Ag-Co3O4 metal nanocomposite, and preparation method and application thereof

Abstract

The application discloses an Ag-Co3O4 metal nanocomposite and a preparation method and application thereof, relates to the technical field of metal composites, and places Co(NO3)2.6H2O and AgNO3 in a container, pours anhydrous ethanol into the container, uniformly stirs at normal temperature, heats the uniformly stirred solution while stirring, stops heating when a small amount of liquid remains, continues stirring until pink powder appears, and stops cooling to room temperature; the red powder is heated to high temperature in a heating device and calcined at the temperature to obtain a final black powder solid sample. The preparation method is simple in operation, safe and controllable, and high in yield; the hydrolysis of a p-amino borane complex to produce hydrogen has high catalytic activity under normal temperature and environmental conditions, the TOF value of silver reaches 265.4min ‑1 ; and the preparation cost is low, and silver and other scarce resources can be effectively utilized; the mass content of silver in the catalyst is 2.002%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal composite materials, and particularly relates to an Ag-Co3O4 metal nanocomposite material and a preparation method and application thereof. BACKGROUND

[0002] At present, the application of hydrogen energy is also very extensive, and the application methods are diversified. Hydrogen energy can be directly combusted to generate heat energy, and can be used as fuel to prepare fuel cells, and has good application prospects in the fields of energy, transportation and industry. Borane ammonia complex has high hydrogen storage capacity, safety, stability and no pollution, and is an ideal solid hydrogen storage material.

[0003] Compared with other hydrogen storage methods, solid hydrogen storage has the advantages of small space for storing hydrogen with large bulk density, easy dissolution in water, ethanol, sodium hydroxide and other solvents, and hydrogen production by hydrolysis of ammonia borane complex is one of the hydrogen production methods. Noble metals such as Pt, Pd and Ru have special electronic structures and exhibit excellent catalytic activity in the hydrolysis of ammonia borane to produce hydrogen. However, the high cost and scarcity of noble metals make it difficult to be widely used, and non-noble metal catalysts exhibit poor catalytic activity in the hydrolysis of ammonia borane to produce hydrogen. Therefore, the preparation of high-efficiency and low-cost catalysts has become a research hotspot.

[0004] Saim et al. (Water soluble nickel(0)and cobalt(0)nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid): Highly active, durable and cost effective catalysts in hydrogen generation from the hydrolysis of ammonia borane, International Journal of Hydrogen Energy, 2011, 36, 1424-1432) synthesized nickel nanocluster and cobalt nanocluster catalysts, respectively. In the hydrogen production reaction by hydrolysis of ammonia borane, the turnover frequency (TOF) of the two catalysts is 10.1 min -1 (nickel cluster) and 25.7 min -1(Co clusters); Yangbin Ren et al. (Ni-Mo2C Nanocomposites as Highly Efficient Catalysts for Hydrogen Generation from Hydrolysis of Ammonia Borane, Energy & Fuels, 2021, 35, 19, 16222-16231) synthesized γ-Al2O3 supported Ni-Mo x C catalysts, wherein 10Ni30Mo x C / γ-Al2O3 has the highest TOF value (75.1 min -1 ) in the series of catalysts for the hydrogen generation reaction from the hydrolysis of ammonia borane; Ahmet Bulut et al. (Carbon dispersed copper-cobalt alloy nanoparticles: A cost-effective heterogeneous catalyst with exceptional performance in the hydrolytic dehydrogenation of ammonia-borane, Applied Catalysis B: Environmental, 2016, 180, 121-129) prepared a new catalyst, copper-cobalt alloy nanoparticles supported on activated carbon (CuCo / C), which has a TOF value of 2700 h -1 .

[0005] However, the catalysts prepared by the above methods have the following disadvantages: the high-efficiency catalysts have high production cost, complicated operation and harsh reaction conditions; and the catalytic activity of the catalysts for the hydrogen generation reaction from the hydrolysis of ammonia borane complex is not high under normal temperature and environmental conditions. SUMMARY

[0006] The purpose of the present application is to provide an Ag-Co3O4 metal nanocomposite material, a preparation method and application thereof, and to solve the problems in the background art.

