Ni-Cr(OH) for hydrogen production by hydrazine hydrate decomposition 3 / C-TiO 2 nano-catalyst, its preparation method and application

Abstract

The present invention belongs to the technical field of hydrogen storage materials, and particularly relates to a Ni-Cr(OH) 3 / C-TiO 2 nano-catalyst and its preparation method and application. In this method, C-TiO 2 powder is first dispersed in water, a nickel source precursor and a chromium source precursor are added, and ultrasonic treatment is carried out at room temperature to obtain a uniform mixed solution. Then, sodium borohydride is added for a reduction reaction until no bubbles are generated, and the Ni-Cr(OH) 3 / C-TiO 2 nano-catalyst is obtained by filtration. The present invention prepares a defective-rich C-TiO 2 supported Cr(OH) 3 doped Ni non-precious metal composite nano-catalyst Ni-Cr(OH) 3 / C-TiO 2 by a simple, green and low-cost wet chemical method, and the defect content of the catalyst is regulated by controlling the amount of glycerol used in the process of synthesizing the carrier C-TiO 2 . The catalyst synthesized by the present invention can provide an efficient, stable and low-cost catalyst, which accelerates the practical application of hydrazine hydrate as an efficient hydrogen supplier in fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage materials, and particularly relates to a Ni-Cr(OH) 3 / C-TiO 2 nano-catalyst for hydrogen production by hydrazine hydrate decomposition, and its preparation method and application. Background Technique

[0002] Hydrogen energy is considered to be one of the new energy sources that have the potential to replace fossil energy in the future. However, efficient hydrogen storage and transportation are the technical keys to realizing a hydrogen economy society. Chemical hydrogen storage materials have received extensive attention due to their high hydrogen content and mild dehydrogenation temperature. Among all chemical hydrogen storage materials, hydrazine hydrate has attracted much attention due to its relatively high hydrogen content, stability at room temperature, and the fact that the products of complete decomposition are only H 2 and N 2 and other advantages. More importantly, due to its liquid physical properties, hydrazine hydrate can be directly used on existing equipment.

[0003] Hydrazine hydrate (N 2 H 4 ·H 2 O) has stable physical and chemical properties and is easy to store and transport. Its hydrogen storage content is 8.0 wt%, far exceeding the requirement index (5.5 wt%) of hydrogen storage materials formulated by the US Department of Energy in 2017, and is considered a chemical hydrogen storage material with application potential. The decomposition of hydrazine hydrate can occur under mild conditions with the promotion of a suitable catalyst. Theoretically, the decomposition of 1 mole of hydrazine hydrate can produce 2 moles of hydrogen and 1 mole of nitrogen (Reaction 1). However, the decomposition of hydrazine is relatively difficult and side reactions will occur (Reaction 2). Therefore, the key to catalytically decomposing hydrazine hydrate to produce hydrogen completely lies in preparing a catalyst with high activity and high hydrogen selectivity.

[0004] N 2 H 4 (l) → N 2 (g) + 2H 2 (g) (1)

[0005] 3N 2 H 4 (l) → 4NH 3 (g) + N 2 (g) (2)

[0006] The currently reported catalysts are mainly noble metal-based catalysts, which exhibit excellent selectivity and catalytic activity in the decomposition of hydrazine hydrate to produce hydrogen (J. Mater. Chem. A, 2019, 7, 9903; Small Methods, 2020, 4, 1900707). Due to the high cost and scarce resources of noble metal catalysts, it seriously hinders the application of hydrazine hydrate as a hydrogen storage material in actual industrial production. Therefore, many researchers have turned their attention to non-noble metal catalysts, and certain progress has been made (J. Am. Chem. Soc, 2011, 133, 19638; Angew. Chem. Int. Ed, 2012, 124, 6295). However, the performance of these non-noble metal catalysts has always been unsatisfactory and far from meeting the requirements of industrial production. Therefore, it is very urgent and of great significance to develop non-noble metal catalysts with high selectivity, high efficiency and high stability. Summary of the Invention

[0007] The purpose of the present invention is to solve the deficiencies of the prior art and provide a Ni-Cr(OH) for the decomposition of hydrazine hydrate to produce hydrogen 3 / C-TiO 2 nano-catalyst and its preparation method and application, specifically adopting the following technical solutions:

[0008] A preparation method of a Ni-Cr(OH) for the decomposition of hydrazine hydrate to produce hydrogen 3 / C-TiO 2 nano-catalyst, comprising the following steps:

[0009] First, disperse C-TiO 2 powder in water, add nickel source precursor and chromium source precursor, ultrasonically treat at room temperature to obtain a uniform mixture, then add sodium borohydride for reduction reaction until no bubbles are generated, and filter to obtain Ni-Cr(OH) 3 / C-TiO 2 nano-catalyst.

