A co-based catalyst modified with w and mo, and a preparation method and application thereof

Abstract

The application discloses a W and Mo modified Co-based catalyst and a preparation method and application thereof, and belongs to the technical field of hydrogen evolution materials. 1‑x -W x -Mo y -B, wherein x is 0.05-0.5, and y is 0.025-0.2.The W and Mo transition metal doping can effectively improve the surface area of the catalyst, avoid excessive aggregation of the catalyst particles, and make as many catalytic active sites of the catalyst as possible exposed to a reaction solution, so that the obtained quaternary catalyst has high catalytic activity and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution materials technology, and more specifically to a W and Mo modified Co-based catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen is a green, clean, and efficient energy source with broad application prospects. In the current energy transition and environmental protection fields, hydrogen is considered an important alternative energy source, which can be used to power fuel cells, generate electricity, and in transportation. Hydrogen production technology is key to hydrogen production, and currently, it mainly includes methods such as water electrolysis, natural gas steam reforming, and chemical hydrogen storage materials. Hydrogen can be stored and transported in different ways, as a compressed gas, liquid, or metal hydride. However, physical hydrogen storage has a low safety factor and requires stringent container requirements, making chemical hydrogen storage more suitable for large-scale applications. Commonly used hydrogen storage materials include sodium borohydride (NaBH4), ammonia borane (NH3BH3), hydrazine hydrate (N2H4·H2O), and formic acid (HCOOH). Among all hydrogen storage materials, sodium borohydride is the most widely used hydride. NaBH4, as a chemical hydrogen storage material, has become the most researched due to its excellent chemical stability, high hydrogen storage capacity (10.7 wt.%), controllable hydrogen release, and high hydrogen purity. In addition, NaBH4 hydrogen storage has the following advantages: (1) mild reaction conditions, environmentally friendly by-products, and large-scale recycling; (2) self-heating; (3) small size and light weight; (4) cheaper than other chemical hydrides; (5) non-toxic and non-flammable.

[0003] However, the conventional NaBH4-H2O system also has several drawbacks. A major reason is the reduced efficiency due to the poor water solubility of the byproduct sodium metaborate, requiring a large amount of excess water to dissolve it. Furthermore, the self-hydrolysis efficiency of sodium borohydride is low, necessitating the addition of a catalyst to the reactor to increase the NaBH4 reaction rate. Currently, noble metal catalysts not only possess high catalytic activity but also excellent properties such as high temperature resistance and corrosion resistance. Common examples include Pt, Ph, Ru, and Pd nanomaterials. Because noble metal materials are scarce and expensive, they cannot be widely used in production and daily life; therefore, exploring inexpensive catalysts with good catalytic performance is essential. Currently, the most studied non-noble metal catalysts with high activity are Co-based catalysts. Amorphous cobalt boride (Co-B) catalysts are prepared by reducing metal salts with reducing agents. They have attracted widespread attention in the catalysis field due to their unique properties such as isotropic structure, high concentration of coordinated unsaturated sites, good chemical stability, and low cost. However, Co-B catalysts tend to agglomerate, meaning that only the catalytically active sites on the surface of the agglomerates participate in the reaction during catalysis, which greatly reduces the performance of the catalyst. Summary of the Invention

[0004] To address the above problems, this invention provides a W and Mo modified Co-based catalyst, its preparation method, and its applications. This invention involves adding Mo and W transition metals to a Co-B catalyst. The addition of transition metals can reduce the agglomeration state of the catalyst, thereby increasing the specific surface area of ​​the metal-boride and improving catalytic performance.

[0005] The first objective of this invention is to provide a W and Mo modified Co-based catalyst, with the structural formula Co, based on the atomic molar percentage. 1-x -W x -Mo y -B, where x is 0.05-0.5 and y is 0.025-0.2.

