EP4700157A1

EP4700157A1 - Organic hydride production device and organic hydride production method

Info

Publication number: EP4700157A1
Application number: EP24792341.0A
Authority: EP
Inventors: Yoshitatsu Misu; Yuto Shimoyama; Atsushi Fukazawa; Kaori Takano; Koji Matsuoka; Yoshikazu Ito
Original assignee: University of Tsukuba NUC; Eneos Corp
Current assignee: University of Tsukuba NUC; Eneos Corp
Priority date: 2023-04-19
Filing date: 2024-02-09
Publication date: 2026-02-25
Also published as: AU2024259307A1; CN120936753A; JPWO2024219065A1; WO2024219065A1

Abstract

This organic hydride production device 2 comprises, as an anode catalyst 11, an anode electrode 10 having a high entropy alloy containing a base metal element, a cathode electrode 8, and an electrolyte membrane 12 positioned between the anode electrode 10 and the cathode electrode 8. The anode electrode 10 oxidizes water or hydroxide ions. The cathode electrode 8 electrochemically reduces a hydride to generate an organic hydride.

Description

TECHNICAL FIELD

The present invention relates to an organic hydride production device and an organic hydride production method.

BACKGROUND ART

Patent Literature 1 describes a water electrolyzer including a high entropy alloy as a catalyst for oxygen evolution reaction.

RELATED-ART LITERATURE

PATENT LITERATURE

Patent Literature 1: WO 2022/080142

SUMMARY OF INVENTION

TECHNICAL PROBLEM

In recent years, organic hydrides have attracted attention as energy carriers for the large-scale transportation and storage of hydrogen derived from renewable energy. With regard to the production of organic hydrides, organic hydride production devices are known that generate protons from water at an anode electrode and generates an organic hydride by hydrogenating a hydrogenation target substance at a cathode electrode.
As in the case of water electrolysis, the anode catalyst of an organic hydride production device is required to have resistance to the hydrogenation target substance and organic hydrides that cross leak from the cathode electrode side in addition to oxygen evolution reaction (OER) activity, acid resistance, oxidation potential resistance, electrical conductivity, etc. In general, conventional organic hydride production devices generally use Ir or the like as anode catalysts; however, as a result of intensive studies, the inventors of the present invention have come to recognize that there is room for improving the durability of the anode catalysts in the conventional organic hydride production devices.
The present invention has been made in view of such a situation, and an object thereof is to improve the durability of an anode catalyst used in an organic hydride production device.

SOLUTION TO PROBLEM

One embodiment of the present invention relates to an organic hydride production device. This device includes an anode electrode having a high-entropy alloy ,as an anode catalyst, containing a base metal element, a cathode electrode, and an electrolyte membrane positioned between the anode electrode and the cathode electrode. The anode electrode oxidizes water or hydroxide ions. The cathode electrode electrochemically reduces the hydrogenation target substance so as to produce an organic hydride.
Another embodiment of the present invention relates to an organic hydride production method that uses an organic hydride production device comprising an anode electrode having a high-entropy alloy, as an anode catalyst, containing a base metal element, a cathode electrode, and an electrolyte membrane positioned between the anode electrode and the cathode electrode. This production method includes oxidizing water or hydroxide ions at the anode electrode and electrochemically reducing the hydrogenation target substance so as to produce an organic hydride at the cathode electrode.
Optional combinations of the aforementioned constituting elements, and implementations of the present disclosure in the form of methods, apparatuses, and systems may also be practiced as additional modes of the present disclosure.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to improve the durability of an anode catalyst used in an organic hydride production device.

