An iron-based / graphene catalyst and its preparation method and application

Abstract

The present invention relates to the field of solid-state hydrogen storage technology, and discloses an iron-based / graphene catalyst and its preparation method and application. The iron-based / graphene catalyst comprises a graphene carrier and FeF2 / FeO2 supported on the graphene carrier. X Heterojunction. Preparation method: FeF3·3H2O, a small molecule alcohol and graphene are uniformly mixed to obtain a precursor solution; the precursor solution is hydrothermally reacted at 190-240°C for 20-36h to obtain the iron-based / graphene catalyst. The iron-based / graphene catalyst provided by the present invention is graphene-supported FeF2 / FeO X The heterojunction, with its rich interface, offers high catalytic activity. The composite hydrogen storage material produced by this invention forms multiple uniform and stable catalysts in situ during the first hydrogen release: FeB, Fe2B, and Li3BO3. These catalysts work synergistically to lower the dehydrogenation temperature and accelerate the dehydrogenation rate of LiBH4, demonstrating excellent low-temperature dehydrogenation performance. Furthermore, the reversible hydrogen storage performance of LiBH4 is effectively enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state hydrogen storage, and in particular relates to an iron-based / graphene catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen is regarded as the ultimate energy source for mankind due to its advantages such as zero pollution, abundant storage and low cost. The preparation, storage, transportation and use of hydrogen are the three key technologies for realizing large-scale practical application of hydrogen energy. However, how to store hydrogen in a high capacity, large scale and economical way is a huge technical challenge facing the application of hydrogen energy. LiBH4 has a high mass (18.5wt%) and volume (121kg / m 3 ) hydrogen storage density has attracted much attention, but due to the + and [BH4] - The strong ionic bond between B and H and the strong covalent bond between B and H result in a dehydrogenation temperature typically above 400°C and a slow hydrogen release rate. In addition, the low reactivity of B towards H leads to particle growth and agglomeration, and phase separation makes the regeneration of LiBH4 require harsh temperatures (600°C) and hydrogen pressures (35 MPa), resulting in poor reversible cycle performance.

[0003] The introduction of a catalyst can effectively lower the dehydrogenation temperature of LiBH4 and increase its hydrogen release rate. Existing catalysts include transition metals such as Ni, Fe, Co, and Mg; metal fluorides such as VCl3, CeCl3, and TiCl3; metal oxides such as Fe2O3, V2O5, Nb2O5, TiO2, and SiO2; and metal fluorides such as FeF3, TiF3, CeF3, NbF5, and AlF3, which have been widely reported. For example, Yuan et al., Journal of Alloys and Compounds 2013, 557:124-129, reported that a 3LiBH4+AlF3 composite system prepared by ball milling absorbed hydrogen at 450°C and 9.2 MPa for 24 hours after the first dehydrogenation. The composite was then heated to 600°C for a second dehydrogenation, releasing 1 wt% H2. However, when these catalysts are combined with light metal borohydrides, the resulting modified light metal borohydrides exhibit poor reversible hydrogen storage properties. Therefore, there is an urgent need to develop a catalyst that can improve the reversible hydrogen storage performance of modified light metal borohydrides. Summary of the Invention

[0004] The present invention provides an iron-based / graphene catalyst and a preparation method and application thereof, which solves the problem that the modified light metal borohydride prepared by the prior art after being compounded with a light metal borohydride has poor reversible hydrogen storage performance.

[0005] The first aspect of the present invention provides an iron-based / graphene catalyst, comprising a graphene carrier, and FeF2 / FeO supported on the graphene carrier. X Heterojunction.

[0006] The second object of the present invention is to provide a method for preparing the iron-based / graphene catalyst, which specifically comprises the following steps:

[0007] FeF3·3H2O, small molecule alcohol and graphene are uniformly mixed to obtain a precursor solution;

[0008] The precursor solution is hydrothermally reacted at 190-240° C. for 20-36 hours to obtain the iron-based / graphene catalyst.

[0009] The morphology of the iron-based catalyst is affected by the hydrothermal reaction time. Within the first 0-5 hours, aggregates of nanoparticles form. As the reaction time increases to 5-15 hours, the nanoparticles begin to assemble, gradually forming smooth nanosheets. Further increases in reaction time to 20 hours or longer produce rod-shaped iron-based catalysts.

