Ti3C2 / nbhx composite material, and preparation method and application thereof

Abstract

The application discloses a Ti3C2 / NbH x composite material x , and relates to the technical field of composite materials. The composite material comprises the following substances in mass percentage: 20-25wt% of NbH x , 75-80wt% of Ti3C2; x in the formula is 1 or 2. The application further discloses a preparation method of the Ti3C2 / NbH x composite material, which comprises the following steps: mixing niobium pentachloride and lithium chloride in an argon atmosphere glove box, and ball milling; adding lithium hydride with a mass of 0.4-0.45 times of the lithium chloride in step one, and ball milling; adding Ti3C2 into the product obtained in step two, and ball milling; cleaning and ultrasonic treatment, centrifugal removal of supernatant, and collection of the remaining sample; and normal-temperature vacuum drying. The application further discloses application of the Ti3C2 / NbH x composite material as an electrocatalyst in improving Mg(BH4)2 hydrogen absorption and release performance. The composite material has good electrocatalytic performance, and can effectively improve Mg(BH4)2 hydrogen absorption and release performance.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalytic composite materials, specifically a Ti3C2 / NbH x Composite materials, preparation methods and applications thereof. Background Art

[0002] The development of clean, economical, and high-energy-density energy has become a research trend organized by various countries. Hydrogen energy has stood out in the energy competition, but storage and transportation issues have limited its large-scale industrial application. Solid-state hydrogen storage technology has shown advantages in the storage and transportation of hydrogen, such as safety, stability, and relatively large hydrogen storage capacity. Mg(BH4)2 stands out among solid-state hydrogen storage materials with a hydrogen storage mass density of 14.7wt%. However, in the process of Mg(BH4)2 absorbing and releasing hydrogen at elevated temperatures, its slow dehydrogenation kinetics and high thermodynamic barriers limit the utilization of hydrogen energy. The thermal dehydrogenation performance of Mg(BH4)2 is still not ideal, and the reversible conditions are harsh, which is not conducive to practical application. Using catalyst doping to improve the hydrogen storage performance of Mg(BH4)2 is the key to breaking through the bottleneck problem of large-scale industrial application of hydrogen energy.

[0003] Currently, transition metal catalysts such as Nb-based, Ni-based and Ti-based have shown great advantages in improving the hydrogen storage performance of Mg(BH4)2, but the catalytic effect has not yet reached the ideal goal. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention aims to provide a Ti3C2 / NbH x Another object of the present invention is to provide a Ti3C2 / NbH composite material with low cost and simple process. x A method for preparing a composite material. Another object of the present invention is to provide a Ti3C2 / NbH x Application of composite materials as electrocatalysts to improve the hydrogen absorption and desorption properties of Mg(BH4)2.

[0005] Technical solution: The Ti3C2 / NbH x Composite material, comprising the following substances in percentage by weight: 20-25wt% NbH x , 75~80wt%Ti3C2;NbH x Where x is 1 or 2.

[0006] Furthermore, NbH x It is evenly dispersed between Ti3C2 layers and on the surface, and has a hazelnut layer shape.

[0007] The above Ti3C2 / NbH x The preparation method of the composite material comprises the following steps:

[0008] Step 1: In an argon atmosphere glove box, niobium pentachloride and niobium chloride are mixed in a mass ratio of 85 to 90:30, and ball milled for 10 to 15 cycles;

[0009] Step 2: Add lithium hydride with a mass of 0.4 to 0.45 times that of lithium chloride in step 1, and ball mill for 20 to 25 cycles, turning the sample over every 5 to 10 cycles to prevent the powder from sticking to the wall;

[0010] Step 3, adding Ti3C2 to the product obtained in step 2, and ball milling for 10 to 15 cycles;

[0011] Step 4: washing the sample obtained in step 3, ultrasonically treating the sample, removing the supernatant by centrifugation, and collecting the remaining sample;

[0012] Step 5: Dry the product obtained in step 4 under vacuum at room temperature for 3-4 hours to obtain Ti3C2 / NbH x Composite materials.

[0013] Furthermore, the revolution speed of the ball mill is 350-450 rpm, the ball-to-material mass ratio is 35-40:1, and the program sets a cycle including: forward rotation for 25-35 minutes, stop for 5-7 minutes, reverse rotation for 25-35 minutes, and stop for 5-7 minutes.

