Production method and production device for ammonia

Abstract

The present invention pertains to a method for producing ammonia, the method comprising: preparing an electrode body in which a hydride ion conductor is disposed between electrodes of a cathode and an anode; and applying a voltage between the electrodes in a state in which a first gas containing hydrogen gas is supplied onto the surface of the cathode, and a second gas containing nitrogen gas is supplied onto the surface of the anode, wherein the voltage is applied so that the potential of the cathode is lower than the potential of the anode.

Description

Method and apparatus for producing ammonia 【0001】 This invention relates to a method and apparatus for producing ammonia. 【0002】 Ammonia is used as a basic raw material for chemical fertilizers and other products, and in recent years, it has also been found to produce CO2 when burned. ２ It is attracting attention as a carbon-free fuel that emits no emissions, and its market size is very large. 【0003】 For the industrial mass production of ammonia, the Haber-Bosch process has been the primary method used. The Haber-Bosch process is a technique that synthesizes ammonia by chemically reacting hydrogen and nitrogen on a catalyst containing iron or other materials. Although low temperature and high pressure are thermodynamically advantageous for this process, in practice, high temperature and high pressure conditions are adopted from the standpoint of reaction rate. 【0004】 To create such a high-temperature, high-pressure environment, a large amount of energy is required for ammonia synthesis. Therefore, attempts to lower the temperature and pressure of ammonia synthesis have been ongoing for many years. For example, regarding the synthesis temperature, while it was initially achieved to lower it from about 1000°C to around 500°C, it is difficult to lower it even further using synthesis methods that utilize thermal catalytic reactions. 【0005】 In contrast, for example, Patent Document 1 discloses that ammonia can be synthesized at a reaction temperature of 500°C by an ammonia electrosynthesis reaction using a proton-conducting solid electrolyte. Non-Patent Document 1 also discloses that ammonia can be synthesized by an ammonia electrosynthesis reaction under conditions of 220°C and atmospheric pressure. 【0006】 Japanese Patent Application Publication No. 2021-059747 【0007】 Y. Yuan et al. , RSC Advances, Issue 14, 8474-8476, 2022 【0008】 Thus, while the synthesis method disclosed in non-patented patent 1 achieved lower temperatures for ammonia synthesis compared to the synthesis method disclosed in patent document 1, the reaction temperature remains high. 【0009】 Therefore, an object of the present invention is to provide a new method for producing ammonia and an apparatus for producing ammonia that enable synthesis at normal temperature and pressure. 【0010】 The inventors of the present invention have conducted intensive studies and conceived of applying a hydride ion (H － ) conductor with expected specific reaction activity to ammonia synthesis. H － has a monovalent valence and an appropriate ionic radius comparable to that of O ２－ or F － and has a large polarizability while being a light element because the electronegativity of hydrogen is comparable to that of carbon (C) or boron (B). All of these characteristics are suitable for fast ion conduction, and it was considered that the development of an ion conductor using H － as a mobile ion could be expected. In addition, since the diffusion mechanism is significantly different from that of the H ＋ conductor and humidification is not required for ion conduction, fast ion conduction is possible even in the medium temperature range where it is difficult to utilize the conduction of H ＋ or O ２－ without humidification. － That is, if it is H 【0011】 As a result of further studies, it was realized that highly electrochemically active hydride ions are continuously supplied even at normal temperature and pressure, and ammonia is continuously synthesized from N ２ 【0012】 That is, the present invention and other aspects of the present invention relate to the following [1] to [8]. [1] Preparing an electrode body in which a hydride ion conductor is disposed between electrodes of a cathode and an anode, and applying a voltage between the electrodes in a state where a first gas containing hydrogen gas is supplied onto the surface of the cathode and a second gas containing nitrogen gas is supplied onto the surface