Power generation element, power generation device, and power generation method

Abstract

The present disclosure provides an advantageous novel power generation element from the viewpoint of being maintenance-free. A power generation element (1a) according to the present disclosure comprises a first electrode (11), a second electrode (12), and a solid electrolyte (15). The first electrode (11) decomposes water. The solid electrolyte (15) is disposed between the first electrode (11) and the second electrode (12). The solid electrolyte (15) causes the ions generated by the decomposition of water at the first electrode (11) to be conducted toward the second electrode (12). The decomposition of water at the first electrode (11) and the generation of ions at the solid electrolyte (15) cause a difference in potential to occur between the first electrode (11) and the second electrode (12), and electrical energy is supplied to the outside of the power generation element (1a).

Description

Power generation element, power generation device, and power generation method

[0001] The present disclosure relates to a power generating element, a power generating device, and a power generating method.

[0002] BACKGROUND ART Conventionally, power generation using electrochemical reactions has been known.

[0003] For example, Patent Document 1 describes a thermochemical battery that can generate electricity when there is a temperature difference between a pair of electrodes. In this thermochemical battery, a pair of electrodes is bonded to both ends of an electrolyte. At least one of the pair of electrodes is a thin-film electrode made of a conductive polymer material. This thermochemical battery can generate electricity when there is a temperature difference between the pair of electrodes by a redox reaction occurring near the bonded surfaces of the electrolyte and the pair of electrodes. For example, a mixed aqueous solution of K3[Fe(CN)6] and K4[Fe(CN)6].3H2O is used as the electrolyte.

[0004] Non-Patent Document 1 describes a copper hexacyanoferrate cathode and a Cu / Cu 2+ The present invention describes an electrochemical system that converts heat into electricity using an anode of the present invention.

[0005] Patent Document 2 describes a thermoelectric power generation element in which a first electrode and a second electrode face each other with a single electrolyte interposed therebetween. In this thermoelectric power generation element, the first electrode and the second electrode contain a material through which the same metal ions reversibly enter and exit. A predetermined electrolytic solution is used as the electrolyte.

[0006] Patent Document 3 describes the use of an ion conductor that is a specific perovskite oxide as a solid electrolyte in a fuel cell.

[0007] International Publication No. 2018 / 079325 Japanese Patent Application Laid-Open No. 2018-73596 Japanese Patent Application Laid-Open No. 2001-307546

[0008] SW Lee, et al., “An electrochemical system for efficiently harvesting low-grade heat energy”, Nature Communications 5, 3942 (2014)

[0009] The present disclosure provides a novel power generating element that is advantageous from the viewpoint of having fewer restrictions on use and being maintenance-free.

[0010] The power generation element of the present disclosure comprises: a first electrode that splits water; a second electrode; and a solid electrolyte disposed between the first electrode and the second electrode and that conducts ions generated by the splitting of water at the first electrode toward the second electrode, and generates a potential difference between the first electrode and the second electrode to supply electrical energy to the outside of the power generation element.

[0011] According to the present disclosure, a novel power generating element can be provided that has few restrictions on use and is advantageous from the viewpoint of being maintenance-free.

[0012] FIG. 1 is a diagram illustrating an example of a power generation element and its power generation principle according to the present disclosure. FIG. 2 is a diagram illustrating an example of a thermochemical battery. FIG. 3A is a graph showing the relationship between the proton conductivity of various solids and temperature. FIG. 3B is a graph showing the relationship between the proton conductivity of BaZr 0.8 Yb 0.2 O 3-α FIG. 4 is an exploded perspective view showing an example of a power generating device according to the present disclosure. FIG. 5 is an exploded perspective view showing another example of a power generating device according to the present disclosure. FIG. 6 is a graph showing the relationship between the electromotive force and temperature of the power generating element according to sample A-2. FIG. 7 is a graph showing the IV characteristics of the power generating element according to sample A-2. FIG. 8 is a graph showing the continuous discharge characteristics of the power generating element according to sample A-2. FIG. 9 is a graph showing the relationship between the electromotive force and temperature in the first cycle and the fifth cycle of the power generating device according to sample A-19.

[0013] (Knowledge forming the basis of the present disclosure) Effective energy utilization is required from the viewpoints of reducing CO2 emissions, zero carbon, and carbon neutrality. It is conceivable to effectively utilize unused heat generated from factories, automobiles, and living environments. Technologies for utilizing such unused heat are being tackled as national projects and could become important technologies for future society. For example, the widespread use of devices in the field known as energy harvesting is expected to enable the effective utilization of unused heat by converting it into electrical energy.

[0014] Thermoelectric conversion elements or thermochemical batteries that utilize physical phenomena such as the Seebeck effect are considered as devices that convert heat into electrical energy. Some thermoelectric conversion elements have already been commercialized. However, to convert heat into electrical energy using a thermoelectric conversion element, a predetermined temperature difference must be generated between both ends of the thermoelectric conversion element. Meanwhile, thermochemical batteries are limited to specific applications, such as rocket exhaust heat recovery and sodium-sulfur batteries, and further technological development is needed to utilize unused heat. Furthermore, when an electrolyte is used in a thermochemical battery, the amount of electrolyte may decrease and leak as heat is supplied to the thermochemical battery, requiring specific maintenance. On the other hand, providing a heat-to-electrical energy conversion device that can be installed in difficult-to-maintain locations, such as enclosed spaces, factory chimneys, and plant facilities, could potentially promote the utilization of unused heat.