[0007] The present application achieves the above-mentioned purpose by the following technical solutions:

[0008] The present application provides a preparation method of an Ag-Co3O4 metal nanocomposite material, comprising the following steps:

[0009] (1) Put Co(NO3)2.6H2O and AgNO3 into a container, then pour anhydrous ethanol into the container, stir uniformly at normal temperature, then heat the stirred solution, stop heating when a small amount of liquid remains, continue stirring until pink powder appears, and then stop stirring, and cool to room temperature;

[0010] (2) Put the red powder into a heating device, heat to 500℃ at a certain heating rate, and calcine at the temperature for 1h to obtain a final black powder sample, namely Ag-Co3O4 metal nanocomposite.

[0011] Further improvement lies in that the mass ratio of Co(NO3)2.6H2O and AgNO3 is (90-100):1.

[0012] Further improvement lies in that the heating temperature in step (1) is 70-80℃, and the reactants will become black when the temperature exceeds 80℃.

[0013] Further improvement lies in that the heating rate in step (2) is 10-15℃ / min.

[0014] The application provides an Ag-Co3O4 metal nanocomposite prepared by the above preparation method.

[0015] Further improvement lies in that the Ag-Co3O4 metal nanocomposite is in the shape of nanoflower particles with a size of about 4.0μm, and silver atoms are uniformly distributed on the surface of the particles.

[0016] The application provides an application of the above Ag-Co3O4 metal nanocomposite in catalyzing hydrogen production by hydrolysis of ammonia borane complex.

[0017] The method for catalyzing hydrogen production by hydrolysis of ammonia borane complex comprises the following steps:

[0018] (1) The above Ag-Co3O4 metal nanocomposite is used as a catalyst, and is added into 1mol·L-1 NaOH aqueous solution, and is ultrasonically dispersed for 5min; -1

[0019] (2) Ammonia borane complex is added into the solution after dispersion in step (1), and hydrogen is collected by drainage method while stirring.

[0020] The application has the following beneficial effects:

[0021] 1. The preparation method is simple in operation, safe and controllable, and has high yield.

[0022] ​2. It exhibits highly efficient catalytic activity for the hydrolysis of ammonia borane complex to produce hydrogen under ambient temperature conditions, with a TOF value of 347.85 min for silver. -1 ;

[0023] 3. The preparation cost is low, and it can effectively utilize scarce resources such as silver (the mass content of silver in this catalyst is 2.002%). Attached Figure Description

[0024] Figure 1 Scanning electron microscope image and energy dispersive spectroscopy (EDS) elemental mapping diagram of Ag-Co3O4 metal nanocomposite material;

[0025] Figure 2 X-ray diffraction pattern of Ag-Co3O4 metal nanocomposite material;

[0026] Figure 3 The graph shows the performance test results of Ag-Co3O4 catalyst in catalyzing the hydrolysis of ammonia boron to produce hydrogen.

[0027] Figure 4 The diagram shows the preparation process of Ag-Co3O4 metal nanocomposite materials; a) during preparation; b) before calcination; c) after calcination.

[0028] Figure 5 The test results show the catalytic hydrogen production performance of Ag-Co3O4 metal nanocomposite catalysts prepared with different amounts of silver nitrate added, catalyzing the hydrolysis of ammonia borane. Detailed Implementation

[0029] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0030] 1. Materials

[0031] Unless otherwise specified, the methods used in this embodiment are conventional methods known to those skilled in the art, and the reagents and materials used are commercially available products.

