JP2005298307A - Fuel reformer for fuel cell and fuel reforming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a reformer capable of taking out a pure hydrogen from a gaseous hydrocarbon such as natural gas or the like and dispensing with a special modifier and to obtain an amount of hydrogen greater than the amount of hydrogen required for the fuel cell even with small power consumption. <P>SOLUTION: The fuel reformer for the fuel cell is characterized by that in an air-tight box holding a proton conductive solid electrolyte layer 1 between a gas-permeable anode 2 and a hydrogen-permeable cathode 3, an anode side is a gaseous mixture supply chamber to which a crude hydrogen or a gaseous mixture of a gaseous hydrocarbon and oxygen and/or steam is supplied and a DC circuit applying an electric field between the anode and the cathode is formed, and also a cathode side is a generating chamber for a super high purity gaseous hydrogen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel reformer and a fuel reforming method for a fuel cell using a proton conductive solid electrolyte layer having a high conductivity and a hydrogen permeable cathode.

Conventionally, fuel reforming for fuel cells uses a catalyst such as platinum at a high temperature of 700 ° C. or higher, and a technique for separating and recovering hydrogen from a mixed gas of hydrogen-containing gas such as natural gas and water vapor has been widely used. However, when natural gas such as methane is reformed with this technology, CO and CO ₂ are generated in addition to hydrogen and poison the catalyst. Therefore, in order to use reformed hydrogen as fuel for fuel cells, CO or the like is used. A transformer is needed. Moreover, since the operating temperature of the reformer is as high as 700 ° C., it is necessary to use an expensive structural material or a sealing material, and there is a problem that the manufacturing cost of the reformer by this technique is expensive.

The present invention provides, at low cost, a fuel reformer that does not require a special transformer that can extract pure hydrogen from hydrocarbon gas such as natural gas by using a hydrogen permeable membrane and a solid electrolyte layer. For the purpose.
Another object of the present invention is to obtain a larger amount of hydrogen than that required by the fuel cell even with low power consumption by using a thin solid electrolyte layer with high conductivity and operating the reformer at a high temperature.

In order to solve the above problems, the present inventor proposes the following fuel reformer and fuel reforming method using a proton conductive solid electrolyte layer and a hydrogen permeable cathode instead of the catalytic method.
(1) In an airtight casing in which a proton conductive solid electrolyte layer is sandwiched between a gas permeable anode and a hydrogen permeable cathode, a mixed gas of crude hydrogen or hydrocarbon gas and oxygen and / or water vapor is placed on the anode side. Fuel reforming for fuel cells, characterized in that a source gas supply chamber is provided, a DC circuit for applying an electric field between the anode and the cathode is formed, and the cathode side is an ultra-high purity hydrogen gas generation chamber It is a vessel.
Here, the solid electrolyte layer is a concept including not only a layer shape but also a thin film shape, a plate shape, and the like, and refers to a shape capable of being in contact with the anode and the cathode.
That is, when a solid electrolyte layer is sandwiched between a hydrogen-permeable cathode and a gas-permeable anode that catalyzes an electrode reaction, and a DC voltage is applied between the electrodes, the gas is supplied to an air-tight source gas supply chamber on the anode side. Only hydrogen ions (protons) are selectively dissolved and permeated into the solid electrolyte layer from the generated hydrocarbon gas, and further passed through a hydrogen permeable cathode that acts as a partition wall. It is recovered as hydrogen gas. Here, the crude hydrogen is a gas containing abundant hydrogen such as low-purity hydrogen gas, water gas or carbon dioxide gas. As hydrocarbon gas, methane (CH ₄ ), propane (C ₃ H ₈ ) and butane are used. (C ₄ H ₁₀ ) and the like.