[0006] A second objective of this invention is to provide a method for preparing the above-mentioned W and Mo modified Co-based catalyst, comprising the following steps:

[0007] According to Co 1-x -W x -Mo y The stoichiometric ratio of Co, W, Mo, and B in -B is determined by weighing cobalt precursor, tungsten precursor, molybdenum precursor, and sodium borohydride.

[0008] Cobalt precursor, tungsten precursor, and molybdenum precursor were dissolved in water to prepare tungsten precursor solution, cobalt precursor solution, and molybdenum precursor solution, respectively. They were mixed evenly at room temperature to obtain a mixed solution. Sodium borohydride solution was added to the mixed solution until no more bubbles were generated and a black precipitate was obtained.

[0009] The black precipitate was centrifuged, washed, and dried to obtain W and Mo modified Co-based catalysts.

[0010] In one embodiment of the present invention, the cobalt precursor is cobalt chloride hexahydrate; the tungsten precursor is sodium tungstate; and the molybdenum precursor is sodium molybdate dihydrate.

[0011] In one embodiment of the present invention, the ratio of cobalt precursor to water is 0.005-0.037 mol: 50 mL, the ratio of tungsten precursor to water is 0.001-0.005 mol: 50 mL, and the molar ratio of cobalt precursor to tungsten precursor is 0.5-0.95: 0.05: 0.5.

[0012] In one embodiment of the present invention, the amount of molybdenum precursor added is 2.5-20% of the total molar amount of cobalt precursor and tungsten precursor, and the ratio of molybdenum precursor to water is 0.00025-0.002 mol: 50 mL.

[0013] In one embodiment of the present invention, the molar ratio of cobalt chloride hexahydrate to sodium borohydride is 1:1-5;

[0014] In a sodium borohydride solution, the ratio of sodium borohydride to water is 0.041-0.16 mol: 50 mL.

[0015] A third objective of this invention is to provide the application of the aforementioned W and Mo modified Co-based catalysts in hydrogen production.

[0016] In one embodiment of the present invention, NaBH4 and NaOH are used as reaction solutions, and a W and Mo modified Co-based catalyst is used for catalytic hydrogen production.

[0017] In one embodiment of the present invention, the mass concentration of sodium borohydride is 5-8%, and the mass concentration of NaOH is 7-9%.

[0018] In one embodiment of the present invention, the amount of W and Mo modified Co-based catalyst added is 2-6 mg / ml of the reaction solution.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention modifies the Co-B catalyst using transition elements, which are less expensive than precious metals, and exhibit significantly superior activity compared to other non-precious metals. The low cost and relatively abundant resources of the metals used make the industrial application of this catalyst in the hydrolysis of sodium borohydride to produce hydrogen possible.

[0021] Tungsten and cobalt doping significantly improves the dispersion of the catalyst, reduces the agglomeration of catalyst particles, exposes more active sites, and enhances the activity of the catalyst. The doping of metals can also reduce the particle size of the catalyst, and the catalyst material is magnetic, making it easy to separate and recycle.

[0022] The preparation method of this invention is simple, easy to operate, and reasonably priced, and the catalyst has high catalytic activity. Attached Figure Description

[0023] Figure 1 The graph shows the effect of W doping on the catalytic hydrogen production of sodium borohydride by the catalyst.

[0024] Figure 2 The graph shows the effect of Mo doping on the catalytic hydrogen production of sodium borohydride by the catalyst.