BRIEF DESCRIPTION OF DRAWINGS

[Fig. 1] Fig. 1 is a schematic diagram of an organic hydride production system including an organic hydride production device according to an embodiment.
[Fig. 2] Fig. 2 is a diagram showing the current density of each cell in a toluene poisoning test.
[Fig. 3] Fig. 3 is a diagram showing by-products generated by constant-potential electrolysis.
[Fig. 4] Fig. 4A is a diagram showing results of FT-IR analysis for a working electrode according to the first exemplary embodiment after a toluene poisoning test. Fig. 4B is a diagram showing results of FT-IR analysis for a working electrode according to the first comparative example after a toluene poisoning test.
[Fig. 5] Fig. 5A is a diagram showing the current density of a cell according to the first exemplary embodiment in a toluene oxidation product poisoning test. Fig. 5B is a diagram showing the current density of a cell according to the first comparative example in a toluene oxidation product poisoning test.
[Fig. 6] Fig. 6A is a diagram showing results of FT-IR analysis for the working electrode according to the first exemplary embodiment after a toluene oxidation product poisoning test. Fig. 6B is a diagram showing results of FT-IR analysis for the working electrode according to the first comparative example after a toluene oxidation product poisoning test.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The embodiments do not limit the technical scope of the present invention and are shown for illustrative purposes, and not all the features described in the embodiments and combinations thereof are necessarily essential to the invention. Therefore, regarding the details of the embodiments, many design modifications such as change, addition, deletion, etc., of the constituent elements may be made without departing from the spirit of the invention defined in the claims. New embodiments resulting from added design change will provide the advantages of the embodiments and variations that are combined. In the embodiments, the details for which such design change is possible are emphasized with the notations "according to the present embodiment," "in the present embodiment," etc. However, design change is also allowed for those without such notations. Optional combinations of the constituting elements described in the embodiments are also valid as embodiments of the present invention. The same or equivalent constituting elements, members, and processes illustrated in each drawing shall be denoted by the same reference numerals, and duplicative explanations will be omitted appropriately. The scales and shapes of parts shown in each figure are set for the sake of convenience in order to facilitate the explanation and shall not be interpreted in a limited manner unless otherwise mentioned. Terms like "first," "second," etc., used in the specification and claims do not indicate an order or importance by any means and are used to distinguish a certain feature from the others. Some of the components in each figure may be omitted if they are not important for explanation.
Fig. 1 is a schematic diagram of an organic hydride production system 1 including an organic hydride production device 2 according to an embodiment. The organic hydride production system 1 as an example includes an organic hydride production device 2, a catholyte tank 4, and an anolyte tank 6. Although only one organic hydride production device 2 is shown in Fig. 1, the organic hydride production system 1 may include a plurality of organic hydride production devices 2. In this case, the respective organic hydride production devices 2 are stacked in the same direction such that a cathode electrode 8 and an anode electrode 10 are arranged in the same direction and are electrically connected in series. Note that the organic hydride production devices 2 may be connected in parallel or may be a combination of series connection and parallel connection. Further, the configuration of the organic hydride production system 1 is not limited to those explained below, and the configuration of each part can be appropriately changed.
The electrochemical reduction device 2 is an electrolysis cell for generating an organic hydride by hydrogenating a hydrogenation target substance, which is a dehydrogenated product of an organic hydride, by an electrochemical reduction reaction. The organic hydride production device 2 has a cathode electrode 8 (cathode), an anode electrode 10 (anode), an electrolyte membrane 12, a pair of plate members 14a and 14b, and a pair of gaskets 16a and 16b. The cathode electrode 8, the anode electrode 10, and the electrolyte membrane 12 constitute a membrane electrode assembly. In the present embodiment, an explanation will be given using the membrane electrode assembly as an example, and the organic hydride production device 2 may have a so-called zero-gap electrode structure in which an electrode having an anode catalyst applied to a hard support substrate is in physical contact with the electrolyte membrane.
The cathode electrode 8 electrochemically reduces the hydrogenation target substance so as to produce an organic hydride. The term "electrochemical" in the present embodiment means that a reaction proceeds when voltage is applied or current is applied from outside the organic hydride production device 2. The cathode electrode 8 has a cathode catalyst 9. For example, the cathode catalyst 9 is included in a cathode catalyst layer. The cathode catalyst 9 includes, for example, precious metals such as platinum (Pt), ruthenium (Ru), palladium (Pd), and base metals such as nickel (Ni). In the cathode catalyst layer, the cathode catalyst 9 can be supported by a porous catalyst support. The catalyst support includes an electron-conductive material such as porous carbon, a porous metal, or a porous metal oxide.
If the electrolyte membrane 12 has proton conductivity, the cathode catalyst 9 is coated with a cation-exchange ionomer. For example, the catalyst support, which is in the state of supporting the cathode catalyst 9, is coated with an ionomer. Examples of the cation-exchange ionomer include perfluorosulfonic acid polymers such as Nafion (registered trademark), Flemion (registered trademark), Aquivion (registered trademark), or Aciplex (registered trademark), and hydrocarbon-based sulfonic acid polymers. It is preferable that the cathode catalyst 9 is partially coated with the ionomer. Preferably, 10 percent or more of the surface of each cathode catalyst 9 is coated with the ionomer. As a result, it is possible to efficiently supply three elements, i.e., the hydrogenation target substance, a proton, and an electron, necessary for an electrochemical reaction at the cathode electrode 8 to the reaction field.
If the electrolyte membrane 12 has anion conductivity, the cathode catalyst 9 is coated with an anion-exchange ionomer. For example, the catalyst support, which is in the state of supporting the cathode catalyst 9, is coated with an ionomer. Examples of the anion-exchange ionomer include polymers such as Fumion (registered trademark). It is preferable that the cathode catalyst 9 is partially coated with the ionomer. Preferably, 10 percent or more of the surface of each cathode catalyst 9 is coated with the ionomer. As a result, it is possible to efficiently supply three elements, i.e., the hydrogenation target substance, water, and an electron, necessary for an electrochemical reaction at the cathode electrode 8 to the reaction field.
The cathode electrode 8 may be provided with a cathode diffusion layer. As an example, the cathode catalyst layer is arranged to be in contact with one of the main surfaces of the electrolyte membrane 12. The cathode diffusion layer is arranged to be in contact with the main surface on the side opposite to the electrolyte membrane 12 in the cathode catalyst layer. The cathode diffusion layer uniformly diffuses the hydrogenation target substance supplied from the outside into the cathode catalyst layer. The organic hydride generated in the cathode catalyst layer is discharged to the outside of the cathode electrode 8 through the cathode diffusion layer. The cathode diffusion layer is composed of a conductive material such as carbon and metal. In addition, the cathode diffusion layer is a porous body such as a sintered or foam-molded body of fibers or particles. Examples of the material forming the cathode diffusion layer include a carbon woven fabric (carbon cloth), a carbon nonwoven fabric, carbon paper, and the like. Note that the cathode diffusion layer may be omitted.
The anode electrode 10 oxidizes water or hydroxide ions. If the electrolyte membrane 12 is proton conductive, the anode electrode 10 oxidizes water to produce protons. If the electrolyte membrane 12 is anion conductive, the anode electrode 10 oxidizes hydroxide ions to produce oxygen. The anode electrode 10 has an anode catalyst 11. For example, the anode catalyst 11 is included in an anode catalyst layer. In the anode catalyst layer, the anode catalyst 11 may be dispersedly supported or coated on an electron conductive base material. The base material is composed of a material containing, for example, a metal such as titanium (Ti) or stainless steel (SUS) as a main component. Examples of the form of the base material include a woven fabric sheet or a nonwoven fabric sheet, a mesh, a porous sintered body, a foam-molded body (foam), an expanded metal, etc.
