JPS6236961B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel hydrogen storage material and a method for producing the same. The hydrogen storage material described in Japanese Patent Application No. 1987-70200 consists of a four-coordinated Si lattice and surrounding SiH ₂
and/or a polycrystalline body consisting of a SiH ₃ shell. This substance is obtained by vapor-depositing it onto a substrate such as glass, synthetic resin, or metal by a reactive sputtering method of Si using H ₂ or a glow discharge method, and is occluded in the voids of the four-coordinate Si lattice. The amount of hydrogen released is about 50 atomic %, and it contains a large amount of hydrogen. However, the manufacturing of this hydrogen storage material has mounting limitations (device size,
For example, in the reactive sputtering method, hydrogen radicals generated by sputtering react with the Si target, a so-called chemical reaction that drives the formation of the deposited material. Since it only acts as a force, the amount of evaporation is significantly smaller than when Ar, etc., which easily ionize, is used in the reaction atmosphere. Although the amount of vapor deposition can be somewhat increased by increasing the high-frequency power using a magnetron, it is not possible to perform economical manufacturing commensurate with the increase in power consumption. Therefore, the current manufacturing cost per kg of product is several tens to several million yen, which is extremely disadvantageous economically. The present inventors have conducted extensive research in order to eliminate the disadvantages of conventional hydrogen storage materials as described above, and were able to produce a new polycrystalline hydrogen storage material that is economically extremely advantageous. That is, according to the present invention, silane SiH ₄ is decomposed by glow discharge to deposit a powdered hydrogen-containing silicon compound onto a Si target. In the former case, if the wall surface of the discharge chamber is cooled to about 0.degree. C. or lower (the lower the better), the hydrogen storage material according to the present invention will be formed on the wall surface as a yellowish brown powder. The IR spectrum of the obtained product is shown in FIG.
From Figure 1, this product is about 2104 cm ^-1 and about 2085 cm -1
It can be seen that there is a peak at cm ^-1 . Note that the broken line is an IR spectrum diagram after hydrogen release. In addition, the SiH ₄ raw material that does not react with hydrogen radicals also promotes the precipitation of the generated powder from the gas phase onto the cooling wall surface. The powdery substance obtained in this way is used in most of the patent applications filed in
Similar to No. 70200, Si microcrystals are surrounded by Si with hydrogen bonded to them. However, the difference is −(SiH ₂ ) _o −
It consists of chain bonds and a small portion of a four-coordinated Si lattice, and contains a large amount of bound hydrogen and a small amount of free hydrogen. That is, in the present invention, the surface of a silicon microcrystal particle is covered with -(SiH ₂ ) _o - bond chains bonded to silicon atoms on the surface of the silicon microcrystal particle,
This is a novel hydrogen storage material characterized by releasing 40 to 70 atomic % of hydrogen from the -(SiH ₂ ) _o - bonded chain when heated at 100 to 200°C. For example, the bound hydrogen contained in a hydrogen storage material obtained by glow discharge shows a change as shown in Figure 2a in response to a change in wall surface temperature, which suggests that the temperature of the wall surface to which the powdered product adheres will be lower. It can be seen that temperature is preferable. Therefore, according to the present invention, the temperature of the wall surface to which the powdered hydrogen storage material is to be attached is 0° C. or lower, and by maintaining the temperature at such a low temperature, it is possible to store 40 atomic percent or more of hydrogen. Also,
The lower the wall temperature, the greater the hydrogen absorption capacity, but it is industrially advantageous to produce a hydrogen absorption capacity of 70 at.% at -100°C. The new hydrogen storage material obtained by the present invention releases bound hydrogen when heated, and the relationship between the hydrogen release rate and heating temperature is as shown in Figure 4.
Almost all of the bonded hydrogen is released, but as can be seen from the IR spectrum in Figure 1, this constitutes a hydrogen storage material - (SiH ₂ ) _o - Hydrogen is released from the bonded chain. It is something. The manufacturing process of the hydrogen storage material according to the present invention will be explained with reference to FIG. 1 is a high frequency power source with a capacity of 300 W, for example, and is connected to a glass bell jar 6 (diameter 300 mm) via a matching box 2. Silane gas flows from gas cylinder 3 to pressure gauge 4,
It is supplied to the upper electrode (made of SUS, diameter 200 mm) 7 of the bell gear 6 through the flow rate controller 5. The inside of the bell gear is maintained at 0.1 to 10 Torr, and glow discharge occurs between the upper electrode and the SUS conveyor 10 facing thereto. Inside the conveyor, a cooler 8 that circulates liquid nitrogen is placed opposite the upper electrode to promote the deposition of the hydrogen storage powder on the conveyor. The conveyor is driven intermittently every time the amount of hydrogen storage material produced reaches a certain level, and the hydrogen storage material is scraped off by a knife edge 14 through a powder backflow prevention weir 13 and collected in a powder holding container 16. The inside of the powder holding container 16 is evacuated through a bag filter 15. Reference numeral 12 denotes a reaction chamber made of stainless steel, and the degree of vacuum in the chamber is monitored by a vacuum gauge 11. The material thus obtained contains 30-70 atomic percent hydrogen. The following example illustrates the production of the hydrogen storage material of the present invention (see Figure 3). Example Silane gas having a purity of about 99% or more is supplied to a reaction chamber at a pressure of about 1 atmosphere (50 Pa, gauge pressure) and a flow rate of 2 to 30 SCCM (standard conditions, cc/min). The pressure inside the reaction chamber is set to below about 10 ^-2 Torr in advance, and the pressure inside the reaction chamber is controlled to 0.1 to 5 Torr by adjusting the supply valve.
The SUS conveyor inside the reaction chamber is cooled at the position opposite the upper electrode (diameter 200 mm) in the bell jar with, for example, Freon, water, or liquid nitrogen depending on the desired cooling temperature, but here it is cooled to below -100℃ with liquid nitrogen. do. After stabilizing the chamber atmosphere by flowing silane gas into the reaction chamber for about 10 minutes, power (6 W or more) is supplied to the above electrodes from a high frequency power source (13.56 MHz). The more power is supplied, the more powder is produced. As soon as the glow discharge starts, powder begins to form on the cooling surface of the conveyor, but when the thickness of the powder layer reaches 5 to 10 mm, the conveyor is driven and the new cooling surface faces the upper electrode and then stopped. Then, new powder is generated. In this way, the conveyor is driven intermittently, and eventually the powder deposited on the conveyor reaches above the powder holding container and is scraped off from the conveyor by a knife edge, and the gas after the reaction is separated from the powder by a bag filter and exhausted. The relationship between the hydrogen content measured by gas chromatography of the hydrogen storage powder thus produced and the conveyor cooling surface temperature (powder adhesion wall surface temperature) was as shown in FIG. 2a. Furthermore, when the silane gas supply amount was 6 SCCM, the relationship between the supplied high frequency power and the amount of hydrogen storage powder produced (g/hour) was as shown in FIG. 2b. That is, the diameter
It can be seen that when a 200 mm upper electrode is used, the amount of hydrogen storage material produced increases almost linearly up to a supplied power of 70 W. Therefore, in the method of the present invention
70W/π (200mm/2) ² = 22×10 ^-2 W/cm ² Glow discharge is performed with a supplied power of less than 2. Furthermore, the relationship between the pressure in the reaction chamber and the amount of hydrogen storage powder produced when the high frequency power source is 10 W and the silane gas flow rate is 15 SCCM is as shown in Figure 5a.
The relationship between the silane gas flow rate (SCCM) and the amount of hydrogen storage powder produced when the reaction chamber pressure was 0.2 Torr was as shown in Figure 5b. From these results, it can be seen that there are optimum values for the reaction chamber pressure and the raw material silane gas flow rate. The amount of hydrogen storage material produced in this example was calculated using the conventional method (magnetron sputtering method;
360W, evaporation substrate area 50cm ² , silane gas flow rate
6SCCM) as shown in Table 1.