[0025] Figure 3 Hydrogen production curves of Co-B catalysts prepared by reduction of sodium borohydride and cobalt chloride hexahydrate at different molar ratios;

[0026] Figure 4Figure 1 shows SEM images of the catalysts. Figure 2 shows the Co-B catalyst prepared in Comparative Example 5, Figure 3 shows a magnified view of Figure 2 (a), and Figure 4 shows the Co-B catalyst prepared in Comparative Example 5. 0.9 -W 0.1 -B catalyst, Figure (d) is a magnified view of Figure (c), and Figure (e) is a Co catalyst. 0.9 -W 0.1 -Mo 0.075 -B catalyst, Figure (f) is a partial enlarged view of Figure (e);

[0027] Figure 5 For Co 0.9 -W 0.1 -Mo 0.075 Stability test results of the -B catalyst. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To address the problem of Co-B catalysts' tendency to agglomerate, resulting in only the catalytic active sites on the surface of the agglomerates participating in the reaction and significantly reducing catalyst performance, this invention reduces the agglomeration state of the catalyst by adding transition metals Mo and W. These transition metals mainly exist in the form of oxides, which can reduce the agglomeration state of the catalyst, thereby increasing the specific surface area of ​​the metal-borides and improving catalytic performance. The low cost and relatively abundant resources of the metals used make the industrial application of this catalyst in the hydrolysis of sodium borohydride to produce hydrogen possible.

[0030] Different proportions of Co doping were obtained by changing the amount of sodium tungstate. 1-x -W x -B nanocatalysts were prepared, and the resulting catalysts are shown in Table 1. The calculation method for the amount of each component added is as follows: where x is the percentage of sodium tungstate, as shown in Table 1, x is 50%, 20%, 15%, 10%, 7.5%, and 5% respectively. The amount of sodium tungstate is used as the standard, and the amount of cobalt chloride hexahydrate is calculated as 1-x. Taking x=20% as an example: if the content of sodium tungstate is 20%, then the content of cobalt chloride hexahydrate is 80%. If the content of sodium tungstate is 0.005 mol, then the amount of cobalt chloride hexahydrate is four times the amount of sodium tungstate, which is 0.02 mol. Other proportions are calculated with this as a reference.

[0031] Table 1. Content of different precursors and content of reducing agent sodium borohydride

[0032]

[0033]

[0034] The following is a detailed description of Examples 1-6:

[0035] Example 1

[0036] Co 0.5 -W 0.5 Preparation of -B nanocatalysts:

[0037] 0.005 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.005 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.1 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0038] Transfer the sodium tungstate solution and cobalt chloride hexahydrate solution to a 250 ml round-bottom beaker. Place the beaker on a magnetic stirrer and stir thoroughly until the two solutions are fully mixed. Then, under magnetic stirring, slowly add sodium borohydride solution. Numerous bubbles and a black precipitate will be observed. After the sodium borohydride solution has been completely added, react at room temperature (25°C) for 10 minutes until no more bubbles are produced, thus obtaining the black suspension catalyst.

[0039] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.5 -W 0.5 -B nanocatalyst.

[0040] Example 2

[0041] Co 0.8 -W 0.2 Preparation of -B nanocatalysts:

[0042] 0.005 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.02 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.04 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0043] Transfer the sodium tungstate solution and cobalt chloride hexahydrate solution to a 250 ml round-bottom beaker. Place the beaker on a magnetic stirrer and stir thoroughly until the two solutions are fully mixed. Then, under magnetic stirring, slowly add sodium borohydride solution. Numerous bubbles and a black precipitate will be observed. After the sodium borohydride solution has been completely added, react at room temperature (25°C) for 10 minutes until no more bubbles are produced, thus obtaining the black suspension catalyst.

[0044] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.8 -W 0.2 -B nanocatalyst.

[0045] Example 3

[0046] Co 0.85 -W 0.15 Preparation of -B nanocatalysts:

[0047] 0.0015 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.0185 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.08 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0048] Transfer the sodium tungstate solution and cobalt chloride hexahydrate solution to a 250 ml round-bottom beaker. Place the beaker on a magnetic stirrer and stir thoroughly until the two solutions are fully mixed. Then, under magnetic stirring, slowly add sodium borohydride solution. Numerous bubbles and a black precipitate will be observed. After the sodium borohydride solution has been completely added, react at room temperature (25°C) for 10 minutes until no more bubbles are produced, thus obtaining the black suspension catalyst.

