阅读说明：本技术 蒲公英状负载型非晶态合金催化剂及其制备方法和应用 (Taraxacum-shaped load type amorphous alloy catalyst and preparation method and application thereof ) 是由 肖学章 陈文政 陈立新 何佳桓 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种蒲公英状负载型非晶态合金催化剂及其制备方法和在催化硼氢化物或氨硼烷水解制氢中的应用。所述催化剂以ZIF-67为载体,将Co、Mo、Ni前驱体按调控比例通过NaBH<Sub>4</Sub>还原完全包裹住ZIF-67纳米颗粒,得到催化性能优异的非晶态合金负载型纳米催化剂。所得催化剂具有蒲公英状结构,分布均匀、比表面积大、催化活性位点多,在硼氢化物或氨硼烷水解制氢领域具有良好的催化活性,与单纯的无载体CoMoNi-B催化剂相比催化性能上升了150％,可达7120mL H<Sub>2</Sub> min/g Co,表观活化能为35.01kJ/mol,且经过5次循环反应之后,保持了86％的催化活性。与传统的贵金属催化剂相比,具有制备简单、成本低廉、原料易得,适合工业化生产,是一种很有应用前景的催化剂。(The invention discloses a dandelion-shaped load type amorphous alloy catalyst, a preparation method thereof and application thereof in catalyzing hydroboron or ammonia borane hydrolysis to prepare hydrogen. The catalyst takes ZIF-67 as a carrier, and Co, Mo and Ni precursors are subjected to NaBH according to a regulation and control ratio 4 Reducing and completely wrapping the ZIF-67 nano particles to obtain the amorphous alloy supported nano catalyst with excellent catalytic performance. The obtained catalyst has a dandelion-shaped structure, is uniformly distributed, has a large specific surface area and a plurality of catalytic active sites, has good catalytic activity in the field of hydrogen production by hydrolysis of borohydride or ammonia borane, and has the catalytic performance which is increased by 150 percent compared with that of a pure unsupported CoMoNi-B catalyst and can reach 7120mL of H 2 min/g Co, the apparent activation energy is 35.01kJ/mol, and 86 percent of catalyst is kept after 5 times of cyclic reactionActivating activity. Compared with the traditional noble metal catalyst, the catalyst has the advantages of simple preparation, low cost, easily obtained raw materials, suitability for industrial production and wide application prospect.)

1. A dandelion-shaped supported amorphous alloy catalyst is characterized in that the catalyst is obtained by loading active ingredients on a zeolite imidazole ester framework material ZIF-67, wherein the active ingredients are amorphous alloys consisting of Co, Mo, Ni and B;

the preparation method of the dandelion-shaped load type amorphous alloy catalyst comprises the following steps:

(1) dissolving cobalt nitrate hexahydrate in absolute methanol, performing ultrasonic dispersion to obtain a first material, dissolving 2-methylimidazole in absolute methanol, and performing ultrasonic dispersion to obtain a second material;

(2) adding the second material into the first material under stirring, and continuously stirring for 11-13 hours to obtain a ZIF-67 precursor solution;

(3) centrifugally washing the ZIF-67 precursor solution with absolute ethyl alcohol, and carrying out vacuum drying at 45-55 ℃ to obtain a carrier ZIF-67;

(4) sealing, stirring and dispersing the carrier ZIF-67 prepared in the step (3) in deionized water, then adding metal salt, continuing to seal and stir for 0.5-1.5 hours, and performing ice-water bath for 10-20 minutes after stirring is completed to obtain an ion impregnation liquid; the metal salt is cobalt salt, molybdenum salt and nickel salt;

(5) under the environment of ice-water bath, NaBH is added₄And dropwise adding the aqueous solution into the ionic impregnation solution, continuously sealing and stirring for 0.5-1.5 hours, and finally centrifuging, washing and vacuum drying to obtain the dandelion-shaped supported amorphous alloy catalyst.

2. The taraxacum-containing amorphous alloy catalyst of claim 1, wherein in step (1), the mass ratio of said cobalt nitrate hexahydrate to 2-methylimidazole is 1: 1.7.

3. The dandelion-like supported amorphous alloy catalyst according to claim 1, wherein in step (4), the ratio of the mass of the carrier ZIF-67, the total mass of the metal salt and the volume of the deionized water is 100mg:57.7mg:20 mL;

the cobalt salt is CoCl₂·6H₂O, molybdenum salt is Na₂MoO₄·2H₂O, the nickel salt being NiCl₂·6H₂O。

4. The dandelion-like supported amorphous alloy catalyst according to claim 3, characterized in that the mass ratio of cobalt in the cobalt salt, molybdenum in the molybdenum salt and nickel in the nickel salt is 5.85:4.17: 1.

