A highly dispersed Ru nanoparticle supported catalyst for hydrogen production by ammonia decomposition and a method for preparing the same

Abstract

This invention discloses a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst and its preparation method, belonging to the field of catalyst technology. This invention first prepares Ce-MgO ( x The support was then used to prepare different Ru-loaded materials. n Ru / Ce-MgO( x To improve the activity of Ru-based catalysts, a strategy of reducing particle size was adopted to prepare Ru colloidal nanoparticles and load them onto a Ce-MgO(x) support. The loading of ruthenium in the catalyst is extremely low. The catalyst of this invention, due to the addition of Ce, strengthens the interaction between Ce and Ru, which helps to improve the conversion rate of ammonia decomposition reaction at low temperatures. Simultaneously, the strong interaction between Ru and the Ce-MgO(x) support also improves the activity and durability of the catalyst, thus solving the technical problems of high energy consumption and high cost in current ammonia decomposition processes.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically to a highly efficient low-temperature ammonia decomposition hydrogen production catalyst supported by highly dispersed Ru nanoparticles with adjustable size and a method for its preparation. Background Technology

[0002] Against the backdrop of energy crisis and climate deterioration, there is an urgent need to find a clean energy source to replace fossil fuels. Hydrogen, as the most abundant element in the universe, produces only water as a byproduct of its combustion, which is harmless to the environment. It is considered one of the most promising new energy sources for the future.

[0003] Hydrogen energy is considered one of the most promising energy carriers in future energy systems due to its abundant reserves and zero emissions. However, the storage and transportation of hydrogen still face significant challenges, which has temporarily stalled the development of hydrogen energy. Hydrogen storage technologies based on hydrogen carriers offer a feasible solution to this problem. Among various hydrogen carriers, ammonia (NH3) is an excellent candidate due to its low cost, high hydrogen storage capacity (17.7 wt%), carbon-free composition, liquefaction at -33°C / 1 bar, and ease of transportation. Catalytic decomposition of NH3 into high-purity hydrogen provides a promising strategy for fuel cells, but achieving high hydrogen production at relatively low temperatures remains a challenge due to the lack of effective catalysts.

[0004] Current research on ammonia decomposition catalysts mainly focuses on metals such as ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), and iron (Fe). Among these, Ru-based catalysts exhibit the highest activity, with catalytic performance at low temperatures far exceeding that of other non-noble metal-based catalysts. For example, patent document CN113019394A discloses a method for preparing a Ni-Pt / CeO2 bimetallic catalyst. After adding Pt, the catalyst's catalytic efficiency at 600℃ increased from 27.9% to 54.3%, but ammonia was only completely converted at 800℃, resulting in high energy consumption. Patent document CN113289693A discloses a Ru-based catalyst prepared using a one-pot method and ball milling. In this catalyst, ruthenium accounts for 3-5% of the catalyst, achieving an ammonia conversion rate of 96.6% at 450℃ and a hydrogen production rate of 16.46 mmol·gRu. -1 ·min -1 (The catalyst of this invention has a lower Ru loading, only 1.35%, and at 450°C, the NH3 conversion of 1.36 nm Ru particles can reach 84.4%. The hydrogen production rate is approximately 837.3 mmol·g.) cat -1 ·min -1This invention overcomes the drawbacks of existing technologies, such as cumbersome and lengthy preparation processes for MgO-supported Ru-based catalysts. To reduce the long-term operating costs of ammonia decomposition catalytic units, sufficiently low reaction temperatures must be designed; under this premise, Ru-based catalysts possess significant advantages.