[0014] Furthermore, in step 1, the pressure of the argon atmosphere glove box is less than 0.1 MPa, and the water and oxygen contents are less than 0.1 ppm.

[0015] Furthermore, in step three, Ti3C2 is obtained by etching Ti3AlC2 with HF acid.

[0016] Furthermore, in step 4, tetrahydrofuran is used for washing, the solvent sample ratio is 1 g: 70-80 mL, the washing times are 8-10 times, the centrifugation speed is 8000-10000 rpm, and the time is 10-15 min.

[0017] Furthermore, in step five, during the vacuum drying process, the vacuum pump is in a normally open state.

[0018] The Ti3C2 / NbH x Application of composite materials as electrocatalysts to improve the hydrogen absorption and desorption properties of Mg(BH4)2.

[0019] Furthermore, Ti3C2 / NbH x The mass percentage of the composite material is 20-40wt%, preferably 30wt%.

[0020] Preparation principle: The electronegativity of Nb (1.6) is between magnesium (1.31), boron (2.04) and hydrogen (2.2), which promotes the absorption and desorption of Mg in the process of hydrogen.2+ and (BH4) - During the process of hydrogen absorption and desorption, NbH x The H atoms in H2 and (BH4) - It previously played a transitional role, shortening the hydrogen conduction path. The unique two-dimensional layered structure of the transition metal-based catalyst Ti3C2 limits molecular aggregation while providing a large number of active sites. Ti3C2's affinity for hydrogen atoms provides numerous diffusion channels after hydrogen desorption, promoting hydrogen release.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0022] 1. Prepared Ti3C2 / NbH x The composite material has good electrocatalytic performance and can effectively improve the hydrogen absorption and desorption performance and reusability of Mg(BH4)2;

[0023] 2. The preparation method is simple and nano-scale NbH x It is evenly loaded between and on the surface of the two-dimensional Ti3C2 layer;

[0024] 3. Prepared Ti3C2 / NbH x The composite material is hazelnut-layered, with a large specific surface area and abundant active sites, which is conducive to the conduction of electrons. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Ti3C2 / NbH x Scanning electron microscopy (SEM) images of the composite material;

[0026] Figure 2 The Ti3C2 / NbH x Energy dispersive spectrum (EDS) of composite materials;

[0027] Figure 3 The Ti3C2 / NbH x XRD of composite materials;

[0028] Figure 4 This is the hydrogen release curve of different Mg(BH4)2 composite materials of the present invention at elevated temperature;

[0029] Figure 5 The present invention is Mg(BH4)2@Ti3C2 / NbH x Heating hydrogen release curves of composite materials with different proportions;

[0030] Figure 6 This is the isothermal hydrogen release curve of Mg(BH4)2 at different temperatures of the present invention;

[0031] Figure 7 The present invention is Mg(BH4)2@Ti3C2 / NbH x Isothermal hydrogen release curves of composite materials at different temperatures. DETAILED DESCRIPTION

[0032] In the following examples, Ti3C2 was obtained by etching Ti3AlC2 with HF acid for 48 hours and then washing with deionized water. 1g of Ti3AlC2 was slowly added in batches to 20ml of HF solution and magnetically stirred in a water bath at 60°C for 24 hours. The turbid liquid was collected and placed in a centrifuge tube. Deionized water was added and the mixture was thoroughly shaken and centrifuged. The supernatant was removed and the solid layer was retained. The washing was repeated until the pH value of the washing water was about 7. The black solid was collected and dried at 60°C for 10 hours, which was Ti3C2. During the vacuum drying process, the vacuum pump was kept in the open state. In the following examples, x is 1 or 2.

[0033] Example 1

[0034] A Ti3C2 / NbH x The preparation method of the composite material comprises the following steps:

[0035] (1) At room temperature, in an argon atmosphere glove box (oxygen value <0.1 ppm, water value <0.1 MPa), 870 mg of niobium pentachloride and 300 mg of lithium chloride were placed in a stainless steel ball mill with a ball-to-material ratio of 40:1. The ball mill was milled at a revolution speed of 400 rpm for 10 cycles. One cycle consisted of: forward rotation for 30 min, stop for 6 min, reverse rotation for 30 min, and stop for 6 min.

