JP5533862B2 - Gas generating apparatus and gas generating method - Google Patents

Description

  The present invention generally relates to a gas processing apparatus, and more particularly to a carbon monoxide or hydrogen gas generator and a carbon monoxide gas or hydrogen gas generation method.

Carbon dioxide gas (CO ₂ ) is one of the major greenhouse gases, and it is said that an increase in carbon dioxide gas in the atmosphere is responsible for global warming and the like. Therefore, techniques for removing carbon dioxide gas from the atmosphere and treating the removed carbon dioxide gas have been studied.

  For example, the so-called carbon capture and storage technology that captures carbon dioxide gas emitted from power plants and factories and embeds it under the seafloor for storage, liquefaction, and solidification is used in the atmosphere. This technology has the potential to remove large amounts of carbon dioxide from the inside.

Japanese Patent Laid-Open No. 9-876 JP 2002-120860 A JP-A-5-293364 JP 2006-298707 A Japanese Patent No. 2931340 JP 2003-88344 A JP-A-8-54364

International Herald Tribune, February 12, 2007 Saito, Y., et al., Fuel Cell vol.5, No.2, 2005

  On the other hand, if carbon dioxide gas removed from the atmosphere and environment can be stored and reacted with other gases, or converted to another form or compound that can be supplied to equipment such as a fuel cell, it can be realized at low cost. It is thought that a great social impact can be obtained.

  Today, hydrogen gas is used in various fields such as energy fields such as fuel cells and the chemical industry. Conventionally, hydrogen gas is mainly produced by electrolysis of water except for extraction from natural gas. However, electrolysis of water requires a large amount of electrical energy. On the other hand, if a technique for extracting hydrogen gas at low cost from water vapor contained in the atmosphere can be realized, it is considered that a great social impact can be obtained as in the case of carbon monoxide gas.

According to one aspect, a gas generator defines a processing space, a processing container holding a support in the processing space, an exhaust system coupled to the processing container and exhausting the processing space, and the support A metal oxide film having a perovskite structure formed on the body and containing oxygen defects, a raw material gas supply port for supplying a raw material gas containing molecules of a raw material compound made of carbon dioxide or water to the processing space, and the processing space from a gas take-out port for discharging the product gas comprising molecules of product compound to remove oxygen atom from the starting compounds, see containing a heating unit, the heating of the support, the metal oxide film, BaSrO _{3 It} is selected from the group consisting of _−δ , Ba (Sr, Ti) O _3−δ , BaTiO _x−δ , SrTiO _3−δ , Pb (Zr, Ti) O _3−δ , CaTiO _{x and} PbTiO _x .

According to another aspect, a gas generation method defines a processing space, a processing container holding a support in the processing space, and a metal oxide having a perovskite structure formed on the support and including oxygen defects. and objects film, provided on said processing vessel, a raw material gas supply ports for supplying a raw material gas containing a molecule of external consisting of carbon dioxide or water from the starting compound of the process vessel into the processing space, provided in the processing container A gas take-out port for taking out from the processing space a product gas which is generated on the surface of the metal oxide film and contains a product compound in which oxygen atoms are removed from the raw material compound in the form of molecules; and heating for heating the support and parts, a gas generating method using gas generator comprising the metal oxide _{film, BaSrO 3-δ, Ba (} Sr, Ti) O 3-δ, BaTiO x-δ, SrTi _{3-δ, Pb (Zr,} Ti) O 3-δ, CaTiO x, selected from the group consisting of PbTiO _x, (A) a step of evacuating the processing space, (B) the raw material gas into the processing space Introducing the raw material gas through a supply port, dissociating the raw material compound into the product compound by the metal oxide film, and (C) the product gas from the processing space to the outside of the processing container, And (D) after the steps (A) to (C), the substrate is heated to release oxygen from the metal oxide film.

  Since the gas generator includes a metal oxide film having a perovskite structure containing oxygen defects, carbon dioxide gas or water molecules introduced into the processing vessel can absorb oxygen atoms in the molecules of the metal oxide film. It is trapped by oxygen defects and dissociates into carbon monoxide molecules and hydrogen molecules.

SrTiO ₃ is a graph showing the surface state density (SDOS) in the crystal. It is sectional drawing which shows the structure of the carbon monoxide gas production | generation apparatus by 1st Embodiment. It is a flowchart which shows the production | generation process of the carbon monoxide by 1st Embodiment using the carbon monoxide gas production | generation apparatus of FIG. It is a graph which shows the result of having detected the carbon monoxide gas produced | generated in the carbon monoxide gas production | generation apparatus of FIG. 2 by TDS method. It is a flowchart which shows the production | generation process of the carbon monoxide by 2nd Embodiment using the carbon monoxide gas production | generation apparatus of FIG. It is sectional drawing which shows the structure of the carbon monoxide gas production | generation apparatus by 3rd Embodiment. It is a flowchart which shows the production | generation process of the carbon monoxide by 3rd Embodiment using the carbon monoxide gas production | generation apparatus of FIG. It is a perspective view which shows a part of carbon monoxide gas production | generation apparatus by 4th Embodiment. It is sectional drawing of one member shown in FIG. It is sectional drawing which shows the structure of the carbon monoxide gas production | generation apparatus by 4th Embodiment. It is sectional drawing of one member shown in FIG. It is a figure which shows the modification of FIG. 11A. It is a figure which shows one modification of 4th Embodiment. It is a figure which shows a part of carbon monoxide gas production | generation apparatus by 5th Embodiment. In connection with the sixth embodiment, it is a graph showing the surface state density (SDOS) in SrTiO ₃ crystal. It is a flowchart explaining 6th Embodiment. It is a graph which shows the result of having detected the hydrogen gas produced | generated in 6th Embodiment by TDS method. It is sectional drawing which shows the structure of the hydrogen gas production | generation apparatus by 7th Embodiment. It is sectional drawing which shows the gas storage tank used with the hydrogen gas production | generation apparatus of FIG. It is a flowchart which shows the hydrogen gas production | generation process by 7th Embodiment. It is FIG. (1) explaining switching of the gas path | route in the hydrogen gas production | generation apparatus of FIG. 17 corresponding to the flowchart of FIG. It is FIG. (2) explaining switching of the gas path | route in the hydrogen gas production | generation apparatus of FIG. 17 corresponding to the flowchart of FIG. It is FIG. (3) explaining switching of the gas path | route in the hydrogen gas production | generation apparatus of FIG. 17 corresponding to the flowchart of FIG. It is FIG. (4) explaining switching of the gas path | route in the hydrogen gas production | generation apparatus of FIG. 17 corresponding to the flowchart of FIG.