[0005] Currently, the Ru-based catalysts developed all maintain a high loading level. However, as Ru is a precious metal, a high loading will undoubtedly increase the cost of the catalyst. Therefore, how to improve the low-temperature activity of catalysts with low Ru loading is a technical problem that needs to be solved in the field of ammonia decomposition. Summary of the Invention

[0006] In view of this, the present invention provides a highly efficient low-temperature ammonia decomposition hydrogen production catalyst supported by highly dispersed Ru nanoparticles with adjustable size and a method for preparing the same, thereby overcoming the problem of low activity of Ru-based ammonia decomposition catalysts under low loading in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst includes the following steps: (1) Preparation of high specific surface area MgO: High specific surface area MgO is obtained by thermal decomposition of magnesium oxalate; (2) Preparation of Ce-MgO(x) support: MgO powder was added to water and stirred to disperse it. Then Ce(NO3)3·6H2O solution was added to obtain a mixed solution. A mixed solution of KOH and K2CO3 was added dropwise to the mixed solution to adjust the pH value to 10-11. The reaction was stirred to form a precipitate. The precipitate was washed and dried to obtain Ce-MgO(x) support, where x is the molar ratio of Mg to Ce. (3) Ru colloidal nanoparticle solution was prepared using ruthenium chloride; (4) Preparation of Ru-based catalyst: Ru colloidal nanoparticles were deposited on a cerium-doped magnesium oxide support by colloidal deposition method to obtain a highly dispersed Ru nanoparticle supported ammonia decomposition hydrogen production catalyst.

[0009] The catalyst prepared in this invention uses Ce-MgO as the support. The introduction of Ce weakens the interaction between Ru and the MgO support and provides electrons to Ru through oxygen vacancies or defect sites, thereby increasing the electron density of Ru. High specific surface area MgO can provide more active sites at the metal-support interface. By optimizing the deposition amount of Ce on the high specific surface area MgO support and controlling the Ru loading, the optimal Mg / Ce ratio of 4 and the Ru loading of only 3.8 wt% were obtained. The corresponding 3.8Ru / Ce-MgO (4) catalyst exhibited the best ammonia decomposition activity at 450℃ and a space velocity of 12,000 mL·g⁻¹.cat -1 ·h -1 Under the given reaction conditions, an ammonia conversion rate of 96.31% can be achieved. Ce-MgO(4) is considered an excellent support. Considering the size effect in the ammonia decomposition reaction, Ru nanoparticles of different sizes were synthesized by controlling the molar ratio of alkali solution to Ru precursor using a polyol reduction method. These nanoparticles were then loaded onto the Ce-MgO(4) support using a colloidal deposition method. With increasing NaOH / Ru molar ratio, the average particle size of the Ru nanoparticles gradually decreased from 4.85 nm to 1.36 nm. Ammonia decomposition tests showed that the catalytic activity increased with decreasing Ru nanoparticle size, indicating a significant structure-activity relationship between the activity of the supported Ru-based catalyst and the size of the Ru nanoparticles. The reaction was carried out at 450 °C and a space velocity of 12,000 mL·g⁻¹. cat -1 ·h -1 Under the reaction conditions, the hydrogen production rate of the Ru NPs-D / Ce-MgO(4) catalyst with a Ru content as low as 1.35 wt% is 2.46 times that of the 3.8Ru / Ce-MgO(4) catalyst.

[0010] The results of this invention show that, as a comparative catalyst, the size of the active Ru particles in the supported catalyst prepared by urea-assisted precipitation of Ru is not controllable at a high loading (3.8 wt%). In contrast, the Ce-MgO(x) used in this invention, as an excellent support, has the advantage of controllable active Ru particle size. In other words, this invention synthesizes Ru colloidal nanoparticles of different sizes (with controllable size) using a polyol reduction method, reducing the size and developing a highly efficient catalyst system with low Ru loading (1-1.5 wt%).

[0011] Further, the preparation method of the high specific surface area MgO in step (1) is as follows: 7.56g of oxalic acid (H2C2O4·2H2O) and 8.58g of magnesium acetate (Mg(CH3COO)2·4H2O) are dissolved in water respectively; then, the magnesium acetate solution is added to the oxalic acid solution under stirring, and the resulting white precipitate is filtered and separated, and repeatedly washed with water until the filtrate is neutral; the washed precipitate is dried in an oven at 80℃ for 12 h, and finally, the dried precipitate is calcined in air at 525℃ for 4 hours to decompose and obtain MgO. The obtained MgO sample has a specific surface area of ​​108.95 m² / g and a pore volume of 0.5508 cm³ / g.