[0010] Preferably, the small molecule alcohol is one of n-propanol, methanol, ethanol, isopropanol, and n-butanol.

[0011] Preferably, when the small molecule alcohol is n-propanol, the ratio of FeF3·3H2O, n-propanol and graphene is 10 mg:6 mL:5 mg.

[0012] The third object of the present invention is to protect the use of the iron-based / graphene catalyst in catalyzing the preparation of light metal borohydrides.

[0013] A method for preparing a composite hydrogen storage material, comprising:

[0014] Under an inert atmosphere, the iron-based / graphene catalyst and the light metal borohydride are ball-milled for 2-3 hours to obtain the composite hydrogen storage material; wherein the mass ratio of the iron-based / graphene catalyst to the light metal borohydride is 6-8:2-4.

[0015] Preferably, the mass ratio of the iron-based / graphene catalyst to the light metal borohydride is 3:7.

[0016] Preferably, the light metal borohydride is one of LiBH4, NaBH4, and Mg(BH4)2.

[0017] Preferably, the ball milling speed is 400-500 rpm, and the ball milling time is 2-3 h.

[0018] The fourth object of the present invention is to protect the composite hydrogen storage material obtained by the preparation method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The iron-based / graphene catalyst provided by the present invention is graphene-supported FeF2 / FeO X Heterojunction, due to FeF2 / FeO X The heterojunction has rich interfaces and provides multiple active sites, which can provide higher catalytic activity. During ball milling, it reacts with LiBH4 as follows: LiBH4+FeF2 / FeO X →Li m Fe n O p +Fe2B+LiF+B2O3+H2↑, producing an Fe2B catalyst on the surface of LiBH4. Simultaneously, since light metal borohydrides are strong reducing agents, and the iron / graphene catalyst is highly oxidizing, a redox reaction occurs with the light metal borohydride during ball milling. Testing indicates that Fe2B forms on the borohydride surface during ball milling, effectively catalyzing the dehydrogenation of the light metal borohydride. The composite hydrogen storage material of the present invention has a simple preparation process, a short cycle time, and minimal equipment requirements, making it easy to implement.

[0021] 2) The composite hydrogen storage material provided by this invention in situ generates multiple uniform and stable catalysts during the first dehydrogenation step: FeB, Fe2B, and Li3BO3. Taking the light metal borohydride LiBH4 as an example, the chemical reaction between LiBH4 and the iron / graphene catalyst during the heating process, combined with the introduction of multiple catalysts, works synergistically to lower the dehydrogenation temperature and accelerate the dehydrogenation rate of LiBH4, demonstrating excellent low-temperature dehydrogenation performance. More importantly, it effectively improves the reversible hydrogen storage performance of LiBH4. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FeF2 / FeO prepared in Example 1 X @G’s XRD;

[0023] Figure 2 FeF2 / FeO prepared in Example 1 X Raman spectrum of @G;

[0024] Figure 3 FeF2 / FeO prepared in Example 1 X XPS spectra of Fe 2p: a, F 1s: b, O 1s: c; C 1s: d of @G;

[0025] Figure 4 FeF2 / FeO prepared in Example 1 XSEM (100 nm): a, SEM (250 nm): b, TEM (5 nm): c, TEM (100 nm): d and EDS image: e of @G;

[0026] Figure 5 The mLiBH4-n(FeF2 / FeO X @G) XRD spectrum;

[0027] Figure 6 The mLiBH4-n(FeF2 / FeO X FTIR spectrum of @G);

[0028] Figure 7 The mLiBH4-n(FeF2 / FeO X @G) Fe 2p, F 1s, O 1s and C 1s XPS spectra;

[0029] Figure 8 The mLiBH4-n(FeF2 / FeO X @G) non-isothermal hydrogen release curve;

[0030] Figure 9 The mLiBH4-n(FeF2 / FeO X HRTEM image of @G);

[0031] Figure 10 The mLiBH4-n(FeF2 / FeO X @G) Isothermal hydrogen release curve at 350℃;

[0032] Figure 11 The mLiBH4-n(FeF2 / FeO X @G) Isothermal hydrogen release curve at 400℃;

[0033] Figure 12 7LiBH4-3(FeF2 / FeO X @G) Isothermal hydrogen release curves of different cycles;