[0010] The present invention prepares a defective C-TiO-rich 2 supported Cr(OH) 3 doped Ni non-noble metal composite nano-catalyst Ni-Cr(OH) 3 / C-TiO 2 . Among them, the defect content of the catalyst is regulated by controlling the amount of glycerol used in the process of synthesizing the support C-TiO 2 . The defects of the catalyst are that during the assembly process, some O atoms are replaced by C atoms, resulting in TiO 2Self-doping disorder forms oxygen vacancies and lattice disorder defects, which is beneficial to optimizing the electronic structure of the catalyst and exposing more active sites. In addition, C-TiO with rich defects 2 makes the reactants easier to adsorb and activate, which can further improve the catalytic activity. The Ni-Cr(OH) prepared in the present invention 3 / C-TiO 2 catalyst exhibits extremely high catalytic performance, 100% H 2 selectivity and remarkable durability. The TOF value for the dehydrogenation of N 2 H 4 ·H 2 O is 266 h -1 . In addition, the development of the efficient, stable and low-cost catalyst provided by the present invention accelerates the practical application of hydrazine hydrate as an efficient hydrogen supplier in fuel cells.

[0011] The average particle size of the Ni-Cr(OH) nanoparticles in the Ni-Cr(OH) / C-TiO nanocatalyst prepared in the present invention 3 / C-TiO 2 is 2.7 ± 0.2 nm. The ultrafine Ni-Cr(OH) nanoparticles with an average particle size of about 2.7 nm are uniformly distributed on the C-TiO 3 support, making the finally prepared nanocatalyst have small, uniform particle size and strong electronic effect. 3 nanoparticles are uniformly distributed on the C-TiO 2 support, resulting in the finally prepared nanocatalyst having small, uniform particle size and strong electronic effect.

[0012] As a further preferred embodiment, the content of Ni in the above-mentioned nanocatalyst is 18.6% - 50.8 wt%, and the content of Cr(OH) 3 is 1.2% - 4.6 wt%. More preferably, the content of Cr(OH) 3 is 3.6 wt%. The catalytic reaction rate of the nanocatalyst prepared in the present invention first increases and then decreases with the increase of the chromium hydroxide loading amount. When the loading amount is 3.6 wt%, the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst shows the best performance for the hydrogen production from the decomposition of hydrazine hydrate. This is mainly attributed to the fact that the doping of chromium hydroxide can not only effectively reduce the size of metal nanoparticles, but also optimize the electronic structure of the catalyst, thus effectively improving the catalytic reaction activity. However, when the amount of chromium hydroxide is too much, it will cover some active sites, resulting in the decrease of the catalytic performance of the finally prepared Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst in the reaction.

[0013] As a further preferred embodiment, the mass ratio of the above nickel source precursor, chromium source precursor, and C-TiO 2 is 0.2 mmol: 0.005 mmol - 0.02 mmol: 10 mg - 40 mg. More preferably, the mass ratio of the nickel source precursor, chromium source precursor, and C-TiO 2 is 0.2 mmol: 0.015 mmol: 30 mg. The selectivity and activity of the nano-catalyst prepared by the present invention for hydrogen production from hydrazine hydrate both increase first and then decrease with the increase in the dosage of C-TiO 2 . When the dosage of the carrier is very small, the selectivity and activity of the catalyst are relatively low. This is mainly because too little carrier leads to too high a loading of the active metal, and the metal nanoparticles cannot be dispersed, so the catalytic performance is poor. However, when the dosage of the carrier increases to 30 mg, the catalyst has the best catalytic activity. Finally, when the dosage of the carrier is further increased, the activity of the catalyst decreases slightly. This shows that the catalyst can effectively disperse the metal nanoparticles and improve the catalytic activity. However, when the dosage of the carrier is too much, it will cause the active metal to be not easy to contact with hydrazine hydrate, so the performance decreases.

[0014] The C-TiO 2 in the above preparation process is synthesized by a solvent-induced method using tetrabutyl titanate as the titanium source, F127 as the template agent, and glycerol as the carbon source. The dosage ratio of tetrabutyl titanate, Pluronic F127, and glycerol is 6.8 g: 3.0 g: 10 mL - 50 mL.