[0012] Furthermore, in step (2), the molar ratio of Mg to Ce in the mixed solution is 1-16:1, and the concentration of the Ce(NO3)3·6H2O solution is 0.5 mol / L.

[0013] Furthermore, in step (2), the molar ratio of KOH to K2CO3 in the mixed solution of KOH and K2CO3 is 1:1.

[0014] Furthermore, step (2) also includes calcining the dried Ce-MgO(x) support at 600°C for 4 hours.

[0015] Furthermore, the preparation method of the Ru colloidal nanoparticle solution in step (3) is as follows: Add NaOH and ruthenium chloride solution (RuCl3·3H2O) to 50 ml of ethylene glycol; then, stir the resulting mixture in an oil bath, heat it to 160 °C under argon protection and keep it at that temperature for 3 hours; finally, after the solution is cooled to room temperature, a dark brown Ru colloidal nanoparticle solution is obtained.

[0016] Furthermore, the molar ratio of NaOH to Ru in the mixture is 3.5-28:1. This invention controls the synthesis of Ru colloidal nanoparticles of different sizes by changing the molar ratio of NaOH to Ru (NaOH / Ru).

[0017] Further, the specific steps of the colloidal deposition method in step (4) are as follows: 0.3 g Ce-MgO(x) is added to water and ultrasonically dispersed; then, Ru colloidal nanoparticles are added to the dispersion and stirred, and the resulting product is aged at room temperature; then, the product is collected by centrifugation and multiple washings; finally, the product is dried to obtain a highly dispersed Ru nanoparticle supported ammonia decomposition hydrogen production catalyst. The mass ratio of Ru colloid to Ce-MgO(x) is 1-1.5:100.

[0018] Furthermore, the actual Ru content in the highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst is 1-1.5 wt%.

[0019] The present invention also provides the application of the highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst obtained by the above scheme in the ammonia decomposition hydrogen production reaction.

[0020] The catalyst prepared by this invention, with Ru nanoparticles supported on a Ce-MgO(4) support, exhibits a high hydrogen production rate. Test results show that at 450℃ and 12,000 mL·g cat -1 ·h -1 Under certain space velocity conditions, the NH3 conversion rate of 1.36 nm Ru particles can reach 84.4%. The hydrogen production rate is approximately 837.3 mmol·g⁻¹. cat -1 ·min -1It is 2.46 times that of the 3.8Ru / Ce-MgO(4) catalyst. When the reaction temperature is raised to 500℃, the 1.36 nm Ru NPs-D / Ce-MgO(4) catalyst achieves an NH3 conversion rate of nearly 98.88%, which is better than most current ammonia decomposition catalysts.

[0021] The beneficial effects of this invention are as follows: This invention provides a unique Ce-MgO(x) support for the catalyst. The deposition of Ce facilitates the desorption of H2 and N2, thereby accelerating the recycling of active sites and contributing to improved conversion rates in ammonia decomposition at low temperatures. Simultaneously, the strong interaction between the Ru active sites and the Ce-MgO(x) support enhances the catalyst's activity and durability. Furthermore, the extremely low Ru loading in this catalyst effectively addresses the high energy consumption and high cost issues present in current ammonia decomposition processes. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 For MgO and Ce-MgO ( x XRD patterns of the vector; Figure 2 The H2-TPR spectra of the synthesis catalysts with different Ru sizes in Example 1 of this invention are shown. Figure 3 These are TEM images of Ru nanoparticles of different sizes in Example 1 of the present invention; Figure 4 This is a test graph showing the ammonia decomposition performance of the catalyst in Example 1 of the present invention; Figure 5 To test Ru nanoparticle catalysts of different sizes at GHSV = 12,000 mL·g cat -1 ·h -1 Arrhenius plot of the decomposition rate of NH3; Figure 6 The stability test diagram of sample Ru NPs-D / Ce-MgO(4) is shown. Figure 7 For Comparative Example 2, different Ru contents n Comparison of ammonia decomposition performance of Ru / Ce-MgO(4) catalyst; Figure 8Comparative Example 3: 3.8Ru / Ce-MgO with different Mg / Ce molar ratios x )( x Comparison chart of ammonia decomposition performance of catalysts (1, 2, 4, 8, 16); Figure 9 The graph shows a comparison of hydrogen production rates between samples 3.8Ru / Ce-MgO(4) and Ru NPs-D / Ce-MgO(4). Detailed Implementation

[0024] 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.