The anode electrode 10 according to the present embodiment has a high-entropy alloy (HEA) containing base metal elements as the anode catalyst 11. High-entropy alloys are solid solution alloys in which the atomic composition ratios of five or more constituent elements are substantially equal. The entropy of mixing is increased by having five or more constituent elements with substantially equal atomic composition ratios. The expression "substantially equal atomic composition ratios" in the present embodiment means that the atomic composition ratios of the elements need to be equal to the extent that the entropy is increased, and differences to the extent of manufacturing errors are acceptable. For example, given that the atomic composition ratio of the element with the highest atomic composition ratio among five or more constituent elements is denoted as C_max and that the atomic composition ratio of the element with the lowest atomic composition ratio is denoted as C_min, the following is established: (C_max - C_min)/( C_max + C_min) ≤ 0.2, and the following is preferably established: (C_max - C_min)/(C_max + C_min) ≤ 0.1. The atomic composition ratio of each metal element in the solid solution alloy is preferably between 4 atm% and 24 atm%, both inclusive, and more preferably between 5 atm% and 20 atm%, both inclusive.
As mentioned above, it is known to use high-entropy alloys for electrodes for oxygen generation in water electrolysis. However, it is not readily conceivable for a person skilled in the art to use a high-entropy alloy containing base metal elements as the anode catalyst 11 of the organic hydride production device 2 as in the present embodiment.
This is because, firstly, in the organic hydride production device 2, the hydrogenation target substance and the organic hydride may leak from the cathode electrode 8 side to the anode electrode 10 side. Therefore, in the organic hydride production device 2, the OER overvoltage at the anode electrode 10 tends to be larger than that in the case of water electrolysis. Therefore, those skilled in the art consider that a high-entropy alloys containing base metal elements with lower OER activity than that of noble metals such as Ir is useless as the anode catalyst 11.
Second, the operating temperature of the organic hydride production device 2 is set lower than that in the case of water electrolysis so as not to exceed the boiling point of the hydrogenation target substance and the boiling point of organic hydrides. The electrolytic voltage of the organic hydride production device 2 is highly dependent on temperature, and the lower the temperature, the higher the electrolytic voltage. Therefore, those skilled in the art consider that a high-entropy alloy containing base metal elements, which is assumed to increase the electrolysis voltage due to low OER activity, is useless as the anode catalyst 11.
Third, it is common general technical knowledge to consider that high-entropy alloys containing base metal elements as constituent elements are less durable than precious metals such as Ir. As mentioned in the first reason, since the hydrogenation target substance and organic hydrides can leak in the organic hydride production device 2, the anode catalyst 11 is prone to deterioration. Therefore, those skilled in the art consider that a high-entropy alloy containing base metal elements, which is less durable, is useless as the anode catalyst 11.
Thus, from a common perspective, it is natural that one would not think of using a high-entropy alloy containing base metal elements as the anode catalyst 11 for producing organic hydrides. However, as a result of extensive research, the present inventors have discovered that, contrary to their prediction, high-entropy alloys containing base metal elements have high durability against hydrogenation target substances, etc. This finding should not be considered as something easily conceivable by those skilled in the art.
Therefore, the use of a high-entropy alloy as the anode catalyst 11 can improve the durability of the anode catalyst 11. This allows the activity of the anode catalyst 11 to be maintained for a long period of time, thereby improving the production efficiency of organic hydrides. Further, since high-entropy alloys containing base metal elements are less expensive than noble metals such as Ir, the cost of organic hydride production can also be reduced. Further, all the constituent elements of the high-entropy alloys containing base metal elements are preferably base metal elements. Although Cu has a smaller ionization tendency than hydrogen and a positive standard electrode potential relative to the hydrogen standard electrode, Cu is treated as a base metal in the present application.
Preferably, the high-entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cr, Ti, Zr, Nb, Mo and Cu. More preferably, the high entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co and Ni (hereinafter referred to as the first group as appropriate), and at least one element selected from the group consisting of Cr, Ti, Zr, Nb, Mo and Cu (hereinafter referred to as the second group as appropriate) .
The elements in the first group are more catalytically active than the elements in the second group. On the other hand, the elements in the second group are more durable to an anolyte LA than the elements in the first group. Therefore, when the high-entropy alloy contains the elements in the first group and the elements in the second group, the improvement of the catalytic performance of the anode catalyst 11 and the improvement of the durability of the anode catalyst 11 can be achieved at the same time. The average particle size D50 of the high-entropy alloy is, for example, between 1 nm and 100 µm, both inclusive.
In the anode catalyst 11, the dissolution rate of elements contained in the high-entropy alloy when a rated current, i.e., the current at the time of rated electrolysis in the organic hydride production device 2 is applied or when a rated voltage, i.e., the voltage at the time of rated electrolysis in the organic hydride production device 2 is applied is 60 µg/h or less per one gram of the anode catalyst, or the dissolution rate of elements contained in the high-entropy alloy when immersed in an acidic solution of pH 4.0 or less is 60 µg/h or less per one gram of the anode catalyst, preferably. Thus, the high-entropy alloy is in a stable state, and the elution of the constituent elements of the high-entropy alloy from the anode catalyst 11 during the operation of the organic hydride production device 1 can thereby be suppressed.
The stable state of the high-entropy alloy can be obtained by applying an aging treatment in advance to the anode catalyst 11. The aging treatment includes at least one of electrolysis of an electrolyte using the anode catalyst 11 and immersion of the anode catalyst 11 in an acidic solution of pH 4.0 or less. In the present embodiment, "in advance" means before the organic hydride production in the organic hydride production device 2 is carried out. For example, "applying an aging treatment in advance" means immersing a single anode electrode 10 in an electrolytic solution such as a sulfuric acid solution and applying an electrolytic current or an electrolytic voltage. Further, "applying an aging treatment in advance" means immersing a single anode electrode 10 in an acidic solution with a pH of 4.0 or less.
The anode electrode 10 may be provided with an anode diffusion layer. As an example, the anode catalyst layer is arranged so as to be in contact with the other main surface of the electrolyte membrane 12. The anode diffusion layer is arranged so as to be in contact with the main surface opposite to the electrolyte membrane 12 in the anode catalyst layer. The anode diffusion layer may have a structure similar to that of the cathode diffusion layer.
The electrolyte membrane 12 is positioned between the cathode electrode 8 and the anode electrode 10. As an example, the electrolyte membrane 12 has protonic conductivity. In this case, the electrolyte membrane 12 moves protons from the anode electrode 10 to the cathode electrode 8. As an example, the electrolyte membrane 12 is composed of a solid polymer electrolyte membrane (PEM) having protonic conductivity. Examples of PEM include a fluorinated ion exchange membrane having a sulfonic acid group such as Nafion (registered trademark) and a hydrocarbon ion exchange membrane such as Fumasep (registered trademark), for example.
Fig. 1 illustrates the electrolyte membrane 12 having proton conductivity. However, this feature is not particularly limiting, and the electrolyte membrane 12 may have anion conductivity. In this case, the electrolyte membrane 12 moves hydroxide ions from the cathode electrode 8 to the anode electrode 10. As an example, the electrolyte membrane 12 is composed of a solid polymer electrolyte membrane (AEM) having anion conductivity. Examples of AEM include known anion exchange membranes such as Fumasep (registered trademark), Pention, and Sustainion (registered trademark).
The plate member 14a and the plate member 14b are made of a metal such as SUS, Ti, etc., for example. The plate member 14a is stacked on the membrane electrode assembly from the side of the cathode electrode 8. The plate member 14b is stacked on the membrane electrode assembly from the side of the anode electrode 10. Accordingly, the membrane electrode assembly is sandwiched between the pair of plate members 14a and 14b. A gap between the plate member 14a and the membrane electrode assembly is sealed with a gasket 16a. A gap between the plate member 14b and the membrane electrode assembly is sealed with a gasket 16b. When the organic hydride production system 1 includes only one organic hydride production device 2, the pair of plate members 14a and 14b can correspond to so-called end plates. When the organic hydride production system 1 includes a plurality of organic hydride production devices 2, and another organic hydride production device 2 is arranged next to the plate member 14a or the plate member 14b, the plate member can correspond to a so-called separator.