[0015] As a further preferred embodiment, the dosage ratio of tetrabutyl titanate, Pluronic F127, and glycerol is 6.8 g: 3.0 g: 40 mL. The catalytic reaction rate of the nano-catalyst prepared by the present invention shows a trend of first increasing and then stabilizing with the increase in the dosage of glycerol. When the dosage is 40 mL, the Ni-Cr(OH) 3 / C-TiO 2 composite nano-catalyst shows the best performance for hydrogen production from the decomposition of hydrazine hydrate. It shows that by regulating the dosage of glycerol during the synthesis of the support, the defect content of the catalyst can be regulated. The defects of the catalyst are that during the assembly process, some O atoms are replaced by C atoms, resulting in self-doping disorder of TiO 2 , forming oxygen vacancies and lattice disorder defects, which is beneficial to optimizing the electronic structure of the catalyst and exposing more active sites. In addition, the C-TiO 2 with rich defects makes the reactants easier to adsorb and activate, which may further improve the catalytic activity. This makes the finally prepared Ni-Cr(OH) 3 / C-TiO 2 composite nano-catalyst have different catalytic performances in the reaction.

[0016] During the above preparation process, C-TiO 2 The specific preparation process is as follows:

[0017] Add 3.0 g of Pluronic F127, 4.8 g of acetic acid, and 7.0 g of concentrated HCl (36%) to 60 mL of tetrahydrofuran (THF). After vigorously stirring for 20 minutes, add 6.8 g of tetrabutyl titanate (TBOT), and then add 0.40 g of H 2 O. Transfer the formed transparent white-yellow solution to two 30 mm×50 mm volumetric flasks and place them in an oven at 50 °C for 24 hours. In a typical procedure, add 4.0 g of the yellow gel obtained above to 40 mL of ethanol under vigorous stirring to form a transparent solution. Then, add 40 mL of glycerol dropwise under vigorous stirring. After 20 minutes, transfer the obtained transparent solution to a 100 ml autoclave. After heating at 100 °C for 10 hours, let the solution cool naturally to room temperature. Collect the white precipitate by centrifugation, wash it with ethanol, and then dry it in an oven. Finally, obtain mesoporous C-TiO 2 nanosheets by further calcining in nitrogen at 350 °C for 6 hours.

[0018] In the above preparation method, the nickel source precursor is at least one of nickel chloride, nickel nitrate, or nickel sulfate; the chromium source precursor is at least one of chromium chloride, chromium nitrate, or chromium sulfate.

[0019] The nanocatalyst prepared by the present invention for hydrogen production by hydrazine decomposition can be used in the preparation of hydrogen sources for fuel cells. When the catalyst is used for catalyzing hydrogen production by hydrazine decomposition, the temperature is 303 K - 333 K. Since the catalytic reaction is carried out in solution, too high a temperature will cause water evaporation, increase the concentration of hydrazine hydrate, and make the decomposition of hydrazine hydrate more difficult. Therefore, the catalytic temperature should not be too high.

[0020] The beneficial effects of the present invention are as follows: The present invention prepares a defective-rich C-TiO 2 supported Cr(OH) 3 doped Ni non-precious metal composite nanocatalyst Ni-Cr(OH) 3 / C-TiO 2 by a simple, green, and low-cost wet chemical method. Among them, the defect content of the catalyst is regulated by controlling the amount of glycerol used during the synthesis of the support C-TiO 2 . The defects of the catalyst are that during the assembly process, some O atoms are replaced by C atoms, resulting in TiO 2Self-doping disorder forms oxygen vacancies and lattice disorder defects, which is beneficial to optimizing the electronic structure of the catalyst and exposing more active sites. In addition, the MOF with abundant defects makes it easier for reactants to be adsorbed and activated, which can further improve the catalytic activity. The Ni-Cr(OH) synthesized in the present invention 3 / C-TiO 2 catalyst exhibits extremely high catalytic performance, 100% H 2 selectivity, and remarkable durability, accelerating the practical application of hydrazine hydrate as an efficient hydrogen supplier in fuel cells by enabling the development of highly efficient, stable, and low-cost catalysts. Description of the Drawings

[0021] Figure 1 Shown are the Raman spectra of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Examples 1-5 and the comparative catalyst;

[0022] Figure 2 Shown are the Raman spectra of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Examples 1-5 and the comparative catalyst;

[0023] Figure 3 Shown are the Fourier transform infrared spectra of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Examples 1-5 and the comparative catalyst;

