An ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent, its preparation method and application

Abstract

This invention belongs to the field of ammonia decomposition catalyst preparation technology, specifically relating to an ammonia decomposition catalyst using in-situ formed BaCeO3 as a promoter, its preparation method, and its application. The ammonia decomposition catalyst prepared by this invention uses rare earth oxides as a support and, through a deposition-precipitation method and synergistic effect with Ba promoter, in-situ forms a BaCeO3 perovskite structure during the ammonia decomposition catalytic reaction, significantly improving its low-temperature activity. Experiments show that the catalyst achieves an H2 yield of 28.8 mmol·g at 500℃. cal ‑1 ·min ‑1 It also exhibits excellent stability and is suitable for efficient ammonia decomposition to produce hydrogen.

Description

Technical Field

[0001] This invention belongs to the field of ammonia decomposition catalyst preparation technology, specifically relating to an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent, its preparation method and application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Hydrogen energy is considered an ideal alternative to fossil fuels due to its abundant sources, green and low-carbon nature, renewability, and high calorific value. However, the safe storage and transportation of hydrogen remains a technological bottleneck. Ammonia, as a hydrogen-rich compound (containing 17.8 wt.% hydrogen by mass), is a highly promising hydrogen storage medium due to its easy liquefaction, safe storage and transportation, high purity of decomposition products, and zero carbon emissions. However, the ammonia decomposition reaction (2NH3(g)→N2(g)+3H2(g); ΔH=+92 kJ·mol⁻¹) is problematic. −1 The activation barrier is high, and most preparation methods focus on controlling the size of the active metal, offering limited control over the catalyst's active sites and electronic structure. This makes it difficult to significantly improve the ammonia decomposition conversion rate, mainly due to the high-temperature, strong-reducing environment of the ammonia decomposition reaction. Therefore, the preparation of low-temperature, high-activity catalysts is a growing trend.

[0004] In existing technologies, noble metal catalysts, such as Ru-based catalysts, exhibit excellent low-temperature activity, but their high cost makes them difficult to apply to practical industrial production. Non-noble metal catalysts, such as Ni-based catalysts, are low-cost, but their ammonia decomposition activity at low temperatures is inferior to that of noble metal catalysts. Therefore, achieving efficient ammonia decomposition for hydrogen production at low temperatures using transition metal Ni-based catalysts has become a current research focus.

[0005] Studies have shown that optimizing the support and promoters can improve the activity of Ni-based catalysts. For example, rare earth oxide supports, due to their unique 4... f The electronic layer structure contributes to chemical stability, and its alkaline surface and other characteristics facilitate catalytic reactions. Perovskite oxide supports possess strong basicity and excellent electronic conductivity, which helps optimize the electronic state of the active metal, promotes the activation of NH3, and accelerates the desorption of N2 and H2. Alkaline earth metal promoters can enhance the electron-donating ability of the catalyst and increase the electron cloud density around the active metal, thereby promoting N2 association and desorption through electronic regulation. However, in existing technologies, the compatibility between promoters and supports is insufficient, and the perovskite structural characteristics are not fully utilized, resulting in limited improvement in catalyst activity. Summary of the Invention

[0006] To address the needs of existing technologies, the purpose of this invention is to provide an ammonia decomposition catalyst using in-situ formed BaCeO3 as a promoter, its preparation method, and its application. This invention introduces in-situ formed BaCeO3 perovskite promoter, combined with a rare earth oxide support, to prepare a low-temperature, highly efficient, stable, and low-cost nickel-based ammonia decomposition catalyst, significantly improving the catalyst's catalytic activity and hydrogen yield.

[0007] Specifically, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent. The ammonia decomposition catalyst comprises a rare earth oxide support CeO2 and an active component, a nickel compound, and an alkaline earth metal auxiliary agent, a barium compound, supported on the support. The nickel loading in the active component nickel compound is 15-25 wt.%, and the barium loading in the alkaline earth metal auxiliary agent barium compound is 1-15 wt.%. The alkaline earth metal auxiliary agent barium compound reacts in-situ with the rare earth oxide support during the ammonia decomposition reaction to form a BaCeO3 perovskite structure.

[0009] Preferably, the active component, the nickel compound, is NiO, and the alkaline earth metal auxiliary barium compound is BaCO3.

[0010] Preferably, the ammonia decomposition catalyst has a nanosphere structure with a size of 60-70 nm and a specific surface area of ​​130-135 m². 2 / g, pore volume 0.3~0.35 cm³ 3 / g, with pore sizes of 4.5~4.7 nm.

