A sodium borohydride hydrolysis hydrogen production catalyst and preparation method thereof

Abstract

The invention discloses a sodium borohydride hydrolysis hydrogen production catalyst and a preparation method thereof, and belongs to the field of hydrogen energy technology. The catalyst is composed of carbon and nanoporous cobalt, and the carbon is coated on the surface of the nanoporous cobalt in a petal shape. During preparation, aluminum and cobalt are first smelted into aluminum-cobalt alloy by a smelting method; then, the alloy powder is poured into a sodium hydroxide solution for dealloying treatment to obtain a nanoporous cobalt powder; then, a glucose aqueous solution and the nanoporous cobalt powder are placed in a reactor together for hydrothermal carbonization treatment; finally, the solid precipitate is washed and vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst. The catalyst provided by the present invention has low cost, simple and environmentally friendly preparation process, good catalytic performance, and has good application prospects in the field of rapid hydrolysis of sodium borohydride for hydrogen production.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen energy, and particularly relates to a sodium borohydride hydrolysis hydrogen production catalyst and a preparation method thereof. Background Art

[0002] Energy is the basis of human survival. With the large-scale exploitation of traditional fossil energy, energy shortage and environmental pollution have become important issues of common concern to the world. Hydrogen has a wide range of sources, high calorific value, and pollution-free combustion products. It can fully achieve clean, green and sustainable development and is an ideal secondary energy source in the future. Hydrogen production technologies mainly include water electrolysis, chemical hydrolysis, fossil resource hydrogen production, and new methods of hydrogen production (such as biomass and photochemistry). Among them, chemical hydrolysis has attracted much attention due to its advantages of controllable hydrogen production, high hydrogen purity, and low requirements for operating conditions. It is a very promising hydrogen production technology.

[0003] Common materials for producing hydrogen by hydrolysis of chemical substances include metals, ammonia borane and sodium borohydride. Hydrogen production by metal hydrolysis is the reaction of active metals (such as zinc, magnesium, aluminum, etc.) with water to produce hydrogen, but a protective layer is easily formed on the metal surface to prevent hydrolysis. Ammonia borane aqueous solution is very stable at room temperature. After adding appropriate catalysts, it can react with water to quickly release 3 equivalents of hydrogen, but the hydrolysis of ammonia borane to produce hydrogen is selective, and only precious metals show excellent catalytic performance. For example, Wang et al. used dendrimers as stabilizers and prepared a series of bimetallic catalysts by reduction method: Rh 0.5 Co 0.5 、Ru 0.5 Co 0.5 , Pt 0.5 Ni 0.5 and Pt 0.5 Cu 0.5 , where Pt 0.5 Co 0.5 It exhibits the highest catalytic activity and selectivity in the hydrolysis reaction of ammonia borane [Wang Q, Fu FY, Yang S, et al, ACS Catalysis, 2018, 9(2): 1110]. Sodium borohydride has high hydrogen storage density, mild reaction conditions and low price, and is considered to be an important hydrogen source in the field of hydrolysis hydrogen production. Sodium borohydride is not very selective for catalysts, and non-precious metal (such as cobalt-based, nickel-based) catalysts have good catalytic effects. For example, the GO-modified Co-B catalyst synthesized by Shi using in-situ chemical reduction method has a hydrolysis hydrogen release rate of 1.43L / (min·g cat), after 5 cycles, the retention rate was about 81.5% [Shi L, Xie W, Jian Z, et al, International Journal of Hydrogen Energy, 2019, 44(33): 17954]. Although great progress has been made in the research and development of hydrolysis hydrogen production catalysts, there is still a certain distance from large-scale commercial application. Summary of the invention

[0004] The invention aims at the shortcomings of producing hydrogen by hydrolyzing sodium borohydride and provides a catalyst with low cost, simple preparation process, high catalytic activity and good cycle performance and a preparation method thereof.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0006] The sodium borohydride hydrolysis hydrogen production catalyst provided by the invention consists of carbon and nanoporous cobalt, and the carbon is coated on the surface of the nanoporous cobalt in a petal shape.

[0007] The preparation method of the sodium borohydride hydrolysis hydrogen production catalyst provided by the present invention comprises the following steps:

[0008] (1) using a smelting method to smelt aluminum and cobalt elements with an atomic ratio of 80:20 into an aluminum-cobalt alloy, and mechanically crushing the alloy into a powder with a particle size of less than 75 μm;

[0009] (2) pouring the alloy powder obtained in step (1) into a sodium hydroxide solution for dealloying treatment, and washing and drying the treated solid product to obtain a nanoporous cobalt powder;

[0010] (3) dissolving glucose in deionized water and pouring the mixture into a polytetrafluoroethylene liner together with the nanoporous cobalt powder obtained in step (2), and then placing the mixture in an oven at 180° C. for hydrothermal carbonization treatment; the mass ratio of the glucose to the nanoporous cobalt is 1:5-6.

