CoBaTiO3 ammonia decomposition hydrogen production catalyst, preparation method and application

Abstract

The application belongs to the technical field of hydrogen energy catalysis and functional materials, and particularly relates to a CoBaTiO3 ammonia decomposition hydrogen production catalyst, a preparation method and application. CoBaTiO3 is prepared by a hydrothermal-impregnation-reduction route, and metal Co is used as a catalytic center. By regulating the dispersion state, reduction behavior, oxygen vacancy concentration and hydrogen adsorption and desorption capacity of Co species, the dispersion stability of Co under high-temperature reaction conditions of 600 DEG C to 650 DEG C is improved, so that the ammonia decomposition activity, high-temperature stability and anti-sintering performance of the cobalt-based catalyst are improved. The Co / BaTiO3 in the application not only improves the ammonia decomposition activity, high-temperature stability and anti-sintering performance of the cobalt-based catalyst, but also realizes ammonia decomposition hydrogen production in different environments of thermal catalysis and photo-thermal catalysis.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy catalysis and functional materials technology, specifically relating to a CoBaTiO3 ammonia decomposition hydrogen production catalyst, its preparation method, and its application. Background Technology

[0002] Currently, cobalt-based catalysts have good application potential in replacing precious metal ammonia decomposition catalysts due to their low cost and abundant reserves. They are frequently used in the ammonia decomposition hydrogen production process in existing technologies.

[0003] Traditional cobalt-based catalysts are typically prepared using metal oxides such as Al₂O₃, SiO₂, or carbon materials as supports, with cobalt atoms loaded onto the support via adsorption or sol-gel methods. The adsorption method involves dissolving cobalt salts in water or organic solvents, impregnating the support, and then calcining. The sol-gel method involves mixing tetraethyl orthosilicate and cobalt salts to form a sol, followed by gelation, aging, drying, and then reduction with hydrogen to obtain a Co / SiO₂ catalyst. However, these preparation methods not only suffer from particle agglomeration but also readily form cobalt aluminates, resulting in poor reducibility of the prepared cobalt-based catalyst. Furthermore, the choice of support weakens the cobalt-support interaction, further affecting the catalyst's activity in later use. It can be seen that cobalt-based catalysts prepared using existing technologies suffer from particle agglomeration, weak metal-support interactions, and insufficient stability of active sites, leading to deactivation during long-term operation. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a CoBaTiO3 ammonia decomposition hydrogen production catalyst, its preparation method, and its applications. CoBaTiO3 is prepared using a simple hydrothermal-impregnation method. With Co as the catalytic center, the ammonia decomposition activity, high-temperature stability, and anti-sintering performance of the cobalt-based catalyst are simultaneously improved by controlling the dispersion state, reduction behavior, oxygen vacancy concentration, and hydrogen adsorption / desorption capacity of Co. Furthermore, ammonia decomposition for hydrogen production is achieved under different thermal and photothermal catalytic environments.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] The first aspect of this invention provides a method for preparing a CoBaTiO3 ammonia decomposition hydrogen production catalyst, comprising the following steps: Using tetrabutyl titanate and barium nitrate as precursors, the reaction was carried out by hydrothermal method at 180℃~185℃ for 24h~26h, followed by calcination to obtain BaTiO3; wherein the mass ratio of tetrabutyl titanate to barium nitrate was 1.4594~1.46:1.12~1.1208. Soluble cobalt salts were impregnated onto a BaTiO3 support and then calcined to obtain a CoBaTiO3 precursor catalyst; wherein the mass ratio of soluble cobalt salts to BaTiO3 was 0.872~0.874:0.998~1. The CoBaTiO3 precursor catalyst was reduced in situ in a reducing atmosphere to obtain the CoBaTiO3 ammonia decomposition hydrogen production catalyst.