[0024] Figure 4 Shown are the electron paramagnetic resonance spectra of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Examples 1-5 and the comparative catalyst;

[0025] Figure 5 Shown are the nitrogen adsorption test graphs of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Examples 1-5 and the comparative catalyst;

[0026] Figure 6 Shown are the scanning electron microscopy image (a), transmission electron microscopy image (b), particle size statistical graph (c) of Ni nanoparticles, and high-resolution transmission electron microscopy image (d) of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst obtained in Example 4;

[0027] Figure 7Shown is the Ni-Cr(OH) obtained in Example 4 3 / C-TiO 2 EDX energy spectrum of the composite nanocatalyst;

[0028] Figure 8 Shown is the Ni-Cr(OH) obtained in Example 4 3 / C-TiO 2 X-ray photoelectron spectroscopy of the composite nanocatalyst and the comparative catalyst;

[0029] Figure 9 Shown are the Ni-Cr(OH) obtained in Examples 1-5 3 / C-TiO 2 Hydrogen production test performance test chart of the nanocomposite catalyst for catalyzing the decomposition of hydrazine hydrate at 323 K;

[0030] Figure 10 Shown are the Ni-Cr(OH) obtained in Examples 1 and 6-9 3 / C-TiO 2 Performance test chart of the nanocomposite catalyst for catalyzing the decomposition of hydrazine hydrate at 323 K;

[0031] Figure 11 Shown are the Ni-Cr(OH) obtained in Examples 1 and 14-16 3 / C-TiO 2 Performance test chart of the nanocomposite catalyst for catalyzing the decomposition of hydrazine hydrate at 323 K;

[0032] Figure 12 Shown is the Ni-Cr(OH) obtained in Example 1 3 / C-TiO 2 Performance test chart of the nanocomposite catalyst for catalyzing the decomposition of hydrazine hydrate at different temperatures;

[0033] Figure 13 Shown is the Ni-Cr(OH) obtained in Example 1 3 / C-TiO 2 Performance test chart of the recycling performance of the nanocomposite catalyst for catalyzing the decomposition of hydrazine hydrate at 323 K. Detailed implementation manners

[0034] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the examples and the drawings to fully understand the purpose, scheme and effects of the present invention.

[0035] Example 1

[0036] A nanocatalyst for the decomposition of hydrazine hydrate to produce hydrogen, and its preparation method specifically includes the following steps:

[0037] Step 1. Preparation of C-TiO 2 : Add 3.0 g of Pluronic F127, 4.8 g of acetic acid, and 7.0 g of concentrated HCl (36%) into 60 mL of tetrahydrofuran (THF). After stirring vigorously for 20 minutes, add dropwise 6.8 g of tetrabutyl titanate (TBOT), and then add 0.40 g of H 2 O. Transfer the formed transparent white-yellow solution into two 30 mm×50 mm volumetric flasks, and place them in an oven at 50 °C for 24 hours. Add 4.0 g of the yellow gel obtained above into 40 mL of ethanol under vigorous stirring to form a transparent solution. Then, add dropwise 40 mL of glycerol under vigorous stirring. After 20 minutes, transfer the obtained transparent solution into a 100 mL autoclave, heat it at 100 °C for 10 hours, and then let the solution cool naturally to room temperature. Collect the white precipitate by centrifugation, wash it with ethanol, and then dry it in an oven. Finally, obtain mesoporous C-TiO 2 nanosheets by further calcining in nitrogen at 350 °C for 6 hours;

[0038] Step 2. Preparation of Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst: Disperse C-TiO 2 (30 mg) in 5 mL of deionized water, and then add 48.4 mg of NiCl 2 ·6H 2 O (0.2 mmol) and 6.0 mg of Cr(NO 2 ) 3 ·9H 3 O (0.015 mmol) into the C-TiO 2 suspension, and perform ultrasonic treatment at 298 K for 30 minutes. Quickly add 30 mg of NaBH 4 into the above mixture and stir vigorously. Filter to obtain a black product of Ni-Cr(OH) 3 / C-TiO 2 (3.6% Cr).

[0039] Example 2

[0040] Change the amount of glycerol in Step 1 of Example 1 to 10 mL, and keep other steps the same as in Example 1 to obtain Ni-Cr(OH)3 / C-TiO 2 composite nanocatalyst.