of the anode, The method for producing ammonia, wherein the voltage is applied so that the potential of the cathode is lower than the potential of the anode. [2] The method for producing ammonia according to [1] above, wherein the hydride ion conductor uses a metal hydride represented by the following formula (1). M １ ｘ M ２ （２－ｘ） H（ｘ＋２） (1) (In formula (1), M １ is at least one element selected from the group consisting of Ca, Sr, and Ba, and M ２ (x is at least one element selected from the group consisting of Li, Na, and K, and 0 < x < 2.) [3] The method for producing ammonia according to [1] or [2], wherein the cathode is an electrode comprising at least one of a metal and a metal hydride, and the metal constituting the metal and metal hydride is at least one selected from the group consisting of La, Pt, and Pd. [4] The method for producing ammonia according to any one of [1] to [3], wherein the anode is an electrode comprising at least one of a metal and a metal hydride, and the metal constituting the metal and metal hydride is at least one selected from the group consisting of Fe, Ru, Ni, Nb, W, Mo, and Pd. [5] The method for producing ammonia according to any one of [1] to [4], wherein the voltage is applied under conditions of 200°C or lower. [6] The first gas is supplied to the surface of the cathode at a hydrogen gas flow rate of 0.02 mL / min·mm per electrode area. ２ ~2.5mL / min・mm ２ A method for producing ammonia according to any one of [1] to [5] above, wherein the ammonia is supplied in such manner. [7] The second gas is supplied on the surface of the anode at a nitrogen gas flow rate of 0.02 mL / min·mm per electrode area. ２ ~2.5mL / min・mm ２ A method for producing ammonia according to any one of [1] to [6] above, wherein the ammonia is supplied in such a manner. 【0013】 [8] An ammonia production apparatus comprising: a pair of electrodes, a cathode and an anode; a hydride ion conductor disposed between the electrodes; a voltage application unit for applying a voltage between the electrodes; a first gas supply unit for supplying a first gas containing hydrogen gas onto the surface of the cathode; and a second gas supply unit for supplying a second gas containing nitrogen gas onto the surface of the anode. 【0014】 According to the manufacturing method of the present invention, ammonia can be synthesized at room temperature and atmospheric pressure. 【0015】 Figure 1 is a schematic diagram showing one embodiment of the method for producing ammonia according to this embodiment. 【0016】 The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified and implemented as appropriate without departing from the spirit of the invention. Furthermore, the "~" indicating a numerical range is used to mean that the numbers written before and after it are included as the lower limit and upper limit. In this specification, mass% and weight% are synonymous. 【0017】 《Method for Producing Ammonia》 The method for producing ammonia according to this embodiment includes the following steps: Step 1: A step of preparing an electrode body in which a hydride ion conductor is placed between the cathode and anode electrodes. Step 2: A step of applying a voltage between the electrodes while supplying a first gas containing hydrogen gas onto the surface of the cathode and a second gas containing nitrogen gas onto the surface of the anode. The voltage applied in Step 2 is performed such that the potential of the cathode is lower than the potential of the anode. 【0018】 Figure 1 shows a schematic diagram of the ammonia production method according to this embodiment. In this embodiment, the electrode body 10 has a hydride ion conductor 3 placed between the cathode 1 and anode 2 electrodes. Then, in step 2, a first gas (gas1(H) containing hydrogen gas is placed on the surface of the cathode 1. ２ )) on the surface of anode 2, a second gas (gas2(N) containing nitrogen gas is added. ２ With the respective supplies of (e)(a － ) plays. 【0019】 As described above, the hydrogen gas supplied to cathode 1 results in 1 / 2 nH ２ +ne － →nH － The following reactions occur, and the H produced － The H ions move to the anode 2 via the hydride ion conductor 3. At the anode 2, the H ions that have moved in － And with the supplied nitrogen gas, 1 / 6 nN２ +nH － → 1 / 3nNH ３ +ne － Ammonia is synthesized through the following reactions. 【0020】 In this embodiment, ammonia is synthesized by the above reaction without the need for a separate catalyst. Therefore, unlike a batch reaction, hydride ions are continuously supplied to anode 2, and thus ammonia can be synthesized continuously. 