[0007] This invention employs a hydrothermal-impregnation-reduction route, which is more conducive to forming a close interfacial structure between Co and BaTiO3, enhancing the metal-support interaction, lowering the reduction energy barrier of Co oxide, and improving the dispersion stability of Co under high-temperature reaction conditions of 600℃~650℃. The reduction peak of Co species in the CoBaTiO3 system shows a significant low-temperature shift, indicating a stronger metal-support interaction between Co and BaTiO3. The prepared CoBaTiO3 system serves as a thermocatalytic or photothermal catalyst for ammonia decomposition, and its mechanism relies on the catalytic ability of Co metal active sites for NH3 adsorption, NH bond breaking, surface dehydrogenation, and hydrogen generation.

[0008] In another preferred embodiment, the soluble cobalt salt is cobalt nitrate. In this invention, only cobalt nitrate is used as the cobalt ion precursor to avoid impurities or side reactions generated by other soluble cobalt salts during impregnation, calcination, and reduction processes, thereby ensuring that the catalyst forms uniformly dispersed metallic Co active centers and improving the catalytic activity and stability of ammonia decomposition.

[0009] In another preferred embodiment, the impregnation method refers to impregnating cobalt nitrate and BaTiO3 in an aqueous environment for 5 to 6 hours. Specifically, after impregnation, the solid is separated and dried at 120°C to 140°C for 12 to 14 hours.

[0010] In another preferred embodiment, the reducing atmosphere comprises hydrogen and an inert carrier gas; The inert carrier gas is selected from one or more of nitrogen, argon, and helium; In the reducing atmosphere, hydrogen accounts for 5% to 5.1% of the volume.

[0011] In another preferred embodiment, the calcination temperature is 600℃~650℃ and the time is 5h~6h; The roasting temperature is 500℃~550℃, and the time is 3h~4h.

[0012] In another preferred embodiment, the reduction temperature is 500℃~550℃ and the time is 1h~2h.

[0013] The second aspect of the present invention provides a CoBaTiO3 ammonia decomposition hydrogen production catalyst prepared by the aforementioned method, wherein the Co / BaTiO3 ammonia decomposition hydrogen production catalyst is used in thermocatalysis or photothermal synergistic catalysis for ammonia decomposition hydrogen production.

[0014] In another preferred embodiment, the mass percentage of Co atoms in the CoBaTiO3 ammonia decomposition hydrogen production catalyst is 14.5% to 15%.

[0015] The third aspect of the present invention provides the application of the CoBaTiO3 ammonia decomposition hydrogen production catalyst in ammonia decomposition hydrogen production, wherein the photothermal response temperature of the CoBaTiO3 photothermal catalyst is 400℃~650℃.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the strong metal-support interaction formed between the BaTiO3 perovskite support and Co, employing a hydrothermal-impregnation-reduction route. This approach is more conducive to forming a tight interfacial structure between Co and BaTiO3, enhancing the metal-support interaction, lowering the reduction energy barrier of Co oxides, and improving the dispersion stability of Co species under high-temperature reaction conditions of 600℃~650℃. This allows the active component Co ions to be reduced to metallic Co active centers at temperatures of 500℃~550℃. Simultaneously, this interaction facilitates high dispersion of Co on the BaTiO3 surface, inhibiting the migration and aggregation of active particles under high-temperature conditions, thereby improving the initial activity and long-term operational stability of the catalyst in ammonia decomposition. The CoBaTiO3 system of this invention can further improve ammonia decomposition efficiency under photothermal synergistic catalysis. This characteristic makes it not only applicable to traditional thermocatalytic ammonia decomposition for hydrogen production but also extend to the field of photothermal synergistic catalysis, providing a new solution for low-energy-consumption, high-efficiency ammonia decomposition for hydrogen production. The CoBaTiO3 prepared by the method of this invention has an NH3 conversion rate of 82.1% at 600℃ and 99% at 650℃, and the NH3 conversion rate is maintained at 85%~90% during a 50h continuous reaction.