A cathode flow path 18 is connected to the cathode electrode 8. The cathode flow path 18 feeds and discharges a catholyte LC to and from the cathode electrode 8. A groove may be provided on a main surface facing the cathode electrode 8 side in the plate member 14a, and this groove may constitute the cathode flow path 18.
An anode flow path 20 is connected to the anode electrode 10. The anode flow path 20 feeds and discharges the anolyte LA to and from the anode electrode 10. A groove may be provided on a main surface facing the anode electrode 10 side in the plate member 14b, and this groove may constitute the anode flow path 20.
The catholyte tank 4 is connected to the cathode flow path 18 via a first cathode pipe 24 and a second cathode pipe 26. The catholyte LC is stored in the catholyte tank 4. One end of the first cathode pipe 24 is connected to the catholyte tank 4, and the other end of the first cathode pipe 24 is connected to the entrance of the cathode flow path 18. The cathode pump 28 is provided in the middle of the first cathode pipe 24. The cathode pump 28 can be constituted by a known pump such as a gear pump or a cylinder pump, for example. The distribution of the catholyte LC may be realized by a liquid feeding device other than a pump. One end of the second cathode pipe 26 is connected to the exit of the cathode flow path 18, and the other end of the second cathode pipe 26 is connected to the catholyte tank 4.
The catholyte LC contains a hydrogenation target substance that is an organic hydride raw material. As an example, the catholyte LC does not contain an organic hydride before the start of the operation of the organic hydride production system 1, and after the start of the operation, the organic hydride generated by electrolysis is mixed in, whereby the catholyte becomes the liquid mixture of the hydrogenation target substance and the organic hydride. The hydrogenation target substance and the organic hydride are preferably a liquid at 20°C and 1 atm.
The hydrogenation target substance and the organic hydride are not particularly limited as long as they are organic compounds capable of adding/desorbing hydrogen by reversibly causing a hydrogenation reaction/dehydrogenation reaction. As the hydrogenation target substance and the organic hydride used in the present embodiment, an acetone-isopropanol type, a benzoquinone-hydroquinone type, an aromatic hydrocarbon type, and the like can be widely used. Among these, the aromatic hydrocarbon type is preferable from the viewpoint of transportability during energy transport or the like.
An aromatic hydrocarbon compound used as the hydrogenation target substance is a compound containing at least one aromatic ring. Examples of the aromatic hydrocarbon compound include benzene, alkylbenzene, naphthalene, alkylnaphthalene, anthracene, diphenylethane, tetralin, and the like. The alkylbenzene contains a compound in which 1 to 4 hydrogen atoms in the aromatic ring are substituted with a linear alkyl group or a branched alkyl group having 1 to 6 carbons. Examples of such a compound include toluene, xylene, mesitylene, ethylbenzene, and diethylbenzene. The alkylnaphthalene contains a compound in which 1 to 4 hydrogen atoms in the aromatic ring are substituted with a linear alkyl group or a branched alkyl group having 1 to 6 carbons. Examples of such a compound include methylnaphthalene. These compounds may be used alone or in combination.
The hydrogenation target substance is preferably at least one selected from the group consisting of toluene, benzene and xylene. It is also possible to use a nitrogen-containing heterocyclic aromatic compound such as quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, or N-alkyldibenzopyrrole as the hydrogenation target substance. The organic hydride is obtained by hydrogenating the above-described hydrogenation target substance, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and decahydroquinoline.
The catholyte LC in the catholyte tank 4 flows into the cathode electrode 8 through the first cathode pipe 24 by driving of the cathode pump 28. The catholyte LC flowing into the cathode electrode 8 is subjected to an electrode reaction at the cathode electrode 8. The catholyte LC in the cathode electrode 8 returns to the catholyte tank 4 through the second cathode pipe 26. As an example, the catholyte tank 4 also functions as a gas-liquid separator. The hydrogen gas may be generated by the side reaction at the cathode electrode 8. Therefore, the hydrogen gas may be mixed in the catholyte LC discharged from the cathode electrode 8. The catholyte tank 4 separates the hydrogen gas in the catholyte LC from the catholyte LC and discharges the hydrogen gas to the outside of the system.
A gas-liquid separator may be provided separately from the catholyte tank 4. Further, the organic hydride production system 1 may be provided with an oil-water separator for separating water from the catholyte LC as necessary. Alternatively, the catholyte tank 4 may function as an oil-water separator. In the organic hydride production system 1 according to the present embodiment, the catholyte LC is circulated between the cathode electrode 8 and the catholyte tank 4. However, the present invention is not limited to this configuration, and the catholyte LC may be sent to the outside of the system from the cathode electrode 8 without being returned to the catholyte tank 4.
The anolyte tank 6 is connected to the anode flow path 20 via the first anode pipe 30 and the second anode pipe 32. The anolyte LA is stored in the anolyte tank 6. One end of the first anode pipe 30 is connected to the anolyte tank 6, and the other end of the first anode pipe 30 is connected to the entrance of the anode flow path 20. An anode pump 34 is provided in the middle of the first anode pipe 30. The anode pump 34 can be constituted by a known pump such as a gear pump or a cylinder pump, for example. The distribution of the anolyte LA may be realized by a liquid feeding device other than a pump. One end of the second anode pipe 32 is connected to the exit of the anode flow path 20, and the other end of the second anode pipe 32 is connected to the anolyte tank 6.
The anolyte LA contains water. When the electrolyte membrane 12 is proton conductive, examples of the anolyte LA include: acidic solutions such as an aqueous sulfuric acid solution, an aqueous nitric acid solution, and an aqueous hydrochloric acid solution; pure water; ion-exchanged water; and the like. Preferably, the pH of the anolyte LA is 8 or less. When the electrolyte membrane 12 is anion conductive, examples of the anolyte LA include: an alkaline solution such as an aqueous solution of potassium hydroxide; ion-exchanged water; an aqueous solution containing an inorganic electrolyte such as potassium sulfate; and the like. Preferably, the pH of the anolyte LA is 6 or more.
The anolyte LA in the anolyte tank 6 flows into the anode electrode 10 through the first anode pipe 30 by driving of the anode pump 34. When the electrolyte membrane 12 is proton conductive, the water in the anolyte LA that flows into the anode electrode 10 is subjected to an electrode reaction at the anode electrode 10. When the electrolyte membrane 12 is anion conductive, the water in the anolyte LA flowing into the anode electrode 10 diffuses to the cathode electrode 8 side via the electrolyte membrane 12 and is subjected to the electrode reaction at the cathode electrode 8. The anolyte LA in the anode electrode 10 is returned to the anolyte tank 6 through the second anode pipe 32. As an example, the anolyte tank 6 also functions as a gas-liquid separator. In the anode electrode 10, oxygen gas is generated by the electrode reaction.
Therefore, the oxygen gas is mixed into the anolyte LA discharged from the anode electrode 10. The anolyte tank 6 separates the oxygen gas in the anolyte LA from the anolyte LA and discharges the oxygen gas to the outside of the system.
A gas-liquid separator may be provided separately from the anolyte tank 6. In the organic hydride production system 1 according to the present embodiment, the anolyte LA is circulated between the anode electrode 10 and the anolyte tank 6. However, the present invention is not limited to this configuration, and the anolyte LA may be sent from the anode electrode 10 to the outside of the system without being returned to the anolyte tank 6.
The organic hydride production device 2 is supplied with power from a power supply 22. The supply of power from the power supply 22 causes a predetermined electrolytic voltage to be applied between the cathode electrode 8 and the anode electrode 10, and an electrolytic current thus flows. The power supply 22 sends power supplied from an external power supply device 38 to the organic hydride production device 2. The power supply device 38 can be constituted by a power generation device that generates power using renewable energy, for example, a wind power generation device 40, a solar power generation device 42, or the like. The power supply device 38 is not limited to a power generation device using renewable energy, and may be a system power supply, a power storage device storing electric power from the renewable energy power generation device or the system power supply, or the like. A combination of two or more of these devices may be used.
When the electrolyte membrane 12 is proton conductive, the reactions that occur in the organic hydride production device 2 are as follows. In the following reaction, toluene (TL) is shown as an example of the hydrogenation target substance. The organic hydride obtained in a case where toluene is used as the hydrogenation target substance is methylcyclohexane (MCH).