[0034] Figure 13 7LiBH4-3(FeF2 / FeO X Comparison of cyclic hydrogen release capacity between G) and pristine LiBH4;

[0035] Figure 14 7LiBH4-3(FeF2 / FeO X@G) XRD patterns of products after different hydrogen absorption and desorption cycles;

[0036] Figure 15 7LiBH4-3(FeF2 / FeO X @G) Fe 2p and B1s XPS spectra of products from different hydrogen absorption and desorption cycles;

[0037] Figure 16 7LiBH4-3(FeF2 / FeO X HRTEM image of @G);

[0038] Figure 17 This is the SEM image of the original LiBH4 after 5 cycles;

[0039] Figure 18 7LiBH4-3(FeF2 / FeO X @G) SEM image after 10 cycles. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the specific implementation of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Unless otherwise specified, the methods described in the embodiments of the present invention are conventional methods. The materials and reagents used are all commercially available unless otherwise specified.

[0042] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural; the single symbol " / " means "or".

[0043] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of A, B or C", or "at least one of A, B and C" can mean any one of A, B, C, or A+B, or A+C, or B+C, or A+B+C, where A, B, and C can be single or multiple, respectively.

[0044] In the following description of this embodiment, the order of serial numbers does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this embodiment.

[0045] In the following description of the present embodiment, the numerical range should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value in the stated range and any other stated value or intermediate value in the stated range is also included in the present embodiment, and the upper and lower limits of the smaller ranges may be independently included or excluded in the range.

[0046] Unless otherwise indicated, the technical / scientific terms used in this embodiment have the same meanings as those generally understood by those skilled in the art. Although this application only describes preferred methods and materials, any similar or equivalent methods and materials may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0047] Example 1

[0048] A method for preparing an iron-based / graphene catalyst, the specific experimental steps are as follows:

[0049] Step 1: Weigh 100mg of FeF3·3H2O and 60mL of n-propanol into a 100mL polytetrafluoroethylene-lined container. Stir at 100rpm for 30 minutes at room temperature. Then, weigh 50mg of graphene and add it to the solution. Stir for another hour to obtain a precursor solution.

[0050] Step 2: The precursor solution is placed in a hydrothermal reactor, and then transferred to a forced air drying oven for hydrothermal reaction at 210° C. for 24 hours to obtain a reaction product.

[0051] Step 3: The reaction product was washed three times with ethanol and centrifuged at 7000 rpm for 3 min. The separated solid was dried in a vacuum oven at 100°C for 8 h to obtain the iron-based / graphene catalyst. The prepared iron-based / graphene catalyst is an in-situ generated heterogeneous stable catalyst, denoted as FeF2 / FeO X @G.

[0052] Figure 1 FeF2 / FeO XThe FeF2 XRD spectrum in @G only detects the FeF2 phase with the steric group P42 / mnm (PDF#45-1026), indicating successful FeF2 synthesis; no other phases were detected. Furthermore, due to the amorphous structure of graphene, no diffraction peaks were observed in the XRD pattern.

[0053] Figure 2 FeF2 / FeO X Raman diagram of @G sample, FeF2 / FeO X @G's Raman spectrum ( Figure 2 ) at 1340 and 1580 cm -1 There are two peaks at , which are attributed to the disorder-induced carbon (d band) and graphite structure (g peak) in the graphene matrix, respectively.

[0054] Figure 3 FeF2 / FeO X The XPS spectrum of @G, combined with the XRD spectrum, confirms the presence of FeF2 and some amorphous FeO X FeF2 / FeO X @G's C1s( Figure 3 a) Deconvolution into five peaks at 284.0, 285.1, 286, 287.9 ​​and 290.1 ​​eV, corresponding to the binding energies of C=C, C-C, C=O, O=CO and π-π bonds, respectively. There is a peak at 284.0 eV, indicating the presence of graphene, with most carbon atoms in the SP2 orbital hybridization region. High-resolution F1s ( Figure 3 b) shows a typical symmetrical peak at 684.6 eV, which is assigned to Fe 2+ -F bond. FeF2 / FeO x @G's O1s zone ( Figure 3 c), four main peaks were observed at 529.7, 531.2, 533.0, and 535.0 eV, belonging to Fe-O, CO, C=O, and FO bonds, respectively. Figure 3 As shown in d, the Fe 2p nuclear energy level spectrum shows obvious satellite peaks at 714.6 and 719.1 eV, which belong to Fe 2+ and Fe 3+ , indicating FeF2 / FeO X @Fe exists in G 2+ and Fe 3+ Combined with O1s and F1s spectral analysis, it was confirmed that FeF2 / FeO X FeO exists in @G X The above XRD, Raman and XPS results show that FeF2 / FeO x @G is composed of FeF2, amorphous FeOx and graphene.