【0021】 <Step 1> Hydride ion conductor In this embodiment, a conventionally known metal hydride can be used as the hydride ion conductor. For example, Ba （２－ｘ－ｍ） A ｘ Mg （１－ｙ－ｎ） B ｙ H （６－ｘ－ｙ－２ｍ－２ｎ） (In the formula, A and B are each one or more alkali metal elements, and 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ m ≤ 0.2, 0 ≤ n ≤ 0.2, except x = y = m = n = 0.) M １ ｘ M ２ （１－ｘ） H （ｘ＋ａ） (In the formula, M １ M is two or more elements selected from the Group 2 elements. ２ x is one or more elements selected from Group 1 elements, where 0 < x < 1. ), M １ ｘ M ２ （２－ｘ） H （ｘ＋２） (In the formula, M １ is at least one element selected from the group consisting of Ca, Sr, and Ba, and M ２ (where x is at least one element selected from the group consisting of Li, Na, and K, and 0 < x < 2.) These can be used individually or in combination of two or more. 【0022】 Among these, hydride ion conductors with high hydride ion conductivity in the room temperature range are preferred, and such hydride ion conductors include, for example, M １ ｘ M ２ （２－ｘ） H（ｘ＋２） (In the formula, M １ is at least one element selected from the group consisting of Ca, Sr, and Ba, and M ２ A is at least one element selected from the group consisting of Li, Na, and K, and 0 < x < 2.) Examples include . Furthermore, a hydride ion conductor having oxidation resistance is preferred, and such a hydride ion conductor is a material in which a part of the hydride is replaced with nitrogen, oxygen, or fluorine M'M''H （４－ｘ） F ｘ (In the formula, M' is Ca, Sr, or Ba, and M'' is Mg or Ca, different from M', and 0 < x < 4.) 【0023】 More specifically, as a hydride ion conductor, Sr ０．８ Na ０．２ LiH ２．８ It is preferable to use 【0024】 The thickness of the hydride ion conductor placed between the cathode and anode electrodes is not particularly limited, but may be, for example, 5 to 1000 μm. Here, from the viewpoint of gas and electron leakage, the thickness is preferably 5 μm or more, and more preferably 10 μm or more. Also, from the viewpoint of resistance, the thickness is preferably 1000 μm or less, and more preferably 500 μm or less. 【0025】 • Cathode In this embodiment, the material of the cathode is not particularly limited, as long as hydride ions are generated on its electrode surface by a reaction between hydrogen gas and electrons. For example, it is preferable to use an electrode containing at least one of a metal and a metal hydride as the cathode, and it is more preferable to use an electrode in which the metal constituting the metal and metal hydride is at least one selected from the group consisting of La, Pt, and Pd. 【0026】 In this embodiment, the cathode more preferably uses an electrode containing a metal hydride from the viewpoint of generating hydride ions and improving hydride ion conductivity within the electrode, and even more preferably uses an electrode containing at least one metal hydride selected from the group consisting of La, Pt, and Pd. These may be used individually or in combination of two or more. 【0027】 In this embodiment, the cathode is more preferably made of a hydride having hydride ion conductivity in addition to the metal hydride, from the viewpoint of increasing the number of reaction active sites. The hydride having hydride ion conductivity can be the same as that exemplified as the hydride ion conductor. Furthermore, the hydride having hydride ion conductivity may be the same as the hydride ion conductor used or a different one, but from the viewpoint of reducing interfacial resistance, it is preferable to use the same one. In addition, two or more types of hydride ion conductive hydrides may be used. 【0028】 When the cathode contains a hydride having hydride ion conductivity in addition to a metal hydride, the total content of the hydride having hydride ion conductivity relative to the entire cathode is preferably, for example, 5 to 80% by mass. Here, from the viewpoint of ionic conductivity within the cathode, the above content is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more. Furthermore, from the viewpoint of obtaining a high energy density, the above content is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less. 【0029】 The cathode in this embodiment may further contain an electron conduction aid. The electron conduction aid is preferable to include in order to maintain good electron conduction as an electrode even when the electron conductivity of the cathode decreases due to electrode reactions in the cathode. 