively addressing issues related to activity, stability, cost, and the dispersion of the ruthenium active component.

[0095] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples.

[0096] Example 1

[0097] (1) Preparation of biochar: 3g of banyan leaf powder obtained by washing, drying, crushing, and sieving banyan leaves was ground with L-cysteine ​​at a ratio of 1:1. After purging with nitrogen for 20 min, the temperature was increased to 400℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After cooling to room temperature, 2g of the product was mixed with 3g of KOH, ground, and placed in a tube furnace. After purging with nitrogen for 20 min, the temperature was increased to 700℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After the tube furnace cooled to room temperature, the sample was acid-washed, filtered, washed with deionized water until neutral, and then the solid was dried to obtain nitrogen-doped biochar LKBC.

[0098] (2) Preparation of biochar / titanium dioxide composite support by liquid phase deposition: 0.6 g of nitrogen-doped biochar was mixed with 100 mL of 0.3 mol / L ammonium fluorotitanate solution and 150 mL of 0.6 mol / L boric acid solution, and magnetically stirred for 20 min. The mixture was then filtered through a water-based microporous membrane and dried at 100 °C. The dried sample was then calcined in a tube furnace at 300 °C in air atmosphere for 1 h to obtain biochar / titanium dioxide support LKBCT20 after liquid phase deposition for 20 min.

[0099] (3) Preparation of ruthenium-supported ammonia decomposition hydrogen production catalyst on biochar / titanium dioxide by impregnation method: 0.36 g of biochar / titanium dioxide support material deposited in liquid phase for 20 min was mixed with 0.104 g of ruthenium chloride in 50 mL of deionized water, and the mixture was sonicated for 30 min. After heating in a water bath at 50 °C for 5 hours, the mixture was continuously heated and stirred at 90 °C until the water was completely evaporated. The evaporated solid sample was collected and dried at 100 °C for 2 hours. Finally, after purging with nitrogen for 20 min, the temperature was increased to 700 °C at a rate of 10 °C / min under a nitrogen atmosphere and held for 2 hours to obtain the ruthenium-supported ammonia decomposition hydrogen production catalyst Ru / LKBCT20 on biochar / titanium dioxide.

[0100] Example 2

[0101] (1) Preparation of biochar: 3g of banyan leaf powder obtained by washing, drying, crushing, and sieving banyan leaves was ground with L-cysteine ​​at a ratio of 1:1. After purging with nitrogen for 20 min, the temperature was increased to 400℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After cooling to room temperature, 2g of the product was mixed with 3g of KOH, ground, and placed in a tube furnace. After purging with nitrogen for 20 min, the temperature was increased to 700℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After the tube furnace cooled to room temperature, the sample was acid-washed, filtered, washed with deionized water until neutral, and then the solid was dried to obtain nitrogen-doped biochar LKBC.

[0102] (2) Preparation of biochar / titanium dioxide composite support by liquid phase deposition: 0.6 g of nitrogen-doped biochar was mixed with 100 mL of 0.3 mol / L ammonium fluorotitanate solution and 150 mL of 0.6 mol / L boric acid solution, and magnetically stirred for 40 min. The mixture was then filtered through a water-based microporous membrane and dried at 100 °C. The dried sample was then calcined in a tube furnace at 300 °C in air atmosphere for 1 h to obtain biochar / titanium dioxide support LKBCT40 after liquid phase deposition for 40 min.

[0103] (3) Preparation of ruthenium-supported biochar / titanium dioxide ammonia decomposition hydrogen production catalyst by impregnation method: 0.36 g of biochar / titanium dioxide support material deposited in liquid phase for 40 min was mixed with 0.104 g of ruthenium chloride in 50 mL of deionized water, and the mixture was sonicated for 30 min. After heating in a water bath at 50 °C for 5 hours, the mixture was continuously heated and stirred at 90 °C until the water was completely evaporated. The evaporated solid sample was collected and dried at 100 °C for 2 hours. Finally, after purging with nitrogen for 20 min, the temperature was increased to 700 °C at a rate of 10 °C / min under a nitrogen atmosphere and held for 2 hours to obtain the ruthenium-supported biochar / titanium dioxide ammonia decomposition hydrogen production catalyst Ru / LKBCT40.