[0055] Figure 4 FeF2 / FeO X The morphology of the @G sample and the EDS spectrum further confirmed the prepared FeF2 / FeO X @G sample contains amorphous FeO X . Figure 4 a is FeF2 / FeO X @G's SEM morphology shows that some rod-like structures grow on the graphene matrix, and these rod-like structures are entangled with each other. In addition, XRD and XPS analysis confirmed that these rods are FeF2 and amorphous FeO X TEM observation ( Figure 4 b) Display FeF2 / FeO X @G has a distinct rod-like morphology, with a large number of gray-black rod-like particles dispersed in a light gray matrix. These gray-black rods are FeF2 and amorphous FeO X , while the light grey layer is the graphene matrix. HRTEM image ( Figure 4 c) shows the FeF2(111) lattice fringes, with a lattice spacing of 0.234 nm, which is similar to that of amorphous FeO X Close contact, while the C distribution has a clear matrix outline, indicating that FeF2 and FeO X Dispersed on the graphene surface. In addition, the distribution of O elements is similar to that of F and Fe elements ( Figure 4 e), combined with the XPS analysis of F1s and Fe 2p, further proved that FeF2 / FeO X The @G sample contains FeF2 and amorphous FeOx, which are evenly dispersed on the graphene matrix. Through the above characterization and analysis, the graphene-supported rod-shaped FeF2 and amorphous FeOx were successfully synthesized. X .

[0056] The FeF2 / FeO prepared in Example 1 X @G is used to prepare mLiBH4-n(FeF2 / FeO X @G) Composite hydrogen storage system, where m:n = 6:4, 7:3, 8:2.

[0057] Example 2

[0058] A composite hydrogen storage material, the specific preparation process includes the following steps:

[0059] Step 1: Weigh 1.2g LiBH4 and 0.8g FeF2 / FeO in the glove box X @G were sequentially loaded into a 220 mL stainless steel ball mill jar, followed by stainless steel ball milling beads with a diameter of 6 mm, with a ball-to-material ratio of 100:1.

[0060] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0061] Step 3: Take out the sample from the ball mill and get 6LiBH4-4(FeF2 / FeO X @G) composite system hydrogen storage material.

[0062] Example 3-4: The preparation method of the composite hydrogen storage material is the same as that of Example 2, except that LiBH4 and FeF2 / FeO X @G The added mass ratios are different.

[0063] Example 3

[0064] A composite hydrogen storage material, the specific preparation process includes the following steps:

[0065] Step 1: Weigh 0.7g LiBH4 and 0.3g FeF2 / FeO in the glove box X @G were sequentially loaded into a 220 mL stainless steel ball mill jar, followed by stainless steel ball milling beads with a diameter of 6 mm, with a ball-to-material ratio of 100:1.

[0066] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0067] Step 3: Take out the sample from the ball mill and get 7LiBH4-3(FeF2 / FeO X @G) composite system hydrogen storage material.

[0068] Example 4

[0069] A composite hydrogen storage material, the specific preparation process includes the following steps:

[0070] Step 1: Weigh 1.2g LiBH4 and 0.8g FeF2 / FeO in the glove box X @G were sequentially loaded into a 220 mL stainless steel ball mill jar, followed by stainless steel ball milling beads with a diameter of 6 mm, with a ball-to-material ratio of 100:1.

[0071] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0072] Step 3: Take out the sample from the ball mill and get 6LiBH4-4(FeF2 / FeO X @G) composite system hydrogen storage material.