[0025] Example 1 (1) Dissolve 7.56 g of oxalic acid (H2C2O4·2H2O) and 8.58 g of magnesium acetate (Mg(CH3COO)2·4H2O) in 100 ml of deionized water respectively; then, add the magnesium acetate solution to the oxalic acid solution under stirring to generate a white precipitate; separate the precipitate by filtration and wash it repeatedly with deionized water until the filtrate is neutral; dry the washed precipitate in an oven at 80℃ for 12 h; finally, calcine the sample in air at 525℃ for 4 hours to obtain MgO powder.

[0026] (2) 1.0 g of the MgO powder prepared above was dispersed in 200 mL of deionized water and stirred continuously at room temperature for 30 min. Then, 0.5 mol / L Ce(NO3)3·6H2O solution was added, with a Mg to Ce molar ratio of 4:1. Under stirring conditions, a mixed solution of 2 mol / L KOH and K2CO3 was added dropwise to adjust the pH of the solution to 10. After stirring for 2 h, the resulting precipitate was filtered and separated, and washed three times with deionized water to remove residual ions. The washed sample was dried in an oven at 80 °C for 12 h. Finally, the dried sample was calcined in air at 600 °C for 4 h to obtain Ce-MgO (4).

[0027] (3) Dissolve NaOH and ruthenium chloride solution (RuCl3·3H2O) in 50 ml of ethylene glycol. Then, stir the resulting mixture in an oil bath, heat it to 160°C under argon protection, and keep it at that temperature for 3 hours. Finally, after the solution cools to room temperature, a dark brown Ru colloidal solution is obtained.

[0028] In this step, the molar ratio of NaOH to Ru (NaOH / Ru) was adjusted to prepare Ru colloidal nanoparticles of different sizes. The molar ratios of NaOH / Ru were 3.5, 7, 14 and 28, respectively.

[0029] (4) 0.3 g Ce-MgO(4) was dispersed in deionized water using ultrasound for 30 minutes. Then, Ru colloid was added to the mixture and stirred for 48 hours. The mass ratio of Ru colloid to Ce-MgO(x) was 1-1.5:100. The resulting sample was further aged at room temperature for 12 hours. Then, the desired sample was collected by centrifugation and multiple washing. Finally, catalysts with Ru nanoparticles of different sizes supported on Ce-MgO(4) support were obtained. According to the molar ratio of NaOH to Ru during the synthesis process (3.5, 7, 14 and 28, respectively), they were named Ru NPs-A, B, C and D, respectively.

[0030] Comparative Example 2 (1) Dissolve 7.56 g of oxalic acid (H2C2O4·2H2O) and 8.58 g of magnesium acetate (Mg(CH3COO)2·4H2O) in a certain volume of deionized water respectively; then, add the magnesium acetate solution to the oxalic acid solution under stirring to generate a white precipitate; separate the precipitate by filtration and wash it repeatedly with deionized water until the filtrate is neutral; dry the washed precipitate in an oven at 80℃ for 12 h; finally, calcine the sample in air at 525℃ for 4 hours to obtain MgO powder.

[0031] (2) 1.0 g of the MgO powder prepared above was dispersed in 200 mL of deionized water and stirred continuously at room temperature for 30 min. Then, 0.5 mol / L Ce(NO3)3·6H2O solution was added, with a Mg to Ce molar ratio of 4:1. Under stirring conditions, a mixed solution of 2 mol / L KOH and K2CO3 was added dropwise to adjust the pH of the solution to 10. After stirring for 2 h, the resulting precipitate was filtered and separated, and washed three times with deionized water to remove residual ions. The washed sample was dried in an oven at 80 °C for 12 h. Finally, the dried sample was calcined in air at 600 °C for 4 h to obtain Ce-MgO (4).

