A core-shell type barium-cobalt@ceria catalyst, a preparation method and application thereof

Abstract

The application discloses a core-shell type barium-cobalt@cerium oxide catalyst and a preparation method and application thereof. The preparation process of the barium-cobalt@cerium oxide catalyst is as follows: ammonia water is added dropwise into a mixed solution of citric acid, cerium nitrate, cobalt nitrate and barium acetate until the mixed solution is neutral, then the mixed solution is placed into an oil bath pot and heated and stirred until a sol-gel state is formed, and finally high-temperature calcination and reduction are carried out. The non-noble metal catalyst prepared by the sol-gel method can efficiently catalyze and promote hydrogen production by solar ammonia decomposition at low temperature, and has great industrial application significance.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and application technology, specifically relating to a core-shell type barium-cobalt@cerium oxide catalyst, its preparation method, and its application as a catalyst in solar ammonia decomposition for hydrogen production. Background Technology

[0002] Hydrogen energy, as a zero-carbon, renewable, and high-energy-density secondary energy source, holds significant strategic importance in achieving energy structure transformation and carbon neutrality goals. However, the storage and transportation of hydrogen face harsh conditions such as high pressure and low temperature, severely restricting the large-scale utilization of hydrogen energy. Ammonia (NH3), due to its high volumetric hydrogen density (17.6 wt%), easy liquefaction, and mature transportation and storage system, is considered a highly promising hydrogen carrier. Ammonia decomposition can enable on-demand hydrogen production, making it a key component in green hydrogen energy systems.

[0003] Currently, the most active catalysts for ammonia decomposition are ruthenium-based catalysts, which can achieve high conversion rates at relatively low temperatures. However, the scarcity, high price, and complex preparation of ruthenium resources significantly limit its industrial application. Therefore, the development of efficient, stable, and low-cost non-precious metal catalysts has become a research hotspot. Traditional transition metal catalysts such as Ni, Co, and Fe exhibit certain activity in ammonia decomposition, but they suffer from problems such as insufficient reaction activation, particle sintering, and poor long-term stability under low-temperature conditions.

[0004] To overcome the aforementioned shortcomings, this invention has gradually turned its attention to bimetallic and composite oxide systems. The electronic synergy between the two transition metals can effectively optimize the metal-nitrogen bond breaking pathway and improve the ammonia decomposition rate; while rare earth oxides (such as CeO2) have excellent oxygen storage and release capabilities and reversible CeO2 decomposition. 3+ / Ce 4+ The conversion properties can stabilize the active metal component and regulate the surface electronic structure during the reaction, thereby enhancing catalytic performance. In addition, alkaline earth metals (such as Ba) can act as electron donors, further regulating the electron density on the metal surface, promoting the activation and dissociation of NH bonds, and improving the reaction kinetics at low temperatures, but there are currently no related reports.

[0005] Based on this, this invention constructs a core-shell barium-cobalt@cerium oxide catalyst, utilizing the oxygen vacancy regulation and electron migration characteristics of the CeO2 shell to achieve high dispersion of Co species and interfacial electronic synergy. Simultaneously, the introduction of Ba element enhances electron supply and optimizes the ammonia decomposition reaction pathway, thereby significantly improving the catalyst's activity and stability under low-temperature conditions. This catalytic system provides a new approach and technical route for the design of low-cost, high-performance non-precious metal ammonia decomposition catalysts. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a low-cost, high-performance core-shell barium-cobalt@cerium oxide catalyst, its preparation method, and its applications. The preparation method of the core-shell barium-cobalt@cerium oxide catalyst provided by this invention is highly efficient, and the resulting catalyst is a core-shell non-precious metal catalyst with high ammonia decomposition activity, capable of efficiently catalyzing the decomposition of ammonia to hydrogen under low-temperature conditions.

