A CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane, and its preparation method and application

Abstract

The present invention belongs to the technical field of hydrogen storage materials, and specifically relates to a CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane, and its preparation method and application. The method comprises dispersing CeO2 powder in water, adding a cobalt source precursor and a platinum source precursor, ultrasonicating at room temperature to obtain a uniform mixed solution, and then adding sodium borohydride for reduction to obtain a CoPt / CeO2 composite nanocatalyst. The high performance of the CoPt / CeO2 composite nanocatalyst prepared by the present invention can be attributed to the small size of CoPt NPs, the alloying effect between Co and Pt, the abundant alkaline sites on the surface of CoPt / CeO, and the electron-metal-carrier interaction between CoPt NPs and CeO2 carriers. The method for preparing the catalyst of the present invention is simple to operate and low in cost. The obtained catalyst has the characteristics of small particle size, multiple catalytic active sites, and high catalytic activity and stability, and is a catalyst with great development prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage materials, and in particular relates to a CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane, and a preparation method and application thereof. Background Art

[0002] Hydrogen is widely considered a potential hydrogen carrier due to its high energy density, widespread availability, and environmental friendliness. However, finding safe and effective hydrogen storage and power generation materials remains one of the most challenging challenges on the road to a hydrogen-powered society. Chemical hydrogen storage materials have attracted considerable attention due to their high hydrogen content and mild dehydrogenation temperatures.

[0003] Hydrazine borane (HB, N2H4BH3) has recently been recognized as a promising candidate due to its stable and safe solid state at room temperature, very high hydrogen content (15.4 wt%), high solubility in water, and, in particular, the stability of its aqueous solution under ambient conditions. Using a suitable catalyst, N2H4BH3 can achieve 100% hydrogen utilization efficiency in aqueous solution after hydrolysis of the BH3 group (Equation 1) and decomposition of the N2H4 moiety (Equation 2). Theoretically, 1 mole of N2H4BH3 can produce 5 moles of H2 and 1 mole of N2. However, the N2H4 moiety can also incompletely decompose into NH3 and N2 (Equation 3). To maximize the effectiveness of N2H4BH3 as a hydrogen storage material, undesirable reaction pathways must be avoided.

[0004] N2H4BH3+ 3H2O → N2H4+ H3BO3+ 3H2(1)

[0005] N2H4→ N2+ 2H2(2)

[0006] 3N2H4→ 4NH3+ N2(3)

[0007] Ni-based bimetallic nanoparticles (NPs), particularly those combined with platinum (Pt), have previously been reported to be effective in the high-efficiency dehydrogenation of N₂H₄BH₃. However, the noble metal content in most of these catalysts is very high, and these nanoparticles exhibit poor kinetics in decomposing the N₂H₄ moiety, which limits the catalyst's future industrial production and application. Therefore, the development of catalysts with low noble metal content, high activity, and high selectivity is crucial for practical applications. Summary of the Invention

[0008] The purpose of the present invention is to address the deficiencies of the prior art and provide a CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane, as well as a preparation method and application thereof, specifically adopting the following technical solutions:

[0009] A method for preparing a CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane comprises the following steps:

[0010] CeO2 powder is dispersed in water, a cobalt source precursor and a platinum source precursor are added, ultrasonicated at room temperature to obtain a uniform mixed solution, and then sodium borohydride is added for reduction to obtain a CoPt / CeO2 composite nanocatalyst.

[0011] The present invention synthesized CeO2 nanorods using cerium nitrate as a cerium source via a hydrothermal method, and used them as a carrier to prepare CoPt / CeO2 via a simple, green, and low-cost wet chemical method. CoPt nanoparticles with an average particle size of approximately 3.2 nm were dispersed on CeO2. Since the atomic radius of Co is smaller than that of Pt, the diffraction peak shifted to a higher value after the formation of the CoPt alloy. At the same time, the small size of the CoPt nanoparticles, the large number of basic sites on the surface of CoPt / CeO2, and the electron transfer between CoPt and between CoPt and CeO2 all promoted catalytic performance. On this basis, CeO2 nanorods can reduce the agglomeration of metal particles and the interaction between the metal and the carrier, and can efficiently catalyze the hydrogen production from hydrazine borane with a selectivity of 100% and a turnover frequency (TOF) of up to 5454 h under alkaline conditions at 323 K. -1 , and has high cycle stability, making it a catalyst with development prospects.