[0036] (2) In the glove box, 130 mg of lithium hydride was added to the ball mill jar. The ball mill was rotated at a speed of 400 rpm for 20 cycles. The sample was turned over every 5 cycles to prevent the wall powder from sticking and causing uneven reaction.

[0037] (3) In a glove box, 1 g of Ti3C2 was added to a ball milling jar and the ball mill was rotated at 400 rpm for 10 cycles.

[0038] (4) The sample powder was taken out from the ball mill and dispersed in centrifuge tubes. 40 ml of tetrahydrofuran solvent was added to each centrifuge tube. The powder was shaken and ultrasonicated for 10 min to uniformly disperse the powder to obtain a mixed solution 1.

[0039] (5) The mixed solution 1 was centrifuged at 8000 rpm for 10 min to obtain a layered solution. The supernatant was poured out in a glove box and then washed with tetrahydrofuran for 9 times to obtain a solid-liquid mixture 1.

[0040] (6) The solid-liquid mixture 1 was dried under vacuum at room temperature, and the vacuum pump was continuously evacuated for 3 hours to obtain Ti3C2 / NbHx Composite materials.

[0041] like Figure 1 From the scanning electron microscope image, it can be seen that the NbH x Evenly dispersed between Ti3C2 layers and on the surface. Figure 2 , the energy spectrum analysis diagram further illustrates the uniformity of the prepared sample. Figure 3 , XRD confirmed that the prepared composite material is Ti3C2 / NbH x , including 25wt% NbH x , 75wt% Ti3C2, x is 1 and 2, mainly NbH2.

[0042] Example 2

[0043] Ti3C2 / NbH obtained in the research example x 、Ti3C2、NbH x Effect on the hydrogen release performance of Mg(BH4)2 at elevated temperature:

[0044] Step 1: Preparation of Mg(BH4)2-30wt%Ti3C2 / NbH x , Mg(BH4)2-30wt%Ti3C2, Mg(BH4)2-30wt%NbH x Composite sample: 300mg Ti3C2 / NbH x 、300mg Ti3C2、300mg NbH x They were respectively ball-milled with 700 mg of Mg(BH4)2 in a stainless steel ball mill in an argon atmosphere glove box with a ball-to-material ratio of 40:1 and a ball mill revolution speed of 500 rpm. Three composite samples were obtained after 20 cycles of ball milling. One cycle included: forward rotation for 30 min, stop for 6 min, reverse rotation for 30 min, and stop for 6 min.

[0045] Step 2: Take 60-70 mg of each of the three samples from the glove box, place them in a Sievert's apparatus, evacuate the chamber, pick out leaks, and heat to 500°C at a heating rate of 5°C / min.

[0046] The hydrogen release curves of composite samples doped with different catalysts are as follows Figure 4 As shown, the composite material Ti3C2 / NbH obtained in Example 1 x The performance improvement of Mg(BH4)2 is more obvious than that of the other two single catalysts, and can significantly increase the hydrogen release rate of Mg(BH4)2 upon heating.

[0047] Example 3

[0048] Study the effect of Ti3C2 / NbHx doping ratio on the hydrogen desorption performance of Mg(BH4)2 at elevated temperature:

[0049] Step 1: Prepare Mg(BH4)2-20wt%Ti3C2 / NbH using Example 1 x 、Mg(BH4)2-40wt%Ti3C2 / NbH x Composite sample: 200mg Ti3C2 / NbH x 、400mg Ti3C2 / NbH x The samples were ball-milled with 700 mg of Mg(BH4)2 in a stainless steel mill under argon atmosphere at a ball-to-material ratio of 40:1. The mill was rotated at 500 rpm for 20 cycles to obtain 20 wt% and 40 wt% composite samples. One cycle consisted of 30 minutes of forward rotation, 6 minutes of rest, 30 minutes of reverse rotation, and 6 minutes of rest.

[0050] Step 2: Take 60-70 mg of 20wt%, 30wt% and 40wt% samples from the glove box respectively, put them into the isovolumetric pressure-switching hydrogen storage performance measurement device, evacuate the air, check for leaks, and heat to 500°C at a heating rate of 5°C / min.

[0051] The hydrogen release curves of composite samples doped with different ratios are as follows Figure 5 As shown, the 30wt% composite material can significantly improve the performance of Mg(BH4)2 and can maintain the hydrogen content of the composite material to a large extent, which can significantly improve the heating and hydrogen release effect of Mg(BH4)2.