[0011] More preferably, the specific surface area of ​​the ammonia decomposition catalyst is 133.2 m². 2 / g, pore volume is 0.31 cm³ 3 / g, with a pore size of 4.65 nm.

[0012] Preferably, the particle size of the ammonia decomposition catalyst is 20-40 mesh.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent, comprising the following steps:

[0014] S1. Cerium salt is dissolved in a mixed solvent and subjected to a solvothermal reaction. The precipitate obtained after centrifugation and washing of the product is calcined to obtain CeO2 nanosphere carrier.

[0015] S2. The mixed solution obtained by adding barium salt to nickel salt solution is added dropwise to the aqueous solution of CeO2 nanosphere carrier, while sodium salt solution is added dropwise to adjust the pH to 8-10. Then, after aging, filtration, drying and calcination, the ammonia decomposition catalyst is obtained.

[0016] Preferably, in step S1, the mixed solvent is a mixed solution of water, ethylene glycol and glacial acetic acid, the volume ratio of water, ethylene glycol and glacial acetic acid is (1.5~2.5):(50~55):(1.5~2.5), and the concentration of glacial acetic acid is ≥99.5%; the volume ratio of cerium salt to mixed solvent is 1 g:(25~30) mL; the cerium salt includes cerium nitrate hexahydrate.

[0017] Preferably, in step S1, the temperature of the solvothermal reaction is 170~190℃ and the reaction time is 180~240min.

[0018] Preferably, in step S1, the calcination treatment involves heating to 350-450°C at a heating rate of 1-3°C / min and calcining for 0.5-1.5 h.

[0019] Preferably, in step S2, the barium salt includes barium nitrate, the nickel salt includes nickel nitrate, and the sodium salt includes sodium carbonate; the concentration of the nickel salt solution is 0.08~0.12 M; the concentration of the sodium salt is 0.4~0.6 M; and the ratio of the amount of barium salt, nickel salt solution to sodium salt solution is (0.1~0.15) g:(25~26) mL:(20~30) mL.

[0020] Preferably, in step S2, the pH is 9; the aging time is 1~1.5 h; the drying temperature is 65~75℃ and the time is 7~9 h; the calcination is carried out by heating to 350~450℃ at a heating rate of 1~3℃ / min and the calcination time is 3~5 h.

[0021] A third aspect of the present invention provides the application of the ammonia decomposition catalyst described in the first aspect, which uses in-situ formed BaCeO3 as an auxiliary agent, in the ammonia decomposition hydrogen production reaction.

[0022] Preferably, the ammonia decomposition catalyst is activated at 600°C in a pure ammonia atmosphere for 0.5 to 1.5 h to reduce NiO to metallic nickel, while the Ba species reacts with the support CeO2 to form BaCeO3.

[0023] The beneficial effects achieved by one or more of the above technical solutions of the present invention are as follows:

[0024] (1) In this invention, rare earth oxide CeO2, which has both surface alkalinity and good thermal stability, is selected as the support, and alkaline earth metal Ba, which has strong electron-donating ability, is used as the promoter. Furthermore, Ni, a transition metal with low price, good performance and great practical application potential, is combined to construct a Ni-Ba / CeO2 ternary catalyst, realizing the efficient ammonia decomposition to hydrogen production of Ni-based catalyst at low temperature.

[0025] (2) In this invention, the catalyst supported on CeO2 forms a new species, BaCeO3, in situ during the ammonia decomposition reaction after the introduction of Ba. This species has strong basicity and excellent electronic conductivity, which is beneficial to the dissociation of NH3 and promotes the association and desorption of N2 and H2. The H2 yield can reach 28.8 mmol·g at 500℃. cat −1 ·min −1 This far surpasses other Ni-based catalysts reported in the prior art, and even exceeds some Ru-based noble metal catalysts (GHSV = 30,000 mL·g). cat -1 ·h -1 ). Attached Figure Description

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 This is a TEM image of the 20Ni-7Ba / CeO2 catalyst prepared in Example 1 of this invention;

[0028] Figure 2 The images show the XRD patterns of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 5 of this invention after catalytic reaction, where a is the XRD pattern of 20Ni-7Ba / CeO2 and b is the XRD pattern of 20Co-7Ba / CeO2.

