Liquid thermoelectric conversion element, method for controlling the electrochemical Seebeck coefficient

Abstract

To provide a liquid thermoelectric conversion element in which a small heat flow causes a large temperature difference between a positive electrode and a negative electrode to obtain high electromotive force, and a method for controlling the electrochemical Seebeck coefficient of the liquid thermoelectric conversion element.SOLUTION: A liquid thermoelectric conversion element 10 includes a first electrode 21, a second electrode 22, and an electrolytic solution 30 interposed between the first electrode 21 and the second electrode 22, and the electrolytic solution 30 contains an organic solvent, and oxide ions, and reduction ions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a liquid thermoelectric conversion element and a method for controlling the electrochemical Seebeck coefficient. [Background technology]

[0002] Thermoelectric cells are a type of energy harvesting technology that converts temperature differences in the environment into electrical energy. The performance of a thermoelectric cell is governed by the electrochemical Seebeck coefficient (S), the electrical conductivity (σ) of the solution, and the thermal conductivity (k) of the solution. Conventionally, thermoelectric cells (liquid thermoelectric conversion elements) using aqueous solutions as electrolytes have been actively researched (see, for example, Non-Patent Document 1).

[0003] The performance of a thermoelectric power cell is expressed by the figure of merit (ZT=S). 2 It is evaluated by σT / k). This parameter determines the thermal efficiency (power generated / thermoelectric cell flowing through the device). The parameter that governs the temperature difference of a thermoelectric cell is thermal conductivity (k). In a thermoelectric cell with high thermal conductivity (k), a huge amount of heat is required to apply a temperature difference. On the other hand, in a thermoelectric cell with low thermal conductivity (k), a temperature difference can be easily obtained using ambient heat.

[0004] In a temperature difference cell having a redox-counter electrolyte whose oxidation-reduction potential changes with temperature and a solvent for dissolving it, between a high-temperature electrode and a low-temperature electrode with different temperatures, [Fe(CN)6] is used as the redox counterion. 3- and [Fe(CN)6] 4- It is known that a solution is used, and water is used as the solvent. In addition, it is known that FeBr2, FeBr3, or CuBr, CuBr2 are used as the redox counter electrolyte, and benzonitrile is used as the solvent (see, for example, Patent Document 1).

[0005] In a thermoelectric cell having a redox-pair electrolyte whose oxidation-reduction potential changes with temperature and a solvent for dissolving it between high-temperature and low-temperature electrodes with different temperatures, it is known that the cations constituting the redox-pair electrolyte are redox counterions, the anions that are its counterions are Br, and the electrode material is a graphite intercalation compound in which the inserted element is Br (see, for example, Patent Document 2).

[0006] A thermoelectric conversion device is known that comprises a redox pair, a capture compound that selectively captures only one of the redox pairs at low temperature and releases it at high temperature, an ionic electrolyte, a first electrode, and a second electrode, wherein the redox pair consists of an oxidizing agent active species and a reducing agent active species, and the ionic solubility consists of an aqueous solvent containing water and an organic solvent or water (see, for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-176800 [Patent Document 2] Japanese Patent Application Publication No. 6-251809 [Patent Document 3] International Publication No. 2017 / 155046 [Non-patent literature]

[0008] [Non-Patent Document 1] Dai Inoue, Hideharu Niwa, Hiroaki Nitani, and Yutaka Moritomo, Scaling Relation between Electrochemical Seebeck Coefficient for Fe2+ / Fe3+ in Organic Solvent and Its Viscosity, Journal of The Physical Society of Japan.90,033602(2021) [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Traditionally, thermoelectric power generation cells using aqueous solutions as electrolytes have been extensively researched. The thermal conductivity (K) of aqueous solutions is 0.6 W / mK, which is relatively high among liquids. Therefore, thermoelectric power generation cells using aqueous solutions cannot achieve a large temperature difference between electrodes with small heat flows.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a liquid thermoelectric conversion element that generates a large temperature difference between the positive and negative electrodes with a small heat flow and can obtain a high electromotive force, and a method for controlling the electrochemical Seebeck coefficient of the liquid thermoelectric conversion element. [Means for solving the problem]