[0015] Therefore, the present inventors conducted extensive research to determine whether it was possible to provide a new power generation element that is maintenance-free and has few restrictions on use. As a result, the present inventors discovered that it is possible to construct an element that can generate electricity using water, which is widely present in the environment. Based on this new finding, the present inventors have completed the thermoelectric conversion material according to the present disclosure.

[0016] (Embodiments of the Present Disclosure) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0017] FIG. 1 is a diagram illustrating an example of a power generation element and its power generation principle according to the present disclosure. As shown in FIG. 1 , a power generation element 1a includes a first electrode 11, a second electrode 12, and a solid electrolyte 15. The first electrode 11 splits water. Water can exist in a liquid or gas phase in an environment in contact with the first electrode 11. When water comes into contact with the first electrode 11, the water splits and specific ions are generated. The solid electrolyte 15 is disposed between the first electrode 11 and the second electrode 12. The solid electrolyte 15 conducts ions generated by the splitting of water at the first electrode 11 toward the second electrode 12. When ions generated by the splitting of water at the first electrode 11 and conducted by the solid electrolyte 15 come into contact with the second electrode 12, the second electrode 12 generates water. Water can be generated in a liquid or gas phase in an environment in contact with the second electrode 12. The splitting of water and the generation of ions at the first electrode 11 generates a potential difference between the first electrode 11 and the second electrode 12, and a current is generated by the conduction of ions. In other words, water is decomposed at the first electrode 11 to generate ions, the generated ions are conducted in the solid electrolyte 15 toward the second electrode 12, and the conducted ions are used to generate water at the second electrode 12, thereby generating a potential difference between the first electrode 11 and the second electrode 12 and generating a current due to the conduction of the ions. As a result, the power generating element 1a supplies electrical energy to the outside of the power generating element 1a.

[0018] FIG. 2 is a schematic diagram illustrating an example of a thermochemical battery. As shown in FIG. 2, the thermochemical battery 9 includes an electrode 91, an electrode 92, and an electrolyte 95. The electrode 91 oxidizes the electrolyte at high temperatures, and the electrode 92 reduces the electrolyte at low temperatures. The electrolyte 95 contains first ions 95a and second ions 95b, which have different valences. For example, the first ions 95a are oxidized at the electrode 91 and converted into second ions 95b. The second ions 95b are reduced at the electrode 92 and converted into the first ions 95a. When a predetermined amount of heat is supplied to the thermochemical battery 9, for example, when the electrode 91 reaches a high temperature, the electrode 91 oxidizes the first ions 95a contained in the electrolyte 95 to generate second ions 95b, and electrons are donated to the electrode 91. Meanwhile, the electrode 92 receives electrons that have passed through the external circuit connected to the thermochemical cell 9 and reduces second ions 95b contained in the electrolyte 95 to produce first ions 95a. In the electrolyte 95, the first ions 95a move toward the electrode 91, and the second ions 95b move toward the electrode 92 due to convection and diffusion. As a result, a redox reaction involving the first ions 95a and the second ions 95b occurs continuously, generating a current in the external circuit. An electromotive force corresponding to the difference in redox potential between the electrodes 91 and 92 at a specific temperature is generated, generating a current from the electrode 91 with a higher redox potential to the electrode 92 with a lower redox potential. In this case, the thermal energy supplied to the thermochemical cell 9 is consumed in the redox reaction and the diffusion of each ion, and the surplus is extracted as electrical energy.

[0019] The thermochemical battery 9 uses an electrolyte 95. When heat is supplied to the thermochemical battery 9, the solvent in the electrolyte 95 may evaporate, potentially reducing the amount of the electrolyte 95. Additionally, the electrolyte 95 may leak from the thermochemical battery 9. For this reason, the thermochemical battery 9 requires predetermined maintenance. Meanwhile, the power generation element 1a can generate electricity when the first electrode 11 comes into contact with a fluid containing water present outside the power generation element 1a. Therefore, power generation is possible as long as water is present in the environment in contact with the first electrode 11. For example, a certain amount of moisture is always present in the air, and the power generation element 1a can generate power using such moisture. Additionally, the power generation element 1a uses a solid electrolyte to conduct ions generated by the decomposition of water, preventing reduction or leakage of the electrolyte. Therefore, the power generation element 1a is advantageous in terms of fewer usage restrictions and maintenance-free operation.

[0020] As described above, the solid electrolyte 15 exhibits ionic conductivity with respect to ions generated by the decomposition of water. The solid electrolyte 15 has ionic conductivity with respect to one ion selected from the group consisting of protons, oxide ions, hydronium ions, and hydroxide ions. In the example shown in FIG. 1 , the solid electrolyte 15 has proton conductivity.

[0021] The power generating element 1a will be described in more detail using an example in which protons are conducted through the solid electrolyte 15. For example, the catalytic activity of the first electrode 11 for water splitting at a predetermined temperature is higher than the catalytic activity of the second electrode 12 for water splitting at a predetermined temperature. In this case, the material of the first electrode 11 is different from the material of the second electrode 12. For example, heat can be supplied to the entire power generating element 1a so that no temperature difference occurs between the first electrode 11 and the second electrode 12. In this case, due to the difference in catalytic activity for water splitting between the first electrode 11 and the second electrode 12, the concentration of protons generated at the first electrode 11 is higher than the concentration of protons generated at the second electrode 12. Heat may be supplied to the power generating element 1a so that the temperature of the first electrode 11 is higher than the temperature of the second electrode 12. In this case, due to the difference in catalytic activity for water splitting between the first electrode 11 and the second electrode 12, the concentration of protons generated at the first electrode 11 is higher than the concentration of protons generated at the second electrode 12.

