TW201623140A - Hydrogen storage composite and method for manufacturing the same - Google Patents

Abstract

Disclosed is a hydrogen storage composite, including a hydrogen storage material, a carbon support embedded on a surface of the hydrogen storage material, and a catalyst covering the carbon support, wherein the carbon support has at least one dimension of 10 nm to 100 nm.

Description

Hydrogen storage composite material and forming method thereof

The present invention relates to hydrogen storage composites, and more particularly to the catalytic properties employed therein.

Hydrogen is a clean energy source and one of its key technologies is the safe and low cost storage and delivery of hydrogen. Because of the low hydrogen storage density, poor safety, energy consumption, and high cost of high-pressure hydrogen storage and transportation of cylinders, the most potential hydrogen storage method is to store hydrogen by metal or alloy materials. The principle of the hydrogen storage alloy is to use the temperature and/or pressure changes of the external environment to cause the alloy to absorb hydrogen to form an alloy hydride. When hydrogen is required to be used, hydrogen is released from the alloy hydride. The process of storing and releasing hydrogen, such as diffusion, phase change, and chemical combination, is limited by thermal effects and speed and is not explosive.

The advantages of using metal hydride as a hydrogen storage medium are high hydrogen storage density, high safety, and high hydrogen release purity. However, the current disadvantage of hydrogen storage alloys is that alloys with high hydrogen storage capacity, such as magnesium-based alloys, have poor hydrogen absorption and desorption power, and the hydrogen discharge operation temperature is still too high (magnesium-based alloys generally require more than 300 °C to release hydrogen), which greatly reduces their Practicality. In summary, there is an urgent need for a hydrogen storage composite that can absorb and release hydrogen at a lower temperature to facilitate the future use of hydrogen energy.

A hydrogen storage composite material according to an embodiment of the invention includes: a hydrogen storage material; a carbon material carrier embedded in the surface of the hydrogen storage material; and a catalyst coated on the surface of the carbon material carrier, wherein at least one dimension of the carbon material carrier is between 10 nm and 100 nm.

A method for forming a hydrogen storage composite material according to an embodiment of the present invention, comprising The method comprises: coating a catalyst on a surface of the carbon material carrier; and embedding a carbon material carrier coated with a catalyst on the surface of the hydrogen storage material to form a hydrogen storage composite material, wherein the carbon material carrier is at least one-dimensional The size is between 10 nm and 100 nm.

10‧‧‧ Hydrogen storage composite

11‧‧‧ Catalyst

13‧‧‧Carbon carrier

15‧‧‧ Hydrogen storage materials

Fig. 1 is a schematic view showing a hydrogen storage composite material in an embodiment of the present invention.

An embodiment of the present invention provides a method for forming a hydrogen storage composite material, which mainly comprises two steps: (1) coating the catalyst 11 on the surface of the carbon material carrier 13; and (2) coating the surface with the carbon of the catalyst 11 The material carrier 13 is inlaid to the surface of the hydrogen storage material 15 to form a hydrogen storage composite 10 as shown in FIG. In order to enhance the effect of catalyst catalytic hydrogen evolution, the present invention coats the catalyst 11 on the carbon material carrier 13 to maintain the nanoparticle size of the catalyst 11 and to have good dispersibility. The method for coating the above-mentioned catalyst 11 on the carbon material carrier 13 may be a thermal cracking method, such as after weighing the catalyst precursor and the carbon material carrier 13 in a glove box, placing it in a ball grinding tank and placing the ball grinding beads for ball milling. mixing. In an embodiment of the invention, the ball milling process lasts from 15 to 30 minutes. The ball milling described above, in addition to uniformly mixing the catalyst precursor with the carbon material carrier 13, simultaneously embeds the catalyst precursor on the surface of the carbon material carrier 13. The appropriate amount of the ball milled composite material was subjected to DSC analysis to confirm the thermal cracking temperature range of the composite material, which was used as the basis for the temperature maintenance of the tubular heating furnace. Then the ball The mixed and mixed composite material is placed in a heating furnace, vacuumed and subjected to urethane purge, and then heated to an argon atmosphere to a thermal cracking temperature of the composite material and held for a period of time to restore the catalyst. The precursor coats the catalyst 11 on the surface of the carbon material carrier 13. In an embodiment of the invention, the thermal cracking described above lasts from 0.5 to 3 hours. The thermal cracking method is characterized in that the catalyst has good dispersibility and short processing time, and the catalyst 11 and the carbon carrier 13 can be quickly combined. Due to the advantage of rapid thermal expansion of the thermal cracking method, the catalyst 11 and the carbon carrier 13 are not destroyed by the excessive heating time. By appropriately adjusting the ratio of the catalyst 11, the catalyst 11 can be controlled to be stably bonded to the surface of the carbon material carrier 13, and the hydrogen absorption efficiency of the catalyst can be improved by the spillover of the carbon material carrier 13.

