Electrochemical device and hydrogen generation method

Abstract

The electrochemical device disclosed herein comprises a first stack, a second stack and a thermal insulation material, wherein the first stack contains an oxygen ion conductor as an electrolyte and decomposes water vapor to generate hydrogen and oxygen, the second stack contains a proton conductor as an electrolyte and separates the hydrogen from a mixed gas of the hydrogen generated in the first stack and the water vapor that is not decomposed in the first stack, and the thermal insulation material covers the first stack and the second stack.

Description

Technical Field

[0001] The present disclosure relates to an electrochemical device and a method for generating hydrogen. Background Art

[0002] As one of the methods for producing hydrogen by electrolysis, high-temperature steam electrolysis using a solid oxide electrochemical cell (SOEC) is known. High-temperature steam electrolysis can achieve high conversion efficiency by using thermal energy as the energy required for the electrolysis reaction. As the electrolyte of the solid oxide electrochemical cell, an oxygen ion conductor such as yttria-stabilized zirconia can be used.

[0003] In high-temperature steam electrolysis, water vapor is supplied to the hydrogen electrode and decomposed into hydrogen and oxygen ions. The oxygen ions are conducted through the electrolyte layer and reach the oxygen electrode, where they are converted into oxygen. A mixed gas containing the generated hydrogen and the remaining water vapor is discharged from the hydrogen electrode.

[0004] Considering the use of hydrogen, it is desirable to improve the purity of the generated hydrogen. Patent Document 1 describes an electric power storage system that passes a mixed gas of hydrogen and water vapor through a condenser to remove water, and then compresses the hydrogen and stores it in a hydrogen storage tank.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-176939 Summary of the invention

[0008] In the conventional system using high-temperature steam electrolysis, there is a problem that the energy loss when separating hydrogen from the mixed gas of hydrogen and steam is large.

[0009] The present disclosure provides a technology for reducing energy loss when separating hydrogen from a mixed gas of hydrogen and water vapor.

[0010] The present disclosure provides an electrochemical device comprising a first stack, a second stack and a thermal insulation material.

[0011] The first stack includes an oxygen ion conductor as an electrolyte and decomposes water vapor to generate hydrogen and oxygen.

[0012] The second stack includes a proton conductor as an electrolyte and separates the hydrogen from a mixed gas of the hydrogen generated in the first stack and the water vapor not decomposed in the first stack.

[0013] The insulating material covers the first stack and the second stack.

[0014] According to the technology disclosed in the present disclosure, it is possible to reduce energy loss when separating hydrogen from a mixed gas of hydrogen and water vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing the configuration of an electrochemical device according to the first embodiment of the present disclosure.

[0016] Figure 2 It is a diagram showing the configuration of an electrochemical device according to a second embodiment of the present disclosure.

[0017] Figure 3 It is a configuration diagram of an electrochemical device according to a third embodiment of the present disclosure.

[0018] Figure 4 It is a configuration diagram of an electrochemical device according to a fourth embodiment of the present disclosure.

[0019] Figure 5 It is a configuration diagram of an electrochemical device according to a fifth embodiment of the present disclosure.

[0020] Figure 6 It is a diagram showing the configuration of an electrochemical device according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] (Insights that form the basis of this disclosure)

[0022] In the power storage system described in Patent Document 1, a mixed gas of water vapor and hydrogen is passed to a condenser to remove water vapor from the mixed gas to obtain high-concentration hydrogen. In the case of condensing water to remove water, in order to sufficiently reduce the saturated water vapor pressure, the temperature of the mixed gas needs to be sufficiently reduced. For example, to reduce the concentration of water vapor to a concentration below 1%, the temperature of the mixed gas needs to be reduced to less than 10°C. A cooling mechanism for cooling the mixed gas and energy for operating the cooling mechanism are indispensable.

[0023] As another method for separating hydrogen from a mixed gas, there is a method of obtaining high-concentration hydrogen by allowing an adsorbent such as zeolite to adsorb water. However, since the capacity of the adsorbent is limited, it is necessary to periodically regenerate the adsorbent. The regeneration of the adsorbent is performed by swinging the pressure and temperature to remove water from the adsorbent. Energy is required to operate the mechanism required for the regeneration.

[0024] There is also a method of obtaining high-concentration hydrogen by using a hydrogen separation membrane that selectively allows hydrogen to pass through. As a hydrogen separation membrane, a palladium membrane is well known. Since the hydrogen concentration difference between one side and the other side of the hydrogen separation membrane is the driving force for separation, in order to ensure sufficient hydrogen permeation, a mechanism is required to increase the difference in hydrogen partial pressure between one side and the other side of the hydrogen separation membrane. Alternatively, the area of ​​the hydrogen separation membrane needs to be sufficiently large. The mechanism for increasing the pressure difference requires energy for the mechanism to work. In the hydrogen separation membrane, expensive palladium is used. Therefore, a large-area hydrogen separation membrane will lead to a substantial increase in equipment costs.

[0025] In any of the above-mentioned conventional methods, when separating hydrogen from a mixed gas to obtain high-concentration hydrogen, a large energy loss occurs. In addition, in any of the conventional methods, energy is consumed in the form of low-temperature heat energy. It is not easy to recover low-temperature heat energy. Therefore, it is also difficult to reduce energy loss by recovering heat energy.