[0022] The material of the first electrode 11 may be the same as the material of the second electrode 12. In this case, heat can be supplied to the power generating element 1a so that the temperature of the first electrode 11 is higher than the temperature of the second electrode 12. Alternatively, heat may be supplied to the entire power generating element 1a so that no temperature difference occurs between the first electrode 11 and the second electrode 12, and the power generating element 1a may be placed in an environment in which the concentration of water supplied to the first electrode 11 is higher than the concentration of water supplied to the second electrode 12. In these cases as well, the concentration of protons generated at the first electrode 11 will be higher than the concentration of protons generated at the second electrode 12.

[0023] Due to this difference in proton concentration between the first electrode 11 and the second electrode 12, an electromotive force E is generated according to the following Nernst equation (3). Furthermore, protons diffuse in the solid electrolyte 15 due to the heat and concentration difference, and protons react with oxygen at the second electrode 12 to generate water vapor. This water vapor diffuses to the outside of the power generating element 1a. An electromotive force is generated between the first electrode 11 and the second electrode 12 due to the difference in ion activity, and electrons move through an external circuit of the power generating element 1a. The heat supplied to the power generating element 1a is consumed in the decomposition of water at the first electrode 11 and the diffusion of protons in the solid electrolyte 15. Excess chemical energy associated with the generation of water at the second electrode 12 is extracted as electrical energy.

[0024] According to the first law of thermodynamics, the extracted free energy G is defined as follows using enthalpy H, thermodynamic temperature T, and entropy S: G = H - TS Equation (1)

[0025] The relationship between the extracted free energy G and the electromotive force accompanying the battery reaction is expressed by equation (2). In equation (2), n is the number of reacting moles, E is the standard electromotive force, and F is the Faraday constant 96485 Cmol -1 ΔG0 = -nE0F Equation (2)

[0026] The ion activity in the oxidized state and the ion activity in the reduced state in the redox reaction are respectively a Ox and a Red In equation (3), the Nernst equation is obtained. 0 is the standard electrode potential, and R is the gas constant 8.31 JK -1 mol -1 where T is the absolute temperature, z is the number of electrons transferred, and F is the Faraday constant. 0 +(RT / zF)ln(a Ox / a Red ) Formula (3)

[0027] The power generating element 1 a can generate electricity by utilizing water present in the environment in contact with the first electrode 11 even when the solid electrolyte 15 conducts ions other than protons generated by decomposition of water.

[0028] Thus, the power generating element 1a is a novel power generating element that combines thermodynamic phenomena and electrochemical principles, using water present in the environment in which the power generating element 1a is placed as an electrolyte source. The power generating element 1a can generate electrical energy, for example, without the temperature difference required by the Seebeck effect or the like. As described above, the power generating element 1a can have the configuration A in which the catalytic activity of the first electrode 11 for water splitting at a predetermined temperature is higher than the catalytic activity of the second electrode 12 for water splitting at a predetermined temperature. The power generating element 1a may also have the configuration B in which the first electrode 11 and the second electrode 12 are made of the same material. When the power generating element 1a has the configuration A, the power generating element 1a can generate electricity even when the water vapor concentration around the power generating element 1a is uniform. When the power generating element 1a has the configuration B, the power generating element 1a can generate electricity by, for example, supplying heat to the power generating element 1a so that the temperature of the first electrode 11 is higher than the temperature of the second electrode 12. In addition, when the power generating element 1a has the configuration B, the concentration of water supplied to the first electrode 11 is higher than the concentration of water supplied to the second electrode 12, which also enables the power generating element 1a to generate electricity.

[0029] The water used for water decomposition at the first electrode 11 of the power generating element 1a may be water contained in the atmosphere, water present in an enclosed space, or water derived from humidified air supplied from the outside.

[0030] Using the power generating element 1a, for example, a power generation method can be provided that includes the following (I), (II), (III), and (IV): (I) placing the power generating element 1a in an environment where water is present and generating ions by decomposing water using the first electrode 11; (II) conducting the ions generated by (I) in the solid electrolyte 15 toward the second electrode 12; (III) generating water by oxidizing or reducing the ions generated by (I) at the second electrode 12; and (IV) generating a current outside the power generating element 1a.

[0031] In the above power generation method, for example, heat of 500°C or less is supplied to the power generation element 1a. The temperature of the heat supplied to the power generation element 1a may be 400°C or less, 300°C or less, or 200°C or less. The temperature of the heat supplied to the power generation element 1a is, for example, 20°C or more.

[0032] The material of the first electrode 11 is not limited to a specific material as long as it can decompose water. The first electrode 11 includes, for example, a predetermined metal or alloy. The predetermined metal or alloy includes, for example, at least one selected from the group consisting of Pt, Ag, Pd, Ru, Au, Cu, and Ni. In this case, the first electrode 11 can exhibit high catalytic activity for water decomposition.

[0033] The first electrode 11 may contain Fe or Ti. The first electrode 11 may contain an Au—Al alloy, a Pt—Ru alloy, or an Ag—Pd alloy. The method for forming the first electrode 11 is not limited to a specific method. The first electrode 11 can be obtained, for example, by forming a film of a paste containing a metal or an alloy by printing or coating, and then baking the coating. The first electrode 11 may also be formed by sputtering, thermal spraying, or plating.