[0017] Compared with the adsorption or sol-gel methods in the prior art, the hydrothermal-impregnation-reduction route adopted in this invention is more conducive to the formation of a stable interface structure between Co and BaTiO3. This structure effectively inhibits the sintering and deactivation of the Co active component under high-temperature reaction conditions, enabling the catalyst to maintain a high NH3 conversion rate and good morphological stability even after long-term continuous operation, overcoming the technical defect of traditional cobalt-based catalysts being prone to deactivation during long-term operation. Attached Figure Description

[0018] Figure 1XRD patterns for different catalysts.

[0019] Figure 2 The figures show the structural characterization of different catalysts; a is the SEM image of CoBaTiO3, b is the SEM image of CuBaTiO3, c is the SEM image of BaTiO3; d is the EDS energy dispersive spectroscopy analysis result of the CoBaTiO3 catalyst; e is the spectrum corresponding to d.

[0020] Figure 3 H2-TPR curves of CoBaTiO3 and BaTiO3 catalysts.

[0021] Figure 4 H2-TPD curves of CoBaTiO3, CuBaTiO3 and BaTiO3 catalysts.

[0022] Figure 5 The figures show the performance comparison results of different catalysts; a is the NH3 conversion result, b is the H2 yield result; in the figure, 1 is CoBaTiO3, 2 is Cu / BaTiO3, 3 is BaTiO3, 4 is the blank control, and Black represents the blank control.

[0023] Figure 6 The diagrams show the structure of the CoBaTiO3 catalyst before and after the reaction; (a) before the reaction and (b) after the reaction. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Example 1: A method for preparing a CoBaTiO3 photothermal catalyst, comprising the following steps: S1. Using 1.4594 g tetrabutyl titanate and 1.1208 g barium nitrate as precursors, they were mixed in a 0.2 M, 50 mL NaOH solution and placed in a polytetrafluoroethylene-lined reactor. The mixture was then hydrothermally treated at 180 °C for 24 h. After cooling, the product was separated, washed until neutral pH=7, dried at 105 °C for 6 h, and then calcined at 600 °C in air for 5 h to obtain the BaTiO3 support.

[0027] S2. Dissolve 1g of BaTiO3 support and 0.872g of cobalt nitrate in water and impregnate for 6h. After impregnation, dry at 120℃ for 13h and calcine at 500℃ for 3h to obtain CoBaTiO3 precursor catalyst.

[0028] The S3 and CoBaTiO3 precursor catalysts were subjected to an in-situ reduction reaction at 500℃ in an H2 / Ar mixed atmosphere for 1 hour to form active metal Co sites, thus obtaining the CoBaTiO3 photothermal catalyst; wherein, the volume percentage of H2 in the H2 / Ar mixed atmosphere was 5%.

[0029] Example 2: A method for preparing a CoBaTiO3 photothermal catalyst, comprising the following steps: S1. Using 1.46 g tetrabutyl titanate and 1.12 g barium nitrate as precursors, they were mixed in a 0.2 M, 50 mL NaOH solution; the mixture was placed in a polytetrafluoroethylene-lined reactor and hydrothermally treated at 180 °C for 24 h; after cooling, the product was separated, washed until neutral pH=7, dried at 105 °C for 6 h, and then calcined at 600 °C in air atmosphere for 5 h to obtain BaTiO3 support.

[0030] S2. Dissolve 1g of BaTiO3 support and 0.872g of cobalt nitrate in water and impregnate for 6h. After impregnation, dry at 130℃ for 12h and calcine at 550℃ for 4h to obtain CoBaTiO3 precursor catalyst.

[0031] The S2 and CoBaTiO3 precursor catalysts were subjected to an in-situ reduction reaction at 520℃ in an H2 / Ar mixed atmosphere for 1 hour to form active metal Co sites, thus obtaining the CoBaTiO3 photothermal catalyst; wherein, the volume percentage of H2 in the H2 / Ar mixed atmosphere was 5.1%.