[0104] Example 3

[0105] (1) Preparation of biochar: 3g of banyan leaf powder obtained by washing, drying, crushing, and sieving banyan leaves was ground with L-cysteine ​​at a ratio of 1:1. After purging with nitrogen for 20 min, the temperature was increased to 400℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After cooling to room temperature, 2g of the product was mixed with 3g of KOH, ground, and placed in a tube furnace. After purging with nitrogen for 60 min, the temperature was increased to 700℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After the tube furnace cooled to room temperature, the sample was acid-washed, filtered, washed with deionized water until neutral, and then the solid was dried to obtain nitrogen-doped biochar LKBC.

[0106] (2) Preparation of biochar / titanium dioxide composite support by liquid phase deposition: 0.6 g of nitrogen-doped biochar was mixed with 100 mL of 0.3 mol / L ammonium fluorotitanate solution and 150 mL of 0.6 mol / L boric acid solution, and magnetically stirred for 20 min. The mixture was then filtered through a water-based microporous membrane and dried at 100 °C. The dried sample was then calcined in a tube furnace at 300 °C in air atmosphere for 1 h to obtain biochar / titanium dioxide support LKBCT60 after liquid phase deposition for 60 min.

[0107] (3) Preparation of ruthenium-supported ammonia decomposition hydrogen production catalyst on biochar / titanium dioxide by impregnation method: 0.36 g of biochar / titanium dioxide support material deposited in liquid phase for 60 min was mixed with 0.104 g of ruthenium chloride in 50 mL of deionized water, and the mixture was sonicated for 30 min. After heating in a water bath at 50 °C for 5 hours, the mixture was continuously heated and stirred at 90 °C until the water was completely evaporated. The evaporated solid sample was collected and dried at 100 °C for 2 hours. Finally, nitrogen gas was introduced for 20 min, and the temperature was increased to 700 °C at a rate of 10 °C / min under a nitrogen atmosphere and held for 2 hours to obtain the ruthenium-supported ammonia decomposition hydrogen production catalyst Ru / LKBCT60 on biochar / titanium dioxide.

[0108] Comparative Example

[0109] (1) Preparation of biochar: 3g of banyan leaf powder obtained by washing, drying, crushing, and sieving banyan leaves was ground with L-cysteine ​​at a ratio of 1:1. After purging with nitrogen for 20 min, the temperature was increased to 400℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After cooling to room temperature, 2g of the product was mixed with 3g of KOH, ground, and placed in a tube furnace. After purging with nitrogen for 20 min, the temperature was increased to 700℃ at a nitrogen atmosphere at a rate of 10℃ / min and held for 2 h. After the tube furnace cooled to room temperature, the sample was acid-washed, filtered, washed with deionized water until neutral, and then the solid was dried to obtain nitrogen-doped biochar LKBC.

[0110] (2) 0.5g of nitrogen-doped biochar was calcined in a tube furnace at 300℃ in air atmosphere for 1h to obtain 300℃ biochar.

[0111] (3) Preparation of ruthenium-supported biochar ammonia decomposition hydrogen production catalyst by wet impregnation method: 0.36 g of nitrogen-doped biochar material at 300 °C was mixed with 0.104 g of ruthenium chloride in 50 mL of deionized water, and the mixture was sonicated for 30 min. After heating in a 50 °C water bath for 5 hours, the mixture was continuously heated and stirred at 90 °C until the water was completely evaporated. The evaporated solid sample was collected and dried at 100 °C for 2 hours. Finally, after purging with nitrogen for 20 min, the temperature was increased to 700 °C at a rate of 10 °C / min under a nitrogen atmosphere and held for 2 h to obtain the ruthenium-supported biochar ammonia decomposition hydrogen production catalyst Ru / LKBC.

[0112] Figure 1XRD patterns of different catalysts are shown. The LKBC and Ru / LKBC samples exhibit a broad diffraction band at 2θ = 25.3°, corresponding to the (002) crystal plane of the graphite structure. This indicates that the prepared biochar matrix is ​​an amorphous carbon structure with certain graphitized microcrystalline regions. The Ru / LKBCTx (x = 20, 40, 60) samples correspond to the standard anatase titanium dioxide structure (PDF#01-075-2547), and the Ru / LKBC and Ru / LKBCTx (x = 20, 40, 60) samples precisely correspond to the standard metallic ruthenium structure (PDF#04-001-7235). Based on these analyses, we can clearly see that titanium dioxide and ruthenium were successfully loaded onto the biochar, further confirming the successful loading of titanium dioxide and ruthenium onto the biochar. Figure 2 The morphology and elemental characteristics revealed by SEM and EDS mapping images are as follows. According to the XRD pattern, the full width at half maximum (FWHM) of the main diffraction peak at 2θ = 25.3° gradually narrows with increasing loading time, while the peak intensity increases. This increase in peak intensity and narrowing of FWHM together indicate that extending the liquid-phase deposition reaction time is beneficial for the further growth and crystallization of titanium dioxide crystal particles, thereby improving the crystallinity of titanium dioxide in the composite material. The relatively low peak for ruthenium indicates a low ruthenium loading and higher ruthenium dispersion on the composite support. The lowest peak in the Ru / LKBCT20 XRD pattern indicates the best Ru dispersion on this catalyst, suggesting that it will be most effective in subsequent ammonia decomposition catalytic hydrogen production.