[0011] (4) filtering the solid precipitate obtained in step (3), washing it with deionized water and anhydrous ethanol, and then vacuum drying it to obtain the sodium borohydride hydrolysis hydrogen production catalyst.

[0012] Furthermore, in step (2), the concentration of the sodium hydroxide solution is 0.5 to 2 mol / L, the dealloying temperature is 25° C., and the dealloying time is 6 to 12 h.

[0013] In step (3), the hydrothermal carbonization time is 4 to 6 hours.

[0014] The catalyst obtained by the above-mentioned preparation method can be used in the production of hydrogen by hydrolysis of sodium borohydride.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] (1) The present invention uses Al-Co alloy as a precursor, and obtains nanoporous cobalt powder with rich pore structure and high specific surface area after dealloying treatment. Combined with the high dispersibility of carbon materials, the sodium borohydride hydrolysis hydrogen production catalyst is prepared by hydrothermal glucose carbonization method. Carbon is coated on the surface of nanoporous cobalt in a petal shape, which effectively avoids the occurrence of agglomeration, protects the active sites of the catalyst, and significantly improves its catalytic activity and durability. At the same time, under the promotion of the high dispersibility of the carbon coating layer, it can show excellent catalytic performance even in a strong alkaline environment or a high-pressure environment.

[0017] (2) The catalyst raw materials provided by the present invention have a wide range of sources, low cost, simple and environmentally friendly preparation process, stable output and short preparation cycle, and are easy to mass produce.

[0018] (3) The microstructure and catalytic performance of the catalyst provided by the present invention can be easily regulated by changing the dealloying and carbonization process conditions.

[0019] (4) The catalyst provided by the present invention has high efficiency and excellent performance in catalyzing the hydrolysis of sodium borohydride to produce hydrogen. The hydrogen release can be completed in 50 seconds at 25°C, and the maximum hydrogen release rate reaches 13.8L / (min·g cat ). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 and 2 are X-ray diffraction patterns of (a) nanoporous cobalt and (b) sodium borohydride hydrolysis hydrogen production catalysts obtained in Example 1 of the present invention.

[0021] Figure 2 This is a scanning electron microscope photograph of the sodium borohydride hydrolysis hydrogen production catalyst obtained in Example 1 of the present invention.

[0022] Figure 3 This is the hydrolysis and hydrogenation curve of sodium borohydride catalyzed by the catalyst obtained in Example 1 of the present invention.

[0023] Figure 4 This is the hydrolysis and hydrogenation curve of sodium borohydride catalyzed by the catalyst obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] Aluminum flakes and cobalt particles with an atomic ratio of 80:20 were melted into an aluminum-cobalt alloy by vacuum induction melting, and the alloy was mechanically crushed into a powder with a particle size of less than 75 μm; then, the alloy powder was slowly poured into a 1 mol / L sodium hydroxide solution and dealloyed at 25°C for 12 h. The treated solid product was washed to neutrality and then vacuum dried to obtain a nanoporous cobalt powder (its X-ray diffraction pattern is shown in Figure 1 a); then, glucose was dissolved in deionized water, and then the nanoporous cobalt powder was weighed in a mass ratio of 1:6 and poured into a polytetrafluoroethylene liner, and hydrothermal carbonization was performed at 180°C for 6 hours; finally, the solid precipitate was filtered, washed with deionized water and anhydrous ethanol, and then vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst (its X-ray diffraction spectrum and morphology are shown in Figure 1 b and Figure 2 ). A sodium borohydride hydrolysis hydrogen production system was constructed according to 20 mL of deionized water, 1 wt.% NaBH4, 5 wt.% NaOH and 5 wt.% catalyst. Figure 3 The hydrolysis hydrogenation curve of the system is shown in Figure 2. It can be seen that the hydrogenation can be completed in 50 seconds at 25°C, and the amount of hydrogen released is 455 mL. The maximum hydrogenation rate is calculated to be 13.8 L / (min·g cat ); and as the temperature increases, the rate of hydrolysis and hydrogen release continues to accelerate.