[0026] The present inventors have conducted intensive studies on a technique for separating hydrogen from a mixed gas and have found that high-concentration hydrogen can be obtained while reducing energy loss by using a proton conductor.

[0027] The above findings of the present inventors are findings that have not been known to date and indicate an electrochemical device with a new configuration. Specifically, the present disclosure provides the following aspects.

[0028] (Overview of one aspect of the present disclosure)

[0029] The electrochemical device according to the first aspect of the present disclosure includes a first stack, a second stack, and a heat insulating material.

[0030] The first stack includes an oxygen ion conductor as an electrolyte and decomposes water vapor to generate hydrogen and oxygen.

[0031] The second stack includes a proton conductor as an electrolyte and separates the hydrogen from a mixed gas of the hydrogen generated in the first stack and the water vapor not decomposed in the first stack.

[0032] The insulating material covers the first stack and the second stack.

[0033] According to the first aspect, it is possible to reduce energy loss when separating hydrogen from a mixed gas of hydrogen and water vapor.

[0034] In the second aspect of the present disclosure, for example, the electrochemical device according to the first aspect may further include a first path, a second path, and a third path, wherein the first path is connected to the first stack and guides the water vapor to the first stack, the second path connects the first stack and the second stack and guides the mixed gas from the first stack to the second stack, and the third path is a path through which the hydrogen separated in the second stack flows. According to the second aspect, high-concentration hydrogen can be obtained continuously and stably.

[0035] In a third aspect of the present disclosure, for example, the electrochemical device according to the first or second aspect may further include an evaporator for generating the water vapor to be supplied to the first stack from liquid water. According to the third aspect, water vapor required for water vapor electrolysis can be stably supplied to the first stack.

[0036] In a fourth aspect of the present disclosure, for example, in the electrochemical device according to the third aspect, the first stack, the second stack, and the evaporator may be covered by the insulating material. According to the fourth aspect, the energy for evaporating water can be supplied by utilizing the heat existing inside the case (frame) when the electrochemical device is operating.

[0037] In the fifth aspect of the present disclosure, for example, the electrochemical device according to any one of the first to fourth aspects may further include a power supply for supplying electricity to the first stack and the second stack. According to the fifth aspect, the required electrical energy can be reliably supplied to the first stack and the second stack. Therefore, according to the fifth aspect, high-concentration hydrogen can be efficiently generated.

[0038] In a sixth aspect of the present disclosure, for example, the electrochemical device according to any one of the first to fourth aspects may further include a first power supply for supplying electricity to the first stack and a second power supply for supplying electricity to the second stack. According to the sixth aspect, the first power supply and the second power supply can be controlled separately.

[0039] In a seventh aspect of the present disclosure, for example, in the electrochemical device according to any one of the first to sixth aspects, the proton conductor may include a material selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δAt least one of them. M1, M2, and M3 may each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In, and Lu. The value of x1 satisfies 0 < x1 < 1, the value of x2 satisfies 0 < x2 < 1, the value of x3 satisfies 0 < x3 < 1, the value of y3 satisfies 0 < y3 < 1, and the value of δ satisfies 0 < δ < 0.5. These proton conductors have high proton conductivity.

[0040] In the eighth aspect of the present disclosure, for example, in the electrochemical device according to the seventh aspect, the proton conductor may be composed of BaZr 1-x1 M1 x1 O 3-δ It is composed of. BaZr 1-x1 Yb x1 O 3-δ has high proton conductivity.

[0041] The hydrogen generation method according to the ninth aspect of the present disclosure includes the following steps:

[0042] Using a first stack including an oxygen ion conductor as an electrolyte to decompose water vapor to generate hydrogen and oxygen; and

[0043] Using a second stack including a proton conductor as an electrolyte to separate hydrogen from the mixed gas of the hydrogen generated in the first stack and the water vapor not decomposed in the first stack.

[0044] According to the ninth aspect, high-concentration hydrogen can be generated with high efficiency.

[0045] The electrochemical device according to the tenth aspect of the present disclosure includes:

[0046] A first stack including an oxygen ion conductor as an electrolyte;

[0047] A second stack including a proton conductor as an electrolyte; and

[0048] Thermal insulation material covering the first stack and the second stack,

[0049] Using oxygen and hydrogen that has passed through the second stack to perform a power generation reaction in the first stack.

[0050] According to the tenth aspect, electric power can be supplied to the outside.

[0051] The electrochemical device according to the eleventh aspect of the present disclosure includes:

[0052] A first stack including an oxygen ion conductor as an electrolyte;

[0053] A second stack including a proton conductor as an electrolyte;

[0054] Insulating material covering the first stack and the second stack; and

[0055] a hydrogen supply path for directing a gas containing hydrogen to the first stack,

[0056] A power generation reaction is performed in the first stack using oxygen and hydrogen supplied from the hydrogen supply path.

[0057] According to the eleventh aspect, electric energy can be supplied to the outside without passing through the second stack.

[0058] Below, while referring to the attached Figure 1 The present disclosure is not limited to the following embodiments.