[First Embodiment]
FIG. 1 shows the surface state density of the surface state density (SDOS) obtained by the first principle calculation for the SrTiO ₃ crystal. However under the side view of FIG. 1, the SrTiO ₃ shows the surface state density when oxygen vacancies on the surface of the crystal occurs, in fact, the surface of the valence band of oxygen O2p orbit formed by SrTiO ₃ crystal surface It represents the density of states. The state shown in the lower part of FIG. 1 is hereinafter referred to as “initial state”.

On the other hand, the upper diagram in FIG. 1 shows the surface state density when the oxygen deficiency on the surface of the SrTiO ₃ crystal captures the oxygen atom of the CO ₂ molecule, and the valence band formed by the O2p orbital. It includes the contribution of the surface state density and the contribution of the surface state density of CO molecules derived from oxygen atoms and CO ₂ trapped in the oxygen vacancies. The state shown in the upper diagram of FIG. 1 is hereinafter referred to as a “final state”. Note E _F is the Fermi level in FIG. 1, E is the energy.

Further, the total energy of the SrTiO ₃ crystal was calculated as Ei and Ef for the “initial state” and “final state”, respectively, from the surface state density of FIG. 1 using density functional theory. The value of Ef is 2.1 eV smaller than the value of Ei (Ef−Ei = −2.1 eV), and when an SrTiO ₃ crystal having such an oxygen vacancy is exposed to carbon dioxide gas, carbon dioxide gas molecules are It was shown that oxygen atoms were trapped by oxygen defects upon dissociation.

Therefore, the inventor of the present invention conducted an experiment to confirm the above prediction using the apparatus 10 shown in FIG. 2 as a carbon monoxide gas generator for SrTiO ₃ single crystal.

  Referring to FIG. 2, the carbon monoxide gas generator 10 includes a processing container 11 that defines a processing space 110 that is exhausted from an exhaust port 11A by an exhaust system (not shown), and the processing space includes a heater 11H. A substrate holder 11B is provided.

  Further, the processing container 11 has a first gas supply port 11a for supplying oxygen gas via a valve 12a, a second gas supply port 11b for supplying hydrogen gas via a valve 12b, and carbon dioxide. A third gas supply port (raw material gas supply port) 11c for supplying gas via a valve 12c and a fourth gas supply port 11d for supplying an inert purge gas such as argon via a valve 12d are formed. Has been. Here, the carbon dioxide gas constitutes a raw material gas containing carbon dioxide molecules as molecules of the raw material compound.

  Further, in the carbon monoxide gas generator 10 of FIG. 2, the processing container 11 is provided with a gas extraction port 11 </ b> C for extracting a gas containing carbon monoxide gas generated inside the processing container 11. The gas containing carbon monoxide gas taken out from the port 11C is supplied to an external storage tank (not shown) via the switching valve 15, or sent to the mass spectrometer 14 for analysis. Here, the carbon monoxide gas constitutes a product gas containing carbon monoxide molecules as molecules of the product compound. The product compound is a compound obtained by removing one oxygen atom from the raw material compound.

  FIG. 3 is a flowchart showing the procedure of the experiment.

Referring to FIG. 3, a commercially available SrTiO ₃ single crystal substrate having a (001) main surface is first placed as a substrate W on the substrate holder 11B. In step 1, first, all valves 12a to 12d and switching are performed. The valve 15 is closed, and the processing space 110 of the processing container 11 is exhausted through the exhaust port 11A and depressurized.

  Next, the valve 13 is closed, and the valve 12a is opened while the valves 12b to 12d and the switch 15 are closed, and oxygen gas is introduced into the processing space 110 in the processing container 11. At the same time, the heater 11H is driven to heat the substrate W to a temperature of 100 ° C. to 1500 ° C. to compensate for oxygen vacancies existing on the surface of the substrate W. Thereby, the surface of the substrate W is initialized.

  Note that this initialization step can be omitted.

  Next, in step 2, with the valves 12a to 12c and the switching valve 15 being closed, argon gas is supplied to the processing space 110 in the processing container 11 from the valve 12d and the gas supply port 11d. Is exhausted through the exhaust port 11A, and oxygen gas is removed from the processing space 110. Further, the valve 12d is closed while continuing the exhaust, and the processing space 110 is decompressed.

Further, in step 2, the valve 12b is opened while the valve 13 and the valves 12a, 12c, 12d and the switching valve 15 are closed, and hydrogen gas is introduced into the processing space 110 in the processing vessel 11. At the same time, the heater 11H is driven to heat the substrate W to a temperature of 100 ° C. to 1000 ° C., and the surface of the processing vessel W is reduced with hydrogen gas to generate oxygen vacancies. As a result of the generation of oxygen vacancies, the surface of the substrate W changes to a non-stoichiometric composition represented by SrTiO _{3 -δ} using the composition parameter δ. When the surface of the substrate W was analyzed by XPS (X-ray photoelectron spectroscopy) and cathodoluminescence spectrum analysis, the surface of the substrate W had a non-stoichiometric amount in the range of the composition parameter δ from 1 to 2.8. It was confirmed that the theoretical composition layer was formed to a depth of 1 nm to 100 nm.