[0027] Example 2

[0028] Aluminum sheets and cobalt particles with an atomic ratio of 80:20 are melted into an aluminum-cobalt alloy by vacuum induction melting, and the alloy is mechanically crushed into a powder with a particle size of less than 75μm; then, the alloy powder is slowly poured into a 1mol / L sodium hydroxide solution, and a dealloying treatment is carried out at 25°C for 12 hours. The treated solid product is washed to neutrality and then vacuum dried to obtain a nanoporous cobalt powder; then, glucose is dissolved in deionized water, and the nanoporous cobalt powder is weighed in a mass ratio of 1:6 and poured into a polytetrafluoroethylene liner, and a hydrothermal carbonization treatment is carried out at 180°C for 4 hours; finally, the solid precipitate is filtered, washed with deionized water and anhydrous ethanol, and then vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst. A sodium borohydride hydrolysis hydrogen production system is constructed according to 20mL of deionized water, 1wt.% NaBH4, 5wt.% NaOH and 5wt.% catalyst. Figure 4 It can be seen that hydrogen release can be completed in 60s at 25°C, the amount of hydrogen released is 435mL, and the maximum hydrogen release rate is 13.1L / (min·g cat ).

[0029] Example 3

[0030] Aluminum sheets and cobalt particles with an atomic ratio of 80:20 are melted into an aluminum-cobalt alloy by a vacuum induction melting method, and the alloy is mechanically crushed into a powder with a particle size of less than 75 μm; then, the alloy powder is slowly poured into a 2 mol / L sodium hydroxide solution, and a dealloying treatment is carried out at 25°C for 6 hours. The treated solid product is washed to neutrality and then vacuum dried to obtain a nanoporous cobalt powder; then, glucose is dissolved in deionized water, and the nanoporous cobalt powder is weighed in a mass ratio of 1:5 and poured into a polytetrafluoroethylene liner together, and a hydrothermal carbonization treatment is carried out at 180°C for 6 hours; finally, the solid precipitate is filtered, washed with deionized water and anhydrous ethanol in succession, and then vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst.

[0031] Example 4

[0032] Aluminum sheets and cobalt particles with an atomic ratio of 80:20 are melted into an aluminum-cobalt alloy by a vacuum induction melting method, and the alloy is mechanically crushed into a powder with a particle size of less than 75 μm; then, the alloy powder is slowly poured into a 0.5 mol / L sodium hydroxide solution, and a dealloying treatment is carried out at 25°C for 8 hours. The treated solid product is washed to neutrality and then vacuum dried to obtain a nanoporous cobalt powder; then, glucose is dissolved in deionized water, and the nanoporous cobalt powder is weighed in a mass ratio of 1:6 and poured into a polytetrafluoroethylene liner together, and a hydrothermal carbonization treatment is carried out at 180°C for 5 hours; finally, the solid precipitate is filtered, washed with deionized water and anhydrous ethanol in succession, and then vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst.

Claims

1. A sodium borohydride hydrolysis hydrogen production catalyst, characterized in that The catalyst consists of carbon and nanoporous cobalt, and the carbon is coated on the surface of the nanoporous cobalt in a petal shape. The preparation of the catalyst comprises the following steps: (1) Aluminum and cobalt with an atomic ratio of 80:20 are melted into an aluminum-cobalt alloy by a melting method, and the alloy is mechanically crushed into a powder with a particle size of less than 75 μm; (2) pouring the alloy powder obtained in step (1) into a sodium hydroxide solution for dealloying treatment, and washing and drying the treated solid product to obtain a nanoporous cobalt powder; (3) dissolving glucose in deionized water and pouring it into a polytetrafluoroethylene liner together with the nanoporous cobalt powder obtained in step (2), and then placing it in a 180°C oven for hydrothermal carbonization treatment; the mass ratio of the glucose to the nanoporous cobalt powder is 1:5-6; (4) The solid precipitate obtained in step (3) is filtered, washed with deionized water and anhydrous ethanol, and then vacuum dried to obtain the sodium borohydride hydrolysis hydrogen production catalyst.

2. The catalyst for producing hydrogen by hydrolysis of sodium borohydride as claimed in claim 1, characterized in that In step (2), the concentration of the sodium hydroxide solution is 0.5-2 mol / L, the dealloying temperature is 25°C, and the dealloying time is 6-12 h.

3. The catalyst for producing hydrogen by hydrolysis of sodium borohydride as claimed in claim 1, characterized in that In step (3), the hydrothermal carbonization treatment time is 4 to 6 h.

4. Use of the catalyst as claimed in any one of claims 1 to 3 in producing hydrogen by hydrolysis of sodium borohydride.

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