JP2010285296A - Hydrogen generator and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen generator that generates hydrogen at a low temperature and is equipped with a material stable even in the air, and a fuel cell system. <P>SOLUTION: The fuel cell system 1 includes the hydrogen generator 2 and a fuel cell 3, wherein the hydrogen generator 2 is equipped with a first vessel (tank loaded with a hydrogen generating material) 21 that holds a hydrogen-generating material 22 containing Mg as the main component and having the surface coated with Mg(OH)<SB>2</SB>and a second vessel (water tank) 24 that is connected with the first vessel 21 by a pipe 23 and supplies water into the first vessel 21. The first vessel 21 is heated or the water in the second vessel 24 is heated to 80°C or higher by a heater, which is not shown in the drawing, and brought into contact with the hydrogen-generating material 22, and thus the hydrogen-generating material 22 and the water are reacted with each other in the first vessel 21 to generate hydrogen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen generation apparatus including a material containing magnesium as a hydrogen generation material and a fuel cell system using the hydrogen generation apparatus.

  In consideration of the global environment, the use of hydrogen as a clean energy source has attracted attention. As a method for producing hydrogen, a method using a metal water decomposition reaction is known.

  Thus, a hydrogen generating material has been proposed in which activation of the metal hydride is achieved using a mechanical grinding method by mechanical alloying (see Patent Document 1). Moreover, the hydrogen generating material which achieved activation of the aluminum-type water-decomposition material by the mechanical alloying method is proposed (refer patent document 2).

JP-A-2005-306724 JP 2006-63405 A

  However, since the material activated by mechanical alloying is unstable, it must be stored in a vacuum, in an inert gas atmosphere, or the like.

The present invention has been made to solve the above problems, and the hydrogen generator according to the present invention includes a first container that contains Mg and stores a hydrogen generating material whose surface is coated with Mg (OH) _2. And a second container connected to the first container by piping and supplying water into the first container, and a heating device for heating the first container and / or the second container. It is characterized by.

  A fuel cell system according to the present invention includes a fuel cell that generates electric power by using the hydrogen generator according to the present invention as a hydrogen generation source.

According to the present invention, by covering the surface of the hydrogen generating material with Mg (OH) ₂ , hydrogen generation proceeds at a low temperature, and at the same time, a hydrogen generating device and a fuel cell having a material that can stably exist in air A system can be realized.

1 is a schematic system diagram showing a fuel cell system according to an embodiment of the present invention. It is the figure which compared the hydrogen generation | occurrence | production speed | rate and generated heat amount of the various materials obtained by water decomposition reaction of Mg. It is a figure which shows the X-ray photoelectron spectroscopy spectrum of various materials.

  Hereinafter, a hydrogen generator and a fuel cell system according to embodiments of the present invention will be described.

FIG. 1 is a schematic system diagram of a fuel cell system 1 according to an embodiment of the present invention. A fuel cell system 1 according to an embodiment of the present invention includes a hydrogen generator 2 according to an embodiment of the present invention, and a fuel cell 3 that generates electric power using the hydrogen generator 2 as a hydrogen generation source. The hydrogen generation apparatus 2 includes a hydrogen generation material filling container (first container) that stores a hydrogen generation material 22 containing Mg (magnesium) as a main component and having a surface coated with Mg (OH) ₂ (magnesium hydroxide). 21, and a water tank (second container) 24 connected to the hydrogen generating material filling container 21 and the pipe 23 and supplying water into the hydrogen generating material filling container 21. Hydrogen is generated in the hydrogen generating material filling container 21 by heating the hydrogen generating material filling container 21 or heating the water in the water tank 24 to 80 ° C. or higher by a heating device (not shown) and bringing it into contact with the hydrogen generating material 22. The material 22 and water react to generate hydrogen.