  Next, in step 3, the temperature of the substrate W is lowered to, for example, room temperature, and the valves 12a to 12c and the switching valve 15 are closed, and argon gas is supplied into the processing space 110 in the processing chamber 11 with the valves 12d and gas. Hydrogen gas is purged from the processing space 110 by supplying from the supply port 11d and exhausting the processing space 110 in the processing container 11 from the exhaust port 11A. Further, the processing space 110 is decompressed by closing the valve 12d and continuing the exhaust.

  Further, in step 3, the valve 12c is opened with the valve 13 and the valves 12a and 12b and the switching valve 15 closed, and carbon dioxide gas is introduced into the processing space 110 in the processing container 11, and all the valves 12a to With the surfaces 12c and 13 closed, the surface of the substrate W is exposed to carbon dioxide gas in the temperature range of room temperature to 1000 ° C. for 1 second to 10,000 seconds, preferably 10 seconds to 1000 seconds. As a result, carbon dioxide gas molecules in the carbon dioxide gas are dissociated and converted into carbon monoxide molecules as a result of oxygen atoms being trapped in the oxygen vacancies.

  Further, in step 4, the valve 15 is opened, this is switched to the mass spectrometer 14, and when the substrate W is heated in the range of 0 ° C. to 600 ° C., the CO gas type having a mass number of 28 is shown in FIG. The indicated TDS signal was obtained.

  Referring to FIG. 4, the release of carbon monoxide is observed with heating, which indicates that the substrate W has an action of dissociating carbon dioxide gas into carbon monoxide by capturing oxygen. In FIG. 4, the release of carbon monoxide gas is observed by heating the substrate W because the carbon monoxide molecules adsorbed on the surface of the substrate W are released as the substrate W is heated. It is.

  The carbon monoxide gas obtained in this way can be used for various purposes such as use in fuel cells and storage of food.

  In step 4, the valve 12 d may be opened, and argon gas may be introduced into the processing space 110 in the processing container 11 to facilitate the extraction of the carbon monoxide gas from the processing space 110.

In this embodiment, SrTiO ₃ single crystal having (001) orientation having oxygen deficiency and thus non-stoichiometric composition is used as the substrate W. However, as can be seen from the above description, in this embodiment, the SrTiO ₃ single crystal is used. The substrate W does not need to be a single crystal and does not need to have (001) orientation. That is, as the substrate W, a polycrystalline layer of SrTiO ₃ can be used.

Further, it is clear that the substrate W is not limited to SrTiO ₃ , and various single crystal or polycrystalline metal oxide films having a perovskite structure whose composition is generally represented by ABO ₃ are formed on a support substrate. Such a structure can be used as the substrate W. Examples of such a metal oxide film include BaTiO ₃ , CaTiO ₃ , PbTiO ₃ and solid solutions thereof in addition to the SrTiO ₃ . These solid solutions include BaSrO _3-δ , Ba (Sr, Ti) O _3-δ , BaTiO _x-δ , SrTiO _3-δ , Pb (Zr, Ti) O _3-δ , CaTiO _x, PbTiO _{x and the} like. Non-stoichiometric compounds are included.

Further, such a polycrystalline layer having oxygen vacancies on the surface is formed on an insulating support substrate made of, for example, an oxide, nitride, oxynitride, high dielectric metal oxide, zero gel, or a combination thereof. be able to. Further, such a polycrystalline layer is formed on a support substrate made of a semiconductor substrate such as silicon (Si), germanium (Ge), or SiGe mixed crystal, or a III-V group compound semiconductor substrate such as GaAs, InAs, or InP. Can be formed.

[Second Embodiment]
FIG. 5 is a flowchart showing a carbon dioxide gas processing method according to the second embodiment of the present invention using the carbon monoxide gas generator 10 of FIG. However, in FIG. 5, the same reference numerals are given to the parts described above, and the description thereof is omitted.

  Referring to FIG. 5, in this embodiment, carbon dioxide gas is converted into carbon monoxide gas in the state of step 4, and when the carbon monoxide gas is taken out from the gas takeout port 11C, the valve 12d is turned on. Open and introduce argon gas into the processing space 110 in the processing vessel 11. Thereby, the removal of the carbon monoxide gas is promoted, and at the same time, the carbon monoxide gas in the processing space 110 is purged.

  Further, in step 4, after purging the carbon monoxide gas, the valve 12 d and the switching valve 15 are closed, and the valve 13 is opened to decompress the processing space 110 in the processing container 11.

  Further, after step 4, in this embodiment, the process returns to step 2, hydrogen gas is introduced into the processing space 110 in the processing container 11, and oxygen vacancies are generated again on the surface of the substrate W.

Therefore, by repeating such steps 2 to 4, the carbon monoxide gas generator 10 shown in FIG. 2 can be operated repeatedly, and carbon monoxide gas can be sequentially generated from carbon dioxide gas.

[Third Embodiment]
FIG. 6 shows a configuration of a carbon monoxide gas generator 20 according to the third embodiment of the present invention. However, in FIG. 6, the same reference numerals are assigned to portions corresponding to the portions described above, and the description thereof is omitted.

  Referring to FIG. 6, the processing vessel 11 is supplied with a gas containing carbon monoxide gas taken out from the gas take-out port 11C from the switching valve 15 or a part of the carbon monoxide gas. A gas feedback port 11D is fed back to the processing space 110 in the processing container 11.

  In this embodiment, by feeding back the CO gas to the processing space 110 in this way, the oxygen partial pressure in the processing space 110 is reduced, oxygen atoms are desorbed from the surface of the substrate W, and oxygen vacancies are formed again. It becomes possible to do.