[0011] The present invention has the following aspects. [1] comprising a first electrode, a second electrode, and an electrolyte interposed between the first electrode and the second electrode, The electrolyte comprises an organic solvent, oxide ions, and reducing ions. The thermal conductivity of the electrolyte is less than that of water. the law of nature, The aforementioned organic solvent is methanol or ethanol. The salt containing the aforementioned oxide ions is Fe(ClO 4 ) 3 The salt containing the aforementioned reducing ions is Fe(ClO 4 ) 2 And, The Fe(ClO) in the electrolyte 4 ) 3 and the aforementioned Fe(ClO 4 ) 2 The concentration is 0.5 mol / L to 0.7 mol / L. A liquid thermoelectric conversion element. [2] A device comprising a first electrode, a second electrode, and an electrolyte interposed between the first electrode and the second electrode, wherein the electrolyte comprises a mixed solvent, oxide ions and reducing ions, The mixed solvent comprises water and at least one organic solvent, or at least two different organic solvents. The thermal conductivity of the electrolyte is less than that of water. the law of nature, The organic solvent is methanol, The salt containing the aforementioned oxide ions is Fe(ClO 4 ) 3 The salt containing the aforementioned reducing ions is Fe(ClO 4 ) 2 And, The Fe(ClO) in the electrolyte 4 ) 3 and the aforementioned Fe(ClO 4 ) 2 The concentration is 0.5 mol / L to 0.7 mol / L. A liquid thermoelectric conversion element. [3] The organic solvent is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butene, 2-butene, isobutene, ethylene glycol, glycerin, acetone, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, propylene carbonate, tetrahydrofuran, acetonitrile and ethyl acetate, The liquid thermoelectric conversion element according to [1] or [2]. [4] The electrochemical Seebeck coefficient of the electrolyte is 1.23 mV / K or more and 3.60 mV / K or less, The liquid thermoelectric conversion element according to any one of [1] to [3]. [5] A method for controlling the electrochemical Seebeck coefficient of the liquid thermoelectric conversion element according to any one of [1] to [4], Using alcohol as the organic solvent, adding water to the electrolyte, coordinating water or hydroxide ions to the oxide ions and the reduction ions contained in the electrolyte, and controlling the electrochemical Seebeck coefficient of the electrolyte. A method for controlling the electrochemical Seebeck coefficient. [Advantages of the Invention]

[0012] According to the present invention, it is possible to provide a liquid thermoelectric conversion element in which a large temperature difference occurs between the positive electrode and the negative electrode due to a small heat flow, and a high electromotive force is obtained, and a method for controlling the electrochemical Seebeck coefficient of the liquid thermoelectric conversion element. [Brief Description of the Drawings]

