Method for producing electrode catalyst containing nitrogen-containing carbon material, and solid electrolyte electrolysis device

Abstract

Provided is a method for producing a catalyst for producing an electrode catalyst comprising a nitrogen-containing carbon material, the method comprising: mixing a carrier comprising carbon; a nickel compound; and a mixing step for mixing a nitrogen-containing compound containing 1-6 heterocyclic rings having 5-14 ring-forming atoms and containing at least two nitrogen atoms. And a calcination step in which the mixture obtained in the mixing step is calcined for a calcination time of 10 seconds or more and 1 hour or less. This production method makes it possible to produce a catalyst in which the amount of a catalyst source supported on a carrier can be increased.

Description

TECHNICAL FIELD

[0001] The technology of the present disclosure relates to a method for manufacturing an electrode catalyst containing a nitrogen-containing carbon material and a solid electrolyte-type electrolytic device. BACKGROUND

[0002] Carbon dioxide is emitted when energy is extracted from fossil fuels and the like. It is said that the increase in the concentration of carbon dioxide in the atmosphere is one of the causes of global warming. Carbon dioxide is an extremely stable substance, and thus, there have been almost no approaches to utilize it in the past. However, there is a demand for a new technology for converting carbon dioxide into other substances and recycling it again in this era when global warming is becoming more serious. For example, a carbon dioxide reduction-type device capable of directly reducing carbon dioxide in the gas phase is being developed.

[0003] Among carbon dioxide reduction devices, a polymer electrolyte-type electrolytic device using a polymer electrolyte is attracting attention from the viewpoint that carbon dioxide in the gas phase can be directly reduced and from the aspect that the ion movement resistance can be sufficiently reduced by using a thin film-shaped polymer electrolyte. A cathode for carbon dioxide reduction generally contains a mixture of catalyst fine particles, an electrically conductive carrier, and an ion exchange resin, and various studies have been made on these components.

[0004] As a catalyst, metal fine particles such as gold and silver are widely used, but from the viewpoint of resource amount, cost, and the like, as an alternative catalyst, a catalyst formed of a nitrogen-containing carbon material on which a metal ligand is supported has been developed and is considered promising (for example, refer to Non-Patent Literature 1).

[0005] In Non-Patent Literature 1, a catalyst was synthesized by using nickel acetate, 1,10-phenanthroline, and carbon black, calcining at 600°C for 2 hours.

[0006] In addition, in Non-Patent Literature 2, a method for synthesizing a nitrogen-containing carbon material by dispersing nickel chloride, pentaethylenehexamine, and graphene oxide in ethanol, evaporating the solvent, and then calcining at 900°C for 45 seconds was disclosed.

[0007] PRIOR ART DOCUMENTS NON-PATENT LITERATURE Non-Patent Literature 1: Hongzhou Yang, Lu Shang, Qinghua Zhang, Run Shi, Geoffrey I. N. Waterhouse, Lin Gu & Tierui Zhang, Nature Communications volume 10, Article number: 4585 (2019) Non-patent literature 2: Panpan Su, Kazuyuki Iwase, Shuji Nakanishi, Kazuhito Hashimoto, and Kazuhide Kamiya, small 2016, 12, 44, 6083-6089. SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION In the catalyst synthesis method disclosed in Non-patent literature 1, in order to produce a catalyst having high activity, the calcination time is set to a long time of 2 hours, and if the calcination time is shorter than that, active sites cannot be sufficiently formed. However, if the calcination time is long, nickel (Ni) undergoes aggregation. In addition, when pentaethylenehexamine is used as in the catalyst synthesis method disclosed in Non-patent literature 2, since the decomposition temperature of pentaethylenehexamine is low, aggregation of nickel proceeds rapidly. Aggregated nickel does not have CO2 reduction activity, and in order to produce H2, it is necessary to wash the catalyst with sulfuric acid after calcination to remove nickel aggregates, and use the same as a catalyst. By this sulfuric acid washing, most of the nickel added at the time of catalyst synthesis is washed away. Thus, in the catalyst synthesis methods disclosed in Non-patent literatures 1 and 2, aggregation of nickel easily proceeds, and thus the amount of nickel supported in a highly dispersed state as active sites decreases.