  FIG. 7 shows a flowchart of carbon monoxide gas generation using the carbon monoxide gas generator 20 of FIG. However, in FIG. 7, the steps described above are denoted by the same reference numerals, and the description thereof is omitted.

  Referring to FIG. 7, after the step 4, a part of the carbon monoxide gas taken out from the gas take-out port 11C in step 5 in the process vessel 11 through the switching valve 15 and the gas feedback port 11D. The oxygen partial pressure of the processing space 110 in the processing vessel 11 is reduced. At the same time, the heater 11H is driven and the temperature of the substrate W is raised to 100 ° C. to 1000 ° C. As a result, oxygen atoms are captured in the process of step 3 and oxygen vacancies are reduced or eliminated. Oxygen atoms are desorbed from the surface of W again, and the surface of the substrate W is prepared in preparation for the carbon dioxide gas dissociation process in the next step 3.

Further, the carbon monoxide generator 20 of FIG. 6 can be operated repeatedly by repeating steps 3 to 5 and, if necessary, forming oxygen vacancies with hydrogen gas in step 2 as indicated by the broken line. .

[Fourth Embodiment]
8 is a perspective view showing a structure 400 carrying a metal oxide film having a perovskite structure used in place of the substrate W in the carbon monoxide gas generator 10 of FIG. 2 or the carbon monoxide gas generator 20 of FIG. FIG.

  Referring to FIG. 8, the structure 400 includes a plurality of disk-like substrates 40W each having a diameter of 30 cm and carrying a polycrystalline metal oxide film 40P having a perovskite structure on the surface, for example, at intervals of about 0.05 mm to 500 mm. The plurality of disk-shaped substrates 40W are held in a state of being supported by support columns 400A and 400B.

  FIG. 9 is a cross-sectional view showing the configuration of the disk-shaped substrate 40W shown in FIG.

  Referring to FIG. 9, the disk-shaped substrate 40W is made of an oxide such as silicon oxide, a nitride such as silicon nitride, an oxynitride such as silicon oxynitride, a high dielectric such as strontium titanate or barium titanate, PZT or PLZT. A support substrate 40Q made of a body metal oxide and further zero gel or the like is included, and a heater made of a spiral or concentric conductor pattern 40H is formed on the upper main surface and the lower main surface of the support substrate 40Q. . The conductor pattern 40H is made of, for example, a noble metal such as platinum (Pt), rhodium (Rh), platinum rhodium alloy, or a refractory metal such as chromium (Cr) or nickel chromium alloy (NiCr), and the support base. Although it depends on the heat-resistant temperature of 40Q, the support base 40Q can be uniformly heated to a temperature range of 100 ° C to 1000 ° C.

  Further, the metal oxide film 40P having the perovskite structure including the side wall surface is continuously formed on the upper main surface and the lower main surface of the support substrate 40Q, for example, by sputtering, MOCVD, or sol-gel method. For example, it is formed to a thickness of 0.001 μm to 1000 μm.

  By using the laminated structure 400, the carbon monoxide generator 40 according to the fourth embodiment of the present invention is configured as shown in FIG.

  However, in the carbon monoxide generator 40 in FIG. 10, a cooling trap filter 16A that allows carbon dioxide molecules in the atmosphere to pass through is provided in the raw material gas supply port 11c that supplies the carbon dioxide, and from the gas extraction port 11C. A cold trap filter 16B that allows carbon monoxide molecules in the extracted gas to pass therethrough is provided. By providing the filters 16A and 16B, the carbon monoxide generator 40 can provide high-purity carbon monoxide gas using carbon dioxide in the atmosphere as a raw material. As the molecular filter 16A, for example, a commercially available cooling trap filter under the trade name “BOLA Cold Trap” operating at a temperature −57 <T <0 ° C. is used, and as the cooling trap filter 16B, for example, a temperature − from KGW Isotherm, Inc. Commercially available molecular filters can be used under the trade name “a Cold Finger Condenser” operating at 205 <T <−57 ° C.

  The molecular filters 16A and 16B in FIG. 10 can also be used in the device 10 in FIG. 2 and the device 40 in FIG.

In this embodiment, instead of the support substrate 40Q made of an insulator shown in FIG. 9, a support substrate 40R made of a semiconductor or metal, further metal oxide, or metal nitride is used as shown in the modification of FIG. 11A. It can also be used. For example, as such a semiconductor substrate, a single crystal substrate such as silicon (Si), germanium (Ge), or SiGe mixed crystal, or a single crystal substrate of a III-V group compound semiconductor such as GaAs, InAs, or InP is used. Is possible. Further, as such a metal substrate, a refractory metal such as titanium (Ti), tungsten (W), chromium (Cr), molybdenum (Mo) can be used, and as a metal oxide substrate or a metal nitride substrate, It is also possible to use metal oxides such as aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), strontium titanate (SrTiO ₃ ), and metal nitrides such as zirconium nitride (ZrN) and hafnium nitride (HfN). is there.

  When the support substrate 40R is formed of a semiconductor, metal, or conductive metal nitride, an insulating film 40I such as an oxide film is formed on the surface of the support substrate 40R, and the heater 40H is formed thereon. Preferably formed.

  FIG. 11B shows a further modification of FIG. 11A.

  In FIG. 11B, a metal substrate is used as the support substrate 40R, and a current is directly supplied to the metal substrate 11R to use it as a heater.

In the configuration of FIG. 11B, an adhesion layer 40Ad made of metal, metal oxide, or metal nitride is formed on the surface of the support substrate 40R. In this embodiment, as shown in FIG. 12, the perovskite structure has a perovskite structure. In order to promote the contact between the metal oxide film 40P and the carbon dioxide gas, it is possible to form a slit 40S in the support substrate 40Q.