[0059] (First embodiment)

[0060] Figure 1 The structure of the electrochemical device 100 involved in the first embodiment of the present disclosure is shown. The electrochemical device 100 includes a first stack 10 and a second stack 20. The first stack 10 has one or more first units. The first stack 10 typically has a plurality of stacked first units. The first unit is composed of a first electrolyte layer 11, a first electrode 12, and a second electrode 13. The first electrolyte layer 11 is arranged between the first electrode 12 and the second electrode 13. The second stack 20 includes one or more second units. The second stack 20 typically has a plurality of stacked second units. The second unit is composed of a second electrolyte layer 21, a third electrode 22, and a fourth electrode 23. The second electrolyte layer 21 is arranged between the third electrode 22 and the fourth electrode 23. Figure 1 In the figure, the first stack 10 and the second stack 20 are respectively represented by a single cell for the sake of convenience.

[0061] The first electrolyte layer 11 contains an oxygen ion conductor as an electrolyte. The second electrolyte layer 21 contains a proton conductor as an electrolyte.

[0062] The electrochemical device 100 further includes a heat-insulating housing 31. The housing 31 is made of a heat-insulating material. The first stack 10 and the second stack 20 are accommodated in the housing 31. In other words, the first stack 10 and the second stack 20 are covered with a heat-insulating material. The housing 31 suppresses the release of heat energy to the outside during the operation of the electrochemical device 100. Figure 1 In the embodiment, a single box 31 covers the first pile 10 and the second pile 20. However, the present embodiment is not limited thereto. For example, two boxes may cover the first pile 10 and the second pile 20, respectively.

[0063] There is no particular limitation on the type of thermal insulation material, and general materials with thermal insulation properties can be used. Examples of thermal insulation materials include glass wool, super wool, asbestos, ceramic fiber, slag wool, calcium silicate, and rigid polyurethane foam. As thermal insulation materials, special heat-resistant thermal insulation materials with fumed silica as the main component and inorganic fibrous substances and infrared blocking materials can also be used. The thermal insulation material can also be a vacuum insulation material. The vacuum insulation material is made of an outer packaging material (external decoration material) and a core material, and its interior is decompressed and sealed. The outer decoration material can be obtained, for example, by stacking metal foil and resin film. It can be a metal laminated film. The core material is, for example, a porous structural material such as glass wool. One or more of the above materials are arranged around the first stack 10 and the second stack 20. As needed, the first stack 10 and the second stack 20 are covered with a supporting material such as a metal plate for fixing and storing the thermal insulation material, thereby forming a box 31 with thermal insulation properties.

[0064] The first stack 10 decomposes water vapor to generate hydrogen and oxygen. This process is high-temperature water vapor electrolysis using SOEC. A mixed gas of hydrogen generated in the first stack 10 and water vapor not decomposed in the first stack 10 is sent from the first stack 10 to the second stack 20. The second stack 20 selectively separates hydrogen from the mixed gas by the action of a proton conductor. In general, hole conduction occurs in a proton conductor under a high oxygen partial pressure. However, as Figure 1 As shown, by supplying the mixed gas generated from the first stack 10 to the second stack 20 having a proton conductor, it is possible to suppress the second stack 20 from being exposed to a high oxygen partial pressure. As a result, hole conduction in the second stack 20 is reduced. Therefore, compared with a configuration in which the proton conductor is exposed to a high oxygen partial pressure, the energy loss of the second stack 20 (for example, the loss of hydrogen separation and the loss of leakage current) is reduced. As a result, a high concentration of hydrogen can be obtained.

[0065] Since the operating temperature of the proton conductor is also high temperature, the first stack 10 and the second stack 20 can be operated while being covered with an insulating material and maintained at a high temperature. If the first stack 10 and the second stack 20 are covered with an insulating material, it is easy to supply the thermal energy required for high-temperature steam electrolysis to the first stack 10. In addition, in the second stack 20, heat is generated during the proton conduction process. According to the present embodiment, the heat generated in the second stack 20 can be used as a part of the thermal energy required for steam electrolysis in the first stack 10. As a result, energy loss can be reduced. In other words, the energy efficiency of the electrochemical device 100 during operation is improved.

[0066] A heating device for increasing the temperature inside the box 31 may be provided inside the box 31. Examples of the heating device include a burner, a resistance heating heater, and an infrared heater.

[0067] In this specification, "hydrogen" and "oxygen" mean "hydrogen gas" and "oxygen gas", respectively, unless otherwise specified.

[0068] The electrochemical device 100 operates as a hydrogen generation system, and as described later, may also operate as a fuel cell system. A hydrogen generation system is a system for generating hydrogen, and a fuel cell system is a system for generating electricity.

[0069] In the first stack 10, examples of the oxygen ion conductor used in the first electrolyte layer 11 include stabilized zirconium oxide, lanthanum gallate oxides, ceria oxides, and the like. The first electrolyte layer 11 may be a dense body.

[0070] The first electrode 12 includes a catalyst for carrying out an electrochemical oxidation reaction of water vapor. As a catalyst, a metal such as Ni can be used. The first electrode 12 can also be made of a cermet. The so-called cermet is a mixture of metal and ceramic materials. Examples of cermet include Ni-YSZ, a mixture of Ni and ceria-based oxides, etc. If the first electrode 12 is made of a cermet, the effect of increasing the reactive active sites for oxidizing water vapor can be expected. In order to promote the diffusion of water vapor, the first electrode 12 can also be a porous body.