[0013] [Figure 1] It is a schematic diagram showing a liquid thermoelectric conversion element according to an embodiment of the present invention. [Figure 2]This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 1. [Figure 3] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 1. [Figure 4] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 2. [Figure 5] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 2. [Figure 6] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 3. [Figure 7] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 3. [Figure 8] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 4. [Figure 9] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 4. [Figure 10] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Comparative Example 1. [Figure 11] This figure shows the relationship between current and voltage, and the relationship between current and power, in Comparative Example 1. [Figure 12] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 6. [Figure 13] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 6. [Figure 14] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 10. [Figure 15] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 10. [Figure 16] This figure shows the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Example 11. [Figure 17]This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 11. [Figure 18] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 12. [Figure 19] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 13. [Figure 20] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 14. [Figure 21] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 15. [Figure 22] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 16. [Figure 23] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 17. [Figure 24] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 18. [Figure 25] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 19. [Figure 26] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 20. [Figure 27] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 21. [Figure 28] This figure shows the relationship between the concentrations of reducing ions and oxidizing ions and the electrochemical Seebeck coefficient of the electrolyte in Examples 1-9, Examples 12-21, and Comparative Example 1-4. [Figure 29] This figure shows the relationship between the concentrations of reducing ions and oxide ions and the electrical conductivity of the electrolyte in Examples 1-9, 12-21, and Comparative Example 1-4. [Figure 30] This figure shows the relationship between the concentrations of reducing ions and oxidizing ions and the power factor of the electrolyte in Examples 1-9, Examples 12-21, and Comparative Example 1-4. [Figure 31]This figure shows the relationship between the concentrations of reducing ions and oxidizing ions and the dimensionless figure of merit of the electrolyte in Examples 1-9, 12-21, and Comparative Example 1-4. [Figure 32] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 22. [Figure 33] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 23. [Figure 34] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 24. [Figure 35] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 25. [Figure 36] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 26. [Figure 37] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 27. [Figure 38] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 28. [Figure 39] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 29. [Figure 40] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 30. [Figure 41] This figure shows the relationship between current and voltage, and the relationship between current and power, in Example 31. [Figure 42] This figure shows the relationship between the concentrations of reducing ions and oxide ions and the electrochemical Seebeck coefficient of the electrolyte in Examples 22 and 31. [Figure 43] This figure shows the relationship between the concentrations of reducing ions and oxide ions and the electrical conductivity of the electrolyte in Examples 22 and 31. [Figure 44] This figure shows the relationship between the concentrations of reducing ions and oxidizing ions and the power factor of the electrolyte in Examples 22 and 31. [Figure 45]This figure shows the relationship between the concentrations of reducing ions and oxidizing ions and the dimensionless figure of merit of the electrolyte in Examples 22 and 31. [Modes for carrying out the invention]

[0014] Embodiments of the liquid thermoelectric conversion element and the method for controlling the electrochemical Seebeck coefficient of the liquid thermoelectric conversion element of the present invention will be described below. This embodiment is provided to give a better understanding of the spirit of the invention and does not limit the present invention unless otherwise specified.

[0015] [Thermoelectric power cell] The following describes a liquid thermoelectric conversion element according to one embodiment of the present invention, with reference to the drawings. Figure 1 is a schematic diagram showing the liquid thermoelectric conversion element of this embodiment. As shown in Figure 1, the liquid thermoelectric element 10 of this embodiment comprises a first electrode 21, a second electrode 22, and an electrolyte 30. In the liquid thermoelectric element 10 of this embodiment, the electrolyte 30 is sandwiched between the first electrode 21 and the second electrode 22. In other words, the first electrode 21 and the second electrode 22 face each other via the electrolyte 30. The liquid thermoelectric element 10 may also have a container (housing) 40 that houses the first electrode 21, the second electrode 22, and the electrolyte 30. By providing the container 40, the entire liquid thermoelectric element 10 can be sealed to prevent leakage of the electrolyte 30.

[0016] "First electrode, second electrode" The first electrode 21 and the second electrode 22 are not particularly limited, but examples include carbon-based electrodes, metal electrodes, and the like. Examples of carbon-based electrodes include electrodes composed of graphite, carbon nanotubes, and fullerenes. Examples of metal electrodes include electrodes made of gold, platinum, silver, and the like.

[0017] The distance (spacing) between the first electrode 21 and the second electrode 22 is preferably 5 mm or more and 50 mm or less, more preferably 7 mm or more and 40 mm or less, and even more preferably 10 mm or more and 30 mm or less. When the distance between the first electrode 21 and the second electrode 22 is greater than or equal to the lower limit, the liquid thermoelectric conversion element 10 is more likely to generate an electromotive force. When the distance between the first electrode 21 and the second electrode 22 is greater than or equal to the lower limit, current flows easily between the first electrode 21 and the second electrode 22, and an electromotive force is generated even with a small heat flow.

[0018] "Electrolyte" The electrolyte 30 used is an electrolyte containing an organic solvent, oxide ions, and reducing ions. That is, the electrolyte 30 is obtained by dissolving oxide ions and reducing ions in an organic solvent. Alternatively, the electrolyte 30 may contain a mixed solvent, oxide ions, and reducing ions, and the mixed solvent may contain water and at least one organic solvent, or at least two different organic solvents.