[Table] From the results in Table 1, it can be seen that according to the present invention, the conventional method
It is clear that 2,000 times the production can be obtained with 60 liters of electric power, and therefore, it can be seen that the present invention has extremely excellent industrial effects suitable for mass production of products with a large hydrogen storage capacity. .

[Brief explanation of the drawing]

FIG. 1 is an IR spectrum diagram of the hydrogen storage material according to the present invention, FIG. 2a is a graph showing the relationship between the powder wall adhesion temperature and the amount of bound hydrogen of the hydrogen storage material according to the present invention, and FIG. 3 is a graph showing the relationship between the production amount of the hydrogen storage material according to the invention and the supplied power, FIG. 3 is a diagram for explaining the method for producing the hydrogen storage material according to the invention, and FIG. 5A and 5B are graphs showing the relationship between the reaction chamber pressure, the amount of silane gas supplied, and the amount of hydrogen storage material produced, respectively. FIG. Codes in the figure: 1...High frequency power supply, 2...Matching box, 3...Gas cylinder, 4...Pressure gauge,
5...Flow rate controller, 6...Belgear, 7...Upper electrode, 8...Cooler, 9...Hydrogen storage material powder, 10...Conveyor, 11...Vacuum gauge, 12
... Reaction chamber, 13 ... Powder backflow prevention weir, 14 ...
Knife Edge, 15... Buzz Filter, 16
...Powder holding container.

Claims (1)

[Claims] 1 The surface of a silicon microcrystalline particle is covered with -(SiH ₂ ) _o - bond chains bonded to silicon atoms on the surface of the silicon microcrystalline particle, and by heating at 100 to 200°C,
40 to 70 atom% of hydrogen from the -(SiH ₂ ) _o - bond chain
A new hydrogen storage material that releases hydrogen. 2 Silane gas under pressure 0.1 to 10 Torr, silane gas flow rate 2 to 30 ml/min (standard condition), supply power 22
×10 ^-2 W/cm ² or less, subject to glow discharge, temperature 0℃
The following cooling surface is coated with a hydrogen-containing silicon compound (the surface of a silicon microcrystal particle is covered with -(SiH ₂ ) _o - bond chains bonded to the silicon atoms on the surface of the silicon microcrystal particle, and heated to 100 to 200°C. According to the above-mentioned −(SiH ₂ ) _o
- A method for producing a novel hydrogen storage material, characterized by attaching a compound (which releases 40 to 70 atomic percent of hydrogen from a bonded chain).