[0032] (3) A series of Ru-loaded products were prepared by urea-assisted deposition-precipitation method. n Ru / Ce-MgO( 4 )( n It is the mass percentage of Ru in the catalyst. n = 0.8, 1.6, 2.4, 3.2, 3.8, 4.4) catalysts.

[0033] The specific steps are as follows: First, dissolve RuCl3·3H2O in deionized water, then add 0.3 g Ce-MgO ( 4 The carrier powder was added to the above Ru precursor solution and diluted with 30 mL of deionized water. The suspension was stirred at room temperature for 1 hour. Then, urea (Ru to urea molar ratio of 1:200) was added as a precipitant. The mixture was reacted at 80°C for 8 hours and then allowed to stand at room temperature for 12 hours to promote sufficient deposition of Ru species. The precipitate was then separated by filtration and washed three times with deionized water to remove residual Cl. - Other impurities. The washed sample was dried in an oven at 80℃ for 12 h, finally obtaining... n Ru / Ce-MgO( 4 )catalyst.

[0034] Comparative Example 3 (1) Dissolve 7.56 g of oxalic acid (H2C2O4·2H2O) and 8.58 g of magnesium acetate (Mg(CH3COO)2·4H2O) in a certain volume of deionized water. Then, add the magnesium acetate solution to the oxalic acid solution under stirring to generate a white precipitate. Separate the precipitate by filtration and wash it repeatedly with deionized water until the filtrate is neutral. Dry the washed precipitate in an oven at 80℃ for 12 h. Finally, calcine the sample in air at 525℃ for 4 h.

[0035] (2) 1.0 g of the MgO powder prepared above was dispersed in 200 mL of deionized water and stirred continuously at room temperature for 30 min. Subsequently, a 0.5 mol / L Ce(NO3)3·6H2O solution was added, with Mg to Ce molar ratios of 1:1, 2:1, 4:1, 8:1, and 16:1, respectively. Under stirring, a mixed solution of 2 mol / L KOH and K2CO3 was added dropwise to adjust the pH of the solution to 10. After stirring for 2 h, the resulting precipitate was filtered and separated, and washed three times with deionized water to remove residual ions. The washed sample was dried in an oven at 80 °C for 12 h. Finally, the dried sample was calcined in air at 600 °C for 4 h to obtain different Ce-MgO(x).

[0036] (3) A series of 3.8Ru / Ce-MgO compounds with the same Ru loading but different Mg / Ce molar ratios were prepared by a urea-assisted deposition-precipitation method. x )( x represents different Mg / Ce molar ratios, x = 1, 2, 4, 8, 16 )catalyst.

[0037] The specific steps are as follows: First, dissolve RuCl3·3H2O in deionized water, then add 0.3 g Ce-MgO ( xThe carrier powder was added to the above Ru precursor solution and diluted with 30 mL of deionized water. The suspension was stirred at room temperature for 1 hour. Then, urea (Ru to urea molar ratio of 1:200) was added as a precipitant. The mixture was reacted at 80°C for 8 hours and then allowed to stand at room temperature for 12 hours to promote sufficient deposition of Ru species. The precipitate was then separated by filtration and washed three times with deionized water to remove residual Cl. - Other impurities. The washed sample was dried in an oven at 80℃ for 12 h, finally yielding 3.8Ru / Ce-MgO( x )catalyst.

[0038] like Figure 1 For MgO and different Ce-MgO ( x The XRD patterns of the support are shown in the figure. As can be seen, all samples exhibit typical MgO characteristic diffraction peaks, along with corresponding CeO2 characteristic diffraction peaks. With decreasing Ce doping concentration (i.e., increasing Mg / Ce molar ratio), the intensity of the MgO diffraction peak gradually increases, while the intensity of the corresponding CeO2 diffraction peak gradually decreases. Furthermore, no other impurity characteristic peaks were detected in the XRD patterns of any samples, indicating that the prepared samples have high purity.