[0032] Example 3: A method for preparing a CoBaTiO3 photothermal catalyst, comprising the following steps: S1. Using 1.4598g of tetrabutyl titanate and 1.1203g of barium nitrate as precursors, they were mixed in a 0.2M NaOH solution with a volume of 50mL. The mixture was then placed in a polytetrafluoroethylene-lined reactor and hydrothermally treated at 180℃ for 24h. After cooling, the product was separated, washed until neutral pH=7, dried at 105℃ for 6h, and then calcined in air at 600℃ for 5h to obtain the BaTiO3 support.

[0033] S2. Dissolve 1g of BaTiO3 support and 0.873g of cobalt nitrate in water and impregnate for 6h. After impregnation, dry at 140℃ for 14h and calcine at 600℃ for 5h to obtain CoBaTiO3 precursor catalyst.

[0034] S3 and Co / BaTiO3 precursor catalysts were subjected to in-situ reduction reaction at 530℃ in an H2 / Ar mixed atmosphere for 1 hour to form active metal Co sites, thus obtaining CoBaTiO3 photothermal catalyst; wherein, the volume percentage of H2 in the H2 / Ar mixed atmosphere was 5%.

[0035] To illustrate the effect of CoBaTiO3, Co was replaced with Cu, and Cu / BaTiO3 was prepared using the same preparation method as in Example 1, as well as BaTiO3 alone was used in the experiment.

[0036] XRD patterns of different catalysts are as follows Figure 1 As shown, SEM results of the CoBaTiO3 photothermal catalyst prepared in Example 1 above indicate that... Figure 2 The CoBaTiO3 catalyst exhibits a relatively regular blocky morphology with a uniform particle size distribution. Co species are uniformly dispersed on the surface of the BaTiO3 support in the form of fine particles, and no obvious agglomeration was observed. After the reaction, the bulk morphology of the sample remained good, and no obvious structural collapse, sintering or detachment of active components was observed.

[0037] The H2-TPR results further indicate that... Figure 3 As shown, the reduction peak of Co species in CoBaTiO3 shifts towards lower temperatures, indicating a strong metal-support interaction between Co and BaTiO3, which is beneficial for the formation of stable and dispersed active centers.

[0038] The H2-TPD curve results are as follows: Figure 4 As shown, from Figure 4It can be seen that H2 adsorption and desorption at low temperatures are generally attributed to interactions with metal active sites, while the H2 desorption peak at high temperatures is related to hydrogen spillover from the metal species. Pure BaTiO3 only shows a weak hydrogen desorption peak in the low-temperature region of 100℃~200℃, indicating its weak hydrogen storage capacity and weak hydrogen adsorption. Compared with Cu / BaTiO3 and BaTiO3, the H2 desorption peak of CoBaTiO3 shifts to a lower temperature range of 150℃~350℃, indicating enhanced H2 adsorption and desorption capabilities. This phenomenon may be attributed to the lower reduction temperature of the catalyst, which increases the availability of surface Co active sites and increases the amount of H2 adsorbed. In addition, both catalysts show high-temperature desorption peaks above 700℃, attributed to the strong capture of hydrogen at oxygen vacancies or defects on the BaTiO3 support, possibly through direct adsorption or spillover from metal sites. The high-temperature desorption peak of CoBaTiO3 shifts to even higher temperatures, indicating that the combination of Co and BaTiO3 significantly promotes the formation of structural defects in the catalyst, leading to a more pronounced hydrogen spillover. Furthermore, it forms hydrogen adsorption sites of varying strengths, which is beneficial for the stable adsorption and activation of H2 intermediates in the ammonia decomposition reaction. Simultaneously, it promotes the migration and coupling of H species, preventing active sites from being poisoned by excessive H species, thereby accelerating the forward progression of the ammonia decomposition reaction. With Co species loading, increased H2 desorption is observed in both low and high temperature ranges, indicating that CoBaTiO3 possesses abundant Co active sites, promoting the effective absorption and release of H2, thus enhancing the performance of ammonia decomposition.