[0007] This invention provides a method for preparing a core-shell type barium-cobalt@cerium oxide catalyst, which specifically includes the following steps: 1) Dissolve citric acid, cerium nitrate, cobalt nitrate and barium acetate in deionized water in sequence and stir until completely dissolved. Adjust the pH of the resulting solution to 7 with ammonia. 2) The solution from step 1) is placed in an oil bath and heated and stirred until it reaches a sol-gel state, and then calcined at high temperature to obtain the catalyst precursor xBa-yCo@CeO2 powder; 3) The catalyst precursor xBa-yCo@CeO2 powder obtained in step 2) is placed in a quartz reaction tube and calcined at high temperature in a tube furnace under hydrogen atmosphere to obtain a core-shell type barium-cobalt@cerium oxide catalyst, namely xBa-yCo@CeO2 catalyst, x=0.05-0.45, y=0.5-6.

[0008] Furthermore, the present invention also specifies that the molar ratio of cobalt to cerium in the catalyst precursor xBa-yCo@CeO2 in step 2) is 0.5-6:1, preferably 1-4:1, and most preferably 2:1; that is, y=0.5-6, preferably 1-4, and most preferably 2.

[0009] Furthermore, the present invention further specifies that the molar ratio of barium to cerium in the catalyst precursor xBa-yCo@CeO2 in step 2) is 0.05-0.45:1, preferably 0.15-0.35:1, and most preferably 0.25:1; that is, x = 0.05-0.45, preferably 0.15-0.35, and most preferably 0.25.

[0010] Furthermore, the present invention also specifies that the oil bath temperature in step 2) is 95-100℃; during high-temperature calcination, the calcination temperature is increased to 400-500℃ at a rate of 5℃ / min, and the calcination time is 4-6 hours.

[0011] Furthermore, the present invention further specifies that the hydrogen environment in step 3) is a pure hydrogen atmosphere with a flow rate of 20 ml / min; the tube furnace is heated to 400-600℃ at a heating rate of 5℃ / min, and the calcination time is 1-2h.

[0012] Furthermore, the present invention also specifies that the particle size of the xBa-yCo@CeO2 catalyst is less than 40 micrometers.

[0013] Furthermore, the present invention also defines a core-shell barium-cobalt@cerium oxide catalyst obtained by a defined preparation method, having the structural formula xBa-yCo@CeO2, where x=0.05-0.45; y=0.5-6.

[0014] Furthermore, the present invention also specifies the application of the core-shell barium-cobalt@cerium oxide catalyst in the solar ammonia decomposition hydrogen production reaction, specifically: the solar ammonia decomposition hydrogen production reaction is as follows: the core-shell barium-cobalt@cerium oxide catalyst is added to a quartz reaction tube, wrapped with quartz wool, placed under a solar simulator, and ammonia gas is introduced under sealed conditions to carry out the reaction, the reaction temperature is 350-600℃, and the ammonia gas pressure is 0.1MPa.

[0015] By adopting the above technical solution, the present invention has the following advantages compared with the prior art: 1) The core-shell structured barium-cobalt@cerium oxide catalyst developed in this invention constructs the core-shell structure through a combination of sol-gel method and calcination. Based on the fundamental principle of alkali metal modification, it utilizes the oxygen vacancy regulation and electron migration characteristics of the CeO2 shell to achieve high dispersion of Co species and interfacial electron synergy. Simultaneously, barium is used as a promoter, and Ba element is introduced to enhance electron supply and optimize the ammonia decomposition reaction pathway, thereby significantly improving the catalyst's activity and stability under low-temperature conditions and enhancing its ammonia decomposition performance at low temperatures. It can efficiently catalyze the ammonia decomposition reaction to produce hydrogen at relatively low temperatures. This catalyst exhibits excellent catalytic activity, enabling ammonia decomposition at 350℃ and 0.1 MPa, and achieving 100% ammonia decomposition conversion at 550℃ and 0.1 MPa. Compared to other non-precious metal catalysts reported in the literature, which typically require reaction conditions above 800℃ to achieve similar catalytic effects, this catalyst can efficiently catalyze ammonia decomposition to produce hydrogen at low temperatures, possessing significant industrial application value. This catalytic system provides a new approach and technical route for the design of low-cost, high-performance non-precious metal ammonia decomposition catalysts. 2) In the preparation of the catalyst of the present invention, staged heating is adopted during calcination to improve the activity and stability of the catalyst under low temperature conditions, so as to make the ammoniation reaction more complete; 3) Through experiments comparing the effects of different Ba and cobalt doping amounts on improving the ammonia decomposition activity of the barium-cobalt@cerium oxide catalyst, this invention found that the ammonia decomposition activity was best when the ratio of barium, cobalt, and cerium was 0.25:2:1. Attached Figure Description