In an embodiment of the invention, the weight of the catalyst 11 and the carbon material carrier 13 The ratio is between 20:80 and 50:50. When the ratio of the catalyst 11 is too high, the catalyst 11 is less likely to be uniformly coated on the surface of the carbon material carrier 13 to form agglomeration and coarsening. If the ratio of the catalyst 11 is too low, the catalytic activity is poor. In an embodiment of the invention, the carbon material carrier 13 comprises a carbon nanotube, graphite, graphene, activated carbon, or a combination thereof, and at least one dimension of the carbon material carrier 13 is between 10 nm and 100 nm. If all the dimensional dimensions of the carbon material carrier 13 are too large, the size of the coating catalyst 11 may be excessively large to lower its hydrogen releasing performance. Taking a carbon nanotube as an example, the length may be between 20 nm and 100 nm, and the diameter may be between 3 nm and 8 nm. In an embodiment of the invention, the catalyst 11 comprises Ni, Fe, Co, V, Ti, Pt, Pd, Cu, Cr, or Ag.

The carbon material carrier 13 coated with the catalyst 11 is inlaid to the hydrogen storage material The step of forming the hydrogen storage composite 10 may be a ball milling method. For example, the carbon material carrier 13 and the hydrogen storage material 15 coated with the catalyst 11 may be placed in a ball mill tank, and subjected to a ball milling process under argon to form a hydrogen storage composite material 10. The ball beads can be tungsten carbide or stainless steel and have a diameter between 1 mm and 5 mm. If the diameter of the ball is too small, then The grinding energy is lower and the mechanical fitting is less efficient. If the diameter of the ball bead is too large, it is easy to cause a dead space in the gap between the grinding bead and the grinding can, and some of the powder cannot be sufficiently impacted by the bead to be fitted. The weight ratio of the ball beads to the object to be abraded (the carbon material carrier 13 and the hydrogen storage material 15 having the catalyst 11 coated on the surface) is between 10:1 and 50:1. If the proportion of the material to be grounded is too high, the efficiency of grinding and fitting is poor. If the proportion of the material to be grounded is too low, the grinding beads are easily worn. The ball milling method can be planetary rotation, stirring, or oscillation, and the ball milling process lasts from 15 minutes to 30 minutes. If the ball milling process is too short, the mechanical fitting effect is poor. If the ball milling process takes too long, the catalyst 11 may be peeled off from the surface of the carbon material carrier 13 and alloyed with the hydrogen storage material 15. The carbon material carrier 13 having the catalyst 11 coated on the surface thereof is directly embedded on the surface of the hydrogen storage material 15 by an impact method of mechanical force grinding, and does not form an alloy with the hydrogen storage material, so that the catalyst 11 can be catalyzed. The activity allows the hydrogen storage material 15 to efficiently perform hydrogen evolution at a lower temperature. Since the catalyst 11 is first coated on the surface of the carbon material carrier 13, in addition to helping to uniformly disperse the catalyst 11, a protective interface can be formed to reduce the possibility of alloying of the catalyst 11 with the hydrogen storage material 15 in the high energy ball milling. Sex.