[0073] The amounts of raw materials added in Examples 3 and 4 are shown in Table 1:

[0074] Table 1 Raw material addition amounts and ball milling conditions for Examples 3 and 4

[0075]

[0076] The composite samples prepared above were characterized: Figure 5 mLiBH4-n(FeF2 / FeO X @G) XRD spectrum of the composite sample, from which no FeF2 diffraction peak was found. Figure 6 mLiBH4-n(FeF2 / FeO X The FTIR spectrum of @G) confirmed the presence of LiBH4 in the composite sample. Figure 7 mLiBH4-n(FeF2 / FeO X @G) XPS spectrum, analysis shows that FeF2 / FeO X FeF2 and FeO in @G samples X It reacted with LiBH4 during ball milling and generated a uniformly distributed catalyst Fe2B on the surface of LiBH4. Figure 8 The mLiBH4-n(FeF2 / FeO X @G) non-isothermal hydrogen release curve. Figure 9 mLiBH4-n(FeF2 / FeO X @G) further illustrates the formation of Fe2B catalyst.

[0077] Comparative Example 1

[0078] A method for preparing a 7LiBH4-3FeF3 composite material, comprising:

[0079] Step 1: In the glove box, weigh 0.7g LiBH4 and 0.3g FeF3 and put them into a 220mL stainless steel ball mill jar, and then put in stainless steel ball mill beads with a diameter of 6mm, with a ball-to-material ratio of 100:1.

[0080] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0081] Step 3: Take out the sample from the ball mill and obtain the 7LiBH4-3FeF3 composite system hydrogen storage material.

[0082] The isothermal dehydrogenation performance test of the prepared 7LiBH4-3FeF3 sample was carried out. The specific steps are as follows:

[0083] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0084] Step 2: First, evacuate the chamber, then set up an isothermal test program, heating from room temperature to the target temperature of 400°C at a rate of 10°C / min and keeping the temperature for 150 minutes.

[0085] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0086] The prepared composite system was further tested for its cyclic stability. The specific experimental steps are as follows:

[0087] Step 1: The test instrument is a Sieverts gas-solid reactor, built by Zhejiang University. Approximately 60 mg of sample is loaded for each test, and the reactor is then connected to a hydrogen storage tester.

[0088] Step 2: First, the sample is isothermally dehydrogenated. Heat it from room temperature to the target temperature and keep it there for a while until the sample completely releases hydrogen (heat it at 10°C / min to 400°C and keep it there for 150 minutes). The dehydrogenated product is then subjected to hydrogen absorption. It is heated to the target temperature under 10MpaH2 pressure and kept there for a while (heat it at 10°C / min to 450°C and keep it there for 150 minutes).

[0089] Step 3: Before testing, evacuate the sample and set up the test program. One isothermal dehydrogenation and one isothermal absorption constitute a dehydrogenation cycle. The cyclic dehydrogenation capacity is calculated using the sample's dehydrogenation capacity.

[0090] Comparative Example 27 LiBH4-3FeF2 composite material

[0091] A method for preparing a 7LiBH4-3FeF2 composite material, comprising:

[0092] Step 1: In the glove box, weigh 0.7g LiBH4 and 0.3g FeF2 and put them into a 220mL stainless steel ball mill jar, and then put in stainless steel ball mill beads with a diameter of 6mm, with a ball-to-material ratio of 100:1.

[0093] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0094] Step 3: Take out the sample from the ball mill and obtain the 7LiBH4-3FeF3 composite system hydrogen storage material.

[0095] The isothermal dehydrogenation performance test of the prepared 7LiBH4-3FeF3 sample was carried out. The specific steps are as follows:

[0096] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0097] Step 2: First, evacuate the chamber, then set up an isothermal test program, heating from room temperature to the target temperature of 400°C at a rate of 10°C / min and keeping the temperature for 150 minutes.

[0098] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0099] The prepared composite system was further tested for its cyclic stability. The specific experimental steps are as follows:

[0100] Step 1: The test instrument is a Sieverts gas-solid reactor, built by Zhejiang University. Approximately 60 mg of sample is loaded for each test, and the reactor is then connected to a hydrogen storage tester.

[0101] Step 2: First, the sample is isothermally dehydrogenated. Heat it from room temperature to the target temperature and keep it there for a while until the sample completely releases hydrogen (heat it at 10°C / min to 400°C and keep it there for 150 minutes). The dehydrogenated product is then subjected to hydrogen absorption. It is heated to the target temperature under 10MpaH2 pressure and kept there for a while (heat it at 10°C / min to 450°C and keep it there for 150 minutes).