[0039] The obtained CoBaTiO3 catalyst was used in the ammonia decomposition to produce hydrogen, and in a fixed-bed ammonia decomposition reaction with pure NH3 and GHSV of 15000 mL·g. - ¹·h - ¹ Under the conditions of 400℃~650℃ and 50W xenon lamp illumination, the activity test was conducted.

[0040] The results are as follows Figure 5 As shown, CoBaTiO3 achieved an NH3 conversion rate of 82.1% at 600℃, while simultaneously producing hydrogen at a rate of 13.7 mmol·g⁻¹. - ¹·h - ¹; The NH3 conversion rate is approximately 99% at 650℃. After continuous reaction at 600℃ for 50 hours, the NH3 conversion rate remains at 85%~90%, indicating that the catalyst has good long-term stability.

[0041] The results above show that the CoBaTiO3 catalyst exhibits high NH3 conversion at higher temperatures and maintains high activity even after prolonged continuous operation. The catalyst bulk morphology remains well-preserved after the reaction, indicating excellent long-term stability. In this invention, the CoBaTiO3 catalyst maintained a stable NH3 conversion rate of 85%–90% after continuous reaction at 600℃ for 50 hours. SEM results before and after the reaction are shown below. Figure 6 As shown, from Figure 6 It can be seen that the Co species in the CoBaTiO3 catalyst are small and uniformly dispersed before the reaction, and the bulk morphology of the catalyst is well maintained after the reaction. No obvious structural collapse, sintering or shedding of active components is observed. Therefore, it can be used as a basis for its anti-sintering performance and high-temperature structural stability.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a CoBaTiO3 ammonia decomposition hydrogen production catalyst, characterized in that, Includes the following steps: Using tetrabutyl titanate and barium nitrate as precursors, the reaction was carried out by hydrothermal method at 180℃~185℃ for 24h~26h, followed by calcination to obtain BaTiO3; wherein the mass ratio of tetrabutyl titanate to barium nitrate was 1.4594~1.46:1.12~1.1208. Soluble cobalt salts were impregnated onto a BaTiO3 support and then calcined to obtain a CoBaTiO3 precursor catalyst; wherein the mass ratio of soluble cobalt salts to BaTiO3 was 0.872~0.874:0.998~1. The CoBaTiO3 precursor catalyst was reduced in situ in a reducing atmosphere to obtain the CoBaTiO3 ammonia decomposition hydrogen production catalyst.

2. The preparation method of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The soluble cobalt salt is cobalt nitrate.

3. The preparation method of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 2, characterized in that, The immersion method refers to immersing cobalt nitrate and BaTiO3 in an aqueous environment for 5 to 6 hours.

4. The preparation method of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The reducing atmosphere comprises hydrogen and an inert carrier gas; The inert carrier gas is selected from one or more of nitrogen, argon, and helium; In the reducing atmosphere, hydrogen accounts for 5% to 5.1% of the volume.

5. The preparation method of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The calcination temperature is 600℃~650℃, and the time is 5h~6h; The roasting temperature is 500℃~550℃, and the time is 3h~4h.

6. The preparation method of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that, The reduction temperature is 500℃~550℃, and the time is 1h~2h.

7. A CoBaTiO3 ammonia decomposition hydrogen production catalyst prepared by the method described in any one of claims 1 to 6, characterized in that, The CoBaTiO3 ammonia decomposition hydrogen production catalyst is used in thermocatalysis or photothermal synergistic catalysis of ammonia decomposition hydrogen production.

8. The CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 7, characterized in that, In the CoBaTiO3 ammonia decomposition hydrogen production catalyst, the mass percentage of Co atoms is 14.5% to 15%.

9. The application of the CoBaTiO3 ammonia decomposition hydrogen production catalyst according to claim 7 in ammonia decomposition hydrogen production, wherein the photothermal response temperature of the CoBaTiO3 photothermal catalyst is 400℃~650℃.

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