[0009] The present technology was made in view of the above circumstances, and an object of the present technology is to provide a technology related to a manufacturing method of a catalyst in which the amount of a catalyst source supported on a support is increased, a catalyst in which the amount of a catalyst source supported on a support is increased, and a cathode, an ion exchange membrane-electrode assembly, and a solid electrolyte-type electrolytic device each of which has high electrolytic activity, which solves the problem.

[0010] MEANS FOR SOLVING THE PROBLEM <1> A manufacturing method of an electrode catalyst containing a nitrogen-containing carbon material, the method comprising: mixing a support containing carbon; a nickel compound; and a nitrogen-containing compound containing 1 to 6 heterocyclic rings having 5 to 14 ring-forming atoms and containing at least 2 nitrogen atoms, a mixing step; and calcining a mixture obtained in the aforementioned mixing step for a calcination time of 10 seconds or more and 1 hour or less, a calcining step.

[0011] <2> A manufacturing method of an electrode catalyst containing a nitrogen-containing carbon material, the method comprising: a mixing step of mixing a support containing carbon; and a nitrogen-containing compound containing 1 to 6 heterocycles having 5 to 14 ring-forming atoms, containing at least 2 nitrogen atoms, and containing nickel ions; and a calcination step of calcining a mixture obtained in the aforementioned mixing step for a calcination time of 10 seconds or more and 1 hour or less.

[0012] <3> The production method of a catalyst according to <1> or <2>, wherein, in the aforementioned calcination step, the aforementioned mixture is calcined at 750°C or higher and less than 1000°C.

[0013] <4> The production method of a catalyst according to any one of <1> to <3>, wherein the aforementioned nitrogen-containing compound contains a pyridine ring, a pyrrole ring, or an isoindole ring.

[0014] <5> The production method of a catalyst according to any one of <1> to <4>, wherein the aforementioned calcination time is 30 minutes or less.

[0015] <6> The production method of a catalyst according to any one of <1> to <5>, wherein the aforementioned calcination time is 1 minute or less.

[0016] <7> A cathode having a catalyst layer and a gas diffusion layer, the catalyst layer containing an electrode catalyst produced by the production method of a catalyst according to any one of <1> to <6>.

[0017] <8> An ion exchange membrane-electrode assembly having the cathode according to <7>, a solid electrolyte, and an anode.

[0018] <9> The ion exchange membrane-electrode assembly according to <8>, wherein the aforementioned solid electrolyte is an anion exchange membrane.

[0019] <10> A solid electrolyte-type electrolytic device having: the cathode according to <7>; an anode that constitutes a pair of electrodes with the aforementioned cathode; a solid electrolyte that is sandwiched in a contact state between the aforementioned cathode and the aforementioned anode; and a voltage application part that applies a voltage between the aforementioned cathode and the aforementioned anode.

[0020] <11> The solid electrolyte-type electrolytic device according to <10>, wherein the aforementioned solid electrolyte is an anion exchange membrane.

[0021] Effects of the Invention According to the technology of the present disclosure, a technology can be provided that relates to a manufacturing method of a catalyst that enables an increase in the supported amount of a catalyst source on a support, a cathode that includes a catalyst with a high supported amount of a catalyst source on a support and has high electrolytic activity, an ion exchange membrane-electrode assembly, and a solid electrolyte-type electrolytic device. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic view of an ion exchange membrane-electrode assembly suitable for use in the present embodiment.

[0023] Figure 2 is a schematic view of a solid electrolyte-type electrolytic device suitable for use in the present embodiment. DETAILED DESCRIPTION

[0024] The upper limit value and the lower limit value of the numerical range described in the present specification can be combined arbitrarily. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges of "A to D" and "C to B" are also included in the scope of the present disclosure.

[0025] In addition, the numerical range "lower limit value to upper limit value" described in the present specification means above the lower limit value and below the upper limit value unless otherwise specified.