[0113] The morphology and elements of LKBC, Ru / LKBC, Ru / LKBCT20, Ru / LKBCT40, and Ru / LKBCT60 were characterized using SEM and EDS mapping, such as... Figure 2As shown, LKBC has a smooth surface with abundant porosity. Ru / LKBC has abundant pores and blocky particle loadings within the pores, indicating that ruthenium metal is loaded onto it. Ru / LKBCT20 has not only blocky particles but also small particles loaded in sheets on both the inner and outer surfaces of the pores. We can also observe that as the liquid phase deposition time increases, more and more small particles are loaded into the abundant pores. Simultaneously observing Ru / LKBCT40 and Ru / LKBCT60, we can see that when the liquid phase deposition time reaches 60 minutes, a large number of particles are loaded in sheets on the surface of the biochar, with some appearing as spherical agglomerates, possibly due to excessive titanium dioxide loading causing agglomeration. According to EDS... Elemental mapping analysis revealed that the bulk particles on the surfaces of LKBC and Ru / LKBC are ruthenium, while the small, sheet-like particles on the surfaces of Ru / LKBCT20, Ru / LKBCT40, and Ru / LKBCT60 are TiO2. The Ti content increased with prolonged liquid-phase deposition, indicating successful loading of ruthenium and titanium dioxide. All catalysts possess abundant porosity, providing ample active sites for subsequent ammonia decomposition reactions.

[0114] Figure 3 (a) is a TEM image of Example 1. It can be observed that a large number of nanoscale particles are uniformly dispersed on a biochar substrate with irregular folds. The material as a whole exhibits a rough and porous structure, providing abundant active sites and mass transfer channels for the reaction. The high-contrast dark areas in the image are mainly titanium dioxide and ruthenium nanoparticles, while the light gray background is the biochar support. This morphological feature is prevalent in samples with different titanium dioxide loading times (T20-T60), indicating the successful construction of a biochar-based composite catalytic material. Figure 3 (b) is a high-resolution TEM (HRTEM) image of the corresponding sample, used to further analyze its fine crystal structure. The image clearly shows two closely adjacent different lattice fringes. By measuring the interplanar spacing and comparing it with the standard card (JCPDS), it can be clearly identified that the lattice fringes with a spacing of approximately 0.35 nm correspond to the (210) crystal plane of anatase titanium dioxide; while the lattice fringes with a spacing of approximately 0.21 nm correspond to the (101) crystal plane of metallic ruthenium. The interface between the two lattice regions is clearly visible, indicating that ruthenium nanoparticles were successfully loaded onto the surface of titanium dioxide, forming a close heterojunction structure. This close interfacial contact facilitates the efficient transfer of electrons among ruthenium, titanium dioxide, and biochar, improving the catalytic performance of the ammonia decomposition hydrogen production catalyst.

[0115] from Figure 4It can be seen that in Example 1, the catalyst achieves a catalytic ammonia conversion rate of 97.52% when the temperature reaches 650℃ during ammonia decomposition to produce hydrogen.

[0116] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An ammonia decomposition hydrogen production catalyst characterized by, The catalyst comprises a carrier and a ruthenium-based active component supported on the carrier, wherein the carrier is a biochar / titania composite carrier prepared by a liquid deposition method, and the ruthenium-based active component is ruthenium metal.

2. The ammonia decomposition hydrogen production catalyst according to claim 1, characterized by, The biochar / titania composite carrier is obtained by mixing a nitrogen-doped biochar with a mixed solution of boric acid and an ammonium fluorotitanate solution, liquid deposition under magnetic stirring, drying after suction filtration, and calcination.