[0034] The material of the second electrode 12 is not limited to a specific material. As described above, the material of the second electrode 12 may be the same as or different from the material of the first electrode 11. The material of the second electrode 12 may contain, for example, a predetermined metal or alloy. The predetermined metal or alloy may include, for example, at least one selected from the group consisting of Pt, Ag, Pd, Ru, Au, Cu, and Ni. When the first electrode 11 and the second electrode 12 contain an alloy, the metals contained in the alloy contained in the first electrode 11 and the alloy contained in the second electrode 12 may be the same type of metal or different types of metal. When the metals contained in the alloy contained in the first electrode 11 and the alloy contained in the second electrode 12 are the same type of metal, the metal content ratios in the alloy contained in the first electrode 11 and the second electrode 12 may be the same or different. For example, if the first electrode 11 and the second electrode 12 are alloys containing Cu and Pt, the Pt content in the alloy of the first electrode 11 may be 20 mass %, and the Pt content in the alloy of the second electrode 12 may be 5 mass %.

[0035] The second electrode 12 may contain Fe or Ti. The second electrode 12 may contain an Au—Al alloy, a Pt—Ru alloy, or an Ag—Pd alloy. The method for forming the second electrode 12 is not limited to a specific method. The second electrode 12 can be obtained, for example, by forming a film of a paste containing a metal or alloy by printing or coating, and then baking the coating. The second electrode 12 may also be formed by sputtering, thermal spraying, or plating.

[0036] The ionic conductivity σ of the solid electrolyte 15 is not limited to a specific value. For example, the ionic conductivity σ is σ≧10 at 500° C. or less. -5 SCM -1 The ionic conductivity σ is the ionic conductivity of ions generated by the decomposition of water and conducting through the solid electrolyte 15. When this condition is satisfied, the amount of power generated in the power generating element 1a tends to be large. For example, the solid electrolyte 15 satisfies the condition σ≧10 at 20° C. or higher. -5 SCM -1The solid electrolyte 15 satisfies the condition of σ≧10 at 400° C. or less, for example. -5 SCM -1 and σ≧10 at 300° C. or less. -5 SCM -1 and σ≧10 at 200° C. or less. -5 SCM -1 The condition may be satisfied. Figure 3A is a graph showing the relationship between the proton conductivity and temperature of various solids. This graph is quoted from the Setsunan University Institute for Advanced Science Research, Vol. 5, No. 1, (2019) Review: Mechanism on appearance of superprotonic conductivity - In the case of zero-dimensional hydrogen-bonded superprotonic conductor. According to Figure 3A, if a given solid has a temperature below 500°C, σ≧10 -5 SCM -1 It is understood that the above conditions are met.

[0037] The material of the solid electrolyte 15 is not limited to a specific material. The solid electrolyte 15 is, for example, an inorganic solid electrolyte. In this case, the power generating element 1a is likely to have high durability even when heat is supplied to the power generating element 1a. Therefore, there are fewer restrictions on the use of the power generating element 1a.

[0038] The solid electrolyte 15 contains, for example, a perovskite oxide, which makes it easier for the solid electrolyte 15 to have a desired ionic conductivity σ.

[0039] The composition of the perovskite oxide contained in the solid electrolyte 15 is not limited to a specific composition as long as it can conduct ions generated by decomposition of water in the first electrode 11. The perovskite oxide contained in the solid electrolyte 15 can be, for example, BaZr 1-x-y Ce x M y O 3-αIn this composition, the conditions 0≦x<0.5 and 0.05≦y≦0.25 are satisfied. In addition, in this composition, M is a trivalent metal element, and α represents the amount of oxygen deficiency. In this case, the proton ionic conductivity in the solid electrolyte 15 is likely to be high, and the amount of power generated in the power generating element 1a is likely to be large.

[0040] In the above composition, M is, for example, at least one selected from the group consisting of In, Y, Yb, Gd, Nd, and Sm. In this case, the proton ion conductivity of the solid electrolyte 15 is likely to be higher. M may also be other trivalent metal elements such as La, Pr, Pm, Eu, Tb, Dy, Tm, and Ga.

[0041] The perovskite oxide contained in the solid electrolyte 15 is, for example, a single-phase polycrystalline body. In the above composition, the oxygen deficiency amount α is, for example, 0.1 or less.

[0042] The perovskite oxide contained in the solid electrolyte 15 may have, for example, any of the following compositions: 0.8 Yb 0.2 O 3-α 3B is a graph showing the relationship between the proton conductivity of BaZr and the temperature. 0.8 Yb 0.2 O 3-α is σ≧10 at 500°C or less -5 SCM -1 It is understood that the condition BaZr 0.8 In 0.2 O 3-α BaZr 0.8 Yb 0.2 O 3-α BaZr 0.8 Y 0.2 O 3-α BaZr 0.8 Gd 0.2 O 3-α BaZr 0.8 Nd 0.2 O 3-α BaZr 0.8 Sm 0.2 O 3-α BaZr 0.4 Ce 0.2 In0.2 O 3-α BaZr 0.6 Ce 0.2 Gd 0.2 O 3-α BaCe 0.8 Gd 0.2 O 3-α BaZr 0.95 Yb 0.05 O 3-α SrCe 0.8 Gd 0.2 O 3-α CaZr 0.95 Y 0.05 O 3-α

[0043] The solid electrolyte 15 may contain a BaCe-based oxide or a CeO2-based oxide, in which case the solid electrolyte 15 can conduct oxide ions.