<Electrode Reaction at Anode Electrode>

3H₂O → 3/2O₂ + 6H⁺ + 6e^-
<Electrode Reaction at Cathode Electrode>

TL + 6H⁺ + 6e^- → MCH

That is, the electrode reaction at the anode electrode 10 and the electrode reaction at the cathode electrode 8 proceed in parallel. At the anode electrode 10, the oxidation reaction of water occurs, producing oxygen, protons, and electrons. The protons produced move through the electrolyte membrane 12 to the cathode electrode 8. The electrons are sent to the cathode electrode 8 via the power source 22. The oxygen is discharged from the anode flow path 20 to the outside of the organic hydride production device 2. At the cathode electrode 8, toluene is electrochemically hydrogenated (reduced) to produce methylcyclohexane by the reaction between the toluene contained in the catholyte LC and the protons transferred from the anode electrode 10 side. The methylcyclohexane generated is discharged from the cathode flow path 18 to the outside of the organic hydride production device 2.
When the electrolyte membrane 12 is anion conductive, the reactions that occur in the organic hydride production device 2 are as follows. In the following reaction, toluene is shown as an example of the hydrogenation target substance.

<Electrode Reaction at Cathode Electrode>

TL + 6H₂O + 6e^- → MCH + 6OH^-
<Electrode Reaction at Anode Electrode>

6OH^- → 3/2O₂ + 3H₂O + 6e^-

That is, the electrode reaction at the cathode electrode 8 and the electrode reaction at the anode electrode 10 proceed in parallel. At the cathode electrode 8, toluene is electrochemically hydrogenated (reduced) to produce methylcyclohexane and hydroxide ions by the reaction between the toluene contained in the catholyte LC and the water diffused from the anode electrode 10 side. The methylcyclohexane is discharged from the cathode flow path 18 to the outside of the organic hydride production device 2. The hydroxide ions pass through the electrolyte membrane 12 and move to the anode electrode 10. At the anode electrode 10, the oxidation reaction of the hydroxide ions migrating from the cathode electrode 8 side occurs, producing oxygen, water, and electrons. The electrons are supplied to the cathode electrode 8 via the power supply 22 and used for the electrode reaction at the cathode electrode 8. The oxygen and the water are discharged from the anode flow path 20 to the outside of the organic hydride production device 2.
Therefore, according to the organic hydride production device 2 according to the present embodiment, the electrolysis of water and the hydrogenation reaction of the hydrogenation target substance can be performed in one step. Alternatively, the oxidation reaction of the hydroxide ions and the hydrogenation reaction of the hydrogenation target substance can be performed in one step. For this reason, organic hydride production efficiency can be increased as compared with a conventional technique in which the organic hydride is produced by a two-step process which includes a process of producing hydrogen by water electrolysis or the like and a process of chemically hydrogenating the hydrogenation target substance in a reactor such as a plant. Furthermore, since the reactor for performing the chemical hydrogenation and a high-pressure vessel for storing the hydrogen produced by the water electrolysis or the like are not required, a significant reduction in facility cost can be achieved.
The organic hydride production device 2 according to the present embodiment has a current decrease rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to the anolyte LA supplied to the anode electrode 10 in predetermined constant voltage electrolysis or has a voltage increase rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to the anolyte LA in the predetermined constant current electrolysis.
By setting the current decrease rate after 10 hours to 1% or less, a prominent current decrease over the lifetime of the organic hydride production device 2 can be prevented. Therefore, the equipment utilization rate of the organic hydride production system 1 can be maintained and the operating costs can be improved. Further, by setting the voltage increase rate after 10 hours to 1% or less, the increase in electricity costs for operating the organic hydride production system 1 can be reduced and the operating costs can be improved.
In addition, the organic hydride production device 2 according to the present embodiment has a Faraday efficiency of 0.1% or less for generating at least one product selected from the group consisting of: a product in which a hydroxy group is bonded to the hydrogenation target substance or the organic hydride (hereinafter referred to as oxidation product I as appropriate); a product in which an aldehyde group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride has been changed to an aldehyde group (hereinafter referred to as oxidation product II as appropriate); and a product in which a carboxy group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride is changed to a carboxy group (hereinafter referred to as oxidation product III as appropriate), when electrolysis is performed for 50 hours after 200 ppm or more of the hydrogenation target substance or the organic hydride is added to the anolyte LA supplied to the anode electrode 10.
This allows the cost of removing oxidation products I to III from the anolyte LA to be controlled, thereby improving the operating costs of the organic hydride production system 1.
The organic hydride production device 2 according to the present embodiment causes a reaction to proceed at each electrode at a pressure between 1 atm and 3 atm, both inclusive, and at a temperature between 20°C and 70°C, both inclusive. The reaction temperature is more preferably between 20°C and 60°C, both inclusive. The potential of the anode electrode 10 is preferably 0 to 2.07 V vs. RHE.
The embodiments may be defined by the items described in the following.