[0029] Figure 3 The H2 reaction order of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 7 of this invention;

[0030] Figure 4 Ni 2 is the ammonia decomposition catalyst prepared in Example 1 and Comparative Example 7 of this invention. p Quasi-in-situ XPS spectra;

[0031] Figure 5 CO2 temperature-programmed desorption (CO2-TPD) experiment of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 7 of this invention;

[0032] Figure 6This is a stability test diagram of the ammonia decomposition catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0033] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0035] Example 1: This example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0036] (1) Preparation of CeO2 nanosphere carrier (solvothermal method): 2.0 g of cerium nitrate hexahydrate was weighed into a 100 mL polytetrafluoroethylene liner, followed by the addition of 2 mL of high-purity water, 52 mL of ethylene glycol, and 2 mL of glacial acetic acid. The mixture was then stirred for 30 min. After stirring, the liner was placed in a stainless steel reactor, and the oven temperature was set to 180 °C for 200 min. After the solvothermal reaction, the obtained product was centrifuged and washed in a centrifuge tube, washed 4 times with high-purity water and once with ethanol. After washing, the precipitate was dried in an oven at 70 °C for 6 h. After drying, it was ground into powder using an agate mortar and pestle. Then, it was heated to 400 °C in a tube furnace at a heating rate of 2 °C / min and calcined for 1 h to obtain the CeO2 nanosphere carrier.

[0037] (2) Preparation of 20Ni-7Ba / CeO2 catalyst (deposition precipitation method): 0.5 g of CeO2 nanosphere support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to ensure complete dispersion, denoted as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: 2.91 g of Ni(NO3)2·6H2O was weighed and dissolved in 100 mL of high-purity water), then 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to ensure thorough mixing, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / CeO2.

[0038] Example 2: This example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0039] The difference between this embodiment and embodiment 1 is that in step (2), this embodiment prepares a 20Ni-2Ba / CeO2 catalyst. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.024 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Ni-2Ba / CeO2.

[0040] Example 3: This example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0041] The difference between this embodiment and embodiment 1 is that in step (2), this embodiment prepares a 20Ni-5Ba / CeO2 catalyst. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.063 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Ni-5Ba / CeO2.

[0042] Comparative Example 1: This comparative example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0043] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 20Ni-1Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.012 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Ni-1Ba / CeO2.

[0044] Comparative Example 2: This example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0045] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 20Ni-15Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 26.2 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.22 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Ni-15Ba / CeO2.

[0046] Comparative Example 3: This comparative example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0047] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 15Ni-7Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 16.4 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.086 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 15Ni-7Ba / CeO2.

[0048] Comparative Example 4: This comparative example provides an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent and its preparation method.

[0049] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 25Ni-7Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 31.4 mL of 0.1 M Ni(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Ni(NO3)2 solution preparation: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.098 g of Ba(NO3)2 is weighed and added to the beaker containing the Ni(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 25Ni-7Ba / CeO2.

[0050] Comparative Example 5: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0051] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 20Co-7Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 25.6 mL of 0.1 M Co(NO3)2 solution is weighed into a 50 mL beaker (0.1 M Co(NO3)2 solution preparation: weigh 2.91 g of Co(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then 0.13 g of Ba(NO3)2 is weighed and added to the beaker containing the Co(NO3)2 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Co-7Ba / CeO2.

[0052] Comparative Example 6: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0053] The difference between this comparative example and Example 1 is that in step (2), the catalyst prepared in this example is 20Fe-7Ba / CeO2. The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 24.5 mL of 0.1 M Fe(NO3)3 solution is weighed into a 50 mL beaker (0.1 M Fe(NO3)3 solution preparation: weigh 4.04 g of Fe(NO3)3·9H2O and dissolve it in 100 mL of high-purity water), then 0.091 g of Ba(NO3)2 is weighed and added to the beaker containing the Fe(NO3)3 solution, and ultrasonically stirred at room temperature to make the two fully mixed, which is recorded as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Fe-7Ba / CeO2.

[0054] Comparative Example 7: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0055] The difference between this comparative example and Example 1 is that Ba(NO3)2 was not added in step (2). The specific preparation method of step (2) is as follows:

[0056] Preparation of 20Ni / CeO2 catalyst (deposition-precipitation method): 0.5 g of CeO2 nanospheres were dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, dried at 70 °C for 8 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / CeO2.

[0057] Comparative Example 8: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0058] The difference between this comparative example and Comparative Example 5 is that Ba(NO3)2 was not added in step (2). The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere carrier was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to ensure complete dispersion, which is denoted as solution A; then 25.6 mL of 0.1 M Co(NO3)2 solution was measured into a 50 mL beaker, which is denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Co / CeO2.

[0059] Comparative Example 9: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0060] The difference between this comparative example and comparative example 6 is that Ba(NO3)2 was not added in step (2). The specific preparation method of step (2) is as follows: 0.5 g of CeO2 nanosphere carrier was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, which is recorded as solution A; then 24.5 mL of 0.1 M Fe(NO3)3 solution was measured into a 50 mL beaker and recorded as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water. The filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was recorded as 20Fe / CeO2.