[Fifth Embodiment]
In the above description, the support substrates 40Q and 40R are disk-shaped substrates, but the support substrate 40Q is not limited to a disk shape.

  For example, FIG. 13 shows an example in which the support substrate 40Q is formed of a generally rectangular member having the comb teeth portion 40T.

In the carbon monoxide generator 40 of FIG. 10, by using the substrate 40W having such a comb tooth portion 40T, the contact area between the carbon dioxide gas and the metal oxide film 40P having the perovskite structure in step 3 of FIG. Can be further increased.

[Sixth Embodiment]
FIG. 14 is a view similar to FIG. 1 showing the surface state density (SDOS) obtained by the first principle calculation for the SrTiO ₃ crystal. However lower graph of FIG. 14, as well as the lower graph of FIG. 1, showing the surface state density when oxygen vacancies on the surface of the SrTiO ₃ crystal is generated, in fact in SrTiO ₃ crystal surface It represents the surface state density of the valence band formed by oxygen O2p orbitals. Also in FIG. 14, the state in the lower diagram is hereinafter referred to as an “initial state”. The lower graph in FIG. 14 is the same as the lower graph in FIG.

On the other hand, the upper graph in FIG. 14 shows the surface state density when the oxygen deficiency on the surface of the SrTiO ₃ crystal captures the oxygen atom of the HO ₂ molecule, and the valence band formed by the O2p orbital. It includes the contribution of the surface state density and the contribution of the surface state density of OH groups derived from oxygen atoms and H ₂ O trapped in the oxygen vacancies. The state of the upper graph in FIG. 14 is hereinafter referred to as the “final state” as in the upper graph of FIG. Note also similarly in FIG. 14 and FIG. 1, E _F is the Fermi level, E is an energy.

Therefore, using the density functional theory from the surface state density of FIG. 14, the total energy of the SrTiO ₃ crystal was calculated as Ei and Ef for the “initial state” and “final state”, respectively. When an SrTiO ₃ crystal having an oxygen deficiency on its surface is exposed to water vapor, the water molecule dissociates and oxygen atoms are trapped in the oxygen defect, which is 2.71 eV smaller than the value of (Ef−Ei = −2.71 eV). Will be shown. Further, by heating the water molecules adsorbed on the SrTiO ₃ crystal by trapping oxygen atoms in the oxygen defects in this way, hydrogen gas can be generated if the bonds between oxygen atoms and hydrogen atoms in the water molecules can be broken. it is conceivable that.

Therefore, the inventor of the present invention conducted an experiment to confirm the above prediction for the SrTiO ₃ single crystal using the apparatus 10 described above with reference to FIG. 2 as a deuterium gas generator. Since the description of the apparatus 10 is duplicated, it will be omitted.

  FIG. 15 is a flowchart showing the procedure of the experiment.

Referring to FIG. 15, first, a commercially available SrTiO ₃ single crystal substrate having a (001) main surface is placed on the substrate holder 11B as a substrate W. In step 11, first, all valves 12a to 12d and switching are performed. The valve 15 is closed, and the inside of the processing container 11 is evacuated and decompressed through the exhaust port 11A.

  Next, the valve 13 is closed, and the valve 12a is opened while the valves 12b to 12d and the switch 15 are closed, and oxygen gas is introduced into the processing vessel 11. At the same time, the heater 11H is driven to heat the substrate W to a temperature of 100 ° C. to 1500 ° C. to compensate for oxygen vacancies existing on the surface of the substrate W. Thereby, the surface of the substrate W is initialized.

  Note that this initialization step can be omitted.

  Next, in step 12, with the valves 12a to 12c and the switching valve 15 closed, argon gas is supplied to the processing space 110 in the processing container 11 from the valve 12d and the gas supply port 11d, and the processing space 110 is supplied. Is exhausted through the exhaust port 11A, and oxygen gas is removed from the processing space 110. Further, the valve 12d is closed while continuing the exhaust, and the processing space 110 is decompressed.

Further, in step 12, the valve 12 b is opened while the valve 13, the valves 12 a, 12 c, 12 d and the switching valve 15 are closed, and hydrogen gas (H ₂ ) is introduced into the processing space 110 in the processing container 11. At the same time, the heater 11H is driven to heat the substrate W to a temperature of 100 ° C. to 1000 ° C., and the surface of the processing vessel W is reduced with hydrogen gas to generate oxygen vacancies. As a result of the generation of oxygen vacancies, the surface of the substrate W changes to a non-stoichiometric composition represented by SrTiO _{3 -δ} using the composition parameter δ. When the surface of the substrate W was analyzed by XPS (X-ray photoelectron spectroscopy) and cathodoluminescence spectrum analysis, the surface of the substrate W had a non-stoichiometric amount in the range of the composition parameter δ from 1 to 2.8. It was confirmed that the theoretical composition layer was formed to a depth of 1 nm to 100 nm.

  Next, in step 13, the temperature of the substrate W is lowered to room temperature, for example, and the valves 12a to 12c and the switching valve 15 are closed, and argon gas is supplied to the processing space 110 in the processing chamber 11 with the valves 12d and gas. Hydrogen gas is purged from the inside of the processing vessel 11 by supplying from the supply port 11d and exhausting the inside of the processing vessel 11 from the exhaust port 11A. Further, the processing space 110 in the processing container 11 is decompressed by closing the valve 12d and continuing the exhaust.