[0041] Example 3

[0042] Change the amount of glycerol in Step 2 of Example 1 to 20 mL, and keep other steps the same as in Example 1 to obtain Ni-Cr(OH) 3 / C-TiO 2 Composite nanocatalyst

[0043] Example 4

[0044] Change the amount of glycerol in Step 2 of Example 1 to 30 mL, and the other steps are the same as in Example 1, to obtain Ni-Cr(OH) 3 / C-TiO 2 Composite nanocatalyst

[0045] Example 5

[0046] Change the amount of glycerol in Step 2 of Example 1 to 50 mL, and the other steps are the same as in Example 1, to obtain Ni-Cr(OH) 3 / C-TiO 2 Composite nanocatalyst

[0047] Example 6

[0048] Adjust the dosage of C-TiO in Step 2 of Example 1 to 10 mg, and the other steps are the same as in Example 1, to obtain Ni, Cr(OH)3 loadings of 50.8 wt% and 4.6 wt% Ni-Cr(OH) 2 respectively, and the composite nanocatalyst Ni-Cr(OH) 3 / C-TiO 2 Composite nanocatalyst

[0049] Example 7

[0050] Adjust the dosage of C-TiO in Step 2 of Example 1 to 20 mg, and the other steps are the same as in Example 1, to obtain Ni, Cr(OH) 2 loadings of 35.4 wt% and 3.6 wt% respectively, and the composite nanocatalyst Ni-Cr(OH) 3 / C-TiO 3 Composite nanocatalyst 2 / C-TiO

[0051] Example 8

[0052] Adjust the dosage of C-TiO in Step 2 of Example 1 to 40 mg, and the other steps are the same as in Example 1, to obtain Ni, Cr(OH) 2 loadings of 27.2 wt% and 2.4 wt% respectively, and the composite nanocatalyst Ni-Cr(OH) 3 / C-TiO 3 Composite nanocatalyst 2 / C-TiO

[0053] Example 9

[0054] Adjust the dosage of C-TiO in Step 2 of Example 1 to 2The dosage was adjusted to 50 mg, and the other steps were the same as in Example 1, obtaining Ni, Cr(OH) 3 with Ni-Cr(OH) loadings of 18.6 wt% and 1.2 wt% respectively 3 / C-TiO 2 composite nanocatalyst.

[0055] Example 10

[0056] In Step 2 of Example 1, the precursor nickel salt nickel chloride was changed to nickel nitrate, and the other steps were the same as in Example 1, obtaining Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst.

[0057] Example 11

[0058] In Step 2 of Example 1, the precursor nickel salt nickel chloride was changed to nickel sulfate, and the other steps were the same as in Example 1, obtaining Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst.

[0059] Example 12

[0060] In Step 2 of Example 1, the precursor chromium salt chromium nitrate was changed to chromium chloride, and the other steps were the same as in Example 1, obtaining Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst.

[0061] Example 13

[0062] In Step 2 of Example 1, the precursor chromium salt chromium nitrate was changed to chromium sulfate, and the other steps were the same as in Example 1, obtaining Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst.

[0063] Example 14

[0064] In Step 2 of Example 1, the dosage of chromium nitrate was adjusted to 0.005 mmol, and the other steps were the same as in Example 1, obtaining Ni-Cr(OH)3 with Ni and Cr(OH)3 loadings of 22.7 wt% and 0.9 wt% respectively 3 / C-TiO 2 composite nanocatalyst.

[0065] Example 15

[0066] Adjust the amount of chromium nitrate in step 2 of Example 1 to 0.01 mmol, and keep other steps the same as in Example 1 to obtain a Ni-Cr(OH) with Ni and Cr(OH)3 loadings of 22.4 wt% and 1.9 wt% respectively 3 / C-TiO 2 composite nanocatalyst.

[0067] Example 16

[0068] Adjust the amount of chromium nitrate in step 2 of Example 1 to 0.02 mmol, and keep other steps the same as in Example 1 to obtain Ni-Cr(OH) 3 with loadings of 22.0 wt% and 3.7 wt% Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst.