[0061] Comparative Example 10: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0062] The difference between this comparative example and Example 1 is that in step (1), CeO2 nanorods are prepared, and the specific amount added is the same as that of the CeO2 nanosphere carrier in Example 1. The content of other components and the preparation method are the same as those in Example 1. The specific preparation method is as follows: 14.4 g of NaOH is dissolved in 40 mL of deionized water, and then 3 mmol of Ce(NO3)3·6H2O aqueous solution is added to the NaOH solution. The solution is stirred for 30 min to make the solution evenly dispersed. The hydrothermal reaction is carried out at 100℃ for 24 h. The resulting mixed solution is then transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor. The temperature in the oven is set at 100℃ and the reaction is carried out for 24 h. After the hydrothermal reaction, the product is centrifuged and washed, washed 4 times with deionized water and 1 time with anhydrous ethanol. After washing, the precipitate is placed in an oven and dried at 60℃ for 24 h to obtain CeO2 nanorods, denoted as CeO2-NR.

[0063] 0.5 g of CeO2 nanorod support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution was prepared by dissolving 2.91 g of Ni(NO3)2·6H2O in 100 mL of high-purity water). Next, 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing the Ni(NO3)2 solution, and the mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / CeO2-NR.

[0064] Comparative Example 11: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0065] The difference between this comparative example and Example 1 is that in step (1), CeO2 nanosheets are prepared, and the specific amount added is the same as that of the CeO2 nanosphere carrier in Example 1. The content of other components and the preparation method are the same as those in Example 1. The specific preparation method is as follows: CeO2 nanosheet carriers are prepared by co-precipitation method. 1.39 g Ce(NO3)3·6H2O and 0.75 g NH4HCO3 are added to 200 mL of deionized water, and magnetic stirring is performed at 0°C to completely dissolve them. The dissolved NH4HCO3 solution is quickly added to the Ce(NO3)3 solution and stirred for 0.5 h. Then it is allowed to stand at 0°C for 15 h and filtered and washed. The filtered product is dried at 110°C for 6 h. Finally, the dried solid is ground into powder and calcined at 450°C for 4 h to obtain the desired CeO2 nanosheet carrier, denoted as CeO2-NS.

[0066] 0.5 g of CeO2 nanosheets were dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed; this solution is denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution was prepared by dissolving 2.91 g of Ni(NO3)2·6H2O in 100 mL of high-purity water). Next, 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed; this solution is denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / CeO2-NS.

[0067] Comparative Example 12: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0068] The difference between this comparative example and Example 1 is that BaCeO3 was first prepared by the sol-gel method, and then reacted with Ni(NO3)2 to prepare a catalyst. The specific preparation method is as follows: 0.784 g of Ba(NO3)2 and 1.302 g of Ce(NO3)3·6H2O were dissolved in 15 mL of high-purity water and stirred to form a mixed solution with a total cation concentration of 0.4 M. 2+ With Ce 3+The molar ratio of total cations to citric acid was 1:1. Then, 1.153 g of citric acid (Sigma-Aldrich, purity ≥99.5%) was added under continuous stirring to achieve a 1:1 molar ratio of total cations to citric acid. The mixture was heated and stirred at 90°C until a gel formed, and then dried in an oven at 110°C for 12 h. The dried, expanded solid was ground into powder and calcined in a muffle furnace at 1000°C for 4 h to obtain the desired BaCeO3 support.

[0069] 0.5 g of BaCeO3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, dried at 70 °C for 8 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / BaCeO3-1.

[0070] Comparative Example 13: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0071] The difference between this comparative example and Example 1 is that 20Ni-BaCeO3-2 is prepared in one step via coprecipitation. The specific preparation method is as follows: 0.52 g of Ba(NO3)2, 0.87 g of Ce(NO3)3·6H2O, and 0.81 g of Ni(NO3)2 are dissolved in 25 mL of high-purity water and stirred until completely dissolved; this is denoted as solution A. Simultaneously, 2.41 g of (NH4)2C2O4·H2O is dissolved in 54 mL of high-purity water and stirred until completely dissolved; this is denoted as solution B. Then, solution A is slowly added to solution B under continuous stirring for 4 h. After stirring, the solution is centrifuged and washed, and the centrifuged product is dried at 85°C for 12 h. The dried solid is then ground into powder and calcined at 800°C for 6 h to obtain the desired 20Ni-BaCeO3-2.