[0071] The second electrode 13 includes a catalyst for the electrochemical oxidation reaction of oxygen ions. As a catalyst, an oxide containing at least one element selected from Mn, Fe, Co and Ni can be cited. As a specific example of the catalyst, lanthanum strontium cobalt iron composite oxide (LSCF), lanthanum strontium cobalt composite oxide (LSC), lanthanum strontium iron composite oxide (LSF), lanthanum strontium manganese composite oxide (LSM), barium strontium cobalt iron composite oxide (BSCF), samarium strontium cobalt composite oxide (SSC), lanthanum nickel iron composite oxide, lanthanum nickel composite oxide, barium gadolinium lanthanum cobalt composite oxide, etc. can be cited. The catalyst can also be a composite of an oxide containing at least one element selected from Mn, Fe, Co and Ni and other oxides or metals. In order to promote the diffusion of the generated oxygen, the second electrode 13 can also be a porous body.

[0072] In the second stack 20, the proton conductor used in the second electrolyte layer 21 may be a proton conductive oxide. Specifically, the second electrolyte layer 21 may include a proton conductive oxide selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δat least one of them as a proton conductor. M1, M2, and M3 can each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In, and Lu. The value of x1 satisfies 0 < x1 < 1. The value of x2 satisfies 0 < x2 < 1. The value of x3 satisfies 0 < x3 < 1. The value of y3 satisfies 0 < y3 < 1. The value of δ satisfies 0 < δ < 0.5. These proton conductors have high proton conductivity. By using a solid electrolyte with high proton conductivity, the electrochemical performance of the second stack 20 can be improved. The proton conductor can also be composed of BaZr 1-x1 Yb x1 O 3-δ constitute. BaZr 1-x1 Yb x1 O 3-δ has high proton conductivity. The variable δ is a value representing the amount of oxygen defects in the lattice of the oxide in terms of composition. The value of δ varies corresponding to x1, x2, x3, y3, temperature, oxygen partial pressure, water vapor partial pressure, etc. The second electrolyte layer 21 can also be a dense body.

[0073] The third electrode 22 contains a catalyst for electrochemically oxidizing hydrogen. As the catalyst, metals such as Ni can be used. The third electrode 22 can also be composed of cermet. As the cermet, a mixture of Ni and a proton-conductive oxide can be cited, such as a mixture of Ni and BaZr 1-x1 Yb x1 O 3-δ etc. If the third electrode 22 is composed of cermet, an effect of increasing the reaction active points for hydrogen oxidation can be expected. In order to promote the diffusion of hydrogen and water vapor, the third electrode 22 can also be a porous body.

[0074] The fourth electrode 23 contains a catalyst for electrochemically reducing protons. As the catalyst, metals such as Ni can be used. The fourth electrode 23 can also be composed of cermet. As the cermet, a mixture of Ni and a proton-conductive oxide can be cited, such as a mixture of Ni and BaZr 1-x1 Yb x1 O 3-δ etc. If the fourth electrode 23 is composed of cermet, an effect of increasing the reaction active points for reducing protons can be expected. In order to promote the diffusion of hydrogen, the fourth electrode 23 can also be a porous body.

[0075] The so-called "dense body" means, for example, a material having a relative density of 85% or more. The relative density can be measured by the Archimedes method or the mercury intrusion method. The so-called "porous body" means, for example, a material having a porosity of 20% or more. The porosity can be measured by the Archimedes method or the mercury intrusion method.

[0076] The electrochemical device 100 includes a first path 3, a second path 4, and a third path 5. The first path 3 is a path for guiding water vapor to the first stack 10, and is connected to the first stack 10. In detail, the first path 3 extends from the outside of the box 31 to the inside of the box 31, and is connected to the first electrode 12 of the first stack 10. The starting end of the first path 3 is connected to an external water source, for example. The second path 4 is a path for guiding the mixed gas from the first stack 10 to the second stack 20, and connects the first stack 10 and the second stack 20. In detail, the second path 4 connects the first electrode 12 of the first stack 10 and the third electrode 22 of the second stack 20. The third path 5 is a path for the hydrogen separated in the second stack 20 to flow, and is connected to the second stack 20. In detail, the third path 5 is connected to the fourth electrode 23 of the second stack 20. The third path 5 extends from the inside of the box 31 to the outside of the box 31, and is connected to a hydrogen storage device or the like.

[0077] The water vapor required for water vapor electrolysis is supplied to the first stack 10 through the first path 3. The mixed gas is supplied from the first stack 10 to the second stack 20 through the second path 4. The separated hydrogen is supplied to the outside of the electrochemical device 100 through the third path 5. According to the configuration of this embodiment, this series of steps can be appropriately performed, and high-concentration hydrogen can be obtained continuously and stably.

[0078] The electrochemical device 100 further includes a fourth path 6 and a fifth path 7. The fourth path 6 is a path through which the mixed gas discharged from the second stack 20 flows, and is connected to the second stack 20. Specifically, the fourth path 6 is connected to the third electrode 22 of the second stack 20. The fourth path 6 extends from the inside of the housing 31 to the outside of the housing 31. The fifth path 7 is a path through which the oxygen generated in the first stack 10 flows, and is connected to the first stack 10. Specifically, the fifth path 7 is connected to the second electrode 13 of the first stack 10. The fifth path 7 extends from the inside of the housing 31 to the outside of the housing 31, and is connected to an oxygen storage device or the like.

[0079] Each path is formed of a heat-resistant pipe such as a metal pipe.