[0069] Example 17

[0070] The present invention has carried out relevant characterization data on some of the materials prepared in the above examples, as follows:

[0071] Figure 1 For the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst and the X-ray diffraction pattern of the comparative catalyst. It can be seen from Figure 1 that the TiO 3 peak in the defective Ni-Cr(OH) 2 / C-TiO 2 becomes broader, indicating the successful incorporation of C;

[0072] Figure 2 For the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst and the Raman spectrum of the comparative catalyst. It can be seen from Figure 2 that the defective Ni-Cr(OH) 3 / C-TiO 2 has an offset at 150 cm -1 , indicating that the introduction of C causes self-doping disorder of TiO 2 and thus generates defects;

[0073] Figure 3 For the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst and the Fourier transform infrared spectrum of the comparative catalyst. It can be seen from Figure 3It can be seen that the introduction of C broadens the infrared absorption peak of Ti-O-Ti and brings more functional groups;

[0074] Figure 4 For the Ni-Cr(OH) obtained in Examples 1-5 3 / C-TiO 2 Composite nanocatalyst and the electron paramagnetic resonance spectrogram of the comparative catalyst, from Figure 4 It can be seen that Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst has more defects, indicating that the introduction of C makes the surface defect amount of TiO 2 more;

[0075] Figure 5 For the Ni-Cr(OH) obtained in Examples 1-5 3 / C-TiO 2 Composite nanocatalyst and the nitrogen adsorption test diagram of the comparative catalyst, from Figure 5 It can be seen that the specific surface area of the catalyst after doping with C is higher than that of the catalyst without doping with C;

[0076] Figure 6 For the Ni-Cr(OH) obtained in Example 4 3 / C-TiO 2 Scanning electron microscope image (a), transmission electron microscope image (b), particle size statistical chart of Ni nanoparticles (c) and high-resolution transmission electron microscope image (d) of the composite nanocatalyst, and from Figure 6 It can be seen that the nanoparticles are evenly distributed on the sheet, and the particle size is only 2.7 nm;

[0077] Figure 7 For the Ni-Cr(OH) obtained in Example 4 3 / C-TiO 2 EDX energy spectrum of the composite nanocatalyst, from Figure 7 It can be seen that the amounts of each element match the corresponding addition amounts;

[0078] Figure 8 For the Ni-Cr(OH) obtained in Example 4 of the present invention 3 / C-TiO 2 X-ray photoelectron energy spectrum of the composite nanocatalyst and the comparative catalyst, from Figure 8 It can be seen that the active metal Ni in the defect-rich Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst shifts more towards lower binding energy, indicating that more electrons are obtained.

[0079] Example 18

[0080] Using the Ni-Cr(OH) prepared in Examples 1, 2, 3, 4, and 5 of the present invention 3 / C-TiO 2 The composite nanocatalyst catalyzes the decomposition of hydrazine hydrate to produce hydrogen. The catalyst is placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (15 mmol) is added. The amount of the catalyst is the amount of the catalyst prepared in each example. At 323 K under atmospheric pressure, 100 μL (2.0 mmol) of hydrazine hydrate is added for the reaction. The hydrogen production performance diagram is as Figure 9 shown. The conditions for preparing the catalysts in Examples 1-5 and the results of the catalytic reaction are shown in Table 1.

[0081] Table 1 Hydrogen production performance list of Ni-Cr(OH) prepared in Examples 1-5 3 / C-TiO 2 composite nanocatalyst for hydrazine hydrate

[0082] Catalyst source Glycerol (mL) H2 selectivity (%) Hydrogen production time (min) TOF value (h-1) 1 10 100 6.7 178 2 20 100 5.8 208 3 30 100 4.9 246 4 40 100 4.5 266 5 50 100 8.6 139

[0083] The results in Table 1 show that Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst for catalyzing the decomposition of hydrazine hydrate to produce hydrogen all shows 100% H 2 selectivity. The catalytic reaction rate shows a trend of first increasing and then stabilizing with the increase of the amount of glycerol. When the amount is 40 mL, Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst shows the best performance for the decomposition of hydrazine hydrate to produce hydrogen. It shows that by regulating the amount of glycerol during the synthesis of the support, the defect content of the catalyst can be regulated. The defects of the catalyst are that during the assembly process, some O atoms are replaced by C atoms, resulting in the self-doping disorder of TiO 2 and the formation of oxygen vacancies and lattice disorder defects, which is beneficial to optimizing the electronic structure of the catalyst and exposing more active sites. In addition, C-TiO with rich defects 2 makes the reactants easier to adsorb and activate, which may further improve the catalytic activity. The finally prepared Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst has different catalytic performances in the reaction.

[0084] Example 19

[0085] Using the Ni-Cr(OH) prepared in Examples 1, 6, 7, 8, and 9 of the present invention 3 / C-TiO 2The composite nanocatalyst catalyzes the decomposition of hydrazine hydrate to produce hydrogen. The catalyst is placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (15 mmol) is added. The amount of the catalyst is the amount of the catalyst prepared in each example. At 323 K under atmospheric pressure, 100 μL (2.0 mmol) of hydrazine hydrate is added for the reaction. The hydrogen production performance diagram is as Figure 10 shown. The preparation conditions of the catalyst and the results of the catalytic reaction are shown in Table 2.