  The fuel cell 3 is connected by a generated water trap 13 for trapping generated water generated therein and a pipe line 14a, and by a hydrogen generating material filling container 21 and a hydrogen flow path 14b. Hydrogen generated in the hydrogen generating material filling container 21 is used as the hydrogen used in the fuel cell reaction, and hydrogen is supplied through the hydrogen flow path 14b. Water 24 a stored in the water tank 24 is used for cooling the fuel cell 3 and is cooled by the fuel cell cooling water channel 15. Water generated by the fuel cell reaction passes through the conduit 14 a and is trapped by the generated water trap 13, or passes through the fuel cell cooling water passage 16 and is stored in the water tank 24. The generated water trap 13 is connected to a water tank 24 by a pipe line 17 with a valve, and water is stored in the water tank 24.

  In the fuel cell system 1 according to the embodiment of the present invention, by combining the hydrogen generator 2 and the fuel cell 3 according to the embodiment of the present invention, the heat discharged from the fuel cell 3 is converted into the hydrogen generating material 22 and water. It can be used for the hydrogen generation reaction. Thus, by using waste heat, it is not necessary to mount a new heat source, and the system can be miniaturized.

  In the fuel cell system 1 according to the embodiment of the present invention, the water generated from the fuel cell 3 is collected and stored in the water tank 24, and the water necessary for generating hydrogen by the reaction between the hydrogen generating material 22 and water. Reuse as. Thus, the amount of water previously installed in the system can be reduced by using the drainage.

The hydrogen generating material 22 stored in the hydrogen generating material filling container 21 contains Mg as a main component and the surface is coated with Mg (OH) ₂ , and reacts with water to generate hydrogen. In general, a material containing Mg as a main component has a surface covered with MgO (magnesium oxide). By covering the surface with Mg (OH) ₂ instead of this MgO, the hydrogen generation reaction when reacted with water proceeds at a low temperature. By configuring the surface with Mg (OH) ₂ , it is presumed that the penetration rate of water into the material is improved and the reaction between Mg and water proceeds. A material whose surface is coated with Mg (OH) ₂ can be synthesized at low cost, and is stable even in the air, so that storage and transportation costs are low. As described above, according to the hydrogen generator according to the embodiment of the present invention, by covering the surface of the hydrogen generating material with Mg (OH) ₂ , hydrogen generation proceeds at a low temperature and at the same time, it is stable in the air. It becomes possible to realize a hydrogen generator and a fuel cell system having materials that can exist.

FIG. 2 shows the difference in the hydrogen generation rate and the amount of generated heat of various materials obtained under various processing conditions in the water decomposition reaction of Mg. The water treatment is performed by enclosing 0.9 mg of Mg and 1.4 mg of water in a cylindrical SUS pan having a diameter of 5 mm and a depth of 5 mm in argon. The amount of water is a condition in which water is twice as much as the stoichiometric ratio. The water-treated material is heated from room temperature under conditions of 10 K / min, and the amount of hydrogen generated is obtained from the generated heat. In FIG. 2, 2A indicates no water treatment, and the hydrogen generation temperature is 170 ° C. In FIG. 2, 2B shows the case where the water treatment is performed at a temperature of 30 ° C. for 60 minutes, and the hydrogen generation temperature is 167 ° C. 2C shows the case where the water treatment is performed at a temperature of 80 ° C. for 45 minutes, and the hydrogen generation temperature is 151 ° C. 2D shows the case where the water treatment is performed at a temperature of 80 ° C. for 60 minutes, and the hydrogen generation temperature is 138 ° C. Regardless of the presence or absence of water treatment, the total hydrogen generation amount of each material is constant at 7 wt%. In particular, by performing heat treatment with water at 80 ° C., the hydrogen releasing reaction proceeds at a low temperature. Thus, by converting the MgO layer on the surface of the hydrogen generating material 22 into Mg (OH) ₂ , the hydrogen generating reaction when reacted with water proceeds at a low temperature. In addition, it is presumed that the surface is composed of Mg (OH) ₂ , so that the penetration rate of water into the hydrogen generating material 22 is improved and the reaction between Mg and water proceeds.