[0012] The average particle size of the CoPt nanoparticles in the CoPt / CeO2 composite nanocatalyst prepared using the above method was 3.2 ± 0.4 nm. Excessively large metal particle size can lead to extensive agglomeration, impairing catalytic performance. Finer metal particle size improves dispersion and enhances catalyst performance. Therefore, the smaller the CoPt particle size, the more exposed active sites, resulting in higher catalytic activity.

[0013] As a further preferred embodiment, the content of Co in the CoPt / CeO2 composite nanocatalyst is greater than 0 and less than 19.5%, and the content of Pt is greater than 0 and less than 46%. More preferably, the molar ratio of Co to Pt in the CoPt / CeO2 composite nanocatalyst is 9:1. Except for the molar ratios of Co to Pt of 0:10, 10:0, 3:7 and 1:9, all other nanocatalysts catalyzed hydrazine borane hydrogen production showed 100% H2 selectivity. When the contents of Co and Pt were 19.5% and 7.2% respectively, that is, when the molar ratio of Co to Pt was 9:1, CoPt / CeO2 showed 100% hydrogen selectivity, and the TOF was 5454 h -1 The excellent performance can be attributed to the small size of CoPt nanoparticles, the large number of basic sites on the CoPt / CeO2 surface, and the strong electronic interactions between Co and Pt and between CoPt and CeO2.

[0014] As a further preferred embodiment, the usage ratio of CeO2, cobalt source precursor and platinum source precursor is 10:1.2~10.9:2.1~18.7.

[0015] As a further preferred embodiment, the cobalt source precursor is cobalt chloride; and the platinum source precursor is potassium tetrachloroplatinate.

[0016] The present invention further provides a method for preparing CeO2 in the above-mentioned preparation steps, comprising the following steps:

[0017] A cerium nitrate solution was added dropwise to a sodium hydroxide solution and stirred vigorously at room temperature for 30 minutes to obtain a white turbid solution. The white turbid solution was then transferred to an autoclave and heated at 100°C for 24 hours. After cooling to room temperature, the pale yellow precipitate was collected by centrifugation, washed with water and anhydrous ethanol, dried, and further calcined in air at 550°C for 2 hours to obtain CeO2 nanorods. The CoPt-loaded CeO2 nanorods prepared by this method exhibited superior catalytic performance in hydrazine borane dehydrogenation to commercially available CeO2.

[0018] Another aspect of the present invention provides the CoPt / CeO2 composite nanocatalyst for catalyzing the decomposition of hydrazine borane to produce hydrogen. The composite nanocatalyst can be used in the preparation of hydrogen sources for fuel cells. The composite nanocatalyst is used to catalyze the decomposition of hydrazine borane to produce hydrogen at a temperature of 303 K to 333 K.

[0019] The present invention provides the following beneficial effects: The high performance of the CoPt / CeO2 composite nanocatalyst prepared by the present invention is attributed to the small size of the CoPt NPs, the alloying effect between Co and Pt, the abundant basic sites on the CoPt / CeO2 surface, and the electron-metal-support interaction between the CoPt NPs and the CeO2 support. Furthermore, the present invention's catalyst preparation method is simple and inexpensive to operate. The resulting catalyst has the characteristics of a small particle size, numerous catalytically active sites, and high catalytic activity and stability, making it a promising catalyst for development. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown are X-ray diffraction patterns of the composite nanocatalysts obtained in Examples 1, 3 and 8 and the comparative catalyst;

[0021] Figure 2 Shown are nitrogen adsorption test graphs of the composite nanocatalyst obtained in Example 1 and a comparative catalyst;