3. The ammonia decomposition hydrogen production catalyst according to claim 1 or 2, characterized by, The nitrogen-doped biochar is prepared by the following method: The leaves of a ficus tree are crushed, and L-cysteine is added for mixing; Nitrogen is introduced, and the temperature is raised to a first preset temperature under a nitrogen atmosphere and kept for a while, and then cooled to room temperature; Hydroxide is added, and nitrogen is introduced again, and the temperature is raised to a second preset temperature under a nitrogen atmosphere and kept for a while, and then cooled to room temperature; Acid washing, suction filtration, and water washing are performed, and then the nitrogen-doped biochar is obtained by drying.

4. The ammonia decomposition hydrogen production catalyst according to claim 1, characterized by, The loading amount of the ruthenium-based active component is 10-40% by mass fraction.

5. A method for producing an ammonia decomposition hydrogen production catalyst, characterized by, The method comprises the following steps: (1) preparing a nitrogen-doped biochar; (2) mixing the nitrogen-doped biochar with a mixed solution of boric acid and an ammonium fluorotitanate solution, liquid deposition under magnetic stirring, drying after suction filtration, and calcination to obtain biochar / titania composite carriers with different liquid deposition times; (3) mixing the biochar / titania composite carrier with ruthenium chloride in water, then heating to evaporate the water, drying, introducing nitrogen, and raising the temperature under a nitrogen atmosphere to obtain a biochar / titania-supported ruthenium catalyst for ammonia decomposition hydrogen production.

6. The method for producing an ammonia decomposition hydrogen production catalyst according to claim 5, characterized by, In step (1), the nitrogen-doped biochar is prepared by the following method: The leaves of a ficus tree are crushed, and L-cysteine is added for mixing; Nitrogen is introduced, and the temperature is raised to a first preset temperature under a nitrogen atmosphere and kept for a while, and then cooled to room temperature; Hydroxide is added, and nitrogen is introduced again, and the temperature is raised to a second preset temperature under a nitrogen atmosphere and kept for a while, and then cooled to room temperature; Acid washing, suction filtration, and water washing are performed, and then the nitrogen-doped biochar is obtained by drying.

7. The method for producing an ammonia decomposition hydrogen production catalyst according to claim 6, characterized by, In step (1), the nitrogen-doped biochar is prepared by the following method: The leaves of a ficus tree are washed, dried, crushed, sieved, and then L-cysteine is added for grinding; Nitrogen is introduced, and the temperature is raised to 300-400℃ at a rate of 5-15℃ / min under a nitrogen atmosphere and kept for a while, and then cooled to room temperature to obtain a product; The product and hydroxide are mixed and ground according to a preset carbon-to-alkali ratio, and then placed in a tube furnace, nitrogen is introduced, and the temperature is raised to 600-700℃ at a rate of 5-15℃ / min under a nitrogen atmosphere and kept for a while, and then cooled to room temperature; Acid washing, suction filtration, and water washing are performed, and then the nitrogen-doped biochar is obtained by drying.

8. The method for producing an ammonia decomposition hydrogen production catalyst according to claim 7, characterized by, In step (1), the mass ratio of the leaves of a ficus tree to L-cysteine is 1:0.1-1:2, and the carbon-to-alkali ratio is 1:1.1-1:2.0; The hydroxide is KOH; The nitrogen is introduced for 10-70 min; The keeping time is 1-4 h.

9. The method for producing an ammonia decomposition hydrogen production catalyst according to Claim 5, characterized by, In step (2), the mixed solution of boric acid and an ammonium fluorotitanate solution comprises 0.1-0.5 mol / L ammonium fluorotitanate solution 50-200 mL and 0.4-1 mol / L boric acid solution 100-250 mL; The mass of the nitrogen-doped biochar is 0.3-1 g; The liquid deposition time under magnetic stirring is 10-90 min; The temperature of the calcination is 250-350℃, and the time of the calcination is 30-90min.

10. The method for preparing the ammonia decomposition hydrogen production catalyst according to claim 5, characterized in that, In step (3), the biochar / titanium dioxide composite carrier 0.1-1g is mixed with ruthenium chloride 0.05-0.6g in water, and the mixture is ultrasonically treated for 10-50min; After heating in a water bath at 40-60℃ for 3-8h, the mixture is continuously heated and stirred at 85-95℃ until the water is completely evaporated; The solid sample after evaporation is collected and dried; After 10-30min of nitrogen gas flow, the temperature is raised at a rate of 5-15℃ / min under nitrogen atmosphere to 600-800℃ and kept for 1-2h, and finally the biochar / titanium dioxide supported ruthenium catalyst for hydrogen production by ammonia decomposition is obtained.

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