[Item 1]

An organic hydride production device (2) including:

an anode electrode (10) having a high-entropy alloy, as an anode catalyst (11), containing a base metal element;
a cathode electrode (8); and
an electrolyte membrane (12) positioned between the anode electrode (10) and the cathode electrode (8),
wherein the anode electrode (10) oxidizes water or hydroxide ions, and
wherein the cathode electrode (8) electrochemically reduces a hydrogenation target substance so as to produce an organic hydride.

[Item 2]

The organic hydride production device (2) according to Item 1,
wherein the high-entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cr, Ti, Zr, Nb, Mo, and Cu.

[Item 3]

The organic hydride production device (2) according to Item 2,
wherein the high-entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co, and Ni and at least one element selected from the group consisting of Cr, Ti, Zr, Nb, Mo, and Cu.

[Item 4]

The organic hydride production device (2) according to any one of Items 1 through 3,
wherein all the constituent elements of the high-entropy alloy are base metal elements.

[Item 5]

The organic hydride production device (2) according to any one of Items 1 through 4, having:
a current decrease rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to an anolyte (LA) supplied to the anode electrode (10) in predetermined constant voltage electrolysis or a voltage increase rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to the anolyte (LA) in predetermined constant current electrolysis.

[Item 6]

The organic hydride production device (2) according to any one of Items 1 through 5, having:
a Faraday efficiency of 0.1% or less for generating at least one product selected from the group consisting of: a product in which a hydroxy group is bonded to the hydrogenation target substance or the organic hydride; a product in which an aldehyde group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride is changed to an aldehyde group; and a product in which a carboxy group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride is changed to a carboxy group, when electrolysis is performed for 50 hours after 200 ppm or more of the hydrogenation target substance or the organic hydride is added to an anolyte (LA) supplied to the anode electrode (10).

[Item 7]

The organic hydride production device (2) according to any one of Items 1 through 6,
wherein in the anode catalyst (11), the dissolution rate of elements contained in the high-entropy alloy when a rated current is applied or when a rated voltage is applied is 60 µg/h or less per one gram of the anode catalyst (11), or the dissolution rate of elements contained in the high-entropy alloy when immersed in an acidic solution of pH 4.0 or less is 60 µg/h or less per one gram of the anode catalyst (11).

[Item 8]

The organic hydride production device (2) according to any one of Items 1 through 7 that causes a reaction to proceed at each electrode (8 and 10) at a pressure between 1 atm and 3 atm, both inclusive, and at a temperature between 20°C and 70°C, both inclusive.

[Item 9]

An organic hydride production method that uses an organic hydride production device (2) including an anode electrode (10) having a high-entropy alloy, as an anode catalyst (11), containing a base metal element, a cathode electrode (8), and an electrolyte membrane (12) positioned between the anode electrode (10) and the cathode electrode (8), including:

oxidizing water or hydroxide ions at the anode electrode (10); and
electrochemically reducing a hydrogenation target substance so as to produce an organic hydride at the cathode electrode (8).

[Item 10]

The organic hydride production method according to Item 9, including:

applying an aging treatment in advance to the anode catalyst (11),
wherein the aging treatment includes at least one of electrolysis of an electrolyte using the anode catalyst (11) and immersion of the anode catalyst (11) in an acidic solution of pH 4.0 or less.

Exemplary Embodiments

Hereinafter, exemplary embodiments of the present invention will be explained. However, the exemplary embodiments are merely examples for suitably explaining the present invention and do not limit the present invention in any way.

[Preparation of Anode Electrode]

(First Exemplary Embodiment)

Ingots of Mn, Fe, Co, Ni, Cr, Ti, Zr, Nb, and Mo metals were added into an arc melting furnace. The amount of each of the ingots added was adjusted such that the composition ratio of each metal in a high-entropy alloy was 11.1 atm%. Then, the ingots were arc-melted in a pure Ar atmosphere. In the arc melting process, the base metal was completely melted, and then the ingots were rotated and remelted. This operation was repeated six times or more so as to mix the metals uniformly. The resulting ingot of high-entropy alloy (9eHEA) was formed into a sheet having a predetermined area so as to obtain an anode electrode according to the first exemplary embodiment.

(Second Exemplary Embodiment)

An anode electrode according to the second exemplary embodiment consisting of a high-entropy alloy (10eHEA) was prepared in the same manner as in the first exemplary embodiment, except that Cu was added to the nine metals used in the first exemplary embodiment so as to use ten metals. The amount of each of the ingots added was adjusted such that the composition ratio of each metal in a high-entropy alloy was 10 atm%.