[0019] The thermal conductivity of the electrolyte 30 is preferably less than that of water. The organic solvent is not particularly limited as long as its thermal conductivity is less than that of water (0.602 W / mK (20°C)), but examples include methanol (0.212 W / mK), ethanol (0.183 W / mK), 1-propanol (0.161 W / mK), 2-propanol, 1-butene (0.167 W / mK), 2-butene, isobutene (0.134 W / mK), ethylene glycol (0.243 W / mK), glycerin (0.143 W / mK), acetone (0.18 W / mK), N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, propylene carbonate, tetrahydrofuran, acetonitrile, ethyl acetate (0.137 W / mK), etc. These organic solvents may be used individually or in combination of two or more.

[0020] The electrochemical Seebeck coefficient of the electrolyte 30 is preferably 1.23 mV / K or more and 3.60 mV / K or less. Preferably, the organic solvent has an electrochemical Seebeck coefficient of 1.23 mV / K or higher and 3.60 mV / K or lower. Examples of organic solvents with an electrochemical Seebeck coefficient of 1.23 mV / K or higher and 3.60 mV / K or lower include 1-propanol (1.24 mV / K), 1-butene (1.34 mV / K), acetone (3.60 mV / K), N,N-dimethylformamide (1.35 mV / K), N-methyl-2-pyrrolidone (1.39 mV / K), dimethyl sulfoxide (1.23 mV / K), propylene carbonate (1.78 mV / K), tetrahydrofuran (2.70 mV / K), acetonitrile (2.16 mV / K), and ethyl acetate (2.57 mV / K). These organic solvents may be used individually or in combination of two or more.

[0021] The electrolyte 30 may contain additives such as sodium chloride (NaCl).

[0022] "Oxidation ions, reduction ions" The oxide ions are not particularly limited as long as they dissolve in the above organic solvent, but for example, iron(III) oxide (Fe 3+ ), cyanoiron(III)([Fe(CN)6] 3- Examples include salts containing oxide ions, such as iron(III) perchlorate (Fe(ClO4)3) and sodium iron(III) cyanoferrate (Na3[Fe(CN)6]). The reducing ions are not particularly limited as long as they dissolve in the above organic solvent, but for example, iron(II) oxide (Fe 2+ ), cyanoiron(II)([Fe(CN)6] 4- Examples include the following. Specifically, salts containing reducing ions are used, such as iron(II) perchlorate (Fe(ClO4)2) and sodium iron(II) cyanoferrate (Na4[Fe(CN)6]).

[0023] The concentration of oxide ions or reducing ions in the electrolyte 30 is not particularly limited, but the upper limit of the concentration is the solubility of each ion in the organic solvent. Furthermore, the concentration of oxide ions in the electrolyte 30 and the concentration of reducing ions in the electrolyte 30 may be equal or different.

[0024] Furthermore, Figure 1 illustrates a case where the liquid thermoelectric conversion element 10 is composed of a single unit having a first electrode 21, a second electrode 22, and an electrolyte 30, but this embodiment is not limited to this. The liquid thermoelectric conversion element of the present invention may have multiple units, each unit connected in series. Series connection means connecting the negative electrode of one unit to the positive electrode of an adjacent unit.

[0025] The liquid thermoelectric conversion element 10 of this embodiment comprises a first electrode 21, a second electrode 22, and an electrolyte 30 interposed between the first electrode 21 and the second electrode 22. The electrolyte 30 contains an organic solvent, oxide ions, and reducing ions. Since the thermal conductivity of the electrolyte 30 is less than that of water, a small heat flow generates a large temperature difference between the first electrode 21 and the second electrode 22, resulting in a high electromotive force.