A structure in which a proton conductive solid electrolyte layer is sandwiched between a gas permeable anode and a hydrogen permeable cathode is obtained by, for example, bonding a metal foil or laminating a metal paste on a porous substrate, and then sintering or metal paste. A hydrogen permeable metal membrane is formed as a cathode by the adhesion used, and a solid electrolyte layer is formed by coating a proton conductive solid electrolyte membrane on the hydrogen permeable metal membrane, and this solid electrolyte layer is then sintered. It can be obtained by forming the anode so as to be in contact with the substrate. There are various methods for forming the anode. For example, the anode can be formed by adhering a net of Ag to the solid electrolyte layer using an Ag paste. However, other manufacturing methods may be used as a manufacturing method of the structure in which the solid electrolyte layer and the hydrogen permeable cathode solid electrolyte layer are sandwiched.
Furthermore, the solid electrolyte layer and the hydrogen permeable cathode need only be in electrical contact, and the solid electrolyte layer and the hydrogen permeable cathode can be brought into contact with each other without electrical resistance across the front surface. For example, such a fuel reformer can be manufactured by applying Pd paste to the cathode-side end surface of the solid electrolyte layer or depositing Pd. Thus, if the hydrogen permeable cathode and the solid electrolyte layer are brought into contact with each other without being integrated, it is possible to replace only the solid electrolyte layer that has deteriorated over time without replacing an expensive metal film such as Pd. .
Since the hydrogen permeable cathode transmits only hydrogen (proton), the reformer is hermetically divided into a gas supply chamber and a hydrogen generation chamber for gases other than hydrogen.
Even if cracks and pores are generated in the solid electrolyte layer by this action, gas such as CO that poisons the electrode does not enter the hydrogen generation chamber side, and the hydrogen generation ability is hardly affected.

(2) The fuel reformer as described in (1) above, wherein the solid electrolyte layer is a thin plate of proton conductive oxide.
(3) A thin plate of proton conductive oxide is AB ′ _1−x B ″ _x O _{3−x / 2} (A: Sr ²⁺ , Ba ²⁺ , B ′: Ti ⁴⁺ , Zr ⁴⁺ , Ce ⁴⁺ B ″: Y ³⁺ , Yb ³⁺ , Nd ³⁺ , Gd ³⁺ ), the fuel reformer according to (2) above.

(4) The fuel modification according to (3) above, wherein the thin plate of the proton conductive oxide is AB _{= 1-x} B ″ _x O _{3-x / 2,} wherein x = 0.1 to 0.2 It is a quality device.
In the thin sheet of proton conductive oxide, conductivity can be obtained by replacing the acceptor contained therein with protons. However, when the acceptor ratio exceeds a certain value, its conductivity decreases. This is because an oxide phase having a different structure is mixed when the value of x in the proton conductive oxide is high. In order to ensure the original conductivity, x is preferably 0.1 or more. For example, in the CaZr _1-x In _x O _{3-x / 2} system, a different phase precipitates when x exceeds 0.1, and in the BaCe _1-x Y _x O _{3-x / 2} system, x exceeds 0.2. As a result, different phases are deposited in the solid electrolyte layer and the electrical conductivity is lowered.

(5) The fuel reformer as described in any one of (1) to (4) above, wherein the hydrogen permeable cathode is a Pd, Pd—Ag alloy or a Zr—Ni based amorphous alloy. is there.
(6) The fuel reformer described in any one of (1) to (5) above, wherein the gas permeable anode is made of Ag or a metal having Ag as a surface layer.

(7) The chemical potential of the solid electrolyte-hydrogen system (hydrogenation potential) decreases from the anode toward the cathode by tilting the chemical composition of the solid electrolyte layer in the direction of the electric field. It is a fuel reformer as described in any one of 1)-(6).
The electrical conductivity of the solid electrolyte layer can be increased by tilting the chemical composition in the solid electrolyte layer and driving force of the resulting hydrogenation potential gradient.
To incline the chemical composition of the solid electrolyte layer in the direction of the electric field, the solid electrolyte layer is formed by coating two or more layers of solid electrolyte thin films having different chemical compositions so that the hydrogenation potential decreases from the anode to the cathode. Form. The method of forming the solid electrolyte layer in which the chemical composition of the solid electrolyte layer is inclined in the direction of the electric field is not limited to the above. For example, a method of forming a single component by a method of laminating and sintering solid electrolyte powders having different chemical compositions into two or more layers may be mentioned.

(8) The fuel reforming as described in any one of (1) to (7) above, wherein the hydrogen permeable cathode is brazed or laser welded so as to have airtightness in the airtight casing. It is a vessel.
(9) The fuel reformer according to any one of (1) to (8), wherein a gas circulation pipe for adsorbing and removing carbon dioxide gas is provided in the raw material gas supply chamber.
When pure hydrogen is produced, carbon dioxide gas may remain in the source gas supply chamber on the anode side. When the carbon dioxide gas concentration increases, there arises a problem that the electrode reaction on the anode side is slowed down. Therefore, by providing a gas circulation pipe for adsorbing and removing carbon dioxide in the source gas supply chamber, the carbon dioxide concentration in the source gas supply chamber can be kept constant by removing carbon dioxide such as CO ₂ .