[0072] Comparative Example 14: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0073] The difference between this comparative example and Example 1 is that in step (2), BaCeO is first prepared by the sol-gel method. 3，Then, the mixture was ball-milled with CeO2 nanospheres, and the resulting mixture was reacted with Ni(NO3)2 to prepare a 20Ni / BaCeO3-CeO2 catalyst. The specific preparation method is as follows: 0.784 g of Ba(NO3)2 and 1.302 g of Ce(NO3)3·6H2O were dissolved in 15 mL of high-purity water and stirred to form a mixed solution with a total cation concentration of 0.4 M. 2+ With Ce 3+ The molar ratio of total cations to citric acid was 1:1. Then, 1.153 g of citric acid (Sigma-Aldrich, purity ≥99.5%) was added under continuous stirring to achieve a 1:1 molar ratio of total cations to citric acid. The mixture was heated and stirred at 90°C until a gel formed, and then dried in an oven at 110°C for 12 h. The dried, expanded solid was ground into powder and calcined in a muffle furnace at 1000°C for 4 h to obtain the desired BaCeO3 support.

[0074] 0.0768 g BaCeO3 and 0.5 g CeO2 nanospheres were mechanically mixed in a planetary ball mill at a speed of 400 r for 2 h. The resulting mixed support was heated to 400 °C in a muffle furnace at a heating rate of 2 °C / min and calcined for 1 h. The calcined support was named BaCeO3-CeO2 support.

[0075] 0.5 g of BaCeO3-CeO2 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, dried at 70 °C for 8 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product was denoted as 20Ni / BaCeO3-CeO2.

[0076] Comparative Example 15: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0077] The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Y2O3 nanosheets) and corresponding catalysts were prepared. The specific preparation methods are as follows:

[0078] (1) Preparation of Y2O3 nanosheet carrier (hydrothermal method): 1.15 g of Y(NO3)3·6H2O was dissolved in 60 mL of deionized water, and the pH was adjusted to 12 with NaOH solution. After stirring for 15 min to mix the solution evenly, the solution was subjected to hydrothermal reaction at 120℃ for 12 h. The resulting precipitate was washed by centrifugation and dried at 60℃ for 12 h. The dried powder sample was ground and calcined in air at 500℃ for 6 h in a tube furnace to obtain white Y2O3 nanosheet carrier.

[0079] (2) Preparation of 20Ni / Y2O3 catalyst: 0.5 g of Y2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to ensure complete dispersion, denoted as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / Y2O3.

[0080] Comparative Example 16: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0081] The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Sm2O3 nanorods) and corresponding catalysts were prepared. The specific preparation methods are as follows:

[0082] (1) Preparation of Sm2O3 nanorod support (hydrothermal method): 14.4 g of NaOH was dissolved in 40 mL of deionized water, and then 3 mmol of Sm(NO3)3·6H2O aqueous solution was added to the NaOH solution. The mixture was stirred for 30 min to ensure homogeneity. The mixture was then subjected to hydrothermal reaction at 100 °C for 24 h. The resulting precipitate was washed by centrifugation and dried at 60 °C for 12 h. The resulting powder sample was ground and then calcined in air at 450 °C for 4 h in a tube furnace to obtain the Sm2O3 nanorod support.

[0083] (2) Preparation of 20Ni / Sm2O3 catalyst: 0.5 g of Sm2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to ensure complete dispersion, denoted as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / Sm2O3.

[0084] Comparative Example 17: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0085] The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Gd2O3 nanorods) and corresponding catalysts were prepared. The specific preparation methods are as follows:

[0086] (1) Preparation of Gd2O3 nanosheet support (hydrothermal method): 0.02 mmol of Gd(NO3)3·6H2O was dissolved in 60 mL of deionized water, and then the pH was adjusted to 12.8 using 2.5 M NaOH solution. The hydrothermal reaction was then carried out at 180 °C for 24 h. The resulting precipitate was washed by centrifugation and dried at 80 °C for 12 h. The dried sample was ground and then calcined in a tube furnace at 450 °C for 2 h to obtain white Gd2O3 nanorod support.

[0087] (2) Preparation of 20Ni / Gd2O3 catalyst: 0.5 g of Gd2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to ensure complete dispersion, denoted as solution A; then 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / Gd2O3.

[0088] Comparative Example 18: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0089] The difference between this comparative example and Comparative Example 7 is that an inert oxide support (SiO2) is added for the preparation of the catalyst. The specific preparation method is as follows:

[0090] Preparation of 20Ni / SiO2 catalyst: 0.5 g of SiO2 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, dried at 70 °C for 8 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / SiO2.