[0052] Example 4

[0053] Study on Ti3C2 / NbH x Effects of different temperatures on the hydrogen release performance of Mg(BH4)2:

[0054] Step 1: Take Mg(BH4)2@30wt%Ti3C2 / NbH in the glove box x Three portions of 60-70 mg were placed in a Sievert's apparatus, evacuated, and leaked, and the temperature was raised to 230°C, 250°C, and 270°C at a heating rate of 15°C / min and kept at this temperature for 30 h.

[0055] Step 2: Take three portions of 60-70 mg of Mg(BH4)2 from the glove box and place them in the Sievert's apparatus respectively. Evacuate the air, check for leaks, and heat to 250℃, 270℃, and 290℃ at a heating rate of 15℃ / min and keep them warm for 30h.

[0056] The isothermal hydrogen desorption curves of the two samples at different temperatures are shown in Figure 2. Figure 6As shown in Figure 7, the prepared composite catalyst greatly improves the hydrogen decomposition performance of Mg(BH4)2, which exceeds the effect of temperature gradient on the hydrogen decomposition performance of Mg(BH4)2. Hydrogen decomposition is basically completed within 12.5 hours at 270°C, while pure Mg(BH4)2 requires nearly 30 hours to complete complete hydrogen decomposition at 290°C.

Claims

1. A Ti3C2 / NbH catalyst for improving the hydrogen absorption and desorption properties of Mg(BH4)2 x The method for preparing a composite material is characterized in that: The following steps are involved: Step 1: In an argon atmosphere glove box, niobium pentachloride and lithium chloride are mixed in a mass ratio of 85-90:30 and ball milled for 10-15 cycles; Step 2: Add lithium hydride with a mass 0.4 to 0.45 times that of lithium chloride in step 1, and ball mill for 20 to 25 cycles, turning the sample over every 5 to 6 cycles; Step 3: Add Ti3C2 to the product obtained in step 2 and ball mill for 10 to 15 cycles; Step 4: washing the sample obtained in step 3, ultrasonically treating the sample, removing the supernatant by centrifugation, and collecting the remaining sample; Step 5: Dry the product obtained in step 4 under vacuum at room temperature for 3-4 hours to obtain Ti3C2 / NbH x Composite materials; The Ti3C2 / NbH x The composite material includes the following substances in the following mass percentages: 20~25wt%NbH x , 75~80wt%Ti3C2; the NbH x Where x is 1 or 2; The NbH x Evenly dispersed between Ti3C2 layers and on the surface, it is hazelnut-like. The revolution speed of the ball mill is 350-450 rpm, the ball-to-material mass ratio is 35-40:1, and one cycle includes: forward rotation for 25-35 minutes, stop for 5-7 minutes, reverse rotation for 25-35 minutes, and stop for 5-7 minutes.

2. The Ti3C2 / NbH2 catalyst for improving the hydrogen absorption and desorption performance of Mg(BH4)2 according to claim 1 x The method for preparing a composite material is characterized by: In the step 1, the pressure of the argon atmosphere glove box is less than 0.1 MPa, and the water and oxygen contents are less than 0.1 ppm.

3. The Ti3C2 / NbH2 catalyst for improving the hydrogen absorption and desorption performance of Mg(BH4)2 according to claim 1 x The method for preparing a composite material is characterized by: In the step 3, Ti3C2 is obtained by etching Ti3AlC2 with HF acid and then washing with deionized water.

4. The Ti3C2 / NbH2 catalyst for improving the hydrogen absorption and desorption performance of Mg(BH4)2 according to claim 1 x The method for preparing a composite material is characterized by: In the step 4, tetrahydrofuran is used for cleaning, the solvent sample ratio is 1 g: 70-80 mL, and the number of cleaning times is 8-10 times.

5. The Ti3C2 / NbH2 catalyst for improving the hydrogen absorption and desorption performance of Mg(BH4)2 according to claim 1 x The method for preparing a composite material is characterized by: In the step 4, the centrifugal speed is 8000-10000 rpm and the time is 10-15 min.

6. The Ti3C2 / NbH2 catalyst for improving the hydrogen absorption and desorption performance of Mg(BH4)2 according to claim 1 x The method for preparing a composite material is characterized by: The Mg(BH4)2 is added with Ti3C2 / NbH x The mass percentage of the composite material is 20~40wt%.

Images