As described above, activation of the hydrogen generating material 22 by water treatment is performed by pretreatment in which the hydrogen generating material containing Mg is brought into contact with water at a temperature of 80 ° C. or higher. When a hydrogen generating material containing Mg is brought into contact with water at a temperature of 80 ° C. or higher, as the Mg (OH) ₂ is formed in the MgO layer on the surface, the Mg (OH) ₂ layer reaches the metallic Mg and hydrogen is appear. This reaction requires a large amount of water supply, and since steam is used, the production rate of Mg (OH) ₂ is slow. Moreover, since there are few active points of material, there exists a problem that the whole quantity of metal Mg does not react. Therefore, a pre-treatment for bringing the hydrogen-containing material containing Mg into contact with water at a temperature of 80 ° C. or more is performed, and Mg (OH) ₂ is formed up to the vicinity of the metal Mg layer. Used for reaction. The material in which Mg (OH) ₂ is formed up to the vicinity of the metal Mg layer is supplied with water that reacts with the metal Mg due to the movement of water molecules in the Mg (OH) ₂ lattice to generate hydrogen. In addition, hydrogen diffuses through the grain boundaries, so that hydrogen goes out. Furthermore, since the material has a plurality of active sites, the metal Mg completely reacts and the efficiency is improved.

  In this way, the activation treatment can be performed only by contacting with high-temperature water of 80 ° C. or higher without using a large-scale underwater milling device. By the activation treatment, a hydroxide can be formed on the material surface, and a material capable of generating hydrogen at a low temperature can be synthesized. Moreover, since water is an inexpensive material, it is suitable for use in the activation treatment. At this time, the water is more preferably ion-exchanged water. The amount of water used for the activation treatment is preferably twice or more in molar ratio with respect to the amount of metal Mg. In order to activate the surface, a certain amount of water is required. However, when a large amount of water is contained, the weight increases, so that it is necessary to separate water and materials after the activation treatment.

The activation treatment needs to be performed at a temperature of 80 ° C. or higher. However, when the temperature is increased, the reaction between the metal Mg inside the material and water proceeds, and hydrogen may be generated. Since water becomes a gas at a temperature of 100 ° C. or higher, it may be difficult to contact the hydrogen generating material, and the activation process may take time. From this point, the activation process needs to be performed at a temperature of 100 ° C. or less. When the activation treatment is performed at 80 ° C. or higher and 100 ° C. or lower, the reaction rate for forming Mg (OH) ₂ is promoted, so that the activation time is short. In addition, alcohol can also be used for an activation process other than water.

The surface structure of the hydrogen generating material having Mg (OH) ₂ formed on the surface obtained by the activation treatment has a peak top X of the binding energy of Mg2p orbital in X-ray photoelectron spectroscopy (XPS) of 49. 4 ≦ X <49.8 eV. FIG. 3 shows X-ray photoelectron spectroscopy spectra of various materials obtained by water decomposition reaction of Mg. The water treatment conditions are the same as those shown in FIG. Here, the charge correction is performed by setting the C (1s) peak top binding energy value to 284.6 eV. In FIG. 3, 3A indicates no water treatment, and the peak top of the binding energy of the Mg2p orbital is 49.8 eV. 3B shows the case where the water treatment is performed at a temperature of 30 ° C. for 60 minutes, and the peak top of the binding energy of the Mg 2p orbit is 49.8 eV. 3C shows the case where the water treatment is performed at a temperature of 80 ° C. for 45 minutes, and the peak top of the binding energy of the Mg2p orbit is 49.7 eV. 3D shows the case where the water treatment is performed at a temperature of 80 ° C. for 60 minutes, and the peak top of the binding energy of the Mg2p orbit is 49.5 eV. The peak top of the binding energy of the Mg2p orbital of Mg (OH) ₂ is 49.5 eV, and the peak top of the binding energy of the Mg2p orbital of MgO is 50.8 eV. From this, it is understood that when the water treatment is performed at 80 ° C. or higher, the material surface is Mg (OH) ₂ . In addition, activation is not achieved in the sample with the peak top of the binding energy of Mg2p orbital being 49.8 eV, and activation is achieved at 49.7 eV. The fact that the peak top X of the binding energy of the Mg2p orbital is 49.4 ≦ X <49.8 eV indicates that the surface composition is Mg (OH) ₂ .