【0030】 Examples of electron conduction aids include conductive carbon. Examples of conductive carbon include graphite, fibrous graphite, amorphous carbon, activated carbon, graphene, carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal black), carbon fiber, mesocarbon microbeads, microencapsulated carbon, fullerene, carbon nanoform, carbon nanotube, and carbon nanohorn. These may be used individually or in combination of two or more. 【0031】When the cathode contains an electron conduction aid in addition to a metal hydride, the total content of the electron conduction aid relative to the entire cathode is preferably, for example, 1 to 30% by mass. Here, from the viewpoint of improving electron conductivity, the above content is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. Furthermore, from the viewpoint of obtaining a high energy density, the above content is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. 【0032】 In addition to the above, the cathode may further contain other components, provided that they do not inhibit the reaction on the electrode. 【0033】 The thickness of the cathode is not particularly limited, but may be, for example, 1 to 100 μm. Here, from the viewpoint of current collection, the thickness is preferably 1 μm or more, and more preferably 5 μm or more. Also, from the viewpoint of electrode resistance, the thickness is preferably 100 μm or less, and more preferably 80 μm or less. 【0034】 The method of producing the cathode is not particularly limited, as long as each component is present in a uniform manner. For example, one method is to mix each component together with a binder or the like as needed. The mixing method is also not particularly limited, but examples include methods using a roll-driven mill, ball mill, bead mill (small-diameter ball mill), media-stirring mill, jet mill, mortar and pestle, etc. The above mixing may be done by mixing all components at once or by mixing them sequentially. 【0035】 - Anode In this embodiment, the anode functions as a working electrode on its electrode surface, generating ammonia through a reaction between nitrogen gas and hydride ions. The material of the anode is not particularly limited as long as such a reaction occurs. For example, it is preferable to use an electrode containing at least one of a metal and a metal hydride as the anode, and it is more preferable to use an electrode in which the metal constituting the metal and metal hydride is at least one selected from the group consisting of Fe, Ru, Ni, Nb, W, Mo, and Pd. 【0036】In this embodiment, the anode is more preferably an electrode containing a metal hydride from the viewpoint of generating hydride ions, and even more preferably an electrode containing at least one metal hydride selected from the group consisting of Fe, Ru, Ni, Nb, W, Mo, and Pd. These may be used individually or in combination of two or more. 【0037】 The anode in this embodiment may further contain an electron conduction aid. The electron conduction aid is preferable to include in order to maintain good electron conduction as an electrode even when the electron conductivity of the anode decreases due to electrode reactions in the anode. 【0038】 Examples of electron conduction aids include conductive carbon. Examples of conductive carbon include graphite, fibrous graphite, amorphous carbon, activated carbon, graphene, carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal black), carbon fiber, mesocarbon microbeads, microencapsulated carbon, fullerene, carbon nanoform, carbon nanotube, and carbon nanohorn. These may be used individually or in combination of two or more. 【0039】 When the anode contains an electron conduction aid, the total content ratio of the electron conduction aid to the entire anode is preferably, for example, 0 to 20% by mass. From the viewpoint of obtaining a high energy density, the above content ratio is preferably 20% by mass or less, and more preferably 10% by mass or less. 【0040】 In addition to the above, the anode may further contain other components, provided that they do not inhibit the reaction on the electrode. 【0041】 The thickness of the anode is not particularly limited, but may be, for example, 1 to 100 μm. Here, from the viewpoint of current collection, the thickness is preferably 1 μm or more, and more preferably 5 μm or more. Also, from the viewpoint of electrode resistance, the thickness is preferably 100 μm or less, and more preferably 80 μm or less. 