[0026] In the liquid thermoelectric element 10 of this embodiment, by using an organic solvent with a lower thermal conductivity than water as the electrolyte 30, a temperature difference can be created between the first electrode 21 and the second electrode 22 with a small heat flow. As a result, a high electromotive force can be obtained from the liquid thermoelectric element 10. The electromotive force obtained from the liquid thermoelectric element 10 is high and of good quality. For example, if an electromotive force of about 100mV is generated from the liquid thermoelectric element 10, a semiconductor can be driven by connecting 20 to 30 units in series. Furthermore, in the liquid thermoelectric element 10 of this embodiment, by using an organic solvent with a lower thermal conductivity than water as the electrolyte 30, a higher electromotive force can be obtained than when an aqueous solution is used under the same ambient heat conditions, reflecting the high electrochemical Seebeck coefficient and low thermal conductivity of the organic solvent. Also, for example, if an electromotive force of about 20mV is generated from the liquid thermoelectric element 10, that electromotive force can be boosted to several volts using an existing boost circuit to drive a semiconductor.

[0027] The liquid thermoelectric element 10 of this embodiment can obtain a high electromotive force from a small heat flow, such as from the surface of the human body. For example, the first electrode 21 of the liquid thermoelectric element 10 is brought into contact with the surface of the human body, and the first electrode 21 is heated by the heat of the human body. On the other hand, the second electrode 22 of the liquid thermoelectric element 10 is placed on the opposite side from the surface of the human body, so that the second electrode 22 is not heated by the heat of the human body. This creates a temperature difference between the first electrode 21 and the second electrode 22, and an electromotive force is obtained from the liquid thermoelectric element 10. In this way, since the liquid thermoelectric element 10 can obtain an electromotive force using the heat of the human body, it can be used as a power source for wearable IoT devices and the like.

[0028] Furthermore, the liquid thermoelectric conversion element 10 can utilize ambient temperatures other than those of the human body if a temperature difference can be created between the first electrode 21 and the second electrode 22.

[0029] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0030] [Method for controlling the electrochemical Seebeck coefficient] A method for controlling the electrochemical Seebeck coefficient according to one embodiment of the present invention is a method for controlling the electrochemical Seebeck coefficient of a liquid thermoelectric conversion element of the above-described embodiment, wherein an alcohol is used as the organic solvent, water is added to the electrolyte, and water or hydroxide ions are coordinated to the oxide ions and reducing ions contained in the electrolyte to control the electrochemical Seebeck coefficient of the electrolyte.

[0031] The amount of water added to the electrolyte is not particularly limited and should be adjusted as appropriate according to the desired electrochemical Seebeck coefficient.

[0032] The method of adding water to the electrolyte is not particularly limited, but examples include adding a predetermined amount of water dropwise to the electrolyte, or using water contained in the solute that is the source of the oxide ions and reducing ions. In the method of adding a predetermined amount of water dropwise to an electrolyte, the electrochemical Seebeck coefficient changes with the amount (concentration) of water added. Specifically, as the amount of water added increases, the electrochemical Seebeck coefficient increases, reaches a maximum value, and then decreases. In the method using water contained in the solute described above, the electrochemical Seebeck coefficient changes with the amount (concentration) of solute added. Specifically, as the amount of solute added increases, the electrochemical Seebeck coefficient increases, reaches a maximum value, and then decreases.

[0033] In the electrochemical Seebeck coefficient control method of this embodiment, alcohols such as methanol and ethanol are preferred as the organic solvent.

[0034] In the electrochemical Seebeck coefficient control method of this embodiment, the electrochemical Seebeck coefficient of the electrolyte can be controlled by adding water to the electrolyte, thereby coordinating water or hydroxide ions with the oxide ions and reducing ions contained in the electrolyte. Furthermore, by using alcohol as the organic solvent in the electrolyte, more water or hydroxide ions can be coordinated with the oxide ions and reducing ions. The electrochemical Seebeck coefficient usually decreases as the concentration of the solute in the electrolyte increases. In the electrochemical Seebeck coefficient control method of this embodiment, by using alcohol as the organic solvent in the electrolyte, the electrochemical Seebeck coefficient initially increases as the concentration of the solute in the electrolyte increases, reaches a maximum value, and then decreases. Therefore, in the electrochemical Seebeck coefficient control method of this embodiment, by adding water to the electrolyte, the electrochemical Seebeck coefficient of the electrolyte can be maximized depending on the oxide ions and reducing ions contained in the electrolyte.