[0049] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.85 -W 0.15 -B nanocatalyst.

[0050] Example 4

[0051] Co 0.9 -W 0.1 Preparation of -B nanocatalysts:

[0052] 0.003 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.027 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.12 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0053] Both sodium tungstate solution and cobalt chloride hexahydrate solution were transferred to a 250 ml round-bottom beaker. The beaker was placed on a magnetic stirrer and stirred thoroughly until the two solutions were completely mixed. Then, under magnetic stirring, sodium borohydride solution was slowly added dropwise. A large number of bubbles and a black precipitate were observed to form. After the sodium borohydride solution was completely added, the reaction was carried out at room temperature (25°C) for 10 minutes until no more bubbles were formed, thus obtaining a black suspension catalyst.

[0054] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -B nanocatalyst.

[0055] Example 5

[0056] Co 0.925 -W 0.075 Preparation of -B nanocatalysts:

[0057] 0.003 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.037 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.16 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0058] Transfer the sodium tungstate solution and cobalt chloride hexahydrate solution to a 250 ml round-bottom beaker. Place the beaker on a magnetic stirrer and stir thoroughly until the two solutions are fully mixed. Then, under magnetic stirring, slowly add sodium borohydride solution. Numerous bubbles and a black precipitate will be observed. After the sodium borohydride solution has been completely added, react at room temperature (25°C) for 10 minutes until no more bubbles are produced, thus obtaining the black suspension catalyst.

[0059] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.925 -W 0.075 -B nanocatalyst.

[0060] Example 6

[0061] Co0.95 -W 0.05 Preparation of -B nanocatalysts:

[0062] 0.001 mol of sodium tungstate was dispersed in 50 mL of deionized water to prepare a sodium tungstate solution; 0.019 mol of cobalt chloride hexahydrate was dispersed in 50 mL of deionized water to prepare a cobalt chloride hexahydrate solution; 0.08 mol of sodium borohydride was dispersed in 50 mL of deionized water to prepare a sodium borohydride solution, for later use.

[0063] Transfer the sodium tungstate solution and cobalt chloride hexahydrate solution to a 250 ml round-bottom beaker. Place the beaker on a magnetic stirrer and stir thoroughly until the two solutions are fully mixed. Then, under magnetic stirring, slowly add sodium borohydride solution. Numerous bubbles and a black precipitate will be observed. After the sodium borohydride solution has been completely added, react at room temperature (25°C) for 10 minutes until no more bubbles are produced, thus obtaining the black suspension catalyst.

[0064] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Afterward, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.95 -W 0.05 -B nanocatalyst.

[0065] The catalysts prepared in Examples 1-6 were subjected to performance testing. 10 mg of catalyst and 50 ml of a water-ethanol mixture with a mass ratio of 9:1 were added to a 100 ml three-necked flask. The flask was then fixed in a constant-temperature magnetically stirred water bath. 5 ml of a reaction solution containing 5 wt.% NaBH4 and 7 wt.% NaOH was added to the flask. Figure 1 As shown, the catalyst exhibits the highest catalytic activity when the cobalt-tungsten molar ratio is 0.9:0.1. Figure 4 As can be seen from Figures c and d, the catalyst is amorphous, with loose and flocculent irregular structures between particles.

[0066] It should be noted that the amount of W and Mo modified Co-based catalyst added is 10 mg, and the reaction is carried out in 5 ml of reaction solution. The amount of catalyst added is independent of the volume of the water and ethanol mixture; only an excess of water and ethanol is required. The final hydrogen production rate of the catalyst is converted to ml / min·g, so the amount of catalyst added can be adjusted according to the actual experimental conditions.