After the above ball milling process, the surface is covered with a carbon material carrier of the catalyst 11 13 will be distributed on the surface of the hydrogen storage material 15 or the interface (grain boundary) between the grains of the material itself. When the hydrogen atoms in the hydrogen storage material 15 pass through the surface of the carbon material carrier 13, an overflow action occurs, that is, hydrogen atoms directly undergo catalytic reaction at the boundary of the two phases, thereby contributing to a reduction in the activation energy barrier of hydrogen release, and further The rate of hydrogen evolution reaction of the hydrogen storage composite 10 is increased.

In an embodiment of the invention, the hydrogen storage material 15 may be magnesium, magnesium hydride, Or magnesium based alloy. In an embodiment of the invention, the total weight of the carbon material carrier 13 and the catalyst 11 is between 1% and 5% by weight of the hydrogen storage material. If the ratio of the carbon material carrier 13 to the catalyst 11 has passed If it is high, it will occupy too much weight of the hydrogen storage composite material 10 and lose some hydrogen storage capacity. If the ratio of the carbon material carrier 13 to the catalyst 11 is too low, the catalytic activity of the hydrogen storage reaction of the hydrogen storage composite material 10 is insufficient.

In an embodiment of the invention, the hydrogen storage material 15 has a size between about 100 nm and 1 mm. If the size of the hydrogen storage material 15 is too large, the hydrogen storage performance is lowered due to the large particle size. If the size of the hydrogen storage material 15 is too small, the carbon material carrier 13 is not easily coated.

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

Example Example 1-1

Take 0.2g of nickel carbonate (Alfa Aesar, Nickell (II) acetate tetrahydrate, 98+%), 0.8g of carbon nanotubes (single-walled carbon nanotubes purchased from ALDRICH, the tube length is about 30nm, and the diameter is about 5nm And 20 g of tungsten carbide grinding balls were placed in a ball mill jar, and the ball mill jar was placed in an oscillating ball mill (SPEX CertiPrep®, Inc., 8000 M) for 15 minutes to embed nickel carbonate on the surface of the carbon nanotubes. A small amount of the ball milled sample was then subjected to DSC testing to find that the sample had a thermal cracking temperature of about 400 °C. Next, the ball-milled sample was placed in a heating furnace, evacuated and subjected to argon purge, and then heated from room temperature to 400 ° C under an argon atmosphere for 1 hour. The nickel carbonate is thermally cracked and reduced to nickel over the surface of the carbon nanotube.

Then, 1 part by weight of the above composite catalyst coated with nickel on the surface of the carbon nanotube, 99 parts by weight of magnesium powder, and 2000 parts by weight of tungsten carbide grinding balls are placed in a ball mill tank, and then the ball mill jar is placed in a shock chamber. The ball mill (SPEX CertiPrep®, Inc., 8000M) was ball milled for 15 minutes to embed the composite catalyst into the magnesium powder to complete the hydrogen storage composite.

Comparative example 1

1 part by weight of carbon nanotubes, 99 parts by weight of magnesium powder, and 2000 parts by weight of tungsten carbide grinding balls were placed in a ball mill jar, and then the ball mill jar was placed in an oscillating ball mill (SPEX CertiPrep®, Inc., 8000M). The ball was milled for 15 minutes, and the carbon nanotubes were embedded in the magnesium powder to complete the hydrogen storage composite. The surface of the carbon nanotube of this comparative example was not coated with any catalyst.

Comparative example 2

100 parts by weight of magnesium powder and 2000 parts by weight of tungsten carbide grinding balls were placed in a ball mill jar, and then the ball mill was placed in an oscillating ball mill (SPEX CertiPrep®, Inc., 8000 M) for 2 hours to complete the ball milling. Magnesium powder.