[0102] Step 3: Before testing, evacuate the sample and set up the test program. One isothermal dehydrogenation and one isothermal absorption constitute a dehydrogenation cycle. The cyclic dehydrogenation capacity is calculated using the sample's dehydrogenation capacity.

[0103] Comparative Example 37 LiBH4-3Fe2O3 composite material

[0104] A method for preparing a 7LiBH4-3Fe2O3 composite material, comprising:

[0105] Step 1: In the glove box, weigh 0.7g LiBH4 and 0.3g Fe2O3 and put them into a 220mL stainless steel ball mill jar, and then put in stainless steel ball mill beads with a diameter of 6mm, with a ball-to-material ratio of 100:1.

[0106] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0107] Step 3: Take out the sample from the ball mill and obtain the 7LiBH4-3FeF3 composite system hydrogen storage material.

[0108] The isothermal dehydrogenation performance test of the prepared 7LiBH4-3FeF3 sample was carried out. The specific steps are as follows:

[0109] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0110] Step 2: First, evacuate the chamber, then set up an isothermal test program, heating from room temperature to the target temperature of 400°C at a rate of 10°C / min and keeping the temperature for 150 minutes.

[0111] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0112] The prepared composite system was further tested for its cyclic stability. The specific experimental steps are as follows:

[0113] Step 1: The test instrument is a Sieverts gas-solid reactor, built by Zhejiang University. Approximately 60 mg of sample is loaded for each test, and the reactor is then connected to a hydrogen storage tester.

[0114] Step 2: First, the sample is isothermally dehydrogenated. Heat it from room temperature to the target temperature and keep it there for a while until the sample completely releases hydrogen (heat it at 10°C / min to 400°C and keep it there for 150 minutes). The dehydrogenated product is then subjected to hydrogen absorption. It is heated to the target temperature under 10MpaH2 pressure and kept there for a while (heat it at 10°C / min to 450°C and keep it there for 150 minutes).

[0115] Step 3: Before testing, evacuate the sample and set up the test program. One isothermal dehydrogenation and one isothermal absorption constitute a dehydrogenation cycle. The cyclic dehydrogenation capacity is calculated using the sample's dehydrogenation capacity.

[0116] Comparative Example 47 LiBH4-3FeO composite material

[0117] A method for preparing a 7LiBH4-3FeO composite material, comprising:

[0118] Step 1: In the glove box, weigh 0.7g LiBH4 and 0.3g FeO and put them into a 220mL stainless steel ball mill jar, and then put in stainless steel ball milling beads with a diameter of 6mm, with a ball-to-material ratio of 100:1.

[0119] Step 2: Fill the ball mill jar with 5 MPa of Ar as a protective gas. Then install the ball mill jar on the ball mill and set the two-way mode to 400 rpm, 30 minutes for each forward and reverse rotation, 6 minutes for each rotation, and 2 runs.

[0120] Step 3: Take out the sample from the ball mill and obtain the 7LiBH4-3FeF3 composite system hydrogen storage material.

[0121] The isothermal dehydrogenation performance test of the prepared 7LiBH4-3FeF3 sample was carried out. The specific steps are as follows:

[0122] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0123] Step 2: First, evacuate the chamber, then set up an isothermal test program, heating from room temperature to the target temperature of 400°C at a rate of 10°C / min and keeping the temperature for 150 minutes.

[0124] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0125] The prepared composite system was further tested for its cyclic stability. The specific experimental steps are as follows:

[0126] Step 1: The test instrument is a Sieverts gas-solid reactor, built by Zhejiang University. Approximately 60 mg of sample is loaded for each test, and the reactor is then connected to a hydrogen storage tester.

[0127] Step 2: First, the sample is isothermally dehydrogenated. Heat it from room temperature to the target temperature and keep it there for a while until the sample completely releases hydrogen (heat it at 10°C / min to 400°C and keep it there for 150 minutes). The dehydrogenated product is then subjected to hydrogen absorption. It is heated to the target temperature under 10MpaH2 pressure and kept there for a while (heat it at 10°C / min to 450°C and keep it there for 150 minutes).

