Method for improving hydrogen desorption performance of lithium borohydride

Abstract

The invention discloses a method for improving hydrogen desorption performance of lithium borohydride, and belongs to the technical field of hydrogen energy. The method comprises the following steps: firstly, carrying out corrosion treatment on Al85Ni10Co5 alloy powder by adopting a sodium hydroxide solution; then carrying out oxidation treatment on the corrosion product in an air atmosphere; putting the obtained oxidation product and potassium fluotitanate into hot water according to a certain mass ratio, stirring, and freeze-drying; and finally, pouring a certain mass of the dried product into anhydrous tetrahydrofuran containing lithium borohydride, stirring, and carrying out vacuumizing treatment, so that the hydrogen desorption performance of lithium borohydride can be improved. The method has the advantages that the method for improving the hydrogen desorption performance of the lithium borohydride is wide in raw material source, low in price, simple in process, safe and reliable; the lithium borohydride modified by the technology provided by the invention has low hydrogen desorption temperature and high hydrogen desorption amount.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen energy, and particularly relates to a method for improving the hydrogen release performance of lithium borohydride. Background Art

[0002] As a new type of renewable energy, hydrogen energy has the advantages of wide sources, high energy density, cleanness and renewability, and is an ideal energy source to replace traditional fossil fuels. Currently, the efficient and safe storage and transportation of hydrogen energy are the main bottlenecks restricting its development, and hydrogen storage technology has become the focus of attention and research in recent years. In comparison, solid-state hydrogen storage has the advantages of high hydrogen storage density, good safety and convenient transportation, and plays an important role in solving the problem of hydrogen energy storage.

[0003] Lithium borohydride (LiBH4) can release up to 13.8 wt.% of hydrogen when decomposed into LiH and B, and it is a solid-state hydrogen storage material with great development potential. However, its high hydrogen release temperature, slow hydrogen release rate and poor reversibility have greatly restricted its practical application process [Züttel A, Wenger P, Rentsch S, et al. J. Power Sources, 2003, 118: 1 - 7]. In recent years, people have tried to modulate the nanostructure of LiBH4 or add additives to improve its performance. For example, Xu et al. successfully confined LiBH4 in hierarchical porous ZnO / ZnCo2O4 (ZZCO) nanoparticles by chemical impregnation method. The formed LiBH4@2ZZCO has an initial hydrogen release temperature as low as 169 °C, a maximum hydrogen release temperature of 275 °C, and can release 8.7 wt.% of hydrogen below 500 °C, which is much higher than that of pure LiBH4 [Xu X H, Zang L, Zhao Y R, et al. J Power Sources, 2017, 359: 134 - 141]. Guo et al. added TiF3 to LiBH4 by ball milling method. The initial hydrogen release temperature of the prepared 3LiBH4-TiF3 system was reduced to 100 °C, and 5.0 and 6.4 wt.% of hydrogen can be released at 250 and 500 °C, respectively [Guo Y H, Yu X B, Gao L, et al. Energy Environ Sci, 2010, 3(4): 465 - 470]. At present, although certain progress has been made in improving the hydrogen storage performance of lithium borohydride, the hydrogen release temperature of lithium borohydride is still relatively high, and the hydrogen release rate and rehydrogenation conditions still need to be further improved. Summary of the Invention

[0004] Aiming at the deficiencies of the existing lithium borohydride hydrogen storage technology, the present invention provides a method for improving the hydrogen release performance of lithium borohydride, expecting that the lithium borohydride modified by the present invention has a low hydrogen release temperature and a high hydrogen release amount.

[0005] The present invention is realized through the following technical solutions.

[0006] The present invention provides a method for improving the hydrogen release performance of lithium borohydride, which specifically includes the following steps:

[0007] (1) Corrode the Al 85 Ni 10 Co5 alloy powder with a sodium hydroxide solution;

[0008] (2) Oxidize the corrosion product obtained in step (1) in an air atmosphere;

[0009] (3) Place the oxidation product obtained in step (2) and potassium fluotitanate in hot water, stir, and then freeze-dry; the mass ratio of the oxidation product to potassium fluotitanate is 10 - 12:1;

[0010] (4) Pour the dried product obtained in step (3) into anhydrous tetrahydrofuran containing lithium borohydride, stir, and then perform vacuum pumping treatment to improve the hydrogen release performance of lithium borohydride; the mass ratio of lithium borohydride to the dried product is 1:3 - 5.