[0039] like Figure 2 The figures show the H2-TPR spectra of the synthesis catalysts with different Ru sizes in Example 1 of this invention. As can be seen from the figures, all catalysts exhibit a distinct reduction peak in the temperature range of 110-230℃, and the peak shape is well-symmetrical. This indicates that RuO x The species are uniformly distributed on the Ce-MgO(4) support surface and exhibit moderate interactions with the support. Notably, the Ru NPs-D / Ce-MgO(4) catalyst exhibits the highest reduction temperature ( T max = 169℃), which is about 21-41℃ higher than other catalysts, confirming the existence of strong metal-support interaction in Ru NPs-D / Ce-MgO(4). This phenomenon can be attributed to the following two factors: First, the smaller Ru nanoparticles have a higher specific surface area, resulting in an increased contact interface between them and the support; second, the size effect enhances the electronic interaction between the metal and the support, forming a stronger metal-support interaction.

[0040] like Figure 3The figures show TEM images of Ru nanoparticles of different sizes synthesized in Example 1 of this invention. As can be seen from the figures, the average particle sizes of the Ru nanoparticles synthesized under different NaOH / Ru molar ratios are 4.85 nm, 3.94 nm, 2.41 nm, and 1.36 nm, respectively. Notably, when the NaOH / Ru molar ratio is adjusted to 28, a Ru nanocluster (NCs) catalyst with an average diameter of approximately 1.36 nm is successfully prepared. This result indicates that by controlling the NaOH / Ru molar ratio, the average particle size of Ru nanoparticles can be effectively controlled between 1.0 and 5.0 nm.

[0041] like Figure 4 The figure shows the ammonia decomposition performance test results of the catalyst in Example 1 of this invention. As can be seen from the figure, the ammonia decomposition activity of the catalyst significantly increases with the gradual decrease in the particle size of Ru nanoparticles. Ru NPs-D / Ce-MgO(4) exhibits the best catalytic performance at a WHSV of 12,000 mL·g⁻¹. cat -1 ·h -1 Under these conditions, the catalyst achieved an ammonia conversion rate of 84.4% at 450℃. At all temperatures, the Ru NPs-D / Ce-MgO(4) catalyst exhibited superior hydrogen production rates compared to other samples in the same group, exceeding 981.0 mmol·g at 500℃. cat -1 ·min -1 These results not only demonstrate that the catalytic activity of supported Ru catalysts is related to particle size, but also reveal that the smallest Ru particle size (1.36 nm) is the optimal particle size for the highest catalytic performance in NH3 decomposition.

[0042] like Figure 5 To test Ru nanoparticle catalysts of different sizes at GHSV = 12,000 mL·g cat -1 ·h -1 The Arrhenius plot of the NH3 decomposition rate shows that the activation energy of catalysts with different Ru nanoparticle sizes is the lowest, and the apparent activation energy of Ru NPs-D / Ce-MgO(4) is the lowest, which theoretically corresponds to the best ammonia decomposition performance, consistent with the experimental results.

[0043] like Figure 6 The figure shows the stability test results of sample Ru NPs-D / Ce-MgO(4). As can be seen from the figure, the NH3 conversion rate of this catalyst remained stable at approximately 84.40% and 98.88% at 450℃ and 500℃, respectively, without significant decrease during 50 hours of operation. The prepared catalyst exhibits excellent catalytic stability, making it a very promising candidate for practical applications in this field.

[0044] like Figure 7 For example 2 with different Ru contents n The performance comparison chart of Ru / Ce-MgO(4) catalysts shows that the catalytic activity exhibits a volcano-shaped curve, first increasing and then decreasing, with the increase of Ru loading. The highest ammonia decomposition activity is achieved when the mass percentage of Ru in the catalyst is 3.8 wt%. This loading maximizes the number of active sites while ensuring a high degree of Ru species dispersion, thus optimizing catalytic performance. However, when the Ru loading further increases to 4.4 wt%, the catalytic activity decreases significantly.