(10) A proton conductive solid electrolyte layer is sandwiched between the gas permeable anode and the hydrogen permeable cathode, and a crude hydrogen or hydrocarbon gas and a mixed gas of oxygen and / or water vapor are supplied to the anode side. A fuel reforming method for a fuel cell, characterized in that an ultra-high purity hydrogen gas is generated on the cathode side by applying a DC electric field between the cathodes.
(11) The above-mentioned characteristic that the chemical potential of the electrolyte-hydrogen system (hydrogenation potential) decreases in the electric field direction by inclining the chemical composition of the proton conductive solid electrolyte layer in the electric field direction ( 10) A fuel reforming method for a fuel cell according to 10).

The present invention provides a low-cost fuel reformer that eliminates the need for a special transformer that can extract pure hydrogen from hydrocarbon gas such as natural gas by using a hydrogen-permeable cathode and a solid electrolyte layer. can do.
If a thin solid electrolyte layer with high conductivity is used and the fuel reformer is operated at a high temperature, a hydrogen amount larger than that required by the fuel cell can be obtained even with low power consumption.
Further, if the hydrogen permeable metal membrane and the solid electrolyte layer are separated without being integrated, it is not necessary to replace an expensive hydrogen permeable metal membrane such as Pd when the solid electrolyte layer is replaced due to deterioration over time. There is an effect.

An example of an embodiment according to the present invention is shown below, but the present invention is not limited to the configurations, materials, and the like described below.
FIG.1 (d) is a conceptual diagram which illustrates typically one Embodiment of the fuel reformer which concerns on this invention. As shown in FIG. 1 (d), a proton conductive oxide solid electrolyte layer 1 is sandwiched between a porous metal anode electrode 2 and a hydrogen permeable metal cathode electrode 3, and the anode electrode 2 contains hydrogen such as methane gas. A gas is supplied and a DC voltage is applied between the electrodes. The solid electrolyte layer 1 and the like are airtightly separated by an airtight housing 9.
When a natural gas such as methane and a mixed gas such as steam or oxygen are supplied to the anode electrode 2 in this fuel reformer, CH ₄ + 2H ₂ O → 8H ⁺ + 8e ⁻ + CO ₂ , CH ₄ + O ₂ → 4H ⁺ + 4e ⁻ + CO Hydrogen ions generated by the polar reaction of ₂ or 2CH ₄ + 2H ₂ O + O ₂ → 2CO ₂ + 12H ⁺ + 12e ⁻ are dissolved in the solid electrolyte layer 1. Since the hydrogen ions are driven toward the cathode electrode 3 by an electric field, a hydrogen permeable metal film is formed by an electrode reaction of 8H ⁺ + 8e ⁻ → 4H ₂ , 4H ⁺ + 4e ⁻ → 2H ₂ or 12H ⁺ + 12e ⁻ → 6H _2. Only hydrogen can be separated and taken out from the cathode electrode 3. As the anode electrode 2 of this fuel reformer, for example, a porous Ag electrode having a catalytic action in the above electrode reaction can be used.