Further, in step 13, the valve 12 c is opened with the valve 13, the valves 12 a and 12 b and the switching valve 15 closed, and heavy water (D ₂ O) water vapor is introduced into the processing space 110 in the processing container 11. In a state where all the valves 12a to 12c and 13 are closed, the surface of the substrate W is changed to the heavy water vapor in the temperature range of room temperature to 1000 ° C. for 1 second to 10,000 seconds, preferably 10 seconds to 1000 seconds, To be exposed. As a result, the heavy water (D ₂ O) molecules in the heavy water water vapor are dissociated and converted into deuterium molecules (D ₂ ) as a result of the oxygen atoms being trapped in the oxygen vacancies. The deuterium molecules thus generated stay in the processing space 110 in the processing vessel 11 in the form of deuterium gas.

Further, in step 14, the valve 15 is opened, this is switched to the mass spectrometer 14, and when the substrate W is heated in the range of 0 ° C. to 600 ° C., heavy water (D ₂ O) having a molecular weight of 20 and a molecular weight are obtained. 16 was obtained for the deuterium (D ₂ ) gas species having a value of 4 as the substrate W was heated. By using heavy water in the experiment of FIG. 16 in this way, H ₂ O and H ₂ existing in the processing vessel 11 from the beginning are D ₂ O supplied from the outside for the experiment by the substrate W to D _2. The problem of masking the phenomenon of dissociation into O and O can be avoided, and the dissociation phenomenon of water vapor by the substrate W can be easily observed.

Referring to FIG. 16, with the heating of the substrate W, the release of D ₂ O having a molecular weight (M / Z) of 20 is first observed at 200 ° C. to 600 ° C. In addition, the molecular weight is observed at 300 ° C. to 600 ° C. Release of D ₂ with (M / Z) of 4 is observed, and it is confirmed that the substrate W has an action of dissociating D ₂ O into D ₂ by capturing oxygen. In FIG. 16, the release of D ₂ O is first observed when the substrate W is heated because the D ₂ O molecules adsorbed on the inner surface of the processing vessel 11 are released as the substrate W is heated. Because. On the other hand, the release of D ₂ observed at a higher temperature is caused by the dissociation of D ₂ O molecules adsorbed on the surface of the substrate W into D ₂ and oxygen atoms as a result of heating the substrate W. It is thought to occur.

Thus, the experiment of FIG. 16 demonstrates that it is possible to dissociate the water vapor of heavy water and generate heavy water gas using the apparatus of FIG. Similarly, water (H ₂ O) can be dissociated by using the apparatus of FIG. 2 to generate hydrogen gas. The hydrogen gas thus obtained can be used for various industrial applications in addition to fuel for fuel cells, rockets, and internal combustion engines, for example.

The present invention is applicable to both ordinary hydrogen having a mass number of 1 represented by the element symbol H and deuterium having a mass number of 2 represented by the chemical formula ² H or D. Hereinafter, in the present invention, “hydrogen” includes deuterium in addition to normal hydrogen. Similarly, in the present invention, "water" also includes a heavy water D ₂ O and DHO other H ₂ O, "water vapor" is intended to also include other heavy water D ₂ O and DHO gas the H ₂ O gas.

  In step 14, the valve 12 d may be opened to introduce argon gas into the processing container 11, thereby facilitating the extraction of the hydrogen gas from the processing container 11.

As in the previous embodiment, as can be seen from the above description, in this embodiment, the substrate W does not have to be a single crystal and does not need to have a (001) orientation. That is, as the substrate W, a polycrystalline layer of SrTiO ₃ can be used.

Also in this embodiment, it is clear that the substrate W is not limited to SrTiO ₃ , and various single crystal or polycrystalline metal oxide films having a perovskite structure whose composition is generally represented by ABO ₃ are formed on the support substrate. The structure formed in (1) can be used as the substrate W. Examples of such a metal oxide film include BaTiO ₃ , CaTiO ₃ , PbTiO ₃ and solid solutions thereof in addition to the SrTiO ₃ . These solid solutions include BaSrO _3-δ , Ba (Sr, Ti) O _3-δ , BaTiO _x-δ , SrTiO _3-δ , Pb (Zr, Ti) O _3-δ , CaTiO _x, PbTiO _{x and the} like. Non-stoichiometric compounds are included.

Further, such a polycrystalline layer having oxygen vacancies on the surface is formed on an insulating support substrate made of, for example, an oxide, nitride, oxynitride, high dielectric metal oxide, zero gel, or a combination thereof. be able to. Further, such a polycrystalline layer is formed on a support substrate made of a semiconductor substrate such as silicon (Si), germanium (Ge), or SiGe mixed crystal, or a III-V group compound semiconductor substrate such as GaAs, InAs, or InP. Can be formed.
[Seventh Embodiment]
FIG. 17 is a schematic sectional view showing the configuration of the hydrogen gas generator 60 according to the seventh embodiment, and FIG. 18 is a flowchart showing the operation of the hydrogen gas generator 60 of FIG. However, in FIG. 17, the same reference numerals are assigned to the portions corresponding to the portions described above, and the description thereof is omitted. Although the present embodiment will be described below with reference to a hydrogen gas generator, the present embodiment can also be applied to the generation of carbon monoxide gas by supplying carbon dioxide gas. Similarly, each of the previous embodiments can be applied to generation of hydrogen gas by supplying water vapor.

  Referring to FIG. 17, for example, atmospheric water vapor that has passed through the water molecule filter 61 is supplied to the processing space 110 in the processing container 11 as a raw material gas through a valve 12 c and a raw material gas supply port 11 c, and Water molecules constituting water vapor are adsorbed on the substrate W when oxygen atoms in the molecules are captured by oxygen vacancies in the substrate W. By supplying the source gas through the water molecule filter 61, for example, introduction of oxygen gas in the atmosphere into the processing container 11 is suppressed. Here, the water vapor constitutes a raw material gas and contains water molecules as molecules of the raw material compound.