[0035] Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Examples]

[0036] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited to the following examples.

[0037] [Example 1] Platinum electrodes were used as the positive and negative electrodes, and acetone containing 1.0 mol / L of Fe(ClO4)2 and 1.0 mol / L of Fe(ClO4)3 was used as the electrolyte to fabricate a liquid thermoelectric conversion element. A Peltier element was attached to the positive and negative electrodes to control the temperatures of the positive and negative electrodes. A thermocouple was attached to the positive and negative electrodes to measure the temperatures of the positive and negative electrodes. The temperatures of the positive and negative electrodes were controlled by a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated with respect to the temperature difference between the electrodes was measured. The results are shown in Fig. 2. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes in Fig. 2 and the electromotive force of the liquid thermoelectric conversion element, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 1.97 mV / K. The results are shown in Fig. 28. Also, one electrode (for example, the positive electrode) was maintained at 25 °C, and the other electrode (for example, the negative electrode) was maintained at 55 °C to measure the electrical conductivity σ of the liquid thermoelectric conversion element. An external resistance was connected to the liquid thermoelectric conversion element to control the current flowing through the liquid thermoelectric conversion element, and as shown in Fig. 3, the relationship between current and voltage and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the current amount and the voltage drop shown in Fig. 3. As a result, the electrical conductivity was 12.01 mS / cm. The results are shown in Fig. 29. Also, based on the following formula (1), the power factor (PF) of the electrolyte was calculated. The results are shown in Fig. 30. PF = α 2 × σ (1) Furthermore, based on the following formula (2), the dimensionless performance index (ZT) of the electrolyte was calculated. The results are shown in Fig. 31. ZT = α 2 × σ × T / κ (2) In the above formula (2), T represents the absolute temperature of the electrolyte, and κ represents the thermal conductivity of the electrolyte.

[0038] [Example 2] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetone containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 4. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 4, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.32 mV / K. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 5. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 5. As a result, the electrical conductivity was 15.10 mS / cm. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0039] [Example 3] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetone containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 6. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 6, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.43 mV / K. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 7. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 7. As a result, the electrical conductivity was 14.58 mS / cm. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0040] [Example 4] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetone containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 8. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 8, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.50 mV / K. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 9. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 9. As a result, the electrical conductivity was 13.36 mS / cm. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0041] [Example 5] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetone containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0042] [Comparative Example 1] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and pure water containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 10. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 10, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 1.557 mV / K. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 11. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 11. As a result, the electrical conductivity was 88.34 mS / cm. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0043] [Comparative Example 2] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and pure water containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0044] [Comparative Example 3] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and pure water containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0045] [Comparative Example 4] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and pure water containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0046] [Example 6] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetonitrile containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 12. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 12, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.14 mV / K. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 13. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 13. As a result, the electrical conductivity was 21.14 mS / cm. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0047] [Example 7] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetonitrile containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0048] [Example 8] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetonitrile containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0049] [Example 9] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and acetonitrile containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured. The electrical conductivity σ was measured from the relationship between the amount of current and the voltage drop. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0050] [Example 10] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and tetrahydrofuran containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 14. From the slope of the graph in Figure 14 showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.79 mV / K. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 15. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 15. As a result, the electrical conductivity was 5.848 mS / cm.

[0051] [Example 11] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethyl acetate containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. Thermocouples were attached to the positive and negative electrodes to measure their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The results are shown in Figure 16. From the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element in Figure 16, the electrochemical Seebeck coefficient α of the electrolyte was determined to be 2.14 mV / K. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 17. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 17. As a result, the electrical conductivity was 8.31 mS / cm.