As the fuel reformer according to the present embodiment, it is preferable to use a thin plate of a proton conductive oxide that allows only solid hydrogen ions to selectively pass through the solid electrolyte layer 1 from a hydrogen-containing gas. Since the proton flow rate through the solid electrolyte layer 1 increases as the proton conductivity of the solid electrolyte layer increases, for example, as the solid electrolyte layer 1 of the fuel reformer, high proton conductivity in the temperature range of 400 to 700 ° C. Proton conductive oxide BaCe _1-x Y _x O _{3−x / 2} (x = 0.1 to 0.2) or the like showing the rate is used.
For the cathode 3 of the fuel reformer, an airtight Pd alloy film or Pd—Ag alloy film free from defects such as pores and cracks is used. These Pd—Ag alloy films and the like are preferable because they have a high hydrogen permeation rate and are less susceptible to embrittlement due to hydride precipitation.
FIG. 1A shows the source gas supply unit on the anode side. As shown in FIG. 1 (a), the source gas supply unit is composed of an Ag lead wire 7 for applying a direct current electric field, a SUS punching support plate 5, and a porous metal 5 such as Ag plated Ni. FIG. 1B shows the solid electrolyte part. As shown in FIG. 1B, the solid electrolyte portion is composed of an Ag paste (may be Pt black) film 4, a proton conductive oxide 1, and a paste film 8 of Pd and proton conductive oxide. Here, the proton conductive oxide 1 may be a gradient conductive film made of a sintered body or a thin film forming body. Further, FIG. 1C shows a hydrogen gas extraction part on the cathode side. As shown in FIG. 1C, the cathode side is composed of a hydrogen permeable metal 3 made of palladium Pd (Pd ₈₀ Ag ₂₀ may be used) and a SUS punching support plate 6.
The fuel reformer according to this embodiment is configured by sandwiching the solid electrolyte portion between the cathode-side electrode and the anode-side electrode.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 2 is a view showing an example of a fuel reformer according to the present invention.
As shown in FIG. 2, in the airtight casing 8 in which the proton conductive solid electrolyte layer 13 is sandwiched between the gas permeable anode electrode 11 and the hydrogen permeable cathode electrode 12 in the airtight compartment, the anode electrode 11 side Is a raw material gas supply chamber 14 to which a mixed gas of hydrocarbon gas and oxygen and / or water vapor is supplied, and a direct current circuit for applying an electric field between the anode electrode 11 and the cathode electrode 12 is formed, and the cathode electrode 12 side is made pure. This is a fuel reformer 10 for a fuel cell, characterized in that it is a hydrogen gas production chamber 15. The anode electrode 11 and the cathode electrode 12 are fixed by electrode support plates 19 and 20. For example, the solid electrolyte layer 13 sandwiched between the anode electrode and the cathode electrode can be removed by removing the bolt of the electrode support plate 19 on the anode electrode side. The mixed gas supply chamber 14 is provided with a source gas inlet 21 and a gas circulation pipe 16 outlet. The gas circulation pipe 16 has a function of circulating the source gas while removing carbon dioxide gas or the like generated on the anode side. The hydrogen gas generation chamber 15 is provided with an outlet 18 for the generated hydrogen. The extracted hydrogen gas is supplied to the fuel cell.

Here, the anode electrode 11 is preferably formed of a porous metal made of Ag or a metal having Ag as a surface layer. The cathode electrode 12 is preferably formed of Pd, Pd—Ag alloy, Zr—Ni based amorphous alloy, or the like.
The hydrogen permeable cathode electrode 12 can be fixed to the hermetic casing 8 or the like by a hermetic brazing method or a sealing method such as laser welding.
As the hydrocarbon gas, for example, methane gas containing hydrogen is preferably used.
The amount of pure hydrogen produced varies depending on temperature conditions and DC applied voltage value. The examples under various conditions are described below.

FIG. 3 shows the temperature and potential of the current value flowing through the fuel reformer using BaCe _0.9 Y _0.1 O _2.95 having a different thickness as the solid electrolyte layer 13 in the fuel reformer 10 having the same configuration as in the first embodiment. It is the graph which showed gradient dependence. In this measurement, a 0.1 mm thick Pd film is used for the cathode, and porous Ag is used for the anode. Since the transport number of BaCe _0.9 Y _0.1 O _2.95 (the ratio of proton conduction in electric conduction) is almost 100%, the current value flowing through the fuel reformer can be converted into the flow rate of protons. The current value of 1 A corresponds to 6.24 × 10 ¹⁸ protons / sec. The solid electrolyte layer 13 thickness at the circle in the graph is t = 0.33 mm and the electrode area is 0.20 cm ^2. The solid electrolyte layer 13 thickness at x is t = 0.92 mm and the electrode area is 0. 25 cm ² . Moreover, it measured on the conditions of 300 degreeC and 400 degreeC as temperature conditions, respectively.

  From the graph of FIG. 3, the current flowing through the fuel reformer 10 increases as the potential gradient (applied voltage / thickness of the solid electrolyte layer) increases. However, when the potential gradient is low at low temperatures, the current value becomes a potential gradient. It turns out that it is not proportional and does not obey Ohm's law. This is considered to be due to a decrease in effective voltage due to an overvoltage of the electrode reaction when the potential gradient is small at low temperature. When the potential gradient was high at high temperature, the relationship between the current value and the potential gradient almost followed Ohm's law, but a higher current value was obtained as the solid electrolyte layer 13 became thinner. This is presumably because proton migration is promoted because the proton concentration gradient increases when the solid electrolyte layer 13 is thin. From the above results, it has been found that in order to extract a large amount of hydrogen, it is more preferable to raise the experimental temperature and make the solid electrolyte layer 13 thinner.