(First Comparative Example)

According to the paper by Zhao et al., Electrochimica Acta 391, 2021, an anode electrode according to the first comparative example was prepared by depositing IrO_X on a Ti film by cyclic voltammetry.

[Preparation of organic Hydride Production Device]

An H-shaped cell divided into two spaces by a proton exchange membrane Nafion 117 fixed in the center was prepared. The anode electrode according to the first exemplary embodiment, the second exemplary embodiment, or the first comparative example was inserted as a working electrode into one space of the H-shaped cell. A reference electrode and a stirrer were also inserted into the space. In the other space of the H-shaped cell, a Pt mesh was inserted as a counter electrode. Then, 15 mL of a 0.5 mol/L aqueous sulfuric acid solution was poured into each of the spaces, and the organic hydride production device (hereinafter, referred to as a cell as appropriate) according to each of the exemplary examples and the comparative example was prepared.

[Toluene Poisoning Test]

A 1/4-inch PTFE tube was inserted into the working electrode side of each cell. The PTFE tube was inserted until the tip thereof reached near the center of the aqueous solution in the cell. While stirring the aqueous solution on the working electrode side, constant potential electrolysis was performed at a potential of 2.0 V vs. RHE at the working electrode. The current in each cell was measured, and the current density was calculated. After the current stabilized, a sufficient amount of toluene was dripped from the top end of the tube while electrolysis continued. Thereby, a two-layer structure of an aqueous sulfuric acid solution and toluene was formed in the tube. This resulted in a condition where the aqueous sulfuric acid solution was saturated with toluene and a condition where undissolved toluene was not attached to the surface of the working electrode. Under these conditions, the constant potential electrolysis was continued.
Fig. 2 is a diagram showing the current density of each cell in a toluene poisoning test. As shown in Fig. 2, a sharp decrease in the current density was observed after the addition of toluene in the first comparative example. On the other hand, the decrease in the current density was gradual even after the addition of toluene in the first and second exemplary embodiments. From this result, it is confirmed that the high-entropy alloys have higher durability against the hydrogenation target substance than Ir. Therefore, it is shown that the use of a high-entropy alloy as an anode catalyst increases the durability of the anode catalyst.
The aqueous sulfuric acid solution on the working electrode side in each of the exemplary embodiments and the comparative example was collected after the test. Each aqueous sulfuric acid solution was then mixed with ether, and by-products in each aqueous sulfuric acid solution were extracted into the ether. This ether was measured using a gas chromatograph mass spectrometer (GC/MS: JMS-T100 GCV, manufactured by JEOL) to analyze the components of the by-products. Component analysis of the byproducts was also conducted for a case where constant potential electrolysis was conducted at a potential of 1.6 V vs. RHE for the working electrode and a case where constant potential electrolysis was conducted at a potential of 1.8 V vs. RHE for the working electrode. The results are shown in Fig. 3.
Fig. 3 is a diagram showing by-products generated by constant-potential electrolysis. As shown in Fig. 3, in the first comparative example, benzaldehyde, benzyl alcohol, and benzoic acid, which are oxidation products of toluene, were detected at a potential of 2.0 V vs. RHE. Benzaldehyde and benzyl alcohol were detected at potentials of 1.6 V vs. RHE and 1.8 V vs. RHE. On the other hand, only benzaldehyde was detected at all of potentials in the first exemplary embodiment. In the second exemplary embodiment, benzaldehyde and benzoic acid were detected at a potential of 2.0 V vs. RHE, and benzaldehyde was detected at a potential of 1.8 V vs. RHE. No toluene oxidation products were detected at a potential of 1.6 V vs. RHE.
Benzaldehyde corresponds to a product in which a part of the hydrogenation target substance, i.e., the methyl group of toluene, is converted into an aldehyde group. Benzyl alcohol corresponds to a product in which a hydroxyl group is bonded to toluene, which is a hydrogenation target substance. Benzoic acid corresponds to a product in which a part of the hydrogenation target substance, i.e., the methyl group of toluene, is converted to a carboxyl group.
After the test, the working electrodes according to the first exemplary embodiment and the first comparative example were taken out, and FT-IR analysis was performed on each working electrode using a Fourier Transform Infrared Spectrophotometer (FT-IR: IRTracer-100, manufactured by Shimadzu Corporation). The removed working electrodes were immersed in ethanol for five days and then washed. Each of the washed working electrodes was then vacuum dried for 24 hours. FT-IR analysis was then performed on each of the working electrodes after washing using FT-IR. The results are shown in Figs. 4A and 4B.
Fig. 4A is a diagram showing results of FT-IR analysis for the working electrode according to the first exemplary embodiment after a toluene poisoning test. Fig. 4B is a diagram showing results of FT-IR analysis for the working electrode according to the first comparative example after a toluene poisoning test. In Figs. 4A and 4B, the results before washing are shown by solid lines, and the results after washing are shown by dashed lines. As shown in Fig. 4B, peaks derived from toluene polymers and polymers of oxidation products, i.e., CH₂ and CH₃ derived peaks, were observed both before and after washing in the first comparative example. On the other hand, as shown in Fig. 4A, no such peaks were observed in the first exemplary embodiment either before or after washing. From this result, it is confirmed that the surface of an anode electrode containing a high-entropy alloy is less susceptible to polymerization of the hydrogenation target substance and the oxidation products thereof and is therefore less susceptible to poisoning by the hydrogenation target substance, etc. Therefore, it is shown that the use of a high-entropy alloy as an anode catalyst increases the durability of the anode catalyst.