5. The taraxacum-containing amorphous alloy catalyst of claim 1, wherein in step (5), NaBH₄The molar ratio to metal salt was 10: 1.

6. The dandelion-like supported amorphous alloy catalyst according to any one of claims 1 to 5, wherein the flocculent amorphous alloy is uniformly coated on the surface of the carrier ZIF-67, and has a dandelion-like structure with a size of 850 to 950nm, wherein the size of the carrier ZIF-67 is 450 to 550 nm.

7. The use of the dandelion-like supported amorphous alloy catalyst according to any of claims 1-6 in catalyzing the hydrolysis of borohydride or ammonia borane to produce hydrogen.

8. The use of claim 7, wherein the taraxacum-like supported amorphous alloy catalyst is used for catalyzing NaBH₄The hydrolysis produces hydrogen, and the apparent activation energy is 35.01 kJ/mol.

Technical Field

The invention relates to the technical field of hydrogen storage, in particular to a dandelion-shaped supported amorphous alloy catalyst and a preparation method and application thereof.

Background

With the continuous consumption and utilization of resources, how to develop, store and convert novel renewable green energy and efficient clean energy has become a key factor of sustainable development in future society. In recent years, scientists and researchers have continuously made efforts to develop energy systems, and research on renewable energy sources has been carried out more deeply. The hydrogen energy is considered as the available next generation green energy source due to the characteristics of abundant reserves, high energy density, environmental friendliness and the like.

Solid-state hydrogen storage with metal hydrides (such as sodium borohydride and the like) has very high hydrogen storage density, can be operated at relatively low temperature and pressure, and is safer than mechanical storage. The sodium borohydride has the characteristics of high hydrogen release density (the hydrogen storage capacity is up to 10.8 wt%), low hydrogen release temperature, high hydrogen release speed and the like. The hydrolysis catalyst can react with water at normal temperature to release hydrogen, and can be regenerated through chemical processes such as ball milling and the like after hydrolysis hydrogen release is realized, and meanwhile, for borohydride, the efficient hydrolysis catalyst can realize controllable hydrogen release at room temperature, so that the research and development of practical mobile hydrogen sources are possible.

The development of a catalyst with excellent performance and low price is the key for promoting the application of sodium borohydride in hydrogen production by hydrolysis. At present, noble metals Pt and Ru and alloys thereof have excellent catalytic activity on the hydrogen production reaction by sodium borohydride hydrolysis. Despite their excellent performance, the use of noble metals as catalysts is hardly feasible on an industrial level due to their high cost and scarcity, which has led researchers to focus more on non-noble metal catalysts, especially Co-based catalysts.

At present, it has been reported that, compared with a single metal catalyst, three or more specific metal elements can form a synergistic effect by combining with each other, so that the catalytic performance of the catalyst is greatly improved. Taking a cobalt-based catalyst as an example, by adding other specific elements (such as Ni, Mo, etc.), a common electron pair is formed, so that cobalt becomes more active, and the deactivation of the catalyst is avoided. These third metals are present in the ternary alloy catalyst primarily as metal oxides. In addition, they also promote the overall catalytic reaction by acting as acidic sites, increasing the absorption of reactive species on the surface; the added metal can also act as an electron donor ligand, enhancing the kinetic activity of the reaction. However, too high surface energy of the unsupported catalyst can cause easy agglomeration of catalyst particles and reduce the performance of the catalyst. Therefore, the research and development of a proper carrier which is adaptive to the metal active component can effectively inhibit the agglomeration phenomenon, and the service life and the performance of the catalyst are further improved, thereby having important significance.

Patent specification CN 107930697 a discloses a Pt/ZIF-67 composite material for catalyzing ammonia borane hydrolysis to produce hydrogen, which can provide higher specific surface area and adsorption capacity by using ZIF-67 to compound with Pt, so that metal nanoparticles are more uniformly dispersed on the surface of MOF material. Wherein ZIF-67 is obtained by the hydrothermal reaction of cobalt acetate tetrahydrate and 2-methylimidazole. The Pt/ZIF-67 composite material prepared by the patent technology is used for catalyzing ammonia borane to hydrolyze and release hydrogen, and the activation energy is 30-40kJ mol^-1The active component corresponding to the activation energy is noble metal Pt. And the catalyst structure obtained by the patent technology has no specificity.

Therefore, there is still a great challenge to develop a simple and convenient method for preparing a borohydride or ammonia borane hydrolysis catalyst with a unique structure and high performance.