[0052] [Example 12] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and methanol containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 18. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 18. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0053] [Example 13] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and methanol containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 19. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 19. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0054] [Example 14] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and methanol containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 20. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 20. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0055] [Example 15] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and methanol containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 21. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 21. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0056] [Example 16] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and methanol containing 1.0 mol / L Fe(ClO4)2 and 1.0 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 22. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 22. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0057] [Example 17] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethanol containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 23. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 23. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0058] [Example 18] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethanol containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 24. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 24. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0059] [Example 19] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethanol containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 25. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 25. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0060] [Example 20] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethanol containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 26. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 26. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0061] [Example 21] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and ethanol containing 1.0 mol / L Fe(ClO4)2 and 1.0 mol / L Fe(ClO4)3 as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 28. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 27. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 27. The results are shown in Figure 29. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 30. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 31.

[0062] As shown in Figure 28, when methanol or ethanol is used as the organic solvent, the electrochemical Seebeck coefficient α of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the electrochemical Seebeck coefficient α of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 29, when methanol or ethanol is used as the organic solvent, the electrochemical Seebeck coefficient α of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the electrical conductivity σ of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 30, when methanol or ethanol is used as the organic solvent, the power factor (PF) of the electrolyte changes depending on the concentration of Fe(ClO4)2 and Fe(ClO4)3, and the power factor (PF) of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 31, when methanol or ethanol is used as the organic solvent, the dimensionless figure of merit (ZT) of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the dimensionless figure of merit (ZT) of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L.

[0063] [Example 22] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 (methanol:pure water = 1:1 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 32. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 32. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0064] [Example 23] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 (methanol:pure water = 1:1 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 33. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 33. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0065] [Example 24] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 (methanol:pure water = 1:1 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 34. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 34. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0066] [Example 25] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 (methanol:pure water = 1:1 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 35. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 35. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0067] [Example 26] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.9 mol / L Fe(ClO4)2 and 0.9 mol / L Fe(ClO4)3 (methanol:pure water = 1:1 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 36. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 36. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0068] [Example 27] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.1 mol / L Fe(ClO4)2 and 0.1 mol / L Fe(ClO4)3 (methanol:pure water = 1:3 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 37. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 37. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0069] [Example 28] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.3 mol / L Fe(ClO4)2 and 0.3 mol / L Fe(ClO4)3 (methanol:pure water = 1:3 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 38. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 38. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0070] [Example 29] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.5 mol / L Fe(ClO4)2 and 0.5 mol / L Fe(ClO4)3 (methanol:pure water = 1:3 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 39. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 39. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0071] [Example 30] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.7 mol / L Fe(ClO4)2 and 0.7 mol / L Fe(ClO4)3 (methanol:pure water = 1:3 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured as shown in Figure 40. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 40. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0072] [Example 31] A liquid thermoelectric conversion element was fabricated using platinum electrodes as the positive and negative electrodes, and a mixed solvent containing 0.9 mol / L Fe(ClO4)2 and 0.9 mol / L Fe(ClO4)3 (methanol:pure water = 1:3 (mass ratio)) as the electrolyte. Peltier elements were attached to the positive and negative electrodes to control their temperatures. The temperatures of the positive and negative electrodes were controlled using a Peltier element to create a temperature difference between the electrodes, and the electromotive force generated in response to this temperature difference was measured. The electrochemical Seebeck coefficient α of the electrolyte was determined from the slope of the graph showing the relationship between the temperature difference between the positive and negative electrodes and the electromotive force of the liquid thermoelectric conversion element. The results are shown in Figure 42. Furthermore, the electrical conductivity σ of the liquid thermoelectric element was measured by keeping one electrode (e.g., the positive electrode) at 25°C and the other electrode (e.g., the negative electrode) at 55°C. An external resistor was connected to the liquid thermoelectric element to control the current flowing through it, and the relationship between current and voltage, and the relationship between current and power were measured, as shown in Figure 41. The electrical conductivity σ was measured from the relationship between current and voltage drop shown in Figure 41. The results are shown in Figure 43. Furthermore, the power factor (PF) of the electrolyte was calculated based on the above equation (1). The results are shown in Figure 44. Furthermore, the dimensionless figure of merit (ZT) of the electrolyte was calculated based on equation (2) above. The results are shown in Figure 45.