[0032] 2. Method

[0033] 2.1 Preparation of Ag-Co3O4

[0034] Weigh 1.8g of Co(NO3)2·6H2O into a beaker, weigh 0.02g of AgNO3 into the beaker containing Co(NO3)2·6H2O, then pour in 5mL of anhydrous ethanol. Stir thoroughly at room temperature until well mixed, then pour the well-mixed solution into an evaporating dish (e.g.,Figure 4 As shown in Figure a), place the solution on a heating mantle and heat it while stirring, maintaining the solution temperature at around 80°C. Stir slowly to prevent splashing. Observe the solution while stirring. When a small amount of liquid remains in the evaporating dish, turn off the heating device and continue stirring until it becomes a pink powder (as shown in Figure a). Figure 4 Stop when shown in (b).

[0035] After cooling to room temperature, transfer the reagent from the evaporating dish and scrape off the adhering reagent with a clean spatula, then weigh it. Next, place the reagent in a clean crucible and calcine it in a muffle furnace at a heating rate of 10°C / min to 500°C for one hour, obtaining the final black powdery solid sample (e.g., ...). Figure 4 (as shown in c).

[0036] Material shape and structure: The Ag-Co3O4 metal nanocomposite material consists of nanoflower-like particles with a size of 4.0-4.0 μm, with silver atoms uniformly distributed on the surface of the nanoparticles (see...). Figure 1 X-ray diffraction analysis of the sample was performed. Figure 2 The nanomaterial exhibited diffraction peaks at 31.2°, 36.8°, 44.7°, 55.5°, 59.2°, and 65.1°, corresponding to the (220), (311), (400), (422), (511), and (440) crystal planes of Co3O4 crystal (PDF card: 078-1969). Due to the high dispersion of Ag on the Co3O4 surface resulting in low loading, no characteristic diffraction peaks of Ag were observed in the figure.

[0037] 2.2 Hydrogen Production

[0038] 10 mg of the Ag-Co3O4 metal nanocomposite material prepared in step 2.1 was added as a catalyst sample at 1 mol·L⁻¹. -1 The mixture was sonicated in NaOH aqueous solution for 5 min to ensure complete dispersion. Then, 30.8 mg (1 mmol) of the ammonia borane complex was added. Hydrogen gas was collected by water displacement with stirring. Test results showed that in the hydrogen production reaction catalyzed by the Ag-Co3O4 catalyst via the hydrolysis of the ammonia borane complex, hydrogen production began at 15 s, and 60 mL of hydrogen gas was produced at 281 s, achieving a final yield of 83%. Figure 3 The graph shows the performance of the Ag-Co3O4 catalyst in catalyzing the hydrolysis of ammonia borane to produce hydrogen. Using the following Time-of-Flight (TOF) calculation formula, the TOF value of the Ag-Co3O4 catalyst is 347.85 mol / L. H2 ·mol -1 Ag·min -1 AB hydrolysis to produce hydrogen (TOF(min)) -1 The value is calculated using the following formula:

[0039]

[0040] wherein, Δn— the difference of the amount of substance of H2 in the corresponding time,

[0041] t 50 — the time for H2 volume to reach 50 mL,

[0042] t 10 — the time for H2 volume to reach 10 mL,

[0043] n M — the amount of substance of Ag in the catalyst.

[0044] In addition, we also synthesized Ni-Co3O4 and AuCu-Co3O4 catalysts. The specific steps are as follows: preparation of Ni-Co3O4 catalyst: take 20 mg Ni6(SC2H4Ph) 12 (preparation method reference: Xiaoqi Chai, Tao Li, Mingyang Chen, Rongchao Jin, Weiping Ding, Yan Zhu, Suppressing the active site-blocking impact of ligands of Ni6(SR) 12 clusters with the assistance of NH3 on catalytic hydrogenation of nitriles, Nanoscale, 2018, 10, 19375) is dissolved in 1 mL of dichloromethane, and is added dropwise to a uniformly dispersed ethanol solution containing 300 mg of ZIF-67 MOF material, stirred for 8 hours, centrifuged to obtain a purple solid, dried at 60°C, then placed in a calcining furnace at 500°C for 1 hour, and finally obtained Ni-Co3O4 catalyst. In the same condition of hydrogen production experiment, that is, 10 mg of Ni-Co3O4 catalyst is put into the reaction, and other conditions remain unchanged.