Disclosure of Invention

The invention aims to provide a dandelion-shaped load type amorphous alloy catalyst with high circulation stability, a preparation method and application thereof, aiming at the defects of high price, low catalytic activity and poor circulation stability of the existing sodium borohydride hydrolysis catalyst. Compared with the traditional catalyst, the catalyst can reduce the cost, simplify the synthesis method and greatly improve the catalytic performance.

A dandelion-shaped supported amorphous alloy catalyst is obtained by loading an active ingredient on a zeolite imidazole ester framework material ZIF-67, wherein the active ingredient is an amorphous alloy consisting of Co, Mo, Ni and B.

As a general inventive concept, the present invention also provides a preparation method of the taraxacum-shaped supported amorphous alloy catalyst, comprising the steps of:

(1) dissolving cobalt nitrate hexahydrate in absolute methanol, performing ultrasonic dispersion to obtain a first material, dissolving 2-methylimidazole in absolute methanol, and performing ultrasonic dispersion to obtain a second material;

(2) adding the second material into the first material under stirring, and continuously stirring for 11-13 hours to obtain a ZIF-67 precursor solution;

(3) centrifugally washing the ZIF-67 precursor solution with absolute ethyl alcohol, and carrying out vacuum drying at 45-55 ℃ to obtain a carrier ZIF-67;

(4) sealing, stirring and dispersing the carrier ZIF-67 prepared in the step (3) in deionized water, then adding metal salt, continuing to seal and stir for 0.5-1.5 hours, and performing ice-water bath for 10-20 minutes after stirring is completed to obtain an ion impregnation liquid; the metal salt is cobalt salt, molybdenum salt and nickel salt;

(5) under the environment of ice-water bath, NaBH is added₄And dropwise adding the aqueous solution into the ionic impregnation solution, continuously sealing and stirring for 0.5-1.5 hours, and finally centrifuging, washing and vacuum drying to obtain the dandelion-shaped supported amorphous alloy catalyst.

The key of the preparation method is that NaBH is dropwise added in ice water bath in the step (5)₄Aqueous solution, otherwise, the taraxacum-shaped supported amorphous alloy catalyst can not be formed.

The invention effectively inhibits the generation of agglomeration phenomenon and improves the service life and performance of the catalyst by loading the specific metal active component on a proper carrier and combining a special preparation method. The ZIF-67 used in the invention is of a rhombic dodecahedron structure, has a high specific surface area, and can improve the effective contact area of the loaded amorphous alloy and a reactant, thereby greatly improving the catalytic activity of the loaded amorphous alloy. Particularly, due to the fact that a dandelion-shaped structure is formed, the specific flocculent amorphous alloy uniformly wrapped on the surface of the carrier can improve the electron transfer capability of the whole catalyst through interaction with the carrier, the specific flocculent amorphous alloy and the carrier are combined together, the catalytic activity and the cycle life of the catalyst can be greatly improved, and no relevant report that the catalyst with a similar structure is applied to sodium borohydride hydrolysis research exists at present.

Compared with a pure supported nano catalyst, the dandelion type catalyst with the special structure can effectively prevent nano particles from agglomerating and inactivating and improve the controllability of the catalyst, and can further realize the integration and integration of various active sites by adjusting the components, the proportion, the structure, the size and the like of an 'internal bud' (carrier) or 'flocculent crown hair' (amorphous alloy) so as to adapt to more complex and diversified catalytic reaction systems. In the catalyst, the surface/interface effect and synergistic effect between the ZIF-67 nanostructure and the uniformly dispersed amorphous alloy endow the material with excellent catalytic performance of hydrogen production by hydrolysis of borohydride or ammonia borane.

The invention regulates and controls the optimal components of the catalyst by changing the metal ratio, takes ZIF-67 as a carrier, and passes Co, Mo and Ni precursors through NaBH according to a certain regulation and control proportion₄Reducing to obtain dandelion-shaped load type amorphous alloy nano catalyst CoMoNi-B/ZIF-67 with excellent catalytic performance, wherein NaBH₄On one hand, the boron source is used as a reducing agent to reduce metal ions, and on the other hand, the boron source is used to form boride with non-noble metals.

Preferably, in the step (1), the mass ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1: 1.7.

Preferably, in the step (4), the ratio of the mass of the carrier ZIF-67 to the total mass of the metal salt to the volume of the deionized water is 100mg:57.7mg:20 mL;

the cobalt salt is CoCl₂·6H₂O, molybdenum salt is Na₂MoO₄·2H₂O, the nickel salt being NiCl₂·6H₂O。

Preferably, the mass ratio of cobalt in the cobalt salt, molybdenum in the molybdenum salt, and nickel in the nickel salt is 5.85:4.17: 1. The proportion has the best catalytic performance and cycling stability.