[0091] Comparative Example 19: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0092] The difference between this comparative example and Comparative Example 7 is that an inert oxide support (Al2O3) is added for the preparation of the catalyst. The specific preparation method is as follows:

[0093] Preparation of 20Ni / Al2O3 catalyst: 0.5 g of Al2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered with 1 L of high-purity water, dried at 70 °C for 8 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained was denoted as 20Ni / Al2O3.

[0094] Comparative Example 20: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0095] The difference between this comparative example and Example 7 is that in step (2), Y2O3 nanosheet support is added (the support preparation method is shown in Comparative Example 9). The specific preparation method of the ammonia decomposition catalyst is as follows:

[0096] Preparation of 20Ni-7Ba / Y2O3 catalyst (deposition-precipitation method): 0.5 g of Y2O3 nanosheet support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, followed by the addition of 0.13 g of Ba(NO3)2 to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / Y2O3.

[0097] Comparative Example 21: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0098] The difference between this comparative example and Example 1 is that in step (2), Sm2O3 nanorod support is added (the support preparation method is shown in Comparative Example 10). The specific preparation method of the ammonia decomposition catalyst is as follows:

[0099] Preparation of 20Ni-7Ba / Sm2O3 catalyst (deposition-precipitation method): 0.5 g of Sm2O3 nanorod support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, followed by the addition of 0.13 g of Ba(NO3)2 to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / Sm2O3.

[0100] Comparative Example 22: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0101] The difference between this comparative example and Example 1 is that in step (2), a Gd2O3 nanorod support is added (the support preparation method is shown in Comparative Example 11). The specific preparation method of the ammonia decomposition catalyst is as follows:

[0102] Preparation of 20Ni-7Ba / Gd2O3 catalyst (deposition-precipitation method): 0.5 g of Gd2O3 nanorod support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, followed by the addition of 0.13 g of Ba(NO3)2 to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / Gd2O3.

[0103] Comparative Example 23: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0104] The difference between this comparative example and Example 1 is that in step (2), a SiO2 support is added. The specific preparation method of the ammonia decomposition catalyst is as follows:

[0105] Preparation of 20Ni-7Ba / SiO2 catalyst (deposition-precipitation method): 0.5 g of SiO2 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, followed by the weighing of 0.13 g of Ba(NO3)2, which was added to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / SiO2.

[0106] Comparative Example 24: This comparative example provides an ammonia decomposition catalyst and its preparation method.

[0107] The difference between this comparative example and Example 1 is that in step (2), an Al2O3 support is added. The specific preparation method of the ammonia decomposition catalyst is as follows:

[0108] Preparation of 20Ni-7Ba / Al2O3 catalyst (deposition-precipitation method): 0.5 g of Al2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, followed by the addition of 0.13 g of Ba(NO3)2 to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, the sample was filtered with 1 L of high-purity water and dried at 70℃ for 8 h. After drying, the sample was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / Al2O3.

[0109] Experimental Example 1: This experimental example tests the structural characteristics of the ammonia decomposition catalysts prepared in Example 1, Comparative Example 5, Comparative Example 7, and Comparative Example 10.

[0110] like Figure 1 As shown in the TEM image of 20Ni-7Ba / CeO2 prepared in Example 1, the catalyst exhibits a nanosphere structure with a size in the range of 60-70 nm.

[0111] The inventors further investigated the differences between single-support CeO2 nanorods and single-support CeO2 nanospheres, and conducted N2 adsorption-desorption tests on both. Table 1 summarizes the physical properties of both, including specific surface area (…). S BET ), pore volume ( V total ) and BJH pore size.

[0112] Table 1

[0113]

[0114] As shown in Table 1, the CeO2 nanospheres exhibit the largest specific surface area among the different supports. A larger specific surface area allows for more uniform dispersion of the active metal, reduces particle aggregation, and increases the number of exposed active sites, thus facilitating the ammonia decomposition reaction.

[0115] like Figure 2 As shown, the fine-scanning XRD images of the 20Ni-7Ba / CeO2 catalyst prepared in Example 1 and the 20Co-7Ba / CeO2 catalyst prepared in Comparative Example 5 reveal that, in the fine-scanning XRD of the 20Ni-7Ba / CeO2 catalyst after the reaction, in addition to a weak BaCO3 diffraction peak, the presence of the new BaCeO3 species was also observed. However, in the XRD of the 20Co-7Ba / CeO2 catalyst after the reaction, only the BaO species was observed, and the formation of this new species was not observed.