  Therefore, in this state, the substrate W is heated to a temperature range of, for example, 300 ° C. to 600 ° C., so that the bonds between oxygen atoms and hydrogen atoms in the water molecules are broken and dissociated as described above with reference to FIG. Hydrogen gas can be obtained by hydrogen atoms. Here, the hydrogen gas constitutes a product gas and contains hydrogen molecules as molecules of the product compound. The product compound is a compound obtained by removing one oxygen atom from the raw material compound.

  The hydrogen gas thus obtained is temporarily stored in the temporary storage tank 63 from the processing space 110 in the processing container 11 through the gas extraction port 11C and the switching valve 15. At this time, as described above with reference to FIG. 16, when the substrate W is heated to the above temperature range, water vapor is desorbed from the substrate W at the same time, so that the gas stored in the storage tank 63 is hydrogen gas and water vapor. It becomes a mixed gas.

  FIG. 18 shows a schematic configuration of the storage tank 63.

  Referring to FIG. 18, the storage tank 63 has a piston 63A and a cylinder 63B, and a port 63b connected to the switching valve 15 is formed in the cylinder 65B. Therefore, the internal volume V of the storage tank 63 is changed between the minimum value Vmin and the maximum value Vmax by driving the piston 63A in the cylinder 63B by air pressure or hydraulic pressure. At this time, it is preferable that the change width ΔV of the volume V is designed to be larger than the volume of the processing vessel 11.

  Therefore, when storing the hydrogen gas in the storage tank 63, the gas take-out port 11C is connected to the storage tank 63 by the valve 15, and the volume V is expanded by driving the piston 63A in this state. The atmosphere containing hydrogen gas and water vapor in the processing vessel 11 can be sucked into the cylinder 63B.

  Thereafter, the valve 15 is closed to disconnect the processing container 11 from the storage tank 63, and the valve 13 is opened to evacuate and decompress the processing space 110 in the processing container 11. Further, the heater 11H is driven to heat the substrate W to a temperature of 100 ° C. to 1000 ° C., thereby desorbing oxygen atoms filled with oxygen vacancies on the surface of the substrate W and discharging them out of the system. . Thereby, the initial oxygen deficiency is recovered in the substrate W. At this stage, an inert gas such as Ar may be introduced into the processing container 11 in order to promote purging.

  Next, the storage tank 63 is connected to the processing container 11 via a gas feedback port 11D formed in the processing container 11 by operating the switching valve 15, and the gas in the storage tank 63 is connected to the processing container 11 11 is fed back to the processing space 110 in the system 11.

  The gas fed back in this manner contains hydrogen and water vapor, and the water vapor is adsorbed on the substrate W by capturing oxygen atoms in the oxygen vacancies of the substrate W as in the previous case.

  Therefore, by repeating the previous process, hydrogen gas is further released into the processing space 110 in the processing container 11 by dissociation of water vapor, and the hydrogen gas concentration is increased in the processing space 110 in the processing container.

  The switching valve 15 is operated by a control device such as a computer (not shown).

  The hydrogen gas thus concentrated is taken out from the switching valve 15 through the hydrogen molecular filter 62 to the outside. Here, as the hydrogen molecular filter 62, carbon nanotubes can be used. As the water molecule filter 61, a cold trap can be used.

  19 shows a flowchart of hydrogen gas generation using the hydrogen gas generator 60 of FIG. 17, and FIG. 20 shows the switching operation of the valve 15 corresponding to the flowchart of FIG. However, in FIG. 19, the steps described above are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 19, after step 2, in step 33, water vapor is introduced into the processing space 110 in the processing vessel 11 while keeping the substrate at room temperature, and the mechanism described above, ie, the water The oxygen atoms of the molecules are trapped by oxygen vacancies in the substrate W, whereby the water vapor molecules are adsorbed onto the substrate W.

  Further, in step 34, the temperature of the substrate W is raised to a temperature of 600K to 800K by driving the heater 11H, thereby dissociating the water molecules and supplying hydrogen gas into the processing space 110 in the processing container 11. Is generated.

  In this step 34, the atmosphere of the processing space 110 in the processing container 11 containing the generated hydrogen gas is sent to the storage tank 63 via the switching valve 15.

  Further, in step 35, the processing space 110 in the processing container 11 is exhausted through the exhaust port 11A and the valve 13 and depressurized. Further, the heater 11H is driven, and the substrate W is heated to a temperature of 100 ° C. to 1000 ° C. As a result, the oxygen partial pressure in the processing space 110 is lowered, and oxygen atoms filled with oxygen vacancies on the surface of the substrate W are released and discharged out of the system in the form of oxygen gas. That is, in step 35, oxygen is purged from the processing space 110, and as a result, oxygen vacancies are formed again on the surface of the substrate W, and the surface of the substrate W is prepared for the hydrogen gas generation step in the next step 34. Is arranged.

  As shown in FIG. 20B, in the step 35, the switching valve 15 disconnects the storage tank 63 and the filter 62 from the processing container 11, and accordingly, in the step 35, the gas in the storage tank 63 is changed to the processing container 11. The exhaust gas is not exhausted from the exhaust port 11A.

  In the step 35, an inert gas such as Ar may be introduced into the processing space 110 in the processing container 11 from the valve 12d and the port 11d to promote the oxygen purge.

  After step 35, the mixed gas composed of hydrogen gas and water vapor taken out from the gas take-out port 11C is processed in the processing vessel 11 through the switching valve 15 and the gas feedback port 11D as shown in FIG. 20C. Feedback is made to the space 110.

  Furthermore, by repeating Steps 33 to 35, the hydrogen gas generator 60 of FIG. 17 can be operated repeatedly.

  Finally, when the hydrogen gas concentration in the atmosphere of the processing space 110 in the processing container 11 is sufficiently increased, the switching valve 15 causes the gas in the processing container 11 to flow to the filter 62 as shown in FIG. 20D. As a result, high purity hydrogen gas is obtained from the filter 62.