[0022] Figure 3Shown are the scanning electron microscopy (a), transmission electron microscopy (b), high-resolution transmission electron microscopy (c) and particle size statistics of CoPt nanoparticles (d) of the composite nanocatalyst obtained in Example 1;

[0023] Figure 4 Shown is the X-ray photoelectron spectrum of the composite nanocatalyst obtained in Example 1;

[0024] Figure 5 Shown are CO2-TPD test graphs of the composite nanocatalyst obtained in Example 1 and the comparative catalyst;

[0025] Figure 6 Shown is a performance test graph of the composite nanocatalyst obtained in Examples 1 and 2 for catalyzing hydrogen production from hydrazine borane at 323 K;

[0026] Figure 7 Shown is a performance test graph of the composite nanocatalyst obtained in Examples 1 and 3 catalyzing hydrogen production from hydrazine borane at 323 K;

[0027] Figure 8 Shown is a performance test graph of the nanocomposite catalysts obtained in Examples 1 and 4-9 and the comparative catalysts in catalyzing hydrogen production from hydrazine borane at 323 K;

[0028] Figure 9 Shown are performance test graphs of the composite nanocatalysts obtained in Examples 1 and 10-12 and the comparative catalysts in catalyzing hydrazine borane at 323 K;

[0029] Figure 10 Shown are performance test graphs of the composite nanocatalysts obtained in Examples 1 and 13-16 and comparative catalysts in catalyzing hydrazine borane at 323 K;

[0030] Figure 11 The figure shows the performance test of the nanocomposite catalyst obtained in Example 1 of the present invention in catalyzing hydrazine borane at different temperatures;

[0031] Figure 12 The graph shows the recycling performance test of the nanocomposite catalyst obtained in Example 1 for catalyzing hydrazine borane at 323 K. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict.

[0033] Example 1

[0034] A method for preparing a CoPt / CeO2 composite nanocatalyst for catalyzing hydrogen production from hydrazine borane, specifically comprising the following steps:

[0035] Step 1: 1.75 g of cerium nitrate and 14.54 g of sodium hydroxide were added to 5 ml and 55 ml of deionized water, respectively. After stirring for 5 minutes, the cerium nitrate solution was added dropwise to the sodium hydroxide solution and stirred vigorously at room temperature for 30 minutes. The white turbid solution was then transferred to a 100 ml autoclave and heated at 100 ° C for 24 hours. The solution was then allowed to cool naturally to room temperature. After centrifugation, the pale yellow precipitate was collected, washed with water and anhydrous ethanol, and then dried in an oven at 80 ° C overnight. Finally, it was further calcined at 550 ° C in air for 2 hours to obtain CeO2 nanorods;

[0036] Step 2: CeO2 (10 mg) was dispersed in 5 ml of deionized water, and then 10.9 mg of CoCl2·6H2O (0.045 mmol) and 2.1 mg of K2PtCl4 (0.005 mmol) were added to the CeO2 suspension and ultrasonicated at 298 K for 30 min. 50 mg of NaBH4 was quickly added to the above mixture and stirred vigorously; finally, a black product was obtained until bubble formation stopped, and the CoPt / CeO2 composite nanocatalyst was finally obtained.

[0037] Example 2

[0038] The CeO2 in step 2 of implementation case 1 was replaced with directly purchased CeO2, and the other steps were the same as in Example 1 to obtain a CoPt / commercial CeO2 nanocatalyst.

[0039] Example 3

[0040] The CeO2 in step 2 of implementation case 1 was replaced by uncalcined Ce(OH)3, and the other steps were the same as in Example 1 to obtain a CoPt / Ce(OH)3 nanocatalyst.

[0041] Example 4

[0042] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 10:0, and the other steps were the same as in Example 1 to obtain a Co / CeO2 nanocatalyst.

[0043] Example 5

[0044] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 7:3, and the other steps were the same as in Example 1 to obtain a CoPt / CeO2 nanocatalyst.

[0045] Example 6

[0046] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 5:5, and the other steps were the same as in Example 1 to obtain a CoPt / CeO2 nanocatalyst.