FIG. 4 shows a fuel reformer 10 having the same configuration as that of the first embodiment, and a fuel reformer having an electrode area of 0.2 cm ² using BaCe _0.9 Y _0.1 O _2.95 having a thickness of 0.33 mm as the solid electrolyte layer 13. 6 is a graph showing the applied voltage dependence of current (proton flow rate) at temperatures of 450 ° C. and 500 ° C. of the vessel 10. When the operating temperature of the fuel reformer 10 approaches 537 ° C., which is the ignition point of the mixed gas of methane and oxygen, the current value increases rapidly as the applied voltage increases, and the voltage of 10 V is 0.65 A / cm ² . The current could be taken out. The phenomenon that the extraction current rapidly increases at this high temperature is considered to be a cause of a significant increase in the hydrogen ion concentration in the electrolyte due to an increase in the electrode reaction rate. Furthermore, when the fuel reformer 10 is operated at a temperature of 300 ° C. or higher, the current gradually increases with the lapse of the operation time, and finally becomes saturated. This phenomenon is considered because the hydrogen ion concentration in the electrolyte layer is saturated at a constant value. In addition, a tendency for the extraction current to increase with an increase in the number of operations of the fuel reformer was observed. From the above results, in order to separate a large amount of hydrogen from methane gas with a small amount of electric power, it is necessary to reduce the thickness of the solid electrolyte layer and to operate the fuel reformer repeatedly in a temperature range where the electrode reaction rate increases rapidly. I found out that

FIG. 5 shows a fuel reformer 10 having the same configuration as that of the first embodiment using a solid electrolyte layer having a thickness of 0.33 mm that has been operated for a long time at each temperature and sufficiently occluded hydrogen ions. It is the graph which showed the applied voltage dependence after the break-in operation. In order to use the fuel reformer according to the present invention as a fuel reformer for a fuel cell, it is required that the power required to extract hydrogen is sufficiently smaller than the power generated by the fuel cell. Is done. As shown in FIG. 5, when operated at a temperature of 450 ° C., a current of about 0.1 A / cm ^{2 was obtained} at a voltage of 0.2V. On the other hand, the amount of hydrogen consumed by a fuel cell with an output of 0.1 W / cm ² is approximately 6.24 × 10 ¹⁷ protons / cm ² per ^second , and this value is equivalent to approximately 0.1 A / cm ² when converted into current. To do. Therefore, the electric power required for taking out the current of 0.2 A / cm ² is 0.02 W / cm ² , which is about 1/5 compared with the electric power of the fuel cell from which the electric current of 0.1 A / cm ² can be taken out. is there.

Figure 6 is a fuel reformer using thickness of BaCe _0.9 Y _0.1 O _2.95 of 0.61mm as the electrolyte, the fuel reforming thickness using SrCe _0.95 Yb _0.05 O _2.975 of 0.46mm as the solid electrolyte layer It is the graph which showed the applied voltage and temperature dependence of the extraction electric current (yield of extraction hydrogen) in a container. Reformer with BaCe _0.9 Y _0.1 O _2.95 which indicates a high conductivity as an electrolyte than the fuel reformer with SrCe _0.95 Yb _0.05 O _2.975 low conductivity in the electrolyte, with thick solid electrolyte layer Nevertheless, a large extraction current is obtained at the same temperature and applied voltage. From the above results, it was found that in order to increase the take-out current of the reformer, it is necessary to use a proton conductive oxide having high conductivity for the solid electrolyte layer.

  FIG. 7 shows a comparison of energy spectra of recoil hydrogen obtained from the film before and after applying the DC voltage in the Pd film used for the cathode. Since the yield of hydrogen recoiled by collision with high-energy He ions is proportional to the amount of hydrogen contained in the Pd film, the yield of recoil hydrogen after voltage application is greater than the yield before voltage application. This indicates that hydrogen flowed into the Pd film, which is the cathode, by applying a DC voltage. Therefore, it was found that the current flowing from the anode to the cathode is certainly caused by the movement of protons.