[0044] The solid electrolyte 15 may include phosphate glass, tungsten oxide, or tungstic acid, in which case the solid electrolyte 15 may conduct hydronium ions.

[0045] The solid electrolyte 15 may contain a layered double hydroxide (LDH) containing Mg and Al or an LDH containing Ni and Al, in which case the solid electrolyte 15 can conduct hydroxide ions.

[0046] The solid electrolyte 15 may be prepared by a solid-state reaction at high temperature, or by sputtering, thermal spraying, or synthesis using an organic intermediate such as an alkoxide.

[0047] 1, the power generating element 1a has a terminal 17. The terminal 17 is a terminal for supplying electrical energy to the outside of the power generating element 1a. For example, by electrically connecting an external circuit to the terminal 17, the power generating element 1a can supply electrical energy to the external circuit.

[0048] Fig. 4 is an exploded perspective view schematically showing an example of a power generation device according to the present disclosure. As shown in Fig. 4, the power generation device 2a includes a power generation element 1a and an adsorbent / desorbent 21. The adsorbent / desorbent 21 is in communication with the space surrounding the first electrode 11 and adsorbs or desorbs water vapor depending on the temperature. With the power generation device 2a, even if the power generation element 1a is placed in an enclosed space, for example, the power generation element 1a can generate electricity by supplying moisture from the adsorbent / desorbent 21. In the power generation device 2a, for example, the adsorbent / desorbent 21 contains a predetermined amount of moisture.

[0049] The adsorbent / desorbent 21 is disposed, for example, in contact with the first electrode 11. The first electrode 11 is disposed, for example, between the solid electrolyte 15 and the adsorbent / desorbent 21. The adsorbent / desorbent 21 may be disposed apart from the first electrode 11, or another member may be disposed between the adsorbent / desorbent 21 and the first electrode 11.

[0050] The material of the adsorbent / desorbent 21 is not limited to a specific material as long as it can adsorb or desorb water vapor depending on the temperature. The adsorbent / desorbent 21 includes, for example, at least one selected from the group consisting of silica gel, layered double hydroxide, phosphate hydrate, zeolite, metal felt, and porous metal. This allows the adsorbent / desorbent 21 to exhibit desired adsorption / desorption characteristics for water vapor. Metal felt is felt formed from metal fibers. An example of a metal felt is nickel felt. An example of a porous metal is foamed nickel.

[0051] 4 , the power generation device 2a further includes, for example, a cap 22. The cap 22 can accommodate the power generation element 1a and the adsorbent / desorber 21. The cap 22 is made of a metal such as stainless steel, and is electrically connected to the first electrode 11. For example, by electrically connecting the cap 22 and the second electrode 12 to a predetermined measuring device 23, the electromotive force and current generated in the power generation device 2a can be measured.

[0052] 4, the power generation device 2a is supplied with heat from the heat source 25. This makes it easy for a high electromotive force to be generated in the power generation device 2a.

[0053] Fig. 5 is an exploded perspective view schematically illustrating another example of a power generation device according to the present disclosure. As shown in Fig. 5, the power generation device 2b includes a power generation element 1a and a first supply path 31a. The first supply path 31a is a flow path that guides a first fluid containing water to the first electrode 11. The first electrode 11 decomposes the water contained in the first fluid. With this configuration, the power generation element 1a generates electrical energy by decomposing the water contained in the first fluid at the first electrode 11. The first supply path 31a is formed, for example, so as to be in contact with the first electrode 11. The first fluid does not contain a gas used as a fuel gas in a fuel cell, such as hydrogen gas.

[0054] The power generation device 2b further includes, for example, a second supply path 31b. The second supply path 31b guides a second fluid containing, for example, water to the second electrode 12. Even with this configuration, electrical energy can be generated in the power generation element 1a. The second supply path 31b is formed, for example, so as to be in contact with the second electrode 12.

[0055] In the power generation device 2b, the first fluid has, for example, a first water vapor pressure. The second fluid has, for example, a second water vapor pressure. The first water vapor pressure is different from the second water vapor pressure. For example, the first water vapor pressure is higher than the second water vapor pressure. In other words, the concentration of water vapor in the first fluid is higher than the concentration of water vapor in the second fluid. Therefore, the concentration of protons generated at the first electrode 11 is higher than the concentration of protons generated at the second electrode 12, and electrical energy can be generated in the power generation element 1a.

[0056] As shown in FIG. 5 , the power generation device 2b includes a flow path member 32a, a flow path member 32b, and a heat-resistant insulating sheet 33. A first supply path 31a is formed inside the flow path member 32a, and a second supply path 31b is formed inside the flow path member 32b. The heat-resistant insulating sheet 33 and the power generation element 1a are disposed between the flow path member 32a and the flow path member 32b. An opening is formed on the surface of the flow path member 32a close to the power generation element 1a, allowing the first fluid flowing through the first supply path 31a to contact the first electrode 11 of the power generation element 1a. An opening is formed on the surface of the flow path member 32b close to the power generation element 1a, allowing the second fluid flowing through the second supply path 31b to contact the second electrode 12 of the power generation element 1a. The heat-resistant insulating sheet 33 has heat resistance and electrical insulation properties. An opening is formed in the center of the heat-resistant insulating sheet 33 that contacts the power generation element 1a.