[0128] Step 3: Before testing, evacuate the sample and set up the test program. One isothermal dehydrogenation and one isothermal absorption constitute a dehydrogenation cycle. The cyclic dehydrogenation capacity is calculated using the sample's dehydrogenation capacity.

[0129] Table 2 Dehydrogenation performance and cycle performance of different comparative examples

[0130] Group Material system Isothermal dehydrogenation Reversible cycle 2 times Comparative Example 1 <![CDATA[7LiBH4-3FeF3]]> 6.7wt% 4.5wt% Comparative Example 2 <![CDATA[7LiBH4-3FeF2]]> 6.0wt% 4.1wt% Comparative Example 3 <![CDATA[7LiBH4-3Fe2O3]]> 8.7wt% 3.9wt% Comparative Example 4 <![CDATA[7LiBH4-3FeO]]> 6.4wt% 3.6wt%

[0131] The prepared mLiBH4-n(FeF2 / FeO X @G) The composite system was tested for non-isothermal dehydrogenation performance. The specific steps are as follows:

[0132] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0133] Step 2: First, evacuate the chamber, then set up a non-isothermal test program, heating from room temperature to 600°C at 2°C / min.

[0134] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0135] See also Figure 10 It can be seen that the initial hydrogen release temperature of Examples 2-4 is lower than 100°C, while the hydrogen release temperature of the original LiBH4 is 310°C. The composite hydrogen storage material prepared by the present invention is more than 200°C lower than the hydrogen release temperature of the original LiBH4, showing good low-temperature dehydrogenation performance.

[0136] The prepared mLiBH4-n(FeF2 / FeO X @G) The composite system was tested for isothermal dehydrogenation performance, and the specific steps are as follows:

[0137] Step 1: The test instrument is a Sieverts-type gas-solid reaction device made by Zhejiang University. For each test, approximately 60 mg of sample is loaded and the reactor is then connected to a hydrogen storage tester.

[0138] Step 2: First, evacuate the chamber, then set up an isothermal test program, heating from room temperature to the target temperatures of 350°C and 400°C at a rate of 10°C / min and keeping them at that temperature for 200 minutes.

[0139] Step 3: After vacuuming, let it stand for 10 minutes, then click the program and record the data. When the test is completed, close the data recording program and save the test data.

[0140] See also Figure 11From the isothermal dehydrogenation results at 350℃, mLiBH4-n(FeF2 / FeO X @G) Compared with the original LiBH4, the hydrogen release rate is significantly accelerated. X @G) When heated at 350℃ for 60min (including 35min heating time), hydrogen release is almost complete, reaching 6.4wt%. Under the same conditions, the hydrogen desorption rate of the original LiBH4 is only 1.1wt%. 8LiBH4-2(FeF2 / FeO X @G) and 7LiBH4-3(FeF2 / FeO X @G) were kept at 350℃ for 80min (including 35min heating time), releasing 3.6wt% H2 and 7.0wt% H2 respectively. In addition, for mLiBH4-n(FeF2 / FeO X @G) isothermal dehydrogenation at 400℃, 6LiBH4-4(FeF2 / FeO X @G) and 7LiBH4-3(FeF2 / FeO X @G) completed dehydrogenation within 45 min (including 40 min heating time), and the hydrogen release rates were very similar, reaching 7.6 wt% and 9.3 wt% H2, respectively. X The dehydrogenation kinetics of @G) has been significantly improved, see Figure 11 .

[0141] The system of Example 3 has good dehydrogenation performance and is the best example.

[0142] The composite system prepared in Example 3 was selected to further test its cyclic stability. The specific experimental steps are as follows:

[0143] Step 1: The test instrument is a Sieverts gas-solid reactor, built by Zhejiang University. Approximately 60 mg of sample is loaded for each test, and the reactor is then connected to a hydrogen storage tester.

[0144] Step 2: First, the sample is isothermally dehydrogenated. Heat it from room temperature to the target temperature and keep it there for a while until the sample completely releases hydrogen (heat it at 10°C / min to 400°C and keep it there for 150 minutes). The dehydrogenated product is then subjected to hydrogen absorption. It is heated to the target temperature under 10MpaH2 pressure and kept there for a while (heat it at 10°C / min to 450°C and keep it there for 150 minutes).