FIG. 1A is a conceptual diagram schematically showing a fuel gas supply part on the cathode side, FIG. 1B is a conceptual diagram schematically showing a solid electrolyte part, and FIG. 1C is a cathode side. FIG. 1 (d) is a conceptual diagram showing an example of an embodiment of a fuel reformer according to the present invention. It is a conceptual diagram which shows typically an example of the fuel reformer which concerns on this invention. In the fuel reformer which concerns on this invention, it is a graph which shows the applied voltage dependence of the taking-out electric current (flow velocity of hydrogen ion) in the difference in the thickness of the solid electrolyte layer of a proton conductive oxide. In the fuel reformer according to the present invention, when BaCe _0.9 Y _0.1 O _2.95 having a thickness of 0.33 mm is used, the dependence of the current (hydrogen ion flow rate) at 450 ° C. and 500 ° C. on the applied voltage is used. It is a graph which shows. In the fuel reformer according to the present invention, temperatures of 300 ° C., 350 ° C., 400 ° C. when using a solid electrolyte layer of 0.33 mm thick BaCe _0.9 Y _0.1 O _2.95 occluded until hydrogen ions are saturated, It is a graph which shows the applied voltage dependence of the electric current (hydrogen ion flow velocity) in 450 degreeC. In the fuel reformer according to the present invention, when the thickness of a solid electrolyte layer and the thickness of BaCe _0.9 Y _0.1 O _2.95 of 0.61mm has a solid electrolyte layer of SrCe _0.95 Yb _0.05 O _2.975 of 0.46mm It is a graph which shows an applied voltage and temperature dependence. It is the energy spectrum of recoil hydrogen which shows the difference in the recoil hydrogen yield obtained from the film | membrane before and behind applying a DC voltage in the Pd film | membrane used for a cathode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,13 Solid electrolyte layer 2,11 Anode electrode 3,12 Cathode electrode 10 Fuel reformer 14 Mixed gas supply chamber 15 Hydrogen gas generation chamber 19,20 Electrode support plate

Claims (11)

In an airtight casing in which a proton conductive solid electrolyte layer is sandwiched between a gas permeable anode and a hydrogen permeable cathode, a crude hydrogen or hydrocarbon gas and a mixed gas of oxygen and / or water vapor are supplied to the anode side. A fuel reformer for a fuel cell, characterized in that a raw material gas supply chamber is formed, a direct current circuit for applying an electric field between an anode and a cathode is formed, and the cathode side is an ultra high purity hydrogen gas generation chamber. 2. The fuel reformer according to claim 1, wherein the solid electrolyte layer is a proton conductive oxide. The proton conductive oxide is AB ′ _1-x B ″ _x O _{3−x / 2} (A: Sr ²⁺ , Ba ²⁺ , B ′: Ti ⁴⁺ , Zr ⁴⁺ , Ce ⁴⁺ , B ″: Y 3. The fuel reformer according to claim 2, wherein the fuel reformer is ³⁺ , Yb3 ⁺ , Nd3 ⁺ , Gd3 ⁺ ). 4. The fuel reformer according to claim 3, wherein x = 0.1 to 0.2 in the proton conductive oxide AB ′ _1-x B ″ _x O _{3-x / 2} . The fuel reformer according to any one of claims 1 to 4, wherein the hydrogen permeable cathode is a Pd, Pd-Ag alloy or a Zr-Ni-based amorphous alloy. 6. The fuel reformer according to claim 1, wherein the gas permeable anode is made of Ag or a metal having Ag as a surface layer. 7. The chemical potential (hydrogenation potential) of the solid electrolyte-hydrogen system decreases from the anode toward the cathode by inclining the chemical composition of the solid electrolyte layer in the direction of the electric field. A fuel reformer according to any one of the above. The fuel reformer according to any one of claims 1 to 7, wherein the hydrogen permeable cathode is brazed or laser welded so as to be airtight to the airtight casing. The fuel reformer according to any one of claims 1 to 8, wherein a gas circulation pipe having a gas circulation function for adsorbing and removing carbon dioxide gas is provided in the raw material gas supply chamber. A proton conductive solid electrolyte layer is sandwiched between the gas permeable anode and the hydrogen permeable cathode, and a crude hydrogen or hydrocarbon gas and a mixed gas of oxygen and / or water vapor are supplied to the anode side. A fuel reforming method for a fuel cell, wherein a high-purity hydrogen gas is produced on the cathode side by applying a direct current electric field to the cathode. 11. The chemical potential of the electrolyte-hydrogen system (hydrogenation potential) decreases in the electric field direction by inclining the chemical composition of the proton conductive solid electrolyte layer in the electric field direction. A fuel reforming method for a fuel cell.

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