[0045] like Figure 8 Comparative Example 3: 3.8Ru / Ce-MgO with different Mg / Ce molar ratios x )( x The ammonia decomposition performance of catalysts (1, 2, 4, 8, 16) is shown in the figure. As can be seen from the figure, the catalyst activity exhibits a typical volcano-shaped curve characteristic with changes in Ce content. Among them, the 3.8Ru / Ce-MgO(4) catalyst shows the best catalytic activity. In contrast, catalysts with excessively high or low Ce contents, such as 3.8Ru / Ce-MgO(1) and 3.8Ru / Ce-MgO(16), show significantly reduced activity.

[0046] like Figure 9 The graph shows a comparison of hydrogen production rates for samples 3.8Ru / Ce-MgO(4) and Ru NPs-D / Ce-MgO(4). The graph indicates that at a space velocity of 12,000 mL·g⁻¹, the hydrogen production rate of these samples is significantly higher than that of samples 3.8Ru / Ce-MgO(4). cat -1 ·h -1 At a temperature of 450℃, the hydrogen production rate of the Ru NPs-D / Ce-MgO(4) catalyst was 2.46 times that of the 3.8Ru / Ce-MgO(4) catalyst. This significant difference indicates that the smaller Ru nanoparticles have more active sites and higher atom utilization, thus exhibiting higher catalytic activity. Furthermore, the Ru loading in NPs-D / Ce-MgO(4) is much lower, only 1.35 wt%.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst, characterized in that, Includes the following steps: (1) Preparation of high specific surface area MgO: High specific surface area MgO is obtained by thermal decomposition of magnesium oxalate; (2) Preparation of Ce-MgO(x) support: MgO powder was added to water and stirred to disperse it. Then Ce(NO3)3·6H2O solution was added to obtain a mixed solution. A mixed solution of KOH and K2CO3 was added dropwise to the mixed solution to adjust the pH value to 10-11. The reaction was stirred to form a precipitate. The precipitate was washed and dried to obtain Ce-MgO(x) support. (3) Ru colloidal nanoparticle solution was prepared using ruthenium chloride; (4) Preparation of Ru-based catalyst: Ru colloidal nanoparticles were deposited on a cerium-doped magnesium oxide support by colloidal deposition method to obtain a highly dispersed Ru nanoparticle supported ammonia decomposition hydrogen production catalyst.

2. The preparation method of the highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The preparation method of high specific surface area MgO in step (1) is as follows: oxalic acid and magnesium acetate are dissolved in water respectively; then, the magnesium acetate solution is added to the oxalic acid solution under stirring, the white precipitate is filtered and separated, and washed repeatedly with water until the filtrate is neutral; the washed precipitate is dried in an oven, and finally, the dried precipitate is calcined in air to decompose and obtain MgO.

3. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, In step (2), the molar ratio of Mg to Ce in the mixture is 1-16:

1.

4. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 1 or 3, characterized in that, In step (2), the molar ratio of KOH to K2CO3 in the mixed solution of KOH and K2CO3 is 1:

1.

5. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The preparation method of Ru colloidal nanoparticle solution in step (3) is as follows: NaOH and ruthenium chloride solution were added to ethylene glycol; then, the resulting mixture was stirred in an oil bath, heated and kept warm under argon protection; finally, after the solution was cooled to room temperature, a dark brown Ru colloidal nanoparticle solution was obtained.

6. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 5, characterized in that, The molar ratio of NaOH to Ru in the mixture is 3.5-28:

1.

7. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The specific steps of the colloidal deposition method in step (4) are as follows: 0.3 g Ce-MgO(x) is added to water and ultrasonically dispersed; then, Ru colloidal nanoparticles are added to the dispersion and stirred, and the resulting product is aged at room temperature; then, the product is collected by centrifugation and multiple washings; finally, the product is dried to obtain a highly dispersed Ru nanoparticle supported ammonia decomposition hydrogen production catalyst. The mass ratio of Ru colloid to Ce-MgO(x) is 1-1.5:

100.

8. The preparation method of a highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 7, characterized in that, The actual Ru content in the highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst is 1-1.5 wt%.

9. A highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the highly dispersed Ru nanoparticle-supported ammonia decomposition hydrogen production catalyst according to claim 9 in the ammonia decomposition hydrogen production reaction.

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