[0057] The power generation device 2b includes, for example, a lead 35a and a lead 35b. The lead 35a is connected to the first electrode 11, and the lead 35b is connected to the second electrode 12. As a result, the electrical energy generated in the power generation element 1a is supplied to an external circuit.

[0058] The power generation device 2b further includes, for example, a drain pipe 36. The drain pipe 36 is attached to, for example, the flow path member 32a. Water generated by condensation of water vapor in the flow path member 32a passes through the drain pipe 36 and is discharged to the outside of the power generation device 2b.

[0059] 5, a heater 40 is disposed near the power generation device 2b. The flow path members 32a and 32b are maintained at a predetermined temperature by heat supplied from the heater 40. A heat insulating material 45 is disposed around the heater 40.

[0060] In the power generation device 2b, the second electrode 12 may be in contact with the atmosphere. Heat may be supplied from the heater 40 from the first electrode 11 side of the power generation element 1a, or the entire power generation element 1a may be heated uniformly.

[0061] The present disclosure will be described in detail below with reference to examples, although the thermoelectric conversion material of the present disclosure is not limited to the specific embodiments shown below.

[0062] <Samples A-1 to A-8> Predetermined amounts of powders of indium oxide, yttrium oxide, ytterbium oxide, gadolinium oxide, neodymium oxide, samarium oxide, and cerium oxide were mixed together with barium acetate and zirconium hydroxide powders, as needed. The mixture thus obtained was ground and mixed in an agate mortar using ethanol. After the powders were thoroughly mixed, the ethanol was evaporated, and the powders were degreased by heating with a burner. The ground and mixed again in the agate mortar. The resulting mixed powder was then pressed into a cylindrical shape to obtain a compact. The compact was fired at 1200°C to 1400°C for 10 to 12 hours. The fired product was coarsely ground and then further ground in benzene or cyclohexane using a planetary ball mill to obtain a powder granulated to 3 μm or less. The resulting powder was vacuum dried at 150°C and then sintered at 2 tons / cm. 2 The compacts were then uniaxially or isostatically pressed at a pressure of 1000 psi to obtain cylindrical compacts. These compacts were then immediately fired at temperatures of 1500°C to 1700°C for 6 to 12 hours to obtain sintered compacts according to Samples A-1 to A-8. The sintered compacts according to each sample were sufficiently dense, and the densities of these sintered compacts were 96% or more of the calculated density (theoretical density). In addition, the sintered compacts according to each sample were single-phase perovskite-type oxides. Furthermore, when the cross sections of the samples prepared from each sintered compact were observed with a scanning electron microscope (SEM), particles having particle sizes ranging from 1 μm to 30 μm were confirmed.

[0063] (Composition Analysis) The composition of the surface of a specimen prepared from the sintered body of each sample was analyzed using an energy dispersive X-ray fluorescence analyzer EDX-700 manufactured by Shimadzu Corporation. The results are shown in Table 1.

[0064] (Crystal Structure Analysis) The X-ray diffraction patterns of specimens prepared from the sintered bodies of each sample were measured using an X-ray diffractometer RINT2100 manufactured by Rigaku Corporation. For this measurement, characteristic X-rays of CuKα were used. A fitting estimation of the crystal lattice constants of the sintered bodies of each sample was performed by Rietveld analysis using the XRD analysis software JADE6. As a result, it was confirmed that the sintered bodies of each sample were single-phase perovskite-type oxides.

[0065] (Density) Using a He gas substitution type multi-volume pycnometer MICROMERITICS 1305, the volume of a specimen prepared from the sintered body of each sample was determined. Separately, the mass of the specimen was measured. From the results of these measurements, the true density of the sintered body of each sample was determined.

[0066] A disk-shaped solid electrolyte having a diameter of 20 mm and a thickness of 0.5 mm was prepared from the sintered body of each sample. Platinum-containing paste TR-7905 manufactured by Tanaka Kikinzoku Co., Ltd. was applied in a circular pattern with a diameter of 16 mm to one main surface of the disk-shaped solid electrolyte. Additionally, Au-containing paste TR-1501A manufactured by Tanaka Kikinzoku Co., Ltd. was applied in a circular pattern with a diameter of 16 mm to the other main surface of the disk-shaped solid electrolyte. The Pt-containing paste coating and the Au-containing paste coating were baked for one hour in an electric furnace set at 900°C. In this manner, power generation elements according to Samples A-1 to A-8 were obtained. It is believed that Pt-containing electrodes derived from Pt-containing pastes exhibit higher activity in water decomposition than Au-containing electrodes derived from Au-containing pastes. For the power generation elements according to Samples A-1 to A-8, disk-shaped solid electrolytes were prepared using the sintered bodies according to Samples A-1 to A-8, respectively.

[0067] The power generating element for each sample was placed on nickel felt made from hydrated nickel fibers, with the Pt-containing electrode of the power generating element serving as the anode. The power generating element was placed with the anode facing the nickel felt. Additionally, as shown in Figure 4, the power generating element and nickel felt were housed in a stainless steel cap. A potentiogalvanostat, Solartron 1287, was connected to the Au-containing electrode, which served as the cathode of the power generating element, and the stainless steel cap. The cathode was exposed to the air. A K-type thermocouple was attached to the solid electrolyte of the power generating element for each sample. The IV characteristics, which indicate the magnitude of the electromotive force generated and the current extracted from the power generating element, were measured while adjusting the temperature of a heater located near the stainless steel cap while supplying heat to the power generating element. Table 1 shows the range of electromotive force and the temperature range in which the electromotive force was generated when using the power generating element for each sample.