[0016] Figure 1 These are TEM images of the catalysts in Examples 43-48 of this invention; Figure 2 These are TEM images of the catalysts in Examples 61-66 of this invention; Figure 3The XRD patterns are of the catalysts in Examples 1-6, 7-12, 13-18, 19-24, and 25-30 of this invention. Figure 4 The XRD patterns are of the catalysts in Examples 31-36, 36-42, 43-48, 49-54, 55-60, and 61-66 of this invention. Figure 5 The graph shows the ammonia decomposition conversion rate of the catalysts in Examples 1-6, 7-12, 13-18, 19-24, and 25-30 of this invention. Figure 6 The graph shows the ammonia decomposition conversion rate of the catalysts in Examples 31-36, 37-42, 43-48, 49-54, 55-60, 61-66, 67-72, 73-78, 79-84, and 85-90 of this invention. Detailed Implementation

[0017] The following examples illustrate the content of the present invention, but the scope of protection of the present invention is not limited thereto: Unless otherwise specified, the equipment, reagents, processes, parameters, etc. involved in this invention are all conventional equipment, reagents, processes, parameters, etc., and no further examples are provided. All ranges listed in this invention include all point values ​​within that range. The terms "approximately," "about," or "around" used in this invention refer to a range or value within ±20%.

[0018] In this invention, "room temperature" refers to the normal ambient temperature, which can be 10 to 30°C.

[0019] Examples 1-6: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), and 0.6705g (0.0023mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0. 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a uniform sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 h from room temperature at a rate of 5°C / min to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor 0.5Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.5Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.5Co@CeO2.

[0020] Kinetics of hydrogen production from ammonia decomposition: 0.05 g of 0.5Co@CeO2 catalyst was added to a quartz reaction tube. The catalyst position in the reaction tube was fixed with quartz wool to ensure stable temperature inside the quartz tube during the reaction. Then, ammonia gas (GHSV = 6000 ml / min) was introduced into the quartz reaction tube at a flow rate of 25 ml / min. NH3 / g cat The temperature inside the quartz reaction tube was adjusted to 350℃, 400℃, 450℃, 500℃, 550℃, and 600℃ respectively by adjusting the tubular furnace. After the outlet flow controller reading stabilized, the data was recorded. The ammonia conversion rate was calculated according to the formula (0.5 * outlet flow rate / inlet flow rate) * 100%, and the results are listed in Table 1, serial numbers 1 to 6.

[0021] Examples 7-12: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), and 1.3410g (0.0046mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0022] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled Co@CeO2.

[0023] Ammonia decomposition hydrogen production kinetics experiment: 0.05g Co@CeO2 catalyst was added to a quartz reaction tube, and the operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated, and the results are listed in Table 1, serial numbers 7 to 12.

[0024] Examples 13-18: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), and 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0025] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor 2Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 2Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 2Co@CeO2.

[0026] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 2Co@CeO2 catalyst was added to a quartz reaction tube, and the operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated, and the results are listed in Table 1, serial numbers 13 to 18.

[0027] Examples 19-24: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), and 5.3640g (0.0184mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0028] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor 4Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 4Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 4Co@CeO2.

[0029] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 4Co@CeO2 catalyst was added to a quartz reaction tube, and the operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated, and the results are listed in Table 1, serial numbers 19 to 24.

[0030] Examples 25-30: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), and 8.0461g (0.0276mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0031] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 h, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor 6Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 6Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 6Co@CeO2.

[0032] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 6Co@CeO2 catalyst was added to a quartz reaction tube, and the operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated, and the results are listed in Table 1, serial numbers 25 to 30.

[0033] Examples 31-36: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.0587g (0.0002mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0034] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.05Ba-2Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.05Ba-2Co@CeO2 catalyst with a final particle size less than 40 μm. The obtained catalyst was a light brown powder, designated as 0.05Ba-2Co@CeO2.

[0035] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.05Ba-2Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 31 to 36.