[0086] Table 2 Ni-Cr(OH) prepared in Example 1 and 6-9 3 / C-TiO 2 List of hydrogen production performance of the composite nanocatalyst for catalyzing hydrazine hydrate

[0087] Catalyst source C-TiO2 (mg) H2 selectivity (%) Hydrogen production time (min) TOF value (h-1) 1 10 100 6.4 187 6 20 100 5.5 218 7 30 100 4.5 266 8 40 100 5.8 206

[0088] The results in Table 2 show that the selectivity and activity of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst for catalyzing hydrazine hydrate to produce hydrogen both increase first and then decrease with the increase of the amount of C-TiO 2 . When the amount of the support is very small, the selectivity and activity of the catalyst are relatively low. This is mainly because too little support leads to too high a loading of the active metal, and the metal nanoparticles cannot be dispersed, so the catalytic performance is poor. However, when the amount of the support increases to 30 mg, the catalyst has the best catalytic activity. Finally, when the amount of the support is further increased, the activity of the catalyst decreases slightly. It shows that the catalyst can effectively disperse the metal nanoparticles and improve the catalytic activity. However, when the amount of the support is too much, it will cause the active metal to be difficult to contact with hydrazine hydrate, so the performance decreases.

[0089] Example 20

[0090] Using the Ni-Cr(OH) prepared in Examples 1, 14, 15, and 16 of the present invention 3 / C-TiO 2 composite nanocatalyst to catalyze the decomposition of hydrazine hydrate to produce hydrogen. The catalyst is placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (15 mmol) is added. The amount of the catalyst is the amount of the catalyst prepared in each example. At 343 K under atmospheric pressure, 100 μL (2.0 mmol) of hydrazine hydrate is added for the reaction. The hydrogen production performance diagram is as Figure 11 shown. The preparation conditions of the catalyst and the results of the catalytic reaction are shown in Table 3.

[0091] Table 3 Ni-Cr(OH) prepared in Examples 1 and 14-16 3 / C-TiO 2 List of hydrogen production performance of the composite nanocatalyst for catalyzing hydrazine hydrate

[0092] Catalyst source Cr(OH)3 (wt%) H2 selectivity (%) Hydrogen production time (min) TOF value (h-1) 1 3.6 100 1.4 266 14 1.2 100 3.0 203 15 2.4 100 2.1 254 16 4.6 100 3.8 151

[0093] The results in Table 3 show that Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst for hydrogen production from hydrazine hydrate shows 100% H 2 selectivity. The catalytic reaction rate first increases and then decreases with the increase of the chromium hydroxide loading. When the loading is 3.6 wt%, Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst shows the best performance for hydrogen production from the decomposition of hydrazine hydrate. This is mainly attributed to the fact that the doping of chromium hydroxide can not only effectively reduce the size of metal nanoparticles but also optimize the electronic structure of the catalyst, thus effectively improving the catalytic reaction activity. However, when the amount of chromium hydroxide is too large, it will cover some active sites, resulting in a decrease in the catalytic performance of the finally prepared Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst in the reaction.

[0094] Example 21

[0095] Using the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst prepared in Example 1 of the present invention, the decomposition of hydrazine hydrate to produce hydrogen was catalyzed at different temperatures. The catalyst was placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (15 mmol) was added. 100 μL (2.0 mmol) of hydrazine hydrate was added for reaction at 303 K, 313 K, 323 K, and 333 K under atmospheric pressure. The hydrogen production performance diagram is as shown in Figure 12 shown, and the conditions for preparing the catalyst and the results of the catalytic reaction are shown in Table 6.

[0096] Table 6 The catalytic hydrogen production performance of Ni-Cr(OH) 3 / C-TiO 2 Composite nanocatalyst prepared in Example 1 for hydrogen production from hydrazine hydrate at different catalytic temperatures

[0097] Catalyst source Temperature (K) H2 selectivity (%) Hydrogen production time (min) TOF value (h-1) Example 1 333 100 2.8 426 Example 1 323 100 4.5 266 Example 1 313 100 10.0 120 Example 1 303 100 21.1 57

[0098] The results in Table 6 show that Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst for hydrogen production from hydrazine hydrate shows 100% H 2 selectivity. The catalytic reaction rate is significantly improved with the increase of temperature. At 323 K, the prepared Ni-Cr(OH) 3 / C-TiO2 The composite nanocatalyst only takes 4.5 min to completely decompose hydrazine hydrate for dehydrogenation, and its turnover frequency (TOF) value is as high as 266 h -1 , which is mainly attributed to the fact that high temperature can activate the catalyst and thus effectively improve the catalytic reaction activity.