[0080] The electrochemical device 100 further includes an evaporator 30. The evaporator 30 extracts water from a liquid phase (in Figure 1 In the embodiment, the evaporator 30 is arranged on the first path 3. According to the evaporator 30, water vapor can be generated using liquid water as a raw material, and water vapor required for water vapor electrolysis can be stably supplied to the first stack 10.

[0081] In the present embodiment, the evaporator 30 is housed in the housing 31 together with the first stack 10 and the second stack 20. In other words, the first stack 10, the second stack 20 and the evaporator 30 are covered with a heat insulating material. According to such a configuration, the heat existing inside the housing 31 when the electrochemical device 100 is in operation can be used to supply energy for evaporating water. Therefore, the energy efficiency of the electrochemical device 100 during operation is improved.

[0082] As the evaporator 30, a known heat exchanger such as a fin tube heat exchanger, a plate heat exchanger, a shell and tube heat exchanger, etc. can be used. In order to evaporate the liquid phase water, a high-temperature heat medium can be used. The high-temperature heat medium can be a gas such as high-temperature air existing inside the box 31. In addition, the high-temperature heat medium can also be a liquid such as oil heated by the high-temperature air existing inside the box 31. The high-temperature heat medium can also be supplied to the evaporator 30 from the outside of the electrochemical device 100.

[0083] The evaporator 30 may be arranged outside the housing 31. The evaporator 30 may be omitted and the water vapor generated outside the electrochemical device 100 may be directly introduced into the first path 3. For example, when a high-temperature heat source is separately present, the evaporator 30 may be configured to generate water vapor outside the housing 31 using the high-temperature heat source. Alternatively, when the water vapor itself is present in excess, the evaporator 30 may be omitted and the water vapor may be directly introduced into the first path 3.

[0084] The electrochemical device 100 also includes a power supply 40. The power supply 40 supplies electricity to the first stack 10 and the second stack 20. In the present embodiment, the power supply 40 is shared by the first stack 10 and the second stack 20. The power supply 40 is connected to the second electrode 13 of the first stack 10 and the fourth electrode 23 of the second stack 20. The first electrode 12 of the first stack 10 and the third electrode 22 of the second stack 20 are electrically connected. In other words, the first stack 10 and the second stack 20 are connected in series. According to the power supply 40, the required electric energy can be reliably supplied to the first stack 10 and the second stack 20, thereby efficiently generating high-concentration hydrogen. The fact that the power supply 40 is shared by the first stack 10 and the second stack 20 helps to reduce costs.

[0085] Next, the operation of the electrochemical device 100 will be described in detail. In the electrochemical device 100, the process of decomposing water vapor to generate hydrogen and oxygen and the process of separating hydrogen from the mixed gas of hydrogen and water vapor are performed in parallel. The process of generating hydrogen and oxygen is performed using the first stack 10 including an oxygen ion conductor as an electrolyte. The process of separating hydrogen from the mixed gas is performed using the second stack 20 including a proton conductor as an electrolyte. The mixed gas includes hydrogen generated in the first stack 10 and water vapor that is not decomposed in the first stack 10. By implementing these processes, high-concentration hydrogen can be generated efficiently.

[0086] If liquid water is introduced into the first path 3, the water evaporates in the evaporator 30 provided in the first path 3. Thus, water vapor is generated. The water vapor reaches the first electrode 12 of the first stack 10 through the first path 3. If the power supply 40 is turned on, electrons are supplied to the first electrode 12 of the first stack 10. At the first electrode 12, a reduction reaction of the water vapor occurs, generating hydrogen and oxygen ions. Hydrogen and unreacted water vapor are discharged from the first stack 10 and supplied to the second stack 20 through the second path 4. The oxygen ions are conducted in the first electrolyte layer 11 and reach the second electrode 13. At the second electrode 13, an oxidation reaction of the oxygen ions occurs, generating oxygen. Oxygen is discharged from the second electrode 13 and guided to the outside of the electrochemical device 100 through the fifth path 7.

[0087] A mixed gas of hydrogen and water vapor is supplied from the first electrode 12 of the first stack 10 to the third electrode 22 of the second stack 20 through the second path 4. At the third electrode 22, an oxidation reaction of hydrogen occurs to generate protons. The protons are conducted in the second electrolyte layer 21 and reach the fourth electrode 23. At the fourth electrode 23, a reduction reaction of the protons occurs to generate hydrogen. Since water molecules are hardly conducted in the second electrolyte layer 21, only protons are conducted in the second electrolyte layer 21, so a high concentration of hydrogen can be obtained. Hydrogen is guided to the outside of the electrochemical device 100 through the third path 5. Hydrogen is stored in a hydrogen storage device, for example. Unreacted hydrogen and unreacted water vapor are discharged from the second stack 20 and guided to the outside of the electrochemical device 100 through the fourth path 6. Hydrogen can also be burned by a burner or catalytic combustion. The combustion heat can be used to maintain the temperature inside the housing 31 at a temperature suitable for each reaction.

[0088] The reactions at each electrode are as follows.

[0089] First electrode 12: 2H2O+4e - →2H2+2O 2-

[0090] Second electrode 13:2O 2- →O2+4e -

[0091] The third electrode 22: H2→2H + +2e -

[0092] Fourth electrode 23: 2H + +2e - →H2

[0093] The gas flowing through each path may contain other components as long as they do not significantly inhibit the reaction at each electrode. For example, when Ni is used in the first electrode 12, hydrogen may be mixed with water vapor and supplied to the first path 3 to suppress oxidation of Ni.