[0036] Examples 37-42: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.1762g (0.0007mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0. 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.15Ba-2Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.15Ba-2Co@CeO2 catalyst with a final particle size less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.15Ba-2Co@CeO2.

[0037] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.15Ba-2Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 37 to 42.

[0038] Examples 43-48: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.2938g (0.0012mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0039] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.25Ba-2Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-2Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.25Ba-2Co@CeO2.

[0040] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-2Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 43 to 48.

[0041] Examples 49-54: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.4113g (0.0016mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0042] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.35Ba-2Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.35Ba-2Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.35Ba-2Co@CeO2.

[0043] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.35Ba-2Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 49 to 54.

[0044] Examples 55-60: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 2.6820g (0.0092mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.5288g (0.0021mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0045] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.45Ba-2Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.45Ba-2Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.45Ba-2Co@CeO2.

[0046] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.45Ba-2Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 55 to 60.

[0047] Examples 61-66: Preparation method of core-shell barium-cobalt@cerium oxide catalyst Dissolve 1.6547 g (0.0156 mol) of anhydrous sodium carbonate (Na2CO3, 99.99%) in 25 ml of water. Heat the solution to 40 °C and stir until fully incorporated. Slowly add the solution to the nitrate solution and stir at room temperature for 1 hour. Wash with deionized water until pH=7.

[0048] 2) The solution from step 1) was placed in a drying oven and dried at 100℃ for 12 hours. Then it was transferred to a muffle furnace and calcined at 550℃ for 3 hours, starting from room temperature and increasing the temperature by 5℃ / min, to obtain a gray-black solid powder. 0.4074 g (0.0016 mol) of barium nitrate (Ba(NO3)2, 99.5%) was weighed and placed in a beaker containing 25 ml of deionized water. The resulting gray-black solid powder was immersed in the barium nitrate aqueous solution. After immersion, it was placed in a drying oven and dried at 120℃ overnight. Then it was transferred to a muffle furnace and calcined at 550℃ for 3 hours, starting from room temperature and increasing the temperature by 5℃ / min. The obtained powder was ground and sieved through a 500-mesh sieve to obtain 0.25Ba-2Co / CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-2Co / CeO2 catalyst with a final particle size less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.25Ba-2Co / CeO2.

[0049] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-2Co / CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 61 to 66.

[0050] Examples 67-72: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 0.6705g (0.0023mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.2938g (0.0012mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0051] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 h, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain a catalyst precursor 0.25Ba-0.5Co@CeO2 powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-0.5Co@CeO2 catalyst with a final particle size less than 40 μm. The obtained catalyst is a light brown powder, labeled 0.25Ba-0.5Co@CeO2.

[0052] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-0.5Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 67 to 72.

[0053] Examples 73-78: Preparation methods of core-shell barium-cobalt@cerium oxide catalysts 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 1.3410g (0.0046mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.2938g (0.0012mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0054] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 h, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.25Ba-Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400-600 °C at a rate of 5 °C / min, and maintained at this temperature for 1-2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst is a light brown powder, labeled 0.25Ba-Co@CeO2.

[0055] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 73 to 78.

[0056] Examples 79-84: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 5.3641g (0.0184mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.2938g (0.0012mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0057] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.25Ba-4Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-4Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst was a light brown powder, labeled 0.25Ba-4Co@CeO2.

[0058] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-4Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 79 to 84.

[0059] Examples 85-90: Preparation method of core-shell barium-cobalt@cerium oxide catalyst 1) Weigh 5.0000g (0.0200mol) citric acid (C6H8O7, ≥99.5%), 2.0000g (0.0046mol) cerium nitrate hexahydrate (Ce(NO3)3·6H2O, 99.99%), 8.0461g (0.0276mol) cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), and 0.2938g (0.0012mol) barium acetate (C4H6O4·Ba, 99%), and add them sequentially to a beaker containing 20 ml of deionized water. Stir until completely dissolved to obtain a mixed solution. Slowly add ammonia water to the mixed solution to adjust the pH to 7.0.