[0099] Example 22

[0100] Using the Ni-Cr(OH) prepared in Example 1 of the present invention 3 / C-TiO 2 The composite nanocatalyst was used to catalyze the decomposition of hydrazine hydrate to produce hydrogen. The catalyst was placed in a 50 mL flask containing 5 mL of deionized water, and then NaOH (15 mmol) was added. At 323 K and atmospheric pressure, 100 uL (2.0 mmol) of hydrazine hydrate was added for reaction, and the cycle was repeated 20 times. The hydrogen production performance diagram is as Figure 13 shown.

[0101] As can be seen from Figure 13 , Ni-Cr(OH) 3 / C-TiO 2 The composite nanocatalyst has good cyclic use stability for the decomposition of hydrazine hydrate to produce hydrogen. After being reused 20 times, the catalyst activity and gas production did not decrease, indicating that the catalyst has good catalytic activity and cyclic stability.

[0102] The excellent activity of the Ni-Cr(OH) 3 / C-TiO 2 composite nanocatalyst prepared by the present invention is attributed to the strong metal-support interaction, ultrafine Ni-Cr(OH) 3 metal nanoparticles, and the electron regulation effect of the defect-rich and porous C-TiO 2 on Ni-Cr(OH) 3 .

[0103] In summary, the method for preparing the catalyst of the present invention is simple in operation and low in cost. The obtained catalyst has the characteristics of small particle size and many catalytic active sites, and has high catalytic activity and stability. It is a catalyst with great development potential.

[0104] The above are only the preferred embodiments of the present invention. The present invention is not limited to the above embodiments. As long as it achieves the technical effects of the present invention by the same means, it should fall within the protection scope of the present invention. Within the protection scope of the present invention, its technical solutions and / or embodiments can have various different modifications and changes.

Claims

1. A preparation method of Ni-Cr(OH) 3 / C-TiO 2 nanocatalyst for hydrogen production by hydrazine hydrate decomposition It is characterized in that The preparation method comprises the following steps: First, disperse the C-TiO 2 powder in water, add the nickel source precursor and the chromium source precursor, and perform ultrasonic treatment at room temperature to obtain a uniform mixed solution. Then, add sodium borohydride for a reduction reaction until no bubbles are generated, and filter to obtain Ni-Cr(OH) 3 / C-TiO 2 nano-catalyst. The content of Ni in the nano-catalyst is 18.6% - 50.8 wt%, and the content of Cr(OH) 3 is 1.2% - 4.6 wt%; Nickel source precursor, chromium source precursor, C-TiO 2 The mass ratio is 0.2 mmol: 0.005 mmol - 0.02 mmol: 10 mg - 40 mg; C-TiO 2 The preparation process is as follows: Mesoporous C-TiO 2 nanosheets were synthesized by a solvent-induced method using tetrabutyl titanate as the titanium source, Pluronic F127 as the template agent, and glycerol as the carbon source; the dosage ratio of tetrabutyl titanate, Pluronic F127, and glycerol was 6.8 g: 3.0 g: 10 mL - 50 mL.

2. The preparation method according to claim 1, It is characterized in that The content of Cr(OH) in the nano-catalyst 3 is 3.6 wt%.

3. The preparation method according to claim 1, It is characterized in that The mass ratio of nickel source precursor, chromium source precursor, and C-TiO 2 is 0.2 mmol: 0.015 mmol: 30 mg.

4. The preparation method according to claim 1, It is characterized in that The dosage ratio of tetrabutyl titanate, Pluronic F127 and glycerol is 6.8 g: 3.0 g: 40 mL.

5. A nanocatalyst for hydrogen production by hydrazine hydrate decomposition, It is characterized in that It is prepared by the preparation method according to any one of claims 1-4.

6. Use of the Ni-Cr(OH) 3 / C-TiO 2 nanocatalyst in the preparation of a hydrogen source for a fuel cell.

7. The Ni-Cr(OH) according to claim 6 3 / C-TiO 2 Application of the nano-catalyst in the preparation of the hydrogen source for fuel cells It is characterized in that The nanocatalyst is used for catalyzing the decomposition of hydrazine hydrate to produce hydrogen, and the temperature is 303 K to 333 K.

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