[0068]

[0069] As shown in Table 1, it can be seen that when any of the solid electrolytes of Samples A-1 to A-8 is used, a predetermined electromotive force is generated in the temperature range of 120°C to 400°C.

[0070] FIG. 6 is a graph showing the relationship between the electromotive force and temperature of the power generation element of sample A-2. FIG. 7 is a graph showing the IV characteristics of the power generation element of sample A-2. FIG. 8 is a graph showing the continuous discharge characteristics of the power generation element of sample A-2. The graph shown in FIG. 8 shows the voltage change when a current load of 0.5 μA is continuously applied. As shown in FIG. 7, it is possible to apply a current load when an electromotive force is generated, and as shown in FIG. 8, it was demonstrated that electricity can be extracted from the power generation element as long as heat is continuously applied. Furthermore, current could be continuously extracted using power generation elements of other samples.

[0071] <Samples A-9 to A-17> Power generating elements according to Samples A-9 to A-17 were fabricated as follows. 0.8 Yb 0.2 O 3-αA disk-shaped solid electrolyte having a diameter of 20 mm and a thickness of 0.5 mm was prepared from a sintered body having a composition represented by the formula (1). A Pt-containing paste, an Ag-containing paste, a Ni-containing paste, a Pd-containing paste, or a Ru-containing paste was applied to one main surface of the disk-shaped solid electrolyte in a circular pattern with a diameter of 16 mm. Additionally, a Cu-containing paste, a Ni-containing paste, an Ag-containing paste, or an Au-containing paste was applied to the other main surface of the disk-shaped solid electrolyte in a circular pattern with a diameter of 16 mm. TR-7905 manufactured by Tanaka Kikinzoku Co., Ltd. was used as the Pt-containing paste. MH-1063 manufactured by Tanaka Kikinzoku Co., Ltd. was used as the Ag-containing paste. A product manufactured by Daiken Chemical Manufacturing Co., Ltd. was used as the Ni-containing paste. A product manufactured by Tanaka Kikinzoku Co., Ltd. was used as the Pd-containing paste. A product manufactured by Tanaka Kikinzoku Co., Ltd. was used as the Ru-containing paste. A product manufactured by Daiken Chemical Manufacturing Co., Ltd. was used as the Cu-containing paste. TR-1501A manufactured by Tanaka Kikinzoku Co., Ltd. was used as the Au-containing paste. The paste coating formed on both sides of the solid electrolyte was baked for 1 hour in an electric furnace set to 900°C. In this way, power generation elements according to Samples A-9 to A-17 were obtained. As shown in Table 2, the anode and cathode of these power generation elements contained metal derived from the metal-containing paste.

[0072] For the power generating elements of Samples A-9 to A-17, the IV characteristics, which indicate the magnitude of the generated electromotive force and the current extracted from the power generating element, were measured in the same manner as for the power generating element of Sample A-2, while heat was being supplied to the power generating element. Each power generating element was positioned so that the anode of each power generating element faced the nickel felt formed from hydrated nickel fibers. In addition, the cathode of each power generating element was in contact with the atmosphere. The maximum electromotive force of the power generating element of each sample and the temperature at which the maximum electromotive force was generated are shown in Table 2.

[0073]

[0074] As shown in Table 2, it was found that electromotive force was generated between 120°C and 400°C when any of the power generation elements according to Samples A-9 to A-17 was used. In addition, it was confirmed that the power generation elements according to all samples were capable of continuous discharge under a current load of 0.5 μA. It was confirmed that electricity could be extracted by applying heat to a power generation element in which different types of electrode materials were combined.

[0075] <Sample A-18> BaZr according to sample A-2 0.8 Yb 0.2 O 3-α A disk-shaped solid electrolyte having a diameter of 20 mm and a thickness of 0.5 mm was prepared from a sintered body having a composition represented by the formula: Pt-containing paste TR-7905 manufactured by Tanaka Kikinzoku Co., Ltd. was applied to both main surfaces of the disk-shaped solid electrolyte in a circular pattern with a diameter of 16 mm. The Pt-containing paste coating formed on both main surfaces of the solid electrolyte was baked for 1 hour in an electric furnace set at 900°C. In this way, a power generation element according to sample A-18 was obtained.

[0076] Using the apparatus shown in Figure 5, humidified air was flowed at a flow rate of 200 ccm to the anode side of the power generation element of sample A-18. The humidified air was adjusted using a bubbler containing a water bath set to a predetermined temperature. The temperature and relative humidity of the humidified air were measured immediately before entering the flow path member. Meanwhile, unhumidified room temperature air was flowed at a flow rate of 200 ccm to the cathode side of the power generation element. In addition, heat was supplied to the device by a heater placed near the flow path member of this device. A K-type thermocouple was attached to the solid electrolyte of the power generation element to measure the temperature of the power generation element. Leads extending from the electrodes on both sides of the power generation element were connected to a Solartron 1287 potentiogalvanostat, and the electromotive force of the power generation element of sample A-18 was measured. Table 3 shows the electromotive force of the power generation element when the temperature of the power generation element was adjusted to 150°C, 200°C, 300°C, and 400°C while the temperature of the humidified air supplied to the anode side of the power generation element was adjusted to room temperature (approximately 25°C), 40°C, and 65°C.