[0067] To enhance the hydrogen production performance of the catalyst, a third metal was further doped onto the three-way catalyst. The purpose of this doping was to reduce the catalyst particle size and agglomeration, thereby improving the hydrogen production performance. Based on the catalysts prepared in Examples 1-6, molybdenum (Co) was further doped into the three-way catalyst with a cobalt-tungsten molar ratio of 0.9:0.1. 0.9 -W 0.1 -Mo y Preparation of -B nanocatalyst: where y is the ratio of n(Na2MoO4·2H2O) to n(CoCl2·6H2O) + n(Na2WO4).

[0068] Sodium molybdate solution and sodium borohydride solution with different amounts of each substance were prepared, as well as 0.009 mol of cobalt chloride hexahydrate solution and 0.001 mol of sodium tungstate solution, as shown in Table 2.

[0069] Table 2. Content of different precursors and content of reducing agent sodium borohydride

[0070]

[0071] The following is a detailed description of Examples 7-12:

[0072] Example 7

[0073] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.00025 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.041 mol of sodium borohydride in 50 mL of deionized water.

[0074] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.025 -B nanocatalyst.

[0075] Example 8

[0076] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.0005 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.042 mol of sodium borohydride in 50 mL of deionized water.

[0077] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.05 -B nanocatalyst.

[0078] Example 9

[0079] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.00075 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.043 mol of sodium borohydride in 50 mL of deionized water.

[0080] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.075 -B nanocatalyst.

[0081] Example 10

[0082] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.001 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.044 mol of sodium borohydride in 50 mL of deionized water.

[0083] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.1 -B nanocatalyst.

[0084] Example 11

[0085] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.0015 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.046 mol of sodium borohydride in 50 mL of deionized water.

[0086] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.15 -B nanocatalyst.

[0087] Example 12

[0088] A sodium tungstate solution was prepared by dispersing 0.001 mol of sodium tungstate in 50 mL of deionized water; a cobalt chloride hexahydrate solution was prepared by dispersing 0.009 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium molybdate dihydrate solution was prepared by dispersing 0.002 mol of sodium molybdate dihydrate in 50 mL of deionized water; and a sodium borohydride solution was prepared by dispersing 0.048 mol of sodium borohydride in 50 mL of deionized water.

[0089] Sodium tungstate solution, cobalt chloride hexahydrate solution, and sodium molybdate dihydrate solution were transferred to a 250 ml round-bottom beaker and mixed thoroughly with a magnetic stirrer. Then, sodium borohydride solution was slowly added dropwise. Numerous bubbles and a black precipitate were observed. After the sodium borohydride solution was completely added, the mixture was reacted at room temperature (25°C) for 10 minutes until no more bubbles were produced, yielding a black suspension catalyst. The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum drying oven for 12 hours to obtain Co. 0.9 -W 0.1 -Mo 0.2 -B nanocatalyst.

[0090] The catalysts prepared in Examples 7-12 were subjected to performance testing. 10 mg of catalyst and 50 ml of a water-ethanol mixture were added to a 100 ml three-necked flask. The flask was then fixed in a constant-temperature magnetically stirred water bath. 5 ml of a reaction solution containing 5 wt.% NaBH4 and 7 wt.% NaOH was added to the flask. Figure 2 As shown, the catalyst exhibits the highest catalytic activity when the relative molar content of molybdenum is 0.00075 mol. Figure 4 As can be seen from the e and f figures, the catalyst is amorphous with a loose and flocculent irregular structure between particles. Furthermore, the particle size of the catalyst decreases with the addition of the tertiary metal molybdenum.

[0091] In order to examine Co 0.9 -W 0.1 -Mo 0.075 The stability of -B nanocatalysts was assessed through stability experiments using catalysts prepared with the optimal cobalt-tungsten-molybdenum molar ratio. Figure 5 The catalyst shown retains high activity even after 5 cycles, indicating that Co 0.9 -W 0.1 -Mo 0.075 -B catalysts exhibit good stability and durability.

[0092] Comparative Example 1

[0093] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.01 mol of sodium borohydride in 50 mL of deionized water.