[0011] Further, in step (1), the concentration of the sodium hydroxide solution is 1 - 2 mol / L, the corrosion temperature is 25 - 30 °C, and the corrosion time is 6 - 12 h.

[0012] Further, in step (2), the oxidation treatment temperature is 120 - 150 °C, and the time is 2 - 3 h.

[0013] Further, in step (3), the hot water temperature is 50 - 60 °C.

[0014] Further, in step (3), the mass ratio of the oxidation product to potassium fluotitanate is 10:1.

[0015] Further, in step (4), the mass ratio of lithium borohydride to the dried product is 1:4.

[0016] The innovation points of the present invention are as follows:

[0017] The present invention first uses a sodium hydroxide solution to treat Al 85 Ni 10The Co5 alloy is subjected to corrosion treatment. By removing aluminum elements and the diffusion and migration of nickel and cobalt atoms, the particle and grain sizes of the corrosion products are reduced, and a large number of defects and active sites are introduced. Then, the corrosion products are oxidized in air to in-situ form nickel-cobalt oxides. Subsequently, potassium fluotitanate is loaded onto the nickel-cobalt oxides to obtain fluorine-containing nickel-cobalt oxides. Finally, lithium borohydride is filled into the pores of the fluorine-containing nickel-cobalt oxides to improve the hydrogen release performance of lithium borohydride. The fluorine-containing nickel-cobalt oxides involved in the present invention have a loose and porous structure, a large specific surface area, and many active sites, which can greatly increase their catalytic efficacy for the hydrogen release of lithium borohydride and play a spatial confinement role on lithium borohydride, thereby further improving the modification effect.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) For the method provided for improving the hydrogen release performance of lithium borohydride, the raw materials have a wide source and low price.

[0020] (2) For the method provided for improving the hydrogen release performance of lithium borohydride, the process is simple, safe, and reliable.

[0021] (3) Lithium borohydride modified by the technology provided by the present invention has a low hydrogen release temperature and a high hydrogen release amount (starting to release hydrogen at 55 °C and basically ending at 305 °C, with a total hydrogen release amount reaching 13.6 wt.%). Brief Description of the Drawings

[0022] Figure 1 It is the X-ray diffraction pattern of the oxidation product obtained in Example 1 of the present invention.

[0023] Figure 2 It is the scanning electron microscope photograph of the oxidation product obtained in Example 1 of the present invention.

[0024] Figure 3 It is the hydrogen release curve of lithium borohydride heated after being modified by the technology provided in Example 1 of the present invention. Detailed Description of the Embodiments

[0025] 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.

[0026] Example 1

[0027] At 25 °C, the Al 85 Ni 10 Co5 alloy powder is subjected to corrosion treatment with a 1 mol / L sodium hydroxide solution for 12 h; then, after washing and drying the corrosion products, they are subjected to oxidation treatment in an air atmosphere at 150 °C for 2 h (the X-ray diffraction pattern and scanning electron microscope photograph of the oxidation product are shown in Figure 1 and Figure 2); Then, the oxidation product and potassium hexafluorotitanate with a mass ratio of 10:1 are simultaneously placed in hot water at 60 °C, stirred, and then freeze-dried; finally, according to the mass ratio of 1:4 of lithium borohydride to the freeze-dried product, the dried product is poured into an anhydrous tetrahydrofuran solution containing lithium borohydride, stirred, and then vacuum-treated to improve the hydrogen release performance of lithium borohydride. From Figure 3 It can be seen that lithium borohydride modified by the above method starts to release hydrogen from 55 °C, and the hydrogen release basically ends at 305 °C, with a total hydrogen release of 13.6 wt.%; in comparison, unmodified pure lithium borohydride only starts to slowly release hydrogen from 300 °C, and the hydrogen release at 500 °C is only 3.1 wt.%.