【0042】The method of producing anode is not particularly limited, as long as each component is present in uniform proportions. For example, one method is to mix each component together with a binder or the like as needed. The mixing method is also not particularly limited, but examples include methods using a roll-driven mill, ball mill, bead mill (small-diameter ball mill), media-stirring mill, jet mill, mortar and pestle, etc. The above mixing may be done by mixing all components at once or by mixing them sequentially. 【0043】 - In the manufacturing process 1 of the electrode body, an electrode body is prepared in which a hydride ion conductor is placed between the cathode and anode electrodes as described above. For example, it is preferable to stack the cathode, hydride ion conductor, and anode in that order and pressurize as necessary to improve the adhesion of the interface. In this case, the combination of electrodes for the cathode and anode is not particularly limited, and for example, the aforementioned ones can be used respectively. However, it is more preferable to use, for example, an electrode containing at least one of a metal and a metal hydride, including at least one metal selected from the group consisting of La, Pt, and Pd, as the cathode, and an electrode containing at least one of a metal and a metal hydride, including at least one metal selected from the group consisting of Fe, Ru, Ni, Nb, W, Mo, and Pd, as the anode. Furthermore, for the above electrode combination, the aforementioned Ba （２－ｘ－ｍ） A ｘ Mg （１－ｙ－ｎ） B ｙ H （６－ｘ－ｙ－２ｍ－２ｎ） M １ ｘ M ２ （１－ｘ） H （ｘ＋ａ） M １ ｘ M ２ （２－ｘ） H （ｘ＋２） It is even more preferable to use the like. 【0044】 The effective pressure when pressurizing is preferably 10 to 1000 MPa. Here, from the viewpoint of reducing interfacial resistance and gas sealing performance, the effective pressure is preferably 10 MPa or more, and more preferably 100 MPa or more. Also, from the viewpoint of workability, the effective pressure is preferably 1000 MPa or less, and more preferably 500 MPa or less. 【0045】 The pressurization time is preferably 1 to 30 minutes. Here, from the viewpoint of reducing interfacial resistance and ensuring gas sealing, the pressurization time is preferably 1 minute or more. Furthermore, from the viewpoint of work efficiency, the pressurization time is preferably 30 minutes or less, and more preferably 5 minutes or less. 【0046】 <Step 2> - First gas In step 2 of this embodiment, a first gas containing hydrogen gas is supplied onto the surface of the cathode. The first gas only needs to contain hydrogen gas, and may also be a mixed gas further containing other gases besides hydrogen gas. 【0047】 The hydrogen gas content in the first gas is preferably 1 to 100% by volume. Here, from the viewpoint of reaction efficiency, the above content is preferably 1% by volume or more, and more preferably 50% by volume or more. Alternatively, the above content may be 100% by volume, i.e., consisting only of hydrogen gas. 【0048】 The flow rate of the first gas is not particularly limited, but is preferably determined by the flow rate of hydrogen gas contained in the first gas. The flow rate of hydrogen gas per electrode area supplied onto the surface of the cathode is 0.02 mL / min·mm ２ ~2.5mL / min・mm ２ This is preferable. Here, from the viewpoint of reactivity in the cathode, the above flow rate of hydrogen gas is 0.02 mL / min·mm. ２ The above is preferred, and 0.2 mL / min·mm ２ The above is more preferable. Furthermore, from the viewpoint of raw material conversion rate, the above flow rate of hydrogen gas is 2.5 mL / min·mm. ２ The following are preferable. 【0049】 • Second gas In step 2 of this embodiment, a second gas containing nitrogen gas is supplied onto the surface of the anode. The second gas only needs to contain nitrogen gas, and may also be a mixed gas further containing other gases besides nitrogen gas. 【0050】 The nitrogen gas content in the second gas is preferably 20 to 100% by volume. Alternatively, the above content may be 100% by volume, i.e., consisting solely of nitrogen gas. 【0051】The flow rate of the second gas is not particularly limited, and it is preferably determined by the flow rate of nitrogen gas contained in the second gas. The flow rate of nitrogen gas per electrode area supplied onto the surface of the anode is 0.02 mL / min·mm ２ to 2.5 mL / min·mm ２ is preferable. Here, from the viewpoint of the reactivity in the anode, the above flow rate of nitrogen gas is preferably 0.02 mL / min·mm ２ or more, and more preferably 0.2 mL / min·mm ２ or more. Also, from the viewpoint of the raw material conversion rate, the above flow rate of nitrogen gas is preferably 2.5 mL / min·mm ２ or less. 