[0116] like Figure 3 As shown, the H2 reaction order of the 20Ni / CeO2 prepared in Comparative Example 7 and the 20Ni-7Ba / CeO2 prepared in Example 1 shows that, compared with the 20Ni / CeO2 catalyst, the 20Ni-7Ba / CeO2 catalyst with in-situ generated BaCeO3 as a promoter has a smaller absolute value of H2 reaction order, which indicates that it has a better resistance to hydrogen poisoning.

[0117] like Figure 4 As shown, Ni2+ prepared in Comparative Example 7 (20Ni / CeO2) and Example 1 (20Ni-7Ba / CeO2) are compared. p XPS energy dispersive spectroscopy shows that from Ni 2p The energy dispersive spectroscopy revealed that the binding energy of metallic Ni in 20Ni-7Ba / CeO2 was lower. Combined with the high alkalinity and excellent electron transport ability of the BaCeO3 surface, it is indicated that the formation of BaCeO3 leads to the increase of the electron cloud density of Ni on the 20Ni-7Ba / CeO2 surface, which is conducive to the ammonia decomposition reaction.

[0118] like Figure 5 As shown, CO2-TPD experiments of CO2 temperature-programmed desorption of 20Ni / CeO2 prepared in Comparative Example 7 and 20Ni-7Ba / CeO2 prepared in Example 1 showed that, due to the generation of BaCeO3, there are more medium-to-strong basic sites on the surface of 20Ni-7Ba / CeO2. This is conducive to promoting the transfer of electrons to the active metal, which is consistent with the results of quasi-in-situ XPS. This is conducive to promoting the association and desorption of product N2 and promoting the ammonia decomposition reaction.

[0119] Experimental Example 1: This experimental example measures the catalytic performance (ammonia decomposition activity at low temperature) of the ammonia decomposition catalysts prepared in Examples 1-13 and Comparative Examples 1-18.

[0120] Experimental Procedure: In the catalyst performance test, 50 mg of the ammonia decomposition catalyst (20-40 mesh) prepared in the above examples and comparative examples was mixed with 500 mg of quartz sand (20-40 mesh), and then placed into a quartz reaction tube with an inner diameter of 8 mm. Before the catalytic test, the catalyst was first activated at 600 °C for 1 h in a pure NH3 atmosphere, and then the ammonia decomposition conversion rate was tested between 450-600 °C. Conversion rate data were collected at 50 °C intervals (GHSV = 30,000 mL·gcat- 1 ·h -1 GHSV is an abbreviation for Gas Hourly Space Velocity, referring to the gas hourly space velocity. The outlet gas is analyzed using an online gas chromatograph (Furi GC 9790) to obtain real-time N2 and NH3 content. The NH3 conversion rate is calculated using the following formula:

[0121]

[0122] in, The concentration of N2 at the chromatographic outlet, This represents the concentration of NH3 at the chromatographic outlet where the reaction was incomplete.

[0123] The test results are shown in Tables 2 and 3 (numerical tests at 500℃):

[0124] Table 2

[0125]

[0126] Table 3

[0127]

[0128] As shown in Table 2, when the Ni loading is 20% and the Ba content is 7%, the ammonia decomposition activity is optimal, and the conversion rate can reach 86.3% at 500℃. Reducing the Ba content will lead to a decrease in activity. This may be because the BaCeO3 content formed in situ is limited when the Ba content is low, and its promoting effect on activity is limited.

[0129] As shown in Table 3, compared to Ni-based catalysts with other oxide supports, the activity of Ba-doped catalysts is lower than that of the 20Ni-7Ba / CeO2 catalyst with in-situ BaCeO3 formation. When the active metal is changed, the activity of Ba-doped catalysts is also significantly lower than that of Ni-based catalysts. For the 20Ni-7Ba / CeO2 catalyst with the best activity, when the Ni content is further increased to 25%, its activity and hydrogen production rate per gram of catalyst not only do not increase compared to Example 1, but actually decrease. This may be due to the active metal being prone to sintering due to excessive Ni content. Its activity and hydrogen production rate per gram of catalyst are higher than those of Examples 2 and 3. This may be due to the increased number of active sites after the Ni content is increased. For Comparative Example 3, its hydrogen production rate per gram of metal is higher than that of Comparative Examples 2 and 3. This is because the Ni content is reduced, but the ammonia conversion rate after catalysis is lower than that of the Examples.