[0094] When the electrochemical device 100 is operated, the temperature around the first stack 10 and the second stack 20 is maintained at, for example, 500° C. or higher and 1000° C. or lower. Since the first stack 10 and the second stack 20 are housed in the housing 31, the first stack 10 and the second stack 20 can each be operated at a temperature suitable for the reaction. The housing 31 can also reduce heat dissipation losses.

[0095] The series of hydrogen separation reactions in the second stack 20 are exothermic reactions. On the other hand, the series of water vapor electrolysis reactions in the first stack 10 are endothermic reactions. By sealing the heat generated in the second stack 20 inside the housing 31 and utilizing the endothermic reaction in the first stack 10, the heat can be efficiently utilized. As a result, energy loss can be further reduced. As a means for utilizing the heat generated in the second stack 20 for the endothermic reaction in the first stack 10, various heat exchange means can be used. For example, a heat exchanger can be cited that causes the fluids flowing in the pipes to exchange heat with each other by bringing the pipes constituting a plurality of paths into contact with each other. Simply by virtue of the first stack 10 and the second stack 20 being housed in a single housing 31, the heat generated in the second stack 20 can also be utilized for the endothermic reaction in the first stack 10.

[0096] In the present embodiment, the evaporator 30 is housed in the housing 31. In this case, the heat present inside the housing 31 when the first stack 10 and the second stack 20 are in operation can be used to evaporate the water in the evaporator 30. For example, the heat energy of the gas flowing in the third path 5, the fourth path 6, or the fifth path 7 is recovered by heat exchange and supplied to the evaporator 30. If this is done, the heat energy released to the outside of the electrochemical device 100 can be reduced. Therefore, the energy efficiency of the electrochemical device 100 during operation can be improved.

[0097] Several other embodiments are described below. The common elements in the first embodiment and other embodiments are provided with the same reference numerals, and their description is sometimes omitted. The descriptions of the various embodiments can be applied to each other as long as they are not technically contradictory. The various embodiments can be combined with each other as long as they are not technically contradictory.

[0098] (Second embodiment)

[0099] Figure 2The structure of the electrochemical device 200 according to the second embodiment of the present disclosure is shown. The electrochemical device 200 includes a first power supply 41 and a second power supply 42 instead of the power supply 40. The first power supply 41 supplies electricity to the first stack 10. The first power supply 41 is connected to each of the first electrode 12 and the second electrode 13 of the first stack 10. The second power supply 42 supplies electricity to the second stack 20. The second power supply 42 is connected to each of the third electrode 22 and the fourth electrode 23 of the second stack 20.

[0100] According to the power supply 40 described previously, the first stack 10 and the second stack 20 are connected in series. Therefore, currents of equal value flow through each of the first stack 10 and the second stack 20. However, there is a possibility that the current value suitable for the water vapor electrolysis reaction in the first stack 10 is different from the current value suitable for the electrochemical hydrogen separation in the second stack 20. According to the present embodiment, the first power supply 41 and the second power supply 42 can be controlled separately. In this case, it is possible to supply power of appropriate magnitude to each of the first stack 10 and the second stack 20, so that the electrochemical device 200 has excellent controllability.

[0101] (Third embodiment)

[0102] Figure 3 The configuration of an electrochemical device 300 according to a third embodiment of the present disclosure is shown. The electrochemical device 300 has the same configuration as that of the reference except that the power source 40 is replaced by an external load 43. Figure 1 The configuration of the electrochemical device 100 described above is the same as that of the first stack 10 and the second stack 20 described in the first embodiment.

[0103] The reaction performed at each electrode of the electrochemical device 300 is a reaction opposite to the reaction performed at each electrode of the electrochemical device 100 of the first embodiment. In this embodiment, the power generation reaction is performed in the first stack 10 using oxygen supplied from the outside and hydrogen passed through the second stack 20. According to this embodiment, electric energy can be supplied to the outside. In this respect, this embodiment is different from the first embodiment.

[0104] The operation of the electrochemical device 300 will be described in detail.

[0105] The operating temperature of the first stack 10 and the second stack 20 is, for example, 500° C. to 1000° C. This is the same in the present embodiment and the first embodiment.

[0106] When hydrogen is introduced into the third path 5, hydrogen flows into the fourth electrode 23 of the second stack 20. At the fourth electrode 23, an oxidation reaction of hydrogen occurs to generate protons. The protons are conducted through the second electrolyte layer 21 and reach the third electrode 22. At the third electrode 22, a reduction reaction of the protons occurs to generate hydrogen. Hydrogen is discharged from the second stack 20 and supplied to the first stack 10 through the second path 4.

[0107] Hydrogen is supplied from the third electrode 22 of the second stack 20 to the first electrode 12 of the first stack 10 through the second path 4. A gas containing oxygen is supplied to the second electrode 13 through the fifth path 7. A typical example of a gas containing oxygen is air. At the second electrode 13, a reduction reaction of oxygen occurs to generate oxygen ions. The oxygen ions are conducted in the first electrolyte layer 11 and reach the first electrode 12. At the first electrode 12, an electrochemical reaction is performed to generate water vapor and electrons from oxygen ions and hydrogen. Water vapor and unreacted hydrogen are discharged from the first stack 10 and guided to the outside of the electrochemical device 300 through the first path 3. Hydrogen can also be burned by a burner or catalytic combustion.