[0073] As shown in Figure 42, when a mixed solvent of methanol and pure water is used, the electrochemical Seebeck coefficient α of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and it was found that the electrochemical Seebeck coefficient α of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 43, when a mixed solvent of methanol and pure water is used, the electrochemical Seebeck coefficient α of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the electrical conductivity σ of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 44, when a mixed solvent of methanol and pure water is used, the power factor (PF) of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the power factor (PF) of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. As shown in Figure 45, when a mixed solvent of methanol and pure water is used, the dimensionless figure of merit (ZT) of the electrolyte changes depending on the concentrations of Fe(ClO4)2 and Fe(ClO4)3, and the dimensionless figure of merit (ZT) of the electrolyte is maximized when the concentrations of Fe(ClO4)2 and Fe(ClO4)3 are in the range of 0.5 mol / L to 0.7 mol / L. [Industrial applicability]

[0074] The liquid thermoelectric conversion element of the present invention can be used in wearable IoT devices and the like that can continuously send, receive, and relay information without the need for a power supply or primary battery. The electrochemical Seebeck coefficient control method of the present invention can maximize the electrochemical Seebeck coefficient of the electrolyte of the liquid thermoelectric conversion element, and thus can contribute to the fabrication of a liquid thermoelectric conversion element that can obtain a high electromotive force. [Explanation of symbols]

[0075] 10 Liquid thermoelectric element 21 First electrode 22 Second electrode 30 Electrolyte 40 containers

Claims

1. The device comprises a first electrode, a second electrode, and an electrolyte interposed between the first electrode and the second electrode. The electrolyte comprises an organic solvent, oxide ions, and reducing ions. The thermal conductivity of the electrolyte is less than that of water. The aforementioned organic solvent is methanol or ethanol. The salt containing the oxide ion is Fe(ClO₄)₃, and the salt containing the reducing ion is Fe(ClO₄)₂. A liquid thermoelectric conversion element, wherein the concentrations of Fe(ClO₄)₃ and Fe(ClO₄)₂ in the electrolyte are 0.5 mol / L to 0.7 mol / L.

2. The device comprises a first electrode, a second electrode, and an electrolyte interposed between the first electrode and the second electrode. The electrolyte comprises a mixed solvent, oxide ions, and reducing ions. The mixed solvent comprises water and at least one organic solvent, or at least two different organic solvents. The thermal conductivity of the electrolyte is less than that of water. The organic solvent is methanol, The salt containing the oxide ion is Fe(ClO₄)₃, and the salt containing the reducing ion is Fe(ClO₄)₂. A liquid thermoelectric conversion element, wherein the concentrations of Fe(ClO₄)₃ and Fe(ClO₄)₂ in the electrolyte are 0.5 mol / L to 0.7 mol / L.

3. The liquid thermoelectric element according to claim 1 or 2, wherein the organic solvent is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butene, 2-butene, isobutene, ethylene glycol, glycerin, acetone, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, propylene carbonate, tetrahydrofuran, acetonitrile, and ethyl acetate.

4. The liquid thermoelectric element according to claim 1 or 2, wherein the electrochemical Seebeck coefficient of the electrolyte is 1.23 mV / K or more and 3.60 mV / K or less.

5. A method for controlling the electrochemical Seebeck coefficient of a liquid thermoelectric element according to claim 1, A method for controlling the electrochemical Seebeck coefficient, wherein an alcohol is used as the organic solvent, water is added to the electrolyte, and water or hydroxide ions are coordinated to the oxide ions and reducing ions contained in the electrolyte to control the electrochemical Seebeck coefficient of the electrolyte.

Images