[0130] Further increasing the Ba content also leads to a decrease in activity, possibly because the increased content may cover some active sites. Additionally, the 20Ni-7Ba / CeO2 catalyst with in-situ formed BaCeO3 exhibits higher activity than related catalysts without in-situ BaCeO3 doping, further illustrating the importance of in-situ BaCeO3 formation. Furthermore, compared to CeO2 nanosheets and CeO2 nanorods, the 20Ni-7Ba / CeO2 catalyst supported on CeO2 nanospheres demonstrates superior ammonia decomposition conversion and hydrogen production rates, likely due to the larger specific surface area and more dispersed active metal of the CeO2 nanosphere support.

[0131] As shown in the comprehensive analysis of the data in Tables 2 and 3, the 20Ni-7Ba / CeO2 catalyst with in-situ formed BaCeO3 exhibits the best ammonia decomposition conversion rate, and its hydrogen production rate can reach 28.8 mmol·g at 500℃. cat −1 ·min −1 .

[0132] Experimental Example 2: This experimental example tested the long-term stability of the 20Ni-7Ba / CeO2 catalyst prepared in Example 1.

[0133] Experimental Procedure: Long-term stability tests were conducted in a vertical fixed-bed reactor. 25 mg of the ammonia decomposition catalyst (20-40 mesh) prepared in the above examples and comparative examples was mixed with 500 mg of quartz sand (20-40 mesh) and then loaded into a quartz reaction tube with an inner diameter of 8 mm. Before the formal catalytic test, the catalyst was first activated at 600℃ for 1 h in a pure NH3 atmosphere (25 mL / min), then cooled to 550℃ for a 100 h stability test, and then cooled to 500℃ for another 100 h stability test (GHSV = 60,000 mL·g). cat -1 ·h -1 GHSV is an abbreviation for Gas Hourly Space Velocity, which refers to the hourly space velocity of gas.

[0134] Test results are as follows Figure 6 As shown, during the stability tests at 550℃ and 500℃ for 100 h each, the activity of 20Ni-7Ba / CeO2 prepared in Example 1 of this invention decreased by only about 3% (the activity decreased from 95.1% to 91.3% during the 100 h stability test at 550℃, and from 51.2% to 47.5% during the 100 h stability test at 500℃), demonstrating excellent stability.

[0135] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent, characterized in that, Includes the following steps: Preparation of S1 and CeO2 nanosphere carriers: 2.0 g of cerium nitrate hexahydrate was weighed into a 100 mL polytetrafluoroethylene liner, followed by the addition of 2 mL of high-purity water, 52 mL of ethylene glycol, and 2 mL of glacial acetic acid. The mixture was stirred for 30 min. After stirring, the liner was placed in a stainless steel reactor, and the oven temperature was set to 180℃. The reaction was carried out for 200 min. After the solvothermal reaction, the obtained product was centrifuged and washed in a centrifuge tube. The product was washed 4 times with high-purity water and once with ethanol. After washing, the precipitate was dried in an oven at 70℃ for 6 h. After drying, the precipitate was ground into powder using an agate mortar and pestle. The powder was then heated to 400℃ in a tube furnace at a heating rate of 2℃ / min and calcined for 1 h to obtain CeO2 nanosphere carriers. Preparation of S2, 20Ni-7Ba / CeO2 catalyst: 0.5 g of CeO2 nanospheres were dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A. Then, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker. The 0.1 M Ni(NO3)2 solution was prepared by dissolving 2.91 g of Ni(NO3)2·6H2O in 100 mL of high-purity water, followed by adding 0.13 g of Ba(NO3)2 to the beaker containing the Ni(NO3)2 solution. The mixture was ultrasonically stirred at room temperature until fully mixed, denoted as solution B. Solution B was then added dropwise to solution A, while simultaneously adding 20 mL of 0.5 M Na2CO3 solution to maintain the pH of the entire system at 9. After the addition was complete, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, 1 The sample was filtered with high-purity water of L and dried at 70℃ for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2℃ / min to 400℃ for 4 h. The final product was denoted as 20Ni-7Ba / CeO2. S3. In the catalyst performance test, 50 mg of the ammonia decomposition catalyst (20-40 mesh) prepared above was mixed with 500 mg of quartz sand (20-40 mesh), and then loaded into a quartz reaction tube with an inner diameter of 8 mm. Before the catalytic test, the catalyst was first activated at 600℃ for 1 h in a pure NH3 atmosphere, and then the ammonia decomposition conversion rate was tested between 450-600℃. Conversion rate data were collected at 50℃, GHSV = 30,000 mL·gcat. -1 ·h -1 GHSV is an abbreviation for Gas Hourly Space Velocity, which refers to the hourly space velocity of gas.

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