【0052】 Since the metal hydride reacts with water in the ammonia synthesis reaction, the production method according to this embodiment is preferably carried out in an atmosphere containing as little moisture as possible. For example, it is preferable to use a dry gas which is an atmosphere with a water vapor partial pressure of about 0.1 kPa or less. 【0053】 ・In the applied current density step 2, a voltage is applied between the electrodes of the cathode and the anode to allow a current to flow, but it may be applied so that the potential of the anode becomes higher than the potential of the cathode. Thereby, electrons flow in the direction opposite to the current, and as described above, at the cathode to which hydrogen gas is supplied, 1 / 2nH ２ + ne － → nH － and the like reactions occur. The H － generated by this reaction moves to the anode through the hydride ion conductor. At the anode, the moved H － and the supplied nitrogen gas cause reactions such as 1 / 6nN ２ + nH － → 1 / 3nNH ３ + ne － and the like reactions occur, and ammonia is synthesized. 【0054】 The current density when applying a voltage between the electrodes is preferably, for example, 0.1 μA / mm ２ to 1000 μA / mm ２ is preferable. Here, from the viewpoint of enhancing the reactivity, the above current density is preferably 0.1 μA / mm ２ or more, and 0.15 μA / mm２ The above is more preferable. Furthermore, from the viewpoint of Faraday efficiency, the above current density is 1000 μA / mm². ２ The following is preferable: 500 μA / mm ２ The following are preferable. 【0055】 The temperature at which a voltage is applied between the electrodes to allow current to flow is not particularly limited, and ammonia can be synthesized even at high temperatures. However, from the viewpoint of taking advantage of the feature that ammonia can be synthesized at a lower temperature than conventional methods, and from the viewpoint of reducing energy consumption during production, the temperature may be 200°C or lower, 180°C or lower, 150°C or lower, 100°C or lower, 80°C or lower, 50°C or lower, 30°C or lower, or even room temperature (around 25°C). Furthermore, the lower limit of the above temperature is not particularly limited as long as ammonia is synthesized, but from the viewpoint of hydride ion conductivity and Faraday efficiency, the above temperature is preferably 15°C or higher. 【0056】 In this embodiment, the temperature and pressure when applying voltage and conducting current can be, for example, 200°C or less and 1.5 atm or less. 【0057】 The ammonia synthesized as described above can be recovered by conventionally known methods. For example, ammonia can be recovered by cooling and liquefying and separating, by absorbing with water and separating, or by separating using a separation membrane. 【0058】 《Ammonia Production Apparatus》 The ammonia production apparatus according to this embodiment comprises a pair of electrodes, a cathode and an anode, a hydride ion conductor disposed between the electrodes, a voltage application unit, a first gas supply unit, and a second gas supply unit. The electrode body is formed by the pair of electrodes and the hydride ion conductor disposed between them. The voltage application unit applies a voltage between the electrodes and causes an electric current to flow. The first gas supply unit supplies a first gas containing hydrogen gas onto the surface of the cathode. The second gas supply unit supplies a second gas containing nitrogen gas onto the surface of the anode. 【0059】The cathode, anode, and hydride ion conductor in the manufacturing apparatus according to this embodiment can be the same as those described in the above-mentioned "Method for Producing Ammonia," and the preferred embodiments are also the same. 【0060】 The voltage application unit in this embodiment is not particularly limited as long as a desired potential difference can be provided between the electrodes, and conventionally known units can be used. For example, when controlling voltage, a voltage-controlled power supply (potentiostat) may be used, and when controlling current, a current-controlled power supply (galvanostat) may be used. 