[Toluene Oxidation Product Poisoning Test]

Using the cell according to the first exemplary embodiment described above, constant potential electrolysis was performed at a potential of 2.0 V vs. RHE for the working electrode. Using the cell according to the first comparative example described above, constant potential electrolysis was performed at a potential of 1.6 V vs. RHE at the working electrode. The current in each cell was measured, and the current density was calculated. Constant potential electrolysis was carried out for two hours while stirring the aqueous solution on the working electrode side, and then 0.2 mmol of benzyl alcohol, benzaldehyde, or benzoic acid was added to the aqueous solution on the working electrode side of each cell while continuing the electrolysis.
Fig. 5A is a diagram showing the current density of a cell according to the first exemplary embodiment in a toluene oxidation product poisoning test. Fig. 5B is a diagram showing the current density of a cell according to the first comparative example in a toluene oxidation product poisoning test. As shown in Fig. 5B, for all of benzyl alcohol, benzaldehyde, and benzoic acid, a significant decrease in the current density was observed after the addition in the first comparative example. In particular, for benzyl alcohol and benzoic acid, the current density dropped rapidly immediately after the addition. On the other hand, as shown in Fig. 5A, the decrease in the current density was more gradual for all of benzyl alcohol, benzaldehyde, and benzoic acid in the first exemplary embodiment compared to the first comparative example. In particular, the current density was remarkably maintained for benzyl alcohol and benzaldehyde compared to benzoic acid.
From this result, it is confirmed that the high-entropy alloys have higher durability against the oxidation products of the hydrogenation target substance than Ir. Therefore, it is shown that the use of a high-entropy alloy as an anode catalyst increases the durability of the anode catalyst. Further, no benzoic acid was produced in the first exemplary embodiment (see Fig. 3), indicating that the anode electrode according to the first exemplary embodiment is even more durable than the anode electrode according to the second exemplary embodiment. In addition, no benzoic acid was produced at a potential of 1.8 V vs. RHE or less in the first and second exemplary embodiments (see Fig. 3), indicating that constant potential electrolysis is preferably performed at a potential of 1.8 V vs. RHE or less for the anode electrode.
After the test, the working electrode of each cell was removed and washed by immersion in ethanol for five days. Each of the washed working electrodes was then vacuum dried for 24 hours. FT-IR analysis was then performed on each of the working electrodes after washing using FT-IR. The results are shown in Figs. 6A and 6B. Figs. 6A and 6B also include the results of the FT-IR analysis shown in Figs. 4A and 4B for reference.
Fig. 6A is a diagram showing results of FT-IR analysis for the working electrode according to first exemplary embodiment after a toluene oxidation product poisoning test. Fig. 6B is a diagram showing results of FT-IR analysis for the working electrode according to the first comparative example after a toluene oxidation product poisoning test. As shown in Fig. 6B, peaks derived from the polymerization of oxidation products, i.e., CH₂ and CH₃ derived peaks, were observed in the first comparative example when benzyl alcohol and benzoic acid were added. On the other hand, as shown in Fig. 6A, no such peaks were observed in the first exemplary embodiment regardless of the addition of any of the oxidation products. From this result, it is confirmed that the surface of an anode electrode containing a high-entropy alloy is less susceptible to polymerization of the oxidation products of the hydrogenation target substance and is therefore less susceptible to poisoning by the hydrogenation target substance, etc. Therefore, it is shown that the use of a high-entropy alloy as an anode catalyst increases the durability of the anode catalyst.

INDUSTRIAL APPLICABILITY

The present invention can be used for organic hydride production devices and organic hydride production methods.

REFERENCE SIGNS LIST

2 organic hydride production device, 8 cathode electrode, 9 cathode catalyst, 10 anode electrode, 11 anode catalyst, 12 electrolyte membrane

Claims

An organic hydride production device comprising:
an anode electrode having a high-entropy alloy, as an anode catalyst, containing a base metal element;

a cathode electrode; and

an electrolyte membrane positioned between the anode electrode and the cathode electrode,

wherein the anode electrode oxidizes water or hydroxide ions, and

wherein the cathode electrode electrochemically reduces a hydrogenation target substance so as to produce an organic hydride.
The organic hydride production device according to Claim 1,
wherein the high-entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cr, Ti, Zr, Nb, Mo, and Cu.
The organic hydride production device according to Claim 2,
wherein the high-entropy alloy contains at least one element selected from the group consisting of Mn, Fe, Co, and Ni and at least one element selected from the group consisting of Cr, Ti, Zr, Nb, Mo, and Cu.
The organic hydride production device according to Claim 1,
wherein all the constituent elements of the high-entropy alloy are base metal elements.
The organic hydride production device according to any one of Claims 1 through 4, having:
a current decrease rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to an anolyte supplied to the anode electrode in predetermined constant voltage electrolysis or a voltage increase rate of 1% or less after 10 hours when 200 ppm or more of the hydrogenation target substance or the organic hydride is added to an anolyte in predetermined constant current electrolysis.
The organic hydride production device according to any one of Claims 1 through 4, having:
a Faraday efficiency of 0.1% or less for generating at least one product selected from the group consisting of: a product in which a hydroxy group is bonded to the hydrogenation target substance or the organic hydride; a product in which an aldehyde group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride is changed to an aldehyde group; and a product in which a carboxy group is bonded to the hydrogenation target substance or the organic hydride or in which a part of the hydrogenation target substance or the organic hydride is changed to a carboxy group, when electrolysis is performed for 50 hours after 200 ppm or more of the hydrogenation target substance or the organic hydride is added to an anolyte supplied to the anode electrode.
The organic hydride production device according to any one of Claims 1 through 4,
wherein in the anode catalyst, the dissolution rate of elements contained in the high-entropy alloy when a rated current is applied or when a rated voltage is applied is 60 µg/h or less per one gram of the anode catalyst, or the dissolution rate of elements contained in the high-entropy alloy when immersed in an acidic solution of pH 4.0 or less is 60 µg/h or less per one gram of the anode catalyst.
The organic hydride production device according to any one of Claims 1 through 4 that causes a reaction to proceed at each electrode at a pressure between 1 atm and 3 atm, both inclusive, and at a temperature between 20°C and 70°C, both inclusive.
An organic hydride production method that uses an organic hydride production device comprising an anode electrode having a high-entropy alloy, as an anode catalyst, containing a base metal element, a cathode electrode, and an electrolyte membrane positioned between the anode electrode and the cathode electrode, comprising:
oxidizing water or hydroxide ions at the anode electrode; and

electrochemically reducing a hydrogenation target substance so as to produce an organic hydride at the cathode electrode.
The organic hydride production method according to Claim 9, comprising:
applying an aging treatment in advance to the anode catalyst,

wherein the aging treatment includes at least one of electrolysis of an electrolyte using the anode catalyst and immersion of the anode catalyst in an acidic solution of pH 4.0 or less.