[0094] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0095] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was dried in a vacuum drying oven for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:1.

[0096] Comparative Example 2

[0097] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.02 mol of sodium borohydride in 50 mL of deionized water.

[0098] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0099] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was placed in a vacuum drying oven and dried for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:2.

[0100] Comparative Example 3

[0101] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.03 mol of sodium borohydride in 50 mL of deionized water.

[0102] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0103] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was placed in a vacuum drying oven and dried for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:3.

[0104] Comparative Example 4

[0105] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.035 mol of sodium borohydride in 50 mL of deionized water.

[0106] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0107] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was dried in a vacuum drying oven for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:3.5.

[0108] Comparative Example 5

[0109] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.04 mol of sodium borohydride in 50 mL of deionized water.

[0110] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0111] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was dried in a vacuum drying oven for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:4.

[0112] Comparative Example 6

[0113] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.045 mol of sodium borohydride in 50 mL of deionized water.

[0114] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0115] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was dried in a vacuum drying oven for 12 hours to obtain the Co-B nanocatalyst, denoted as Co / B = 1:4.5.

[0116] Comparative Example 7

[0117] A cobalt chloride hexahydrate solution was prepared by dispersing 0.01 mol of cobalt chloride hexahydrate in 50 mL of deionized water; a sodium borohydride solution was prepared by dispersing 0.04 mol of sodium borohydride in 50 mL of deionized water.

[0118] Transfer the cobalt chloride hexahydrate solution to a 250ml round-bottom beaker. Place the beaker on a magnetic stirrer and slowly add sodium borohydride solution under magnetic stirring. A large number of bubbles and a black precipitate can be observed. After the sodium borohydride solution is completely added, react at room temperature (25℃) for 10 minutes until no more bubbles are produced to obtain the black suspension catalyst.

[0119] The resulting black suspension was then placed in a centrifuge tube and washed 3-4 times with deionized water and anhydrous ethanol. After that, it was placed in a vacuum drying oven and dried for 12 hours to obtain the Co-B nanocatalyst, which was denoted as Co / B = 1:5.

[0120] Different molar amounts of sodium borohydride were used to reduce cobalt chloride hexahydrate, yielding a black powdered Co-B catalyst. The hydrogen production performance of the Co-B catalyst was then tested. The results showed that the Co-B catalyst exhibited the best hydrogen production performance when the molar ratio of sodium borohydride to cobalt chloride hexahydrate was 4:1. Figure 3As shown. At this point, the hydrogen production rate of the Co-B catalyst was 1160 ml / (min·g). After successful doping with W and Mo, the catalyst performance was significantly improved, with the hydrogen production rate increasing to 3860 ml / (min·g), approximately 1.64 times higher than that of the Co-B catalyst. Furthermore, the doping of W and Mo improved the catalyst's agglomeration state and increased its specific surface area. This is demonstrated by… Figure 4 It can be seen that, as Figure 4 As shown in Figures a and b, the aggregation of the Co-B catalyst is quite severe. To address this problem, this invention solves it through the doping of W and Mo, as follows: Figure 4 The c-plot and f-plot.

[0121] NaBH4 solution can produce high-purity hydrogen gas on demand when a certain amount of metal catalyst is added. The hydrolysis reaction equation is as follows:

[0122] NaBH4+2H2O→4H2+NaBO2ΔH=-217 kJ·mol -1 (1)

[0123] The process of hydrolysis of sodium borohydride solution catalyzed by a metal catalyst is generally divided into the following steps:

[0124]

[0125]

[0126] BH3+OH - →BH3(OH) - (4)

[0127] M+e - +H₂O→M–H+OH - (5)

[0128] M–H+M–H→H2+2M(6)