Comparative example 3

First, the α-Al ₂ O ₃ powder was subjected to sensitization processing. The sensitizer was prepared by dissolving 5 g of SnCl ₂ in 7.5 mL of 37% HCl ₍₁₎ , and then diluting the whole solution to 50 mL with deionized water. Then, 2 g of α-Al ₂ O ₃ powder (TM-DAR from Daming Co., Ltd., having a size between 100 nm and 1 mm) was immersed in the above-mentioned formulated sensitizer, and stirred at room temperature for 5 minutes. The Sn ²⁺ ion is adsorbed on the surface of the α-Al ₂ O ₃ powder, and the filtrate is removed by centrifugation to obtain a sensitized α-Al ₂ O ₃ powder. The sensitized α-Al ₂ O ₃ powder was immersed in a 45 mL aqueous solution of palladium chloride. The solution was prepared by dissolving 1 g of PdCl ₂ in 30 mL of 37% HCl ₍₁₎ , and then the whole solution. It can be used after diluting to 100 mL with deionized water. At this time, the Sn ²⁺ ions on the surface of the powder will reduce the palladium ions and adsorb on the surface of the α-Al ₂ O ₃ powder. After the reaction for 5 minutes, the powder is collected by centrifugation to obtain the composite catalyst α. -Al ₂ O ₃ /Pd.

The above composite catalyst α-Al ₂ O ₃ /Pd is mechanically embedded in a hydrogen storage material of magnesium hydride. First, the magnesium hydride and the composite catalyst α-Al ₂ O ₃ /Pd are mixed in a ratio of 92:8 by weight, and then the mixed powder and the tungsten carbide grinding ball are filled into the carbonization at a weight ratio of 1:32. Tungsten is ground in the tank and filled with argon. The grinding jar was placed in an oscillating ball mill (SPEX CertiPrep®, Inc., 8000M) for 30 minutes to perform ball milling impact, and then the composite catalyst α-Al ₂ O ₃ /Pd was embedded on the surface of the magnesium hydride to form a reservoir. Hydrogen composite material.

The amount of hydrogen storage and desorption of the products of Example 1-1 and Comparative Examples 1 to 4 was confirmed by the Sievert system. The above product is placed in a sealed and fixed volume, and the amount of hydrogen stored and discharged is measured by measuring the amount of change in gas pressure during charge and discharge. The hydrogen pressure test used a hydrogen pressure of 20 atm and a temperature of 300 °C. The hydrogen pressure used in the hydrogen evolution test was less than 1 atm. The measurement of hydrogen release is to let the material fully hydrogen release under the pressure environment of <1 atm for one day after the first hydrogen absorption, and then measure the second hydrogen absorption curve to determine the hydrogen release amount of the material. The above measurement results are shown in Table 1:

It can be seen from the first table that the hydrogen storage composite material (Comparative Example 1) on which the catalyst is not coated on the carbon nanotubes has a hydrogen release amount much lower than that of the hydrogen storage composite material of the catalyst on the carbon nanotubes (Example 1). -1). On the other hand, when the carbon nanotubes were replaced with alumina (Comparative Example 3), both the amount of hydrogen absorption and the amount of hydrogen released were lower than those of the composite catalyst of the carbon nanotubes as a carrier (Example 1-1). As for the magnesium powder (Comparative Example 2), the amount of hydrogen absorption was lower than that of the hydrogen storage composite in which the composite catalyst was embedded (Example 1-1).

Example 1-2

Similar to Example 1-1, the difference is that the weight ratio of the composite catalyst to the magnesium powder is 3:97. Other thermal cracking methods in which nickel was coated on the surface of the carbon nanotubes, and ball milling process parameters in which the composite catalyst was embedded in the magnesium powder were similar to those in Example 1-1.

Examples 1-3

Similar to Example 1-1, the difference was that the weight ratio of the composite catalyst to the magnesium powder was 5:95. Other thermal cracking methods in which nickel was coated on the surface of the carbon nanotubes, and ball milling process parameters in which the composite catalyst was embedded in the magnesium powder were similar to those in Example 1-1.