[0047] Example 7

[0048] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 3:7, and the other steps were the same as in Example 1 to obtain a CoPt / CeO2 nanocatalyst.

[0049] Example 8

[0050] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 1:9, and the other steps were the same as in Example 1 to obtain a CoPt / CeO2 nanocatalyst.

[0051] Example 9

[0052] The metal molar ratio of Co and Pt in step 2 of Example 1 was adjusted to 0:10, and the other steps were the same as in Example 1 to obtain a Pt / CeO2 nanocatalyst.

[0053] Example 10

[0054] The precursor cobalt salt cobalt chloride in step 2 of Example 1 was replaced with nickel chloride, and the other steps were the same as in Example 1 to obtain a NiPt / CeO2 nanocatalyst.

[0055] Example 11

[0056] The precursor cobalt salt cobalt chloride in step 2 of Example 1 was replaced with copper chloride, and the other steps were the same as in Example 1 to obtain a CuPt / CeO2 nanocatalyst.

[0057] Example 12

[0058] The precursor cobalt salt cobalt chloride in step 2 of Example 1 was replaced with ferrous sulfate, and the other steps were the same as in Example 1 to obtain a FePt / CeO2 nanocatalyst.

[0059] Example 13

[0060] The precursor platinum salt potassium tetrachloroplatinate in step 2 of Example 1 was replaced with iridium chloride, and the other steps were the same as in Example 1 to obtain a CoIr / CeO2 nanocatalyst.

[0061] Example 14

[0062] The precursor platinum salt potassium tetrachloroplatinate in step 2 of Example 1 was replaced with rhodium chloride, and the other steps were the same as in Example 1 to obtain a CoRh / CeO2 nanocatalyst.

[0063] Example 15

[0064] The precursor platinum salt potassium tetrachloroplatinate in step 2 of Example 1 was replaced with ruthenium chloride, and the other steps were the same as in Example 1 to obtain a CoRu / CeO2 nanocatalyst.

[0065] Example 16

[0066] The precursor platinum salt potassium tetrachloroplatinate in step 2 of Example 1 was replaced with sodium tetrachloropalladate, and the other steps were the same as in Example 1 to obtain a CoPd / CeO2 nanocatalyst.

[0067] Example 17

[0068] The present invention has carried out relevant characterization data on some materials prepared in the above embodiments, which are as follows:

[0069] Figure 1 Shown are the X-ray diffraction patterns of the composite nanocatalysts obtained in Examples 1, 4 and 9 of the present invention and the comparative catalyst; Figure 1 It can be seen that after loading CoPt, the diffraction peak of CeO2 did not change significantly, indicating that the structure of CeO2 is stable.

[0070] Figure 2 Shown are the scanning electron microscopy (a), transmission electron microscopy (b), high-resolution transmission electron microscopy (c) and particle size statistics of CoPt nanoparticles (d) of the composite nanocatalyst obtained in Example 1 of the present invention; Figure 2 It can be seen that the prepared CeO2 presents a regular rod shape and the loaded CoPt particle size is about 3.2nm.

[0071] Figure 3 The X-ray photoelectron spectrum of the composite nanocatalyst obtained in Example 1 of the present invention is shown; Figure 3 It can be seen that C, Ce, O, Co and Pt elements exist in the prepared catalyst.

[0072] Figure 4 The graphs are nitrogen adsorption test graphs of the composite nanocatalyst obtained in Example 1 of the present invention and the comparative catalyst; Figure 4 It can be seen that the specific surface area decreases after loading CoPt, indicating that CoPt is successfully loaded onto the CeO2 surface.

[0073] Figure 5 The CO2-TPD test diagram of the composite nanocatalyst obtained in Example 1 of the present invention and the comparative catalyst is shown; Figure 5 As can be seen from the results, the basic site strength of CoPt / CeO2 is higher than that of pure CoPt particles. The presence of more basic sites in the catalyst is conducive to the cleavage of NH in hydrazine borane, thereby improving its catalytic activity.