[0028] Example 2

[0029] At 30 °C, Al 85 Ni 10 Co5 alloy powder is subjected to a 6-hour corrosion treatment with 1 mol / L sodium hydroxide solution; then, after washing and drying the corrosion product, it is subjected to a 3-hour oxidation treatment in an air atmosphere at 120 °C; then, the oxidation product and potassium hexafluorotitanate with a mass ratio of 12:1 are simultaneously placed in hot water at 60 °C, stirred, and then freeze-dried; finally, according to the mass ratio of 1:5 of lithium borohydride to the freeze-dried product, the dried product is poured into an anhydrous tetrahydrofuran solution containing lithium borohydride, stirred, and then vacuum-treated to improve the hydrogen release performance of lithium borohydride. Lithium borohydride modified by the above method starts to release hydrogen from 60 °C, and the hydrogen release basically ends at 315 °C, with a total hydrogen release of 13.2 wt.%.

[0030] Example 3

[0031] At 30 °C, Al 85 Ni 10 Co5 alloy powder is subjected to a 6-hour corrosion treatment with 1 mol / L sodium hydroxide solution; then, after washing and drying the corrosion product, it is subjected to a 2-hour oxidation treatment in an air atmosphere at 150 °C; then, the oxidation product and potassium hexafluorotitanate with a mass ratio of 10:1 are simultaneously placed in hot water at 50 °C, stirred, and then freeze-dried; finally, according to the mass ratio of 1:3 of lithium borohydride to the freeze-dried product, the dried product is poured into an anhydrous tetrahydrofuran solution containing lithium borohydride, stirred, and then vacuum-treated to improve the hydrogen release performance of lithium borohydride. Lithium borohydride modified by the above method starts to release hydrogen from 75 °C, and the hydrogen release basically ends at 320 °C, with a total hydrogen release of 12.5 wt.%.

[0032] Example 4

[0033] At 25 °C, Al 85 Ni 10The Co5 alloy powder was subjected to an 8-hour corrosion treatment; then, after washing and drying the corrosion products, an oxidation treatment was carried out in an air atmosphere at 140 °C for 2 hours; then, the oxidation products and potassium hexafluorotitanate with a mass ratio of 12:1 were simultaneously placed in hot water at 60 °C, stirred, and then freeze-dried; finally, according to the mass ratio of lithium borohydride to the freeze-dried product of 1:4, the dried product was poured into an anhydrous tetrahydrofuran solution containing lithium borohydride, stirred, and then vacuumed, thus realizing the improvement of the hydrogen release performance of lithium borohydride. The lithium borohydride modified by the above method started to release hydrogen from 60 °C, and the hydrogen release basically ended at 315 °C, and the total hydrogen release amount reached 12.8 wt.%.

Claims

1. A method for improving the hydrogen release performance of lithium borohydride, characterized in that It includes the following steps: (1) Corrode the Al 85 Ni 10 Co5 alloy powder with sodium hydroxide solution; (2) Oxidize the corrosion product obtained in step (1) in an air atmosphere; (3) Place the oxidation product obtained in step (2) and potassium fluotitanate in hot water, stir, and then freeze-dry; the mass ratio of the oxidation product to potassium fluotitanate is 10-12:1; (4) Pour the dried product obtained in step (3) into anhydrous tetrahydrofuran containing lithium borohydride, stir, and then perform vacuum pumping treatment to improve the hydrogen release performance of lithium borohydride; the mass ratio of lithium borohydride to the dried product is 1:3-5.

2. The method for improving the hydrogen release performance of lithium borohydride according to claim 1, characterized in that, In step (1), the concentration of the sodium hydroxide solution is 1-2 mol / L, the corrosion temperature is 25-30 °C, and the corrosion time is 6-12 h.

3. The method for improving the hydrogen release performance of lithium borohydride according to claim 1, characterized in that, In step (2), the temperature of the oxidation treatment is 120-150 °C, and the time is 2-3 h.

4. The method for improving the hydrogen release performance of lithium borohydride according to claim 1, characterized in that, In step (3), the temperature of the hot water is 50-60 °C.

5. The method for improving the hydrogen release performance of lithium borohydride according to claim 1, characterized in that, In step (3), the mass ratio of the oxidation product to potassium fluotitanate is 10:

1.

6. The method for improving the hydrogen release performance of lithium borohydride according to claim 1, characterized in that, In step (4), the mass ratio of lithium borohydride to the dried product is 1:4.

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