[0077]

[0078] As shown in Table 3, when humidified air of any temperature was supplied to the anode side of the power generation element, a small amount of electromotive force was generated between 150°C and 400°C. Furthermore, in all cases, it was confirmed that continuous discharge was possible with a current load of 0.1 μA when the maximum electromotive force was generated. Even when the electrodes formed on both sides of the solid electrolyte in the power generation element were made of the same material, it was confirmed that the power generation element could generate electricity by adjusting the temperature and humidity of the air supplied to both sides. For example, placing a moisture-retaining material such as nickel felt or silica gel near the anode of the power generation element can create a difference in water vapor concentration in the air in contact with the electrodes on both sides of the solid electrolyte. It is understood that even in such cases, power generation is possible by supplying heat to the power generation element.

[0079] <Sample A-19> A power generation element according to Sample A-2 was placed on nickel felt so that the anode of the power generation element faced the hydrated nickel felt. In addition, a commercially available adsorbent containing silica gel SiO2·nH2O was placed near the power generation element. In this way, a power generation device according to Sample A-18 was produced. In this power generation device, the temperature of the power generation element was increased from room temperature to 400°C and then returned to room temperature, and this cycle was repeated five times to evaluate the power generation characteristics of the power generation device.

[0080] 9 is a graph showing the relationship between the electromotive force and temperature in the first and fifth cycles of the power generating device according to sample A-19. As shown in FIG. 9, it was confirmed that the power generating element according to sample A-2 was able to generate electricity in the fifth cycle as well as in the first cycle.

[0081] The power generating element of the present disclosure can be used in a variety of applications, including applications for conventional power generating elements.

[0082] REFERENCE SIGNS 1a Power generating element 2a, 2b Power generating device 11 First electrode 12 Second electrode 15 Solid electrolyte 17 Terminal 21 Adsorption / desorption body 31a First supply path 31b Second supply path

Claims

1. A power generating element, A first electrode; A second electrode; a solid electrolyte disposed between the first electrode and the second electrode, for conducting ions generated by the decomposition of water at the first electrode toward the second electrode; a potential difference is generated between the first electrode and the second electrode without the power generating element being immersed in a liquid that functions as an electrolyte, thereby supplying electrical energy to the outside of the power generating element; Power generating element.

2. the solid electrolyte has ionic conductivity with respect to one ion selected from the group consisting of protons, oxide ions, hydronium ions, and hydroxide ions; The power generating element according to claim 1 .

3. The solid electrolyte has a σ≧10 at 500° C. or less. -5 SCM -1 Meet the conditions of In the above condition, σ is the ionic conductivity of the ions in the solid electrolyte. The power generating element according to claim 1 .

4. The solid electrolyte is an inorganic solid electrolyte. The power generating element according to claim 1 .

5. The solid electrolyte contains a perovskite-type oxide. The power generating element according to claim 1 .

6. The perovskite oxide is BaZr 1-x-y Ce x M y O 3-α It has a composition represented by In the composition, the conditions 0≦x<0.5 and 0.05≦y≦0.25 are satisfied, In the above composition, M is a trivalent metal element, and α represents the amount of oxygen deficiency. The power generating element according to claim 5 .

7. In the above composition, M is at least one selected from the group consisting of In, Y, Yb, Gd, Nd, and Sm. The power generating element according to claim 6 .

8. The power generating element according to claim 1 , wherein the material of the second electrode is different from the material of the first electrode.

9. the first electrode contains a metal or an alloy including at least one selected from the group consisting of Pt, Ag, Pd, Ru, Au, Cu, and Ni; The power generating element according to claim 1 .

10. the first electrode is in contact with a fluid containing water present outside the power generating element; The power generating element according to claim 1 .

11. Further provided with a terminal for supplying electrical energy to the outside of the power generating element, The power generating element according to claim 1 .

12. The power generating element according to any one of claims 1 to 11, a first supply path for introducing a first fluid containing water to the first electrode; The first electrode decomposes water contained in the first fluid. Power generation equipment.

13. a second supply path for introducing a second fluid containing water to the second electrode; the second electrode contacts the second fluid; The power generating device according to claim 12.

14. the first fluid has a first water vapor pressure; the second fluid has a second water vapor pressure; the first water vapor pressure is different from the second water vapor pressure; The power generating device according to claim 13.

15. A power generating element including a first electrode, a second electrode, and a solid electrolyte; an adsorption / desorption body that communicates with a space surrounding the first electrode and adsorbs or desorbs water vapor depending on temperature; the solid electrolyte is disposed between the first electrode and the second electrode and conducts ions generated by the decomposition of water at the first electrode toward the second electrode; generating a potential difference between the first electrode and the second electrode to supply electrical energy to the outside of the power generating element; Power generation equipment.

16. the adsorbent / desorbent comprises at least one selected from the group consisting of silica gel, layered double hydroxide, phosphate hydrate, zeolite, metal felt, and a metal porous body; The power generating device according to claim 15.

17. placing a power generating element including a first electrode, a second electrode, and a solid electrolyte disposed between the first electrode and the second electrode in an environment where water is present without immersing the element in a liquid that functions as an electrolyte, and generating ions by decomposing water using the first electrode; conducting the ions in the solid electrolyte toward the second electrode; oxidizing or reducing the ions at the second electrode to produce water; and generating a current outside the power generating element. Power generation method.

18. Further comprising supplying heat of 500°C or less to at least a portion of the power generating element. The method for generating electricity according to claim 17.