[0145] Step 3: Before testing, evacuate the sample and set up the test program. One isothermal dehydrogenation and one isothermal absorption constitute a dehydrogenation cycle. The cyclic dehydrogenation capacity is calculated using the sample's dehydrogenation capacity.

[0146] See also Figure 12 and Figure 13 Compared with the original LiBH4, 7LiBH4-3(FeF2 / FeO X @G) showed excellent reversible hydrogen storage performance. 7LiBH4-3(FeF2 / FeO X The hydrogen release of the pristine LiBH4 (@G) decreased from 9.4 wt% in the first cycle to 5.5 wt% in the 10th cycle, corresponding to a reversible capacity retention of 58.8 wt%. In contrast, the pristine LiBH4 only released 4.4 wt% of H2 in the first dehydrogenation, and the dehydrogenation capacity dropped to 2.9 wt% after 5 cycles.

[0147] In addition, 7LiBH4-3(FeF2 / FeO X @G) The phase evolution during the composite cycle was analyzed, such as Figure 14 The XRD spectra show the decomposition and regeneration of LiBH4 under different hydrogen absorption and desorption states. In addition, the diffraction peaks of Li3BO3 and FeB of the catalyst are observed to be stable during hydrogen absorption and desorption. Figure 15 7LiBH4-3(FeF2 / FeO X @G) Fe 2p and B1s XPS spectra of different hydrogen absorption and dehydrogenation cycle products. The Fe 2p and B1s spectra further confirm the presence of FeB and Fe2B catalysts and their stable existence during hydrogen absorption and dehydrogenation. Combined with XRD analysis, it is demonstrated that a heterogeneous catalyst is formed in the first dehydrogenation product and that the synergy between the catalysts is beneficial to improve the reversible cycle performance of LiBH4. In addition, Figure 16 7LiBH4-3(FeF2 / FeO X @G) HRTEM, where clear lattice fringes can be seen, further confirms the existence of these catalysts.

[0148] Figure 17 This is the SEM image of the original LiBH4 after 5 cycles. Figure 18 7LiBH4-3(FeF2 / FeO X @G) SEM morphology of 10 cycles. It can be seen that the original LiBH4 has serious agglomeration and particle growth after 5 dehydrogenation cycles, and has formed large and dense agglomerates. X @G) After 10 dehydrogenation cycles, the product consists of many small particles. This is mainly because the graphene in the sample plays a role in dispersing and inhibiting particle growth, preventing product agglomeration, and also making the formed catalyst evenly dispersed.

[0149] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0150] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. An iron-based / graphene catalyst, characterized in that Comprising a graphene carrier and FeF2 / FeO loaded on the graphene carrier X Heterojunction.

2. A method for preparing the iron-based / graphene catalyst according to claim 1, characterized in that: The specific steps include: FeF3·3H2O, small molecule alcohol and graphene are uniformly mixed to obtain a precursor solution; The precursor solution is hydrothermally reacted at 190-240° C. for 20-36 hours to obtain the iron-based / graphene catalyst.

3. The preparation method according to claim 2, characterized in that The small molecule alcohol is one of n-propanol, methanol, ethanol, isopropanol and n-butanol.

4. The preparation method according to claim 2, characterized in that When the small molecule alcohol is n-propanol, the ratio of FeF3·3H2O, n-propanol and graphene is 10 mg:6 mL:5 mg.

5. Use of the iron-based / graphene catalyst according to claim 1 in catalyzing the preparation of light metal borohydrides.

6. A method for preparing a composite hydrogen storage material, characterized in that: include: Under an inert atmosphere, the iron-based / graphene catalyst and the light metal borohydride according to claim 1 are ball-milled for 2-3 hours to obtain the composite hydrogen storage material; wherein the mass ratio of the iron-based / graphene catalyst to the light metal borohydride is 6-8:2-4.

7. The preparation method according to claim 6, characterized in that The mass ratio of the iron-based / graphene catalyst to the light metal borohydride is 3:

7.

8. The preparation method according to claim 6, characterized in that The light metal borohydride is one of LiBH4, NaBH4, and Mg(BH4)2.

9. The preparation method according to claim 6, characterized in that The ball milling speed is 400-500 rpm, and the ball milling time is 2-3 h.

10. A composite hydrogen storage material prepared by the preparation method according to any one of claims 6 to 9.

Images