【0061】 The first gas supply unit is not particularly limited in its specific form, as long as it can supply a first gas containing hydrogen gas onto the surface of the cathode. The second gas supply unit is not particularly limited in its specific form, as long as it can supply a second gas containing nitrogen gas onto the surface of the anode. 【0062】 In addition to the above, the manufacturing apparatus according to this embodiment preferably further includes a mechanism for recovering the synthesized ammonia and a mechanism for exhausting the waste. The mechanism for recovering the synthesized ammonia can be a conventionally known mechanism. For example, ammonia can be recovered by the aforementioned methods of cooling and liquefying for separation, absorbing with water for separation, or separating using a separation membrane. 【0063】 The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. Example 1 is a reference example, and Example 2 is an example. 【0064】 • Hydride ion conductor: Sr ０．８ Na ０．２ LiH ２．８ Manufacturing of Sr ０．８ Na ０．２ LiH ２．８ It was manufactured using the following procedure: Starting material: SrH ２The mixture was weighed in an Ar glove box so that the ratio of (Aldrich):LiH (Alfa Aesar):NaH (Aldrich) was 0.8:0.2:1 (molar ratio). Synthesis was carried out by a mechanochemical reaction of the mixture using a planetary ball mill (Fritch, P-7) at 600 rpm for 12 hours under an Ar atmosphere. The planetary ball mill used a zirconia pot (45 mL, inner diameter 4 cm) and 18 zirconia balls (diameter 10 mm). The sample synthesized above was measured by X-ray diffraction (XRD) using CuKα1 radiation (Rigaku, SmartLab) to determine the presence of Sr ０．８ Na ０．２ LiH ２．８ We confirmed that the composition was as described above, and that a single perovskite phase could be synthesized. 【0065】 [Example 1] - Manufacturing of cathode composite electrodes Sr manufactured as described above ０．８ Na ０．２ LiH ２．８ Using LaH in an argon glove box ｘ (2≦x<3): Sr ０．８ Na ０．２ LiH ２．８ The acetylene black was weighed to a ratio of 20:75:5 (mass ratio). Then, the cathode electrode mixture was synthesized by ball mill mixing under an Ar atmosphere (planetary ball mill, Fritch, P-7). A zirconia pot (45 mL, inner diameter 4 cm) and 75 zirconia balls (diameter 5 mm) were used in the ball mill. Here, LaH ｘ For (2 ≤ x < 3), lanthanum hydrogenate manufactured by Kojun Chemical Co., Ltd. was used. Acetylene black HS-100 manufactured by Denka Co., Ltd. was used. 【0066】 Inside the argon glove box, a stainless steel (SUS) lower punch is fitted into a Macol die with an inner diameter of 10 mm, and the sr hydride ion conductive material synthesized above is used as the solid electrolyte. ０．８ Na ０．２ LiH ２．８70 mg was carefully laid down to ensure it was even. Then, after lightly pressing it down with the upper punch, it was pressurized at a uniaxial molding pressure of 91 MPa for 1 minute to obtain a hydride ion conductor pellet with a diameter of 10 mm and a thickness of 500 μm. After that, the lower punch, which would be the cathode side, was removed, and 5.7 mg of the cathode mixture electrode prepared above was laid down evenly, lightly pressed down with the lower punch, and then pressurized at a uniaxial molding pressure of 91 MPa for 1 minute. Also, the upper punch, which would be the anode side, was removed, and LaH ｘ 8 mg of (2 ≤ x < 3, manufactured by High Purity Chemicals Co., Ltd.) was laid flat, lightly pressed down with an upper punch, and then pressurized at a uniaxial forming pressure of 273 MPa for 1 minute. As a result, an electrode body was obtained in which the cathode, solid electrolyte, and anode were stacked in that order. After that, the upper and lower punches were removed, and stainless steel (SUS) perforated metal (outer diameter 10 mm, thickness 1 mm, through-hole diameter 1 mm, through-hole pitch 1.6 mm, number of through-holes 31) was attached as the outermost layer on both sides to serve as a current collector. 【0067】 The electrode body with the current collector obtained above was installed in a stainless steel airtight electrochemical cell (custom-made cell manufactured by Miclab Co., Ltd.), and the cathode and anode were connected to potentiostats (VSP-300 manufactured by Biologic Co., Ltd.) to form a circuit. Hydrogen (H) was placed on the surface of the cathode. ２ ) gas, nitrogen (N) on the surface of the anode ２ The following gases were supplied to each electrode. The hydrogen gas flow rate per electrode area was 0.25 mL / min·mm. ２ The nitrogen gas flow rate per electrode area is 0.25 mL / min·mm. ２ That's what I decided. 