The invention adopts a co-reduction method,and completely wrapping the Co, Mo and Ni precursors with ZIF-67 according to the regulation and control proportion to form a dandelion-shaped structure. Preferably, in step (5), NaBH₄The molar ratio to metal salt was 10: 1.

Preferably, the dandelion-shaped supported amorphous alloy catalyst is formed by uniformly wrapping flocculent amorphous alloy on the surface of the carrier ZIF-67, is in a dandelion-shaped structure and has the size of 850-950 nm, wherein the size of the carrier ZIF-67 is 450-550 nm. The dandelion-shaped structure of the invention obtains a very large specific surface area and can effectively inhibit the agglomeration and growth of the transition metal nano catalyst.

The invention also provides application of the dandelion-shaped load type amorphous alloy catalyst in catalyzing hydroboron or ammonia borane hydrolysis to prepare hydrogen.

The dandelion-shaped load type amorphous alloy catalyst is used for catalyzing NaBH₄Hydrolysis to produce hydrogen, and apparent activation energy can be reduced to 35.01 kJ/mol.

Compared with the prior art, the invention has the main advantages that:

(1) the prepared catalyst has a dandelion structure, and the activity and the cycle life of the catalyst are greatly improved by utilizing the electron transfer in the multielement metal and the dispersion effect of the carrier. In addition, the invention firstly wraps the amorphous CoMoNi-B alloy with high amorphization degree around the ZIF-67 with high crystallization degree by a dropwise adding co-reduction method to obtain the dandelion-shaped nano catalyst with the diameter of about 900 nanometers, and can further realize the integration and integration of various active sites by adjusting the components and structures of the 'internal buds' or the 'flocculent crowns' to adapt to more complex and diversified catalytic reaction systems.

(2) The dandelion-shaped load type amorphous alloy catalyst can present a macroporous honeycomb structure after catalytic reaction, is favorable for dispersion, is not easy to cause the aggregation of the by-product sodium metaborate, and can not obstruct a reaction channel, thereby prolonging the cycle life of the catalyst. Compared with the unsupported catalyst, the catalytic activity is improved by 150 percent, and the NaBH is added to the catalyst at room temperature₄The hydrolysis hydrogen production rate is as high as 7120mL H₂min/g Co, apparent activation energy 35.01kJ/mol。

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) photograph of a dandelion-like CoMoNi-B catalyst prepared in example 2 of the present invention;

FIG. 2 is a Transmission Electron Microscope (TEM) photograph of a dandelion-like CoMoNi-B catalyst prepared in example 2 of the present invention;

FIG. 3 is a graph showing performance test of a CoMoNi-B/ZIF-67 series catalyst prepared in examples 1-3 of the present invention in catalyzing hydrolysis of sodium borohydride at room temperature to release hydrogen;

FIG. 4 is an SEM photograph of a CoMoNi-B/ZIF-67 catalyst prepared in example 2 of the present invention after five cycles at room temperature;

FIG. 5 is a graph showing calculation of Arrhenius activation energy for catalyzing hydrolysis of sodium borohydride to release hydrogen at 25 ℃, 35 ℃, 45 ℃ and 55 ℃ in a CoMoNi-B/ZIF-67 catalyst prepared in example 2 of the present invention;

FIG. 6 is a graph fitting the reaction rate of the CoMoNi-B/ZIF-67 catalyst prepared in example 2 of the present invention to hydrolyze sodium borohydride at room temperature with 10mg, 20mg, 30mg, and 40mg, respectively;

FIG. 7 is an XRD pattern of 5 cycles of reaction of the CoMoNi-B/ZIF-67 catalyst prepared in example 2 of the present invention, the CoMoNi-B catalyst prepared in comparative example 1, the ZIF-67 carrier, and the CoMoNi-B/ZIF-67 catalyst;

FIG. 8 is a graph showing the performance of the catalysts of comparative examples 1 to 2, example 2 and carrier ZIF-67 for hydrogen release from sodium borohydride hydrolysis at room temperature;

FIG. 9 is a TEM image of a CoMoNi-B/ZIF-67 catalyst of conventional morphology prepared in comparative example 3 of the present invention;

FIG. 10 is a performance test chart of the dandelion-shaped CoMoNi-B/ZIF-67 catalyst prepared in example 2 and the common-morphology CoMoNi-B/ZIF-67 catalyst prepared in comparative example 3 for catalyzing hydrolysis of sodium borohydride to release hydrogen at room temperature.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.