[0060] 2) The solution from step 1) was placed in an oil bath and stirred at 100°C to form a homogeneous sol. The resulting sol was then transferred to a muffle furnace and calcined at 450°C for 6 hours, increasing the temperature from room temperature to 5°C / min, to obtain a gray-black solid powder. The powder was then ground and sieved through a 500-mesh sieve to obtain 0.25Ba-6Co@CeO2 catalyst precursor powder with a particle size of less than 40 μm. 3) The precursor powder from step 2) was placed in a quartz reaction tube and loaded into a tube furnace. Under a pure hydrogen atmosphere (flow rate 20 ml / min), the temperature was increased to 400 °C at a rate of 5 °C / min and maintained at this temperature for 2 h. The resulting powder was ground and passed through a 500-mesh sieve to obtain a 0.25Ba-6Co@CeO2 catalyst with a final particle size of less than 40 μm. The obtained catalyst is a light brown powder, labeled 0.25Ba-6Co@CeO2.

[0061] Ammonia decomposition hydrogen production kinetics experiment: 0.05g of 0.25Ba-6Co@CeO2 catalyst was added to a quartz reaction tube. The operation process was the same as in Examples 1 to 6. The ammonia conversion rate was calculated and the results are listed in Table 1, serial numbers 85 to 90.

[0062] Table 1 Ammonia decomposition conversion rate in each example , , , ,

[0063] In the examples, the core-shell xBa-yCo@CeO2 catalyst and the conventional 0.25Ba-2Co / CeO2 catalyst were prepared using the sol-gel method specified in this invention and the conventional co-precipitation method, respectively. In the preparation method of this invention, citric acid (as a chelating agent in the sol-gel process) is added and the pH is adjusted to 7 (achieved by adding ammonia water to make CeO2 more soluble in solubles). 3+ The slow oxidation of ions to CeO2 nanoparticles is one of the two key factors for achieving the core-shell structure. Traditional Ba-Co / CeO2 catalysts require a co-precipitation step to synthesize Co / CeO2 and an impregnation step to support Ba. Figure 1 , Figure 2 The images are transmission electron microscope (TEM) images of 0.25Ba-2Co@CeO2 obtained in Examples 43-48 (sol-gel method) and 0.25Ba-2Co / CeO2 obtained in Examples 61-66 (coprecipitation method). Figure 1As can be seen from the image of the catalyst, the reduced Ba-Co@CeO2 catalyst exhibits a core-shell structure: cobalt nanoparticles uniformly form the core, and the surface is wrapped by a CeO2 shell. Figure 2 The reduced Ba-Co / CeO2 catalyst exhibits a disordered distribution of Ba, Co, and CeO2, without forming a coating structure. It shows a typical morphology of Co loaded at the edge of CeO2. In addition, Co and CeO2 are tightly stacked, and the number of cobalt nanoparticles overlaps even more.

[0064] Figure 3 , Figure 4 The figures show the XRD patterns of 0.25 Ba-2Co / CeO2 in Examples 1-30 (yCo@CeO2), Examples 31-60 (xBa-2Co@CeO2), and Examples 61-66 (0.25Ba-2Co / CeO2). The figures show that in the reduced yCo@CeO2 catalyst, the XRD pattern clearly indicates the presence of the metallic Co phase through the Co (111) characteristic peak at 44.23°, while the characteristic peaks of CeO2 remain unchanged after reduction. With increasing Co:Ce ratio, the intensity of the CeO2 diffraction peaks at 28.49°, 36.89°, 47.53°, and 55.66° decreases, while the Co diffraction peak at 44.23° gradually increases. For the Ba-Co@CeO2 catalyst, no Ba crystalline phase was observed, which is attributed to the high dispersion of Ba on the Co@CeO2 surface.

[0065] Figure 5 The figures show the ammonia decomposition conversion rates of the yCo@CeO2 catalysts in Examples 1-30 of the invention. It can be seen from the figures that, for different Co:Ce ratios of the yCo@CeO2 catalysts, the 2Co@CeO2 catalyst exhibits the highest catalytic activity. This is because, based on the XRD results of the yCo@CeO2 catalyst and the Scherer equation, it can be known that the particle size of the yCo@CeO2 catalyst changes with the Co:Ce ratio, and a minimum particle size occurs near Co:Ce=2.