Many elements that constitute Mg and metal compounds are known, such as copper and nickel. However, these metals themselves have low water splitting activity, so it is considered that there is no merit of adding low hydrogen generation amount per weight. . It is preferable that 70 mass% or more of the hydrogen generating material is composed of metal Mg and / or MgH ₂ . The water splitting reaction of Mg and MgH ₂ proceeds according to the following formulas (1) and (2), and generates hydrogen at a high density.

Mg + 2H ₂ O → Mg (OH) ₂ + H ₂ Formula (1)
MgH ₂ + 2H ₂ O → Mg (OH) ₂ + 2H ₂ Formula (2)
The activation process of the hydrogen generating material can be performed on the hydrogen generating apparatus 2. As a pre-process for hydrogen production, water is supplied from the water tank 24 to the material mainly composed of Mg filled in the hydrogen generating material filling container 21. At this time, the activation treatment of the material mainly composed of Mg can be performed by setting the temperature of water to 80 ° C. or higher, and the hydrogen generating material 22 used in the hydrogen generator 2 according to the embodiment of the present invention. Can be obtained on the hydrogen generator 2 without using a pretreated and activated material. The water used for the treatment may be the same as that supplied when hydrogen is generated, and alcohols may be used in addition to water. Further, since the activation process is performed at a temperature of 80 ° C. or higher, it is possible to use the waste heat of the fuel cell 3 that generates power using hydrogen as a fuel.

  As described above, by using the hydrogen generator 2 according to the embodiment of the present invention as a hydrogen generation source, the fuel cell system 1 according to the embodiment of the present invention can be obtained. It can be used as a fuel cell system such as a battery car, a stationary fuel cell, and a portable fuel cell. For example, when applied to a fuel cell vehicle, the fuel cell that supplies hydrogen can be applied to all power generation devices that use hydrogen as fuel, from solid polymer fuel cells to solid oxide fuel cells. It can be used in the same manner in a fuel cell mounted for extending the cruising distance of an electric vehicle. In this case, it is possible to construct a lightweight and compact hydrogen generation system for other hydrogen storage systems such as a high-pressure hydrogen tank. Further, by utilizing the waste heat of the fuel cell 3, it is possible to realize a reduction in size or abolition of a radiator of a fuel cell vehicle, an internal combustion engine vehicle or the like. Further, the hydrogen generation reaction can proceed only with waste heat without having a separate heating device. When applied to a stationary fuel cell, this applies to fuel cells generally using hydrogen as fuel. When applied to a portable fuel cell, it can be used as an electric device for portable electric devices such as notebook PCs and mobile phones, electric carts, electric wheelchairs, and the like.

As described above, according to the present invention, by covering the surface of the hydrogen generating material 22 with Mg (OH) ₂ , the hydrogen generation proceeds at a low temperature, and at the same time, a material that can exist stably in the air is provided. Further, the hydrogen generator 2 and the fuel cell system 1 can be realized.

  As mentioned above, although embodiment which applied the invention made by the present inventors was described, this invention is not limited by description and drawing which make a part of indication of this invention by this embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Hydrogen generator 3 ... Fuel cell 13 ... Generated water trap 14a ... Pipe line 14b ... Hydrogen flow path 15 ... Fuel cell cooling water path 16 ... Fuel cell cooling water flow path 17 ... Pipe line 21 ... Hydrogen generating material Filling container (first container)
22 ... Hydrogen generating material 23 ... Piping 24 ... Water tank (second container)
24a ... water

Claims (5)

A first container storing a hydrogen generating material containing Mg and having a surface coated with Mg (OH) ₂ ;
A second container connected to the first container by piping and supplying water into the first container;
And a heating device for heating the first container and / or the second container.   The hydrogen generation apparatus according to claim 1, wherein the hydrogen generation material is subjected to a pretreatment for contacting with water at a temperature of 80 ° C. or higher.   The hydrogen generator according to claim 1 or 2, wherein the material containing Mg and the water are brought into contact with each other at a temperature of 80 ° C or higher in the first container.   A fuel cell system comprising a fuel cell that generates electric power by using the hydrogen generator according to any one of claims 1 to 3 as a hydrogen generation source.   The fuel cell system according to claim 4, wherein heat discharged from the fuel cell is used for a hydrogen generation reaction.

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