[0074] Example 18

[0075] The CoPt / CeO2 nanocatalyst prepared in Examples 1 and 2 of the present invention was used to catalyze the production of hydrogen from hydrazine borane. NaOH (2 M) was added to the catalyst system, and 1 mmol of hydrazine borane was added at 323 K and normal pressure to carry out the reaction. The hydrogen production performance was as follows: Figure 6 As shown, from Figure 6 It can be seen that the performance of the CoPt / CeO2 nanocatalyst prepared by the present invention in catalyzing hydrogen production from hydrazine borane is better than that of directly purchased commercial CeO2.

[0076] Example 19

[0077] The nanocatalysts prepared in Examples 1 and 3 of the present invention were used to catalyze hydrogen production from hydrazine borane. NaOH (2 M) was added to the catalyst system, and 1 mmol of hydrazine borane was added at 323 K and normal pressure to carry out the reaction. The hydrogen production performance was as follows: Figure 7 As shown, from Figure 7 It can be seen that the performance of the CoPt / CeO2 nanocatalyst prepared by the present invention in catalyzing hydrogen production from hydrazine borane is better than that of CoPt / Ce(OH)3.

[0078] Example 20

[0079] The CoPt / CeO2 nanocatalysts prepared in Examples 1 and 4-9 of the present invention were used to catalyze the production of hydrogen from hydrazine borane. NaOH (2 M) was added to the catalyst system, and 1 mmol of hydrazine borane was added at 323 K and normal pressure to carry out the reaction. The hydrogen production performance was as follows: Figure 8 The conditions for preparing the catalysts of Examples 1, 4-9 and the results of the catalytic reactions are shown in Table 1.

[0080] Table 1 Summary of the performance of CoPt / CeO2 nanocatalysts prepared in Examples 1, 3-8 for catalytic hydrogen production from hydrazine borane

[0081]

[0082] The results in Table 1 indicate that, with the exception of Co:Pt molar ratios of 0:10, 10:0, 3:7, and 1:9, all other CoPt / CeO2 nanocatalysts exhibited 100% H2 selectivity for hydrogen production from hydrazine borane. The nanocatalyst exhibited optimal performance for hydrogen production from hydrazine borane when the Co:Pt molar ratio was 9:1. This suggests a strong synergistic effect between Co and Pt. The electronic structures of the catalysts prepared with different Co:Pt molar ratios differ, leading to different catalytic performance of the resulting CoPt / CeO2 nanocatalysts in the reaction.

[0083] Example 21

[0084] The CoPt / CeO2 nanocatalysts prepared in Examples 1 and 10-16 of the present invention were used to catalyze the production of hydrogen from hydrazine borane. NaOH (2 M) was added to the catalyst system, and 1 mmol of hydrazine borane was added to react at 323 K and normal pressure. The hydrogen production performance was as follows: Figure 9 and 10 The conditions for preparing the catalysts of Examples 1 and 10-16 and the results of the catalytic reactions are shown in Table 2.

[0085] Table 2 Summary of the performance of CoPt / CeO2 nanocatalysts prepared in Examples 1 and 10-16 for catalytic hydrogen production from hydrazine borane

[0086]

[0087] The results in Table 2 show that among the prepared Co-noble metal and non-noble metal-Pt, only CoPt / CeO2 and NiPt / CeO2 exhibit 100% hydrogen selectivity, among which CoPt / CeO2 has a higher TOF (TOF = 5454 h -1 ), indicating that the synergistic effect between Co and Pt is much greater than that of other bimetallic combinations.

[0088] Example 22

[0089] The CoPt / CeO2 nanocatalyst prepared in Example 1 of the present invention was used to catalyze the production of hydrogen from hydrazine borane at different temperatures. The catalyst was placed in a 50 mL flask containing 5 mL of deionized water. 1.0 mmol of hydrazine borane was added at 303 K, 313 K, 323 K, and 333 K under normal pressure to react. The hydrogen production performance is shown in the figure below. Figure 11 The conditions for catalyst preparation and the results of the catalytic reaction are shown in Table 3.