[0045] The results show that in the reaction of using Ni-Co3O4 catalyst to catalyze the hydrolysis of ammonia borane complex to produce hydrogen, hydrogen begins to be produced at 77s, hydrogen is generated at 361s, and the final yield is 83%. Similarly, the preparation method of AuCu-Co3O4 catalyst is as follows: the preparation method of Ni-Co3O4, and the AuCu precursor comes from [Au4Cu5(Dppm)2(C6H 11 S)6] + [BPh4] -(Preparation method reference: Manman Zhou, Shan Jin, Xiao Wei, Qianqin Yuan, Shuxin Wang, Yuanxin Du, and Manzhou Zhu, Reversible Cu-S motif transformation and Au4 distortion via thiol ligand exchange engineering, The journal of physical chemistry C, 2020, 124, 13, 7531-7538). While the AuCu-Co3O4 catalyst did not exhibit catalytic activity in the hydrogen production reaction of ammonia borane complex hydrolysis.

[0046] In addition, we also compared the influence of different amounts of silver nitrate on the catalytic activity of Ag-Co3O4 catalysts in the hydrogen production reaction of ammonia borane complex hydrolysis. The preparation method is as follows: 2.1, Ag-Co3O4 preparation method, except that 0.02g AgNO3 in the reaction was replaced by 0.01g AgNO3, 0.04g AgNO3, and 0.06g AgNO3, respectively. In the same hydrogen production experiment, i.e. 10mg catalyst was put into the reaction, and other conditions were unchanged. As shown in Figure 5 , the test results show that, on the basis of the standard of silver, the TOF value of the Ag-Co3O4 catalyst prepared by adding 20mg silver nitrate is the best. The TOF of the Ag-Co3O4 catalyst prepared by 0.01g AgNO3 is 280.22mol H2 ·mol -1 Ag ·min -1 (the mass content of silver element in the catalyst is 0.8785%), the TOF of the Ag-Co3O4 catalyst prepared by 0.04g AgNO3 is 213.90mol H2 ·mol -1 Ag ·min -1 (the mass content of silver element in the catalyst is 4.625%), and the TOF of the Ag-Co3O4 catalyst prepared by 0.06g AgNO3 is 113.24mol H2 ·mol -1 Ag ·min -1 (the mass content of silver element in the catalyst is 6.316%).

[0047] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for preparing Ag-Co3O4 metal nanocomposite, characterized in that: It comprises the following steps: (1) Put Co(NO3)2·6H2O and AgNO3 into a container, then pour anhydrous ethanol into the container, stir them at normal temperature, then heat the stirred solution to 70-80℃ while stirring, stop heating when there is a small amount of liquid left, continue stirring until pink powder appears, then stop and cool to room temperature; The mass ratio of Co(NO3)2·6H2O and AgNO3 is (90-100):1; (2) Put the pink powder into a heating device, heat it to 500℃ at a heating rate of 10-15℃ / min, and calcine it at this temperature for 1h to obtain a final black powder sample, which is Ag-Co3O4 metal nanocomposite.

2. An Ag-Co304 metal nanocomposite, characterized in that: It is prepared by the preparation method of claim 1.

3. Application of the Ag-Co3O4 metal nanocomposite of claim 2 in catalyzing the hydrolysis of ammonia borane complex to produce hydrogen.

4. A method of catalyzing the hydrolysis of an ammonia borane complex to produce hydrogen, characterized by: It comprises the following steps: (1) The Ag-Co3O4 metal nanocomposite material as claimed in claim 2 is added to 1 mol•L -1 NaOH aqueous solution, and ultrasonic treatment is performed for 5 min to make it fully dispersed; (2) Add ammonia borane complex to the solution dispersed in step (1), collect hydrogen gas by drainage method while stirring.

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