[0108] The reactions at each electrode are as follows.

[0109] First electrode 12: 2H2+2O 2- →2H2O+4e -

[0110] Second electrode 13: O2+4e - →2O 2-

[0111] The third electrode 22: 2H + +2e - →H2

[0112] Fourth electrode 23: H2→2H + +2e -

[0113] According to the present embodiment, even if the gas to be introduced into the third path 5 contains not only hydrogen but also impurities such as water vapor and carbon dioxide, pure hydrogen can be generated in the second stack 20 and supplied to the first stack 10. As a result, the effects of improving power generation performance and suppressing carbon deposition can be obtained in the first stack 10. The gas to be introduced into the third path 5 may be, for example, a hydrogen-containing gas obtained by modifying a raw gas such as methane, or a hydrogen-containing gas obtained by electrolyzing water vapor.

[0114] The reaction performed in the first stack 10 is an electrochemical reaction (i.e., a fuel cell reaction) in which water vapor and electric energy are generated from hydrogen and oxygen. The electric energy can be supplied to an external load 43 connected to the first stack 10. A portion of the electric energy can be used as energy for proton conduction in the second stack 20. The electrochemical device 300 functions as a fuel cell system to generate electric energy.

[0115] As long as the reaction at each electrode is not significantly hindered, the gas flowing in each path may also contain other components. For example, when Ni is used in the third electrode 22, hydrogen can be introduced into the fourth path 6 at a small flow rate to suppress oxidation of Ni. In order to improve the proton conductivity of the second electrolyte layer 21, water vapor can be introduced into the third path 5 or the fourth path 6 at a small flow rate.

[0116] (Fourth embodiment)

[0117] Figure 4 The configuration of an electrochemical device 400 according to a fourth embodiment of the present disclosure is shown. In the electrochemical device 400, an external load 43 is connected only to the first stack 10. A second power source 42 is connected to the second stack 20. The electric energy generated in the first stack 10 is supplied to the external load 43. The conduction of protons in the second stack 20 is performed using the electric energy supplied from the second power source 42. Since the electric energy generated in the first stack 10 and the electric energy consumed in the second stack 20 can be separately controlled, the electrochemical device 400 has excellent controllability.

[0118] (Fifth embodiment)

[0119] Figure 5 The configuration of an electrochemical device 500 according to a fifth embodiment of the present disclosure is shown. In the electrochemical device 500 , the external load 43 is connected only to the first stack 10 . The second power source 42 is connected to the second stack 20 . The fourth path 6 is connected to the third electrode 22 of the second stack 20 .

[0120] The gas containing hydrogen is supplied to the third electrode 22 through the fourth path 6. In this respect, the electrochemical device 500 is different from the electrochemical device 400 of the fourth embodiment. After the gas containing hydrogen passes through the third electrode 22, it is supplied to the first stack 10 through the second path 4. At this time, no electrochemical reaction occurs in the second stack 20, and the power source 42 does not operate. The following reactions occur at the first electrode 12 and the second electrode 13 of the first stack 10, respectively.

[0121] First electrode 12: 2H2+2O 2- →2H2O+4e -

[0122] Second electrode 13: O2+4e - →2O2-

[0123] This reaction is a fuel cell reaction. Electric energy can be generated by this reaction. The generated electric energy is supplied to the external load 43.

[0124] Unlike the electrochemical device 400 according to the fourth embodiment, according to this embodiment, electrochemical reaction, that is, conduction of protons, does not occur in the second stack 20. Therefore, there is no need to conduct proton electrical energy in the second stack 20, and the efficiency of the electrochemical device 500 can be expected to be improved.

[0125] (Sixth Implementation Method)

[0126] Figure 6 The structure of the electrochemical device 600 involved in the sixth embodiment of the present disclosure is shown. In the electrochemical device 600, the external load 43 is connected only to the first stack 10. The second power supply 42 is connected to the second stack 20. The electrochemical device 600 has a sixth path 8. The sixth path 8 is a hydrogen supply path for supplying a gas containing hydrogen to the first stack 10. In the present embodiment, the sixth path 8 is connected to the first stack 10. In detail, the sixth path 8 is connected to the first electrode 12 of the first stack 10. The sixth path 8 extends from the inside of the casing 31 to the outside of the casing 31, and is connected to a hydrogen storage device, etc.

[0127] The sixth path 8 may be directly connected to the first electrode 12 of the first stack 10 or connected to the second path 4. When the sixth path 8 is connected to the second path 4, the gas containing hydrogen can be supplied to the first electrode 12 of the first stack 10 through the sixth path 8 and the second path 4.

[0128] The following reactions occur at the first electrode 12 and the second electrode 13 of the first stack 10 .

[0129] First electrode 12: 2H2+2O 2- →2H2O+4e -

[0130] Second electrode 13: O2+4e - →2O 2-

[0131] This reaction is a fuel cell reaction. Electric energy can be generated by this reaction. The generated electric energy is supplied to the external load 43. At this time, in the second stack 20, no electrochemical reaction occurs, and the power source 42 does not operate.