[0090] Table 3 Catalytic performance of CoPt / CeO2 composite nanocatalyst prepared in Example 1 for hydrogen production from hydrazine borane at different catalytic temperatures

[0091]

[0092] The results in Table 3 show that the CoPt / CeO2 composite nanocatalyst exhibits 100% H2 selectivity for catalyzing the hydrogen production from hydrazine borane. The catalytic reaction rate and reaction activity are significantly improved with the increase of temperature. At 323 K, the prepared CoPt / CeO2 composite nanocatalyst only takes 1.1 min to catalyze the hydrogen production from hydrazine borane, and its conversion frequency (TOF) value is as high as 5454 h -1 This is mainly attributed to the fact that high temperature can activate the catalyst and thus effectively improve the catalytic reaction activity.

[0093] Example 23

[0094] The CoPt / CeO2 composite nanocatalyst prepared in Example 1 of the present invention was used to catalyze the production of hydrogen from hydrazine borane. The catalyst was placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (2 M) was added. 1 mmol of hydrazine borane was added at 323 K and atmospheric pressure to react for 5 cycles. The hydrogen production performance is shown in the figure below. Figure 12 As shown. Figure 11 It can be seen that the CoPt / CeO2 composite nanocatalyst has good cyclic stability for hydrogen production from hydrazine borane. After repeated use for 5 times, the catalyst activity and gas production did not decrease significantly, indicating that the catalyst has good catalytic activity and cyclic stability.

[0095] The high performance of the CoPt / CeO2 composite nanocatalyst prepared in the present invention is attributed to the small size of CoPt NPs, the alloying effect between Co and Pt, the abundant basic sites on the CoPt / CeO2 surface, and the electron-metal-support interaction between CoPt NPs and CeO2 support.

[0096] In summary, the method for preparing the catalyst of the present invention is simple to operate and low in cost. The obtained catalyst has the characteristics of small particle size, multiple catalytic active sites, and high catalytic activity and stability, and is a catalyst with great development prospects.

[0097] Although the present invention has been described in considerable detail and with particularity with respect to several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but rather should be construed as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively encompassing the intended scope of the invention. In addition, the invention has been described above in terms of embodiments foreseen by the inventors for the purpose of providing a useful description, and those insubstantial modifications of the invention that are not currently foreseen may still represent equivalent modifications of the invention.

Claims

1. Application of a CoPt / CeO2 composite nanocatalyst in catalyzing hydrogen production from hydrazine borane, characterized in that: The preparation method of the CoPt / CeO2 composite nanocatalyst comprises the following steps: CeO2 powder was dispersed in water, and a cobalt source precursor and a platinum source precursor were added. Ultrasonication was performed at room temperature to obtain a uniform mixed solution, and then sodium borohydride was added for reduction to obtain a CoPt / CeO2 composite nanocatalyst. The molar ratio of Co to Pt in the CoPt / CeO2 composite nanocatalyst is 9:1; CeO2 is prepared by the following steps: The cerium nitrate solution was added dropwise to the sodium hydroxide solution and stirred vigorously at room temperature for 30 minutes to obtain a white turbid solution. The white turbid solution was then transferred to an autoclave and heated at 100°C for 24 hours. After cooling to room temperature, the pale yellow precipitate was collected by centrifugation, washed with water and anhydrous ethanol, dried, and finally further calcined at 550°C in air for 2 hours to obtain CeO2 nanorods. The CoPt / CeO2 composite nanocatalyst uses CeO2 nanorods as a carrier, and CoPt nanoparticles are dispersed on CeO2; the average particle size of the CoPt nanoparticles is 3.2 nm.

2. The use according to claim 1, characterized in that The usage ratio of CeO2, cobalt source precursor and platinum source precursor is 10 mg: 1.2 mg~10.9 mg: 2.1 mg~18.7 mg.

3. The use according to claim 2, characterized in that The cobalt source precursor is cobalt chloride.

4. The use according to claim 2, characterized in that The platinum source precursor is potassium tetrachloroplatinate.

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