【0068】 The system was left standing for one hour with the hydrogen and nitrogen gases supplied separately. As a result, it was confirmed that no current flowed and that no ammonia was present in the anode exhaust gas. This confirmed that even when a circuit was formed using the electrodes obtained above, ammonia synthesis due to contamination did not occur. 【0069】[Example 2] An electrode body with a current collector, similar to that in Example 1, was similarly installed in a stainless steel airtight electrochemical cell (Miclab Co., Ltd., custom-made cell), and the cathode and anode were connected to potentiostats (Biological Corporation, VSP-300) to form a circuit. Hydrogen (H) was present on the surface of the cathode. ２ ) gas, nitrogen (N) on the surface of the anode ２ The following gases were supplied to each electrode. The hydrogen gas flow rate per electrode area was 0.25 mL / min·mm. ２ The nitrogen gas flow rate per electrode area is 0.25 mL / min·mm. ２ Next, while supplying hydrogen gas and nitrogen gas respectively, a voltage was applied under conditions of 25°C and 1 atm such that the anode potential was nobler than the cathode potential, and the potential difference was 10V. As a result, current flowed and ammonia was produced. The production of ammonia and its amount were confirmed by the indophenol method. The amount of current applied, current density, amount of ammonia produced, and Faraday efficiency are shown in Table 1. 【0070】 【0071】 Based on the results above, the manufacturing method according to this embodiment enabled ammonia synthesis at room temperature and atmospheric pressure. Furthermore, since the manufacturing method according to this embodiment allows for a continuous supply of hydride ions, it also offers excellent productivity for industrialization. 【0072】 Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-213748, filed on 6 December 2024, the contents of which are incorporated herein by reference. 【0073】 1. Cathode 2. Anode 3. Hydride ion conductor 10. Electrode body

Claims

1. A method for producing ammonia, comprising: preparing an electrode body in which a hydride ion conductor is placed between the cathode and anode electrodes; and applying a voltage between the electrodes while supplying a first gas containing hydrogen gas to the surface of the cathode and a second gas containing nitrogen gas to the surface of the anode, wherein the voltage is applied such that the potential of the cathode is lower than the potential of the anode.

2. The method for producing ammonia according to claim 1, wherein the hydride ion conductor is a metal hydride whose compositional formula is represented by the following formula (1). １ ｘ M ２ （２－ｘ） H （ｘ＋２） (1) (In formula (1), M １ is at least one element selected from the group consisting of Ca, Sr, and Ba, and M ２ (x is at least one element selected from the group consisting of Li, Na, and K, and 0 < x < 2.) 3. The method for producing ammonia according to claim 1 or 2, wherein the cathode is an electrode comprising at least one of a metal and a metal hydride, and the metal constituting the metal and metal hydride is at least one selected from the group consisting of La, Pt and Pd.

4. The method for producing ammonia according to claim 1 or 2, wherein the anode contains at least one of a metal and a metal hydride, and the metal constituting the metal and metal hydride is at least one selected from the group consisting of Fe, Ru, Ni, Nb, W, Mo, and Pd.

5. The method for producing ammonia according to claim 1 or 2, wherein the voltage is applied under conditions of 200°C or lower.

6. On the surface of the cathode, the first gas is supplied such that the flow rate of hydrogen gas per electrode area is 0.02 mL / min·mm ２ to 2.5 mL / min·mm ２ The method for producing ammonia according to claim 1 or 2.

7. On the surface of the anode, the second gas is introduced at a nitrogen gas flow rate of 0.02 mL / min·mm per electrode area. ２ ~2.5mL / min・mm ２ A method for producing ammonia according to claim 1 or 2, wherein the ammonia is supplied in such a manner.

8. An ammonia production apparatus comprising: a pair of electrodes, a cathode and an anode; a hydride ion conductor disposed between the electrodes; a voltage application unit for applying a voltage between the electrodes; a first gas supply unit for supplying a first gas containing hydrogen gas onto the surface of the cathode; and a second gas supply unit for supplying a second gas containing nitrogen gas onto the surface of the anode.

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