[0132] Unlike the electrochemical device 400 according to the fourth embodiment, according to this embodiment, electrochemical reaction, that is, conduction of protons, does not proceed in the second stack 20. Therefore, electric energy for conducting protons is not required in the second stack 20, and improvement in the efficiency of the electrochemical device 600 can be expected.

[0133] Industrial Applicability

[0134] The electrochemical device according to the present disclosure can be used as a hydrogen generation device or a fuel cell system.

[0135] Description of Reference Numerals

[0136] 3 First Path

[0137] 4 Second Path

[0138] 5 The Third Path

[0139] 6 The Fourth Path

[0140] 7 The Fifth Path

[0141] 8 Sixth Path

[0142] 10 The first pile

[0143] 11. First electrolyte layer

[0144] 12. First electrode

[0145] 13. Second electrode

[0146] 20 The second pile

[0147] 21 Second electrolyte layer

[0148] 22. Third electrode

[0149] 23 Fourth electrode

[0150] 30 Evaporator

[0151] 31 Box (insulation material)

[0152] 40 Power Supply

[0153] 41 First Power

[0154] 42 Second power supply

[0155] 43 External load

[0156] 100, 200, 300, 400, 500, 600 Electrochemical Devices

Claims

1. An electrochemical device comprising a first stack, a second stack and a thermal insulation material, The first stack includes an oxygen ion conductor as an electrolyte and decomposes water vapor to generate hydrogen and oxygen. The second stack includes a proton conductor as an electrolyte and separates the hydrogen from a mixed gas of the hydrogen generated in the first stack and the water vapor not decomposed in the first stack. The thermal insulation material covers the first stack and the second stack, And the electrochemical device is configured so that the hydrogen generated in the first stack passes through the first stack and then passes through the second stack.

2. The electrochemical device according to claim 1, further comprising a first path, a second path and a third path, The first path is connected to the first stack and guides the water vapor to the first stack, The second path connects the first stack and the second stack and guides the mixed gas from the first stack to the second stack. The third path is a path through which the hydrogen separated in the second stack flows.

3. The electrochemical device according to claim 1 or 2, The device further includes an evaporator for generating the water vapor to be supplied to the first stack from liquid water.

4. The electrochemical device according to claim 3, The first stack, the second stack, and the evaporator are covered by the insulation material.

5. The electrochemical device according to any one of claims 1, 2 and 4, A power source for supplying electricity to the first stack and the second stack is further provided.

6. The electrochemical device according to claim 3, A power source for supplying electricity to the first stack and the second stack is further provided.

7. The electrochemical device according to any one of claims 1, 2, and 4, further comprising: a first power source for supplying electricity to the first stack; and A second power source supplies electricity to the second stack.

8. The electrochemical device according to claim 3, further comprising: a first power source for supplying electricity to the first stack; and A second power source supplies electricity to the second stack.

9. The electrochemical device according to any one of claims 1, 2, 4, 6 and 8, The proton conductor comprises a member selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δ At least one of M1, M2 and M3 each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In and Lu, The value of x1 satisfies 0 <x1<1, The value of x2 satisfies 0 <x2<1, The value of x3 satisfies 0 <x3<1, The value of y3 satisfies 0 <y3<1, The value of δ satisfies 0<δ<0.

5.

10. The electrochemical device according to claim 3, The proton conductor comprises a member selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δ At least one of M1, M2 and M3 each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In and Lu, The value of x1 satisfies 0 <x1<1, The value of x2 satisfies 0 <x2<1, The value of x3 satisfies 0 <x3<1, The value of y3 satisfies 0 <y3<1, The value of δ satisfies 0<δ<0.

5.

11. The electrochemical device according to claim 5, The proton conductor comprises a member selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δ At least one of M1, M2 and M3 each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In and Lu, The value of x1 satisfies 0 <x1<1, The value of x2 satisfies 0 <x2<1, The value of x3 satisfies 0 <x3<1, The value of y3 satisfies 0 <y3<1, The value of δ satisfies 0<δ<0.

5.

12. The electrochemical device according to claim 7, The proton conductor comprises a member selected from BaZr 1-x1 M1 x1 O 3-δ ,BaCe 1-x2 M2 x2 O 3-δ and BaZr 1-x3-y3 Ce x3 M3 y3 O 3-δ At least one of M1, M2 and M3 each contain at least one selected from Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, In and Lu, The value of x1 satisfies 0 <x1<1, The value of x2 satisfies 0 <x2<1, The value of x3 satisfies 0 <x3<1, The value of y3 satisfies 0 <y3<1, The value of δ satisfies 0<δ<0.

5.

13. The electrochemical device according to claim 9, The proton conductor is composed of BaZr 1-x1 M1 x1 O 3-δ constitute.

14. The electrochemical device according to any one of claims 10 to 12, The proton conductor is composed of BaZr 1-x1 M1 x1 O 3-δ constitute.

15. A method for generating hydrogen, comprising the following steps: Using a first stack including an oxygen ion conductor as an electrolyte, water vapor is decomposed to generate hydrogen and oxygen; separating the hydrogen from a mixed gas of the hydrogen generated in the first stack and the water vapor not decomposed in the first stack using a second stack including a proton conductor as an electrolyte; and thermally insulating the first and second stacks by coating the first and second stacks with thermally insulating material, In the method, the hydrogen generated in the first stack passes through the second stack after passing through the first stack.

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