[0066] Figure 6The figures show the ammonia decomposition conversion rates of xBa-2Co@CeO2 catalysts with different Ba doping amounts in Examples 31-60, the conventional 0.25Ba-2Co / CeO2 catalyst in Examples 61-66, and 0.25Ba-yCo@CeO2 catalysts with different Co amounts in Examples 67-90. The figures show that the appropriate addition of Ba significantly improves the ammonia decomposition activity of the 2Co@CeO2 catalyst, with the 0.25Ba-2Co@CeO2 catalyst in Examples 43-48 exhibiting the best catalytic activity at low temperatures. Furthermore, comparing the data from Examples 49-54 with those from Examples 55-60 reveals that excessive Ba modification inhibits the ammonia decomposition activity of the 2Co@CeO2 catalyst. This is because the excess Ba exists on the catalyst surface, covering the active sites. In addition, compared to the conventional 0.25Ba-2Co / CeO2 catalyst, the core-shell Ba-Co@CeO2 catalyst shows a significant improvement in ammonia decomposition catalytic activity.

Claims

1. A method for preparing a core-shell type barium-cobalt@cerium oxide catalyst, characterized in that... Includes the following steps: 1) Dissolve citric acid, cerium nitrate, cobalt nitrate and barium acetate in deionized water in sequence and stir until completely dissolved. Adjust the pH of the resulting solution to 7 with ammonia. 2) The solution from step 1) is placed in an oil bath and heated and stirred until it reaches a sol-gel state, and then calcined at high temperature to obtain the catalyst precursor xBa-yCo@CeO2 powder; 3) The catalyst precursor xBa-yCo@CeO2 powder obtained in step 2) is placed in a quartz reaction tube and calcined at high temperature in a tube furnace under hydrogen atmosphere to obtain a core-shell type barium-cobalt@cerium oxide catalyst, namely xBa-yCo@CeO2 catalyst, x=0.05-0.45, y=0.5-6.

2. The method for preparing a core-shell barium-cobalt@cerium oxide catalyst according to claim 1, characterized in that... In step 2), the molar ratio of cobalt to cerium in the catalyst precursor xBa-yCo@CeO2 is 0.5-6:1, preferably 1-4:1, and optimally 2:1; that is, y=0.5-6, preferably 1-4, and optimally 2.

3. The method for preparing a core-shell barium-cobalt@cerium oxide catalyst according to claim 1, characterized in that... In step 2), the molar ratio of barium to cerium in the catalyst precursor xBa-yCo@CeO2 is 0.05-0.45:1, preferably 0.15-0.35:1, and optimally 0.25:1; that is, x = 0.05-0.45, preferably 0.15-0.35, and optimally 0.

25.

4. The method for preparing a core-shell barium-cobalt@cerium oxide catalyst according to claim 1, characterized in that... In step 2), the oil bath temperature is 95-100℃; during high-temperature calcination, the calcination temperature is increased to 400-500℃ at a rate of 5℃ / min, and the calcination time is 4-6 hours.

5. The method for preparing a core-shell barium-cobalt@cerium oxide catalyst according to claim 1, characterized in that... In step 3), the hydrogen environment is a pure hydrogen atmosphere with a flow rate of 20 ml / min; the tube furnace is heated to 400-600℃ at a heating rate of 5℃ / min, and the calcination time is 1-2h.

6. A method for preparing a core-shell barium-cobalt@cerium oxide catalyst according to any one of claims 1-5, characterized in that... The xBa-yCo@CeO2 catalyst has a particle size of less than 40 micrometers.

7. A core-shell barium-cobalt@cerium oxide catalyst prepared according to the method described in claim 1, having the structural formula xBa-yCo@CeO2, wherein x = 0.05-0.45; y = 0.5-6.

8. The application of the core-shell barium-cobalt@cerium oxide catalyst according to claim 7 in the solar ammonia decomposition hydrogen production reaction.

9. The application according to claim 8, characterized in that... The solar-powered ammonia decomposition hydrogen production reaction is as follows: a core-shell type barium-cobalt@cerium oxide catalyst is added to a quartz reaction tube, wrapped with quartz wool, and placed under a solar simulator. Ammonia gas is introduced under sealed conditions to carry out the reaction at a temperature of 350-600℃ and an ammonia gas pressure of 0.1MPa.

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