[0129] Since sodium borohydride reacts with water to produce sodium metaborate, which is insoluble in water, the purpose of adding ethanol is to dilute the sodium metaborate produced by the hydrolysis of sodium borohydride, so that it adheres to the metal catalyst as little as possible. In addition, sodium borohydride can also react with ethanol, and the resulting byproduct NaB(OCH2CH3)4 is readily soluble in water. The reaction equation is as follows:

[0130] NaBH4+4CH3CH2OH→NaB(OCH2CH3)4+4H2 (7)

[0131] The reaction mechanism of its metal catalyst is as follows:

[0132]

[0133]

[0134] BH3+OH - →BH3(OH) - (10)

[0135] M+e - +CH3CH2OH→M–H+CH3CH2O - (11)

[0136] M–H+M–H→H2+2M(12)

[0137] In this context, M stands for metal catalyst.

[0138] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0139] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A W and Mo modified Co-based catalyst, characterized in that, Based on the molar percentage of each atom, the structural formula is Co. 1-x -W x -Mo y -B, where x is 0.05-0.5, y is 0.025-0.2, and the atomic molar percentage of W is greater than that of Mo; The doping of W and Mo is used to increase the specific surface area; and in the catalytic hydrolysis of NaBH4 to produce hydrogen, the hydrogen production rate is increased to 3860 ml / (min·g).

2. The method for preparing a W and Mo modified Co-based catalyst according to claim 1, characterized in that, Includes the following steps: According to Co 1-x -W x -Mo y The stoichiometric ratio of Co, W, Mo, and B in -B is determined by weighing cobalt precursor, tungsten precursor, molybdenum precursor, and sodium borohydride. Cobalt precursor, tungsten precursor, and molybdenum precursor were dissolved in water to prepare tungsten precursor solution, cobalt precursor solution, and molybdenum precursor solution, respectively. At room temperature, the tungsten precursor solution, cobalt precursor solution, and molybdenum precursor solution were mixed evenly to obtain a mixed solution. Sodium borohydride solution was added to the mixed solution, and the reaction was carried out at room temperature for 10-15 min to obtain a black precipitate. The black precipitate was centrifuged, washed, and dried to obtain W and Mo modified Co-based catalysts.

3. The method for preparing a W and Mo modified Co-based catalyst according to claim 2, characterized in that, The cobalt precursor is cobalt chloride hexahydrate; the tungsten precursor is sodium tungstate; and the molybdenum precursor is sodium molybdate dihydrate.

4. The method for preparing a W and Mo modified Co-based catalyst according to claim 2, characterized in that, The ratio of cobalt precursor to water was 0.005-0.037 mol: 50 mL, and the ratio of tungsten precursor to water was 0.001-0.005 mol: 50 mL.

5. The method for preparing a W and Mo modified Co-based catalyst according to claim 4, characterized in that, The amount of molybdenum precursor added is 2.5-20% of the total molar amount of cobalt and tungsten precursors, and the ratio of molybdenum precursor to water is 0.00025-0.002 mol: 50 mL.

6. The method for preparing a W and Mo modified Co-based catalyst according to claim 3, characterized in that, The molar ratio of cobalt chloride hexahydrate to sodium borohydride is 1:1-5; In a sodium borohydride solution, the ratio of sodium borohydride to water is 0.041-0.16 mol: 50 mL.

7. The application of the W and Mo modified Co-based catalyst of claim 1 in hydrogen production.

8. The application of the W and Mo modified Co-based catalyst according to claim 7 in hydrogen production, characterized in that, Hydrogen was produced by catalytic reaction using NaBH4 and NaOH as reaction solutions and W and Mo modified Co-based catalysts.

9. The application of the W and Mo modified Co-based catalyst according to claim 8 in hydrogen production, characterized in that, The mass concentration of sodium borohydride is 5-8%, and the mass concentration of NaOH is 7-9%.

10. The application of the W and Mo modified Co-based catalyst according to claim 9 in hydrogen production, characterized in that, The amount of W and Mo modified Co-based catalyst added per milliliter of reaction solution is 2-6 mg.

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