  Also in this embodiment, as the substrate W, those described above with reference to FIGS. 8, 11A and 11B, and FIGS. 12 and 13 can be used.

  In the flowchart of FIG. 19, after the feedback step of Step 36, the process can be returned to Step 33 as indicated by a broken line, and water vapor can be introduced into the processing space 110 in the processing vessel 11.

  In the hydrogen gas generator 60 of FIG. 17, the filter 61 is replaced with the filter 16A described with reference to FIG. 10, and the filter 62 is replaced with the filter 16B described with reference to FIG. It can be clearly used as a carbon monoxide gas generator.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope described in the claims.

  This international application claims priority based on the international application PCT / JP2009 / 059078 filed on May 15, 2009, and the entire contents of PCT / JP2009 / 059078 are incorporated herein by reference.

10, 20, 40 Carbon monoxide gas generator 11 Processing vessel 11A Exhaust port 11B Substrate holder 11C Gas extraction port 11D Gas feedback port 11H Heater 11a Oxygen gas supply port 11b Hydrogen gas supply port 11c Raw material gas supply port 11d Purge gas supply port 12a to 12d, 13 Valve 14 Mass spectrometer 15 Switching valve 16A CO ₂ molecular filter 16B CO molecular filter 40H Heater 40I Insulating film 40P Perovskite structure metal oxide film 40Q, 40R Support substrate 40S Slit 40T Comb portion 40W Substrate 40ad Adhesion layer 400 Laminated structure 400A, 400B Prop 60 Hydrogen gas generator 61 Water molecular filter 62 Hydrogen molecular filter 63 Storage tank 63A Piston 63B Cylinder 63b Doo 110 processing space

Claims (9)

A processing vessel defining a processing space and holding a support in the processing space;
An exhaust system coupled to the processing vessel and exhausting the processing space;
A metal oxide film having a perovskite structure and oxygen defects formed on the support;
A raw material gas supply port for supplying a raw material gas containing molecules of a raw material compound consisting of carbon dioxide or water to the processing space;
A gas extraction port for discharging a product gas containing molecules of a product compound obtained by removing oxygen atoms from the raw material compound from the processing space;
Look including a heating unit for heating the substrate,
The metal oxide _{film, BaSrO 3-δ, Ba (} Sr, Ti) O 3-δ, BaTiO x-δ, SrTiO 3-δ, Pb (Zr, Ti) O 3-δ, CaTiO x, from PbTiO _x A gas generator selected from the group consisting of: The gas generator according to claim 1, wherein the metal oxide film generally has a composition represented by the formula ABO _3-δ , and the composition parameter δ is 1 or more and 2.8 or less. It said support includes a plurality of support members, each of said plurality of support members, the gas generator of claim 1, wherein the carrying the metal oxide film. The gas generator according to claim 3 , wherein the plurality of support members are separated from each other and stacked one above the other.   Further, a switching valve connected to the gas extraction port for switching the path of the product gas; a storage tank connected to the switching valve for storing the product gas; and connected to the switching valve; obtained from the gas extraction port. An output-side filter for purifying the product gas and extracting the product compound; and a feedback port connected to the switching valve and returning the product gas obtained from the gas extraction port to the processing container. The gas generator according to claim 1. The switching valve has a first state in which the product gas is supplied to the storage tank, and a second state in which the connection between the gas take-out port, the feedback port, the storage tank, and the output side filter is cut off. When, according to claim, characterized a third state connecting said storage tank to said feedback port, sequentially switches that the state between the fourth state for connecting the gas extraction port to the output side filter 5 The gas generator described. A processing space is defined, a processing container holding a support in the processing space, a metal oxide film having a perovskite structure including oxygen defects formed on the support, and provided in the processing container. a raw material gas supply ports for supplying a raw material gas containing a molecule of external consisting of carbon dioxide or water from the starting compound of the process vessel into the processing space, provided in the processing container, generated on the surface of the metal oxide film And a gas generator including a gas take-out port for taking out a product gas containing molecules of the product compound from which oxygen atoms have been removed from the raw material compound from the processing space, and a heating unit for heating the support. A gas generation method,
The metal oxide _{film, BaSrO 3-δ, Ba (} Sr, Ti) O 3-δ, BaTiO x-δ, SrTiO 3-δ, Pb (Zr, Ti) O 3-δ, CaTiO x, from PbTiO _x Selected from the group
(A) exhausting the processing space;
(B) introducing the source gas into the processing space via the source gas supply port, and dissociating the source compound into the product compound by the metal oxide film;
(C) extracting the product gas from the processing space to the outside of the processing container from the gas extraction port,
And (D) a gas generation method including a step of heating the support and releasing oxygen from the metal oxide film after the steps (A) to (C). The gas generation method according to claim 7, wherein the step (D) is performed after the steps (A) to (C) are repeated a plurality of times. Further, the gas generator is connected to the gas take-out port, and is connected to the switching valve for switching the path of the product gas, the switching valve, a storage tank for storing the product gas, and the switching valve, An output filter for purifying the product gas obtained from the gas take-out port and taking out the product compound, and a feedback port connected to the switching valve and returning the product gas obtained from the gas take-out port to the processing vessel And
In the step (A), the switching valve takes a first state in which the connection between the gas take-out port, the feedback port, the storage tank, and the output filter is cut off,
In the step (B), the switching valve takes a second state in which the storage tank is connected to the feedback port;
In the step (C), the switching valve takes a third state of supplying the product gas to the storage tank,
In the step (D), the switching valve takes the first state in which the connection between the gas extraction port, the feedback port, the storage tank, and the output side filter is cut off,
The gas generation method according to claim 7 , wherein after the steps (A) to (D) are repeated a plurality of times, the switching valve connects the gas extraction port to the output filter.

Images