The amount of hydrogen storage and desorption of the products of Examples 1-1 to 1-3 and Comparative Example 1 was then confirmed using a Sievert system. The above product is placed in a sealed and fixed volume, and the amount of hydrogen stored and discharged is measured by measuring the amount of change in gas pressure during charge and discharge. The hydrogen pressure test used a hydrogen pressure of 20 atm and a temperature of 300 ° C or 150 ° C. The hydrogen pressure used in the hydrogen evolution test was less than 1 atm. The measurement of hydrogen release is to let the material fully hydrogen release under the pressure environment of <1 atm for one day after the first hydrogen absorption, and then measure the second hydrogen absorption curve to determine the hydrogen release amount of the material. The above measurement results are shown in Table 2:

It can be seen from the second table that the hydrogen storage composite material (Comparative Example 1) on which the catalyst is not coated on the carbon nanotubes has a hydrogen release amount much lower than that of the hydrogen storage composite material of the catalyst on the carbon nanotubes (Example 1). -1 to 1-3).

10‧‧‧ Hydrogen storage composite

11‧‧‧ Catalyst

13‧‧‧Carbon carrier

15‧‧‧ Hydrogen storage materials

Claims (17)

A hydrogen storage composite material comprising: a hydrogen storage material; a carbon material carrier embedded in a surface of the hydrogen storage material; and a catalyst coated on a surface of the carbon material carrier, wherein the carbon material carrier is at least The one-dimensional size is between 10 nm and 100 nm. The hydrogen storage composite according to claim 1, wherein the total weight of the carbon material carrier and the catalyst accounts for between 1% and 5% by weight of the hydrogen storage composite. The hydrogen storage composite material according to claim 1, wherein the weight ratio of the catalyst to the carbon material carrier is between 20:80 and 50:50. The hydrogen storage composite material according to claim 1, wherein the hydrogen storage material comprises magnesium, magnesium hydride, or a magnesium-based alloy. The hydrogen storage composite material according to claim 1, wherein the carbon material carrier comprises a carbon nanotube, graphite, graphene, activated carbon, or a combination thereof. The hydrogen storage composite material according to claim 1, wherein the catalyst comprises Ni, Fe, Co, V, Ti, Pt, Pd, Cu, Cr, or Ag. The hydrogen storage composite material according to claim 1, wherein the catalyst coated on the carbon material carrier does not form an alloy with the hydrogen storage material. A method for forming a hydrogen storage composite material, comprising: coating a catalyst on a surface of a carbon material carrier; and inlaying the carbon material carrier having the catalyst surface coated with a hydrogen storage material The surface is formed to form a hydrogen storage composite, wherein at least one dimension of the carbon support is between 10 nm and 100 nm. The method for forming a hydrogen storage composite according to claim 8, wherein the method of coating the catalyst on the surface of the carbon material carrier comprises a thermal cracking method. The method for forming a hydrogen storage composite according to claim 9, further comprising first embedding a catalyst precursor on the surface of the carbon support by ball milling prior to the thermal cracking method. The method for forming a hydrogen storage composite according to claim 8, wherein the method of inlaying the carbon material carrier having the catalyst coated on the surface of the hydrogen storage material comprises a ball milling method. The method for forming a hydrogen storage composite according to claim 8, wherein the total weight of the carbon material carrier and the catalyst is between 1% and 5% by weight of the hydrogen storage composite. The method for forming a hydrogen storage composite according to claim 8, wherein the weight ratio of the catalyst to the carbon material carrier is between 20:80 and 50:50. The method for forming a hydrogen storage composite according to claim 8, wherein the hydrogen storage material comprises magnesium, magnesium hydride, or a magnesium-based alloy. The method for forming a hydrogen storage composite according to claim 8, wherein the carbon carrier comprises a carbon nanotube, graphite, graphene, activated carbon, Or a combination of the above. The method for forming a hydrogen storage composite according to claim 8, wherein the catalyst comprises Ni, Fe, Co, V, Ti, Pt, Pd, Cu, Cr, or Ag. The method for forming a hydrogen storage composite according to claim 8, wherein the catalyst coated on the carbon material carrier does not form an alloy with the hydrogen storage material.