[0026] <Manufacturing method of catalyst> The manufacturing method of a catalyst according to the first embodiment of the present disclosure includes a mixing step of mixing a support including carbon; a nickel compound; and a nitrogen-containing compound including 1 to 6 heterocycles having 5 to 14 ring-forming atoms and including at least 2 nitrogen atoms; and a calcination step of calcining a mixture obtained in the aforementioned mixing step for a calcination time of 10 seconds or more and 1 hour or less, to manufacture an electrode catalyst including a nitrogen-containing carbon material.

[0027] The manufacturing method of a catalyst according to the second embodiment of the present disclosure includes a mixing step of mixing a support including carbon; and a nitrogen-containing compound including 1 to 6 heterocycles having 5 to 14 ring-forming atoms, including at least 2 nitrogen atoms, and including a nickel ion; and a calcination step of calcining a mixture obtained in the aforementioned mixing step for a calcination time of 10 seconds or more and 1 hour or less, to manufacture an electrode catalyst including a nitrogen-containing carbon material.

[0028] Sometimes, the manufacturing method of a catalyst according to the first embodiment of the present disclosure and the manufacturing method of a catalyst according to the second embodiment of the present disclosure are collectively referred to as only "the manufacturing method of a catalyst according to the embodiments of the present disclosure".

[0029] In addition, the mixing step in the method for producing a catalyst according to the first embodiment of the present disclosure may be referred to as "mixing step (1)". The mixing step in the method for producing a catalyst according to the second embodiment of the present disclosure may be referred to as "mixing step (2)". The mixing step (1) and the mixing step (2) may be collectively referred to as simply "the mixing step according to the embodiment of the present disclosure".

[0030] The "nitrogen-containing compound containing 1 to 6 heterocyclic rings having 5 to 14 ring atoms and at least 2 nitrogen atoms" used in the mixing step (1) may be simply referred to as "nitrogen-containing heterocyclic compound (1)".

[0031] The "nitrogen-containing compound containing 1 to 6 heterocyclic rings having 5 to 14 ring atoms, at least 2 nitrogen atoms, and nickel ions" used in the mixing step (2) may be simply referred to as "nitrogen-containing heterocyclic compound (2)".

[0032] The nitrogen-containing heterocyclic compound (1) and the nitrogen-containing heterocyclic compound (2) may be collectively referred to as simply "the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure."

[0033] The electrode catalyst produced by the method for producing a catalyst according to an embodiment of the present disclosure may be simply referred to as a "catalyst."

[0034] The method for producing a catalyst according to an embodiment of the present disclosure may further include a washing step, a pulverization step, a coating step, and the like in addition to the mixing step and the calcination step.

[0035] The catalyst produced by the catalyst production method described in the embodiments of the present disclosure is in the form of nickel derived from a nickel compound supported on a carrier via a nitrogen-containing compound. In the catalyst described in the embodiments of the present disclosure, the component that exhibits a catalytic effect in the reduction reaction of carbon dioxide is the nickel. However, in the technology of the present disclosure, the composition of the nickel coordinated to the nitrogen atoms derived from the nitrogen-containing compound and the carrier is referred to as a "catalyst." In addition, the nickel that is the component that exhibits a catalytic effect is referred to as a "catalyst source." For example, nickel forms a complex with the nitrogen-containing compound to exhibit a catalytic effect.

[0036] The catalyst obtained by the catalyst production method according to the embodiment of the present disclosure adopts the above-mentioned configuration, which can suppress nickel aggregation and increase the amount of catalyst source (nickel) supported on the carrier. This is presumably due to the following reasons.

[0037] In the mixing step (1), a nitrogen-containing heterocyclic compound (1), a nickel compound containing nickel ions as a catalyst source, and a support containing carbon are mixed. In the mixing step (2), the nitrogen-containing heterocyclic compound (2) containing nickel ions as a catalyst source and a support containing carbon are mixed.

[0038] The nitrogen-containing heterocyclic compound has a higher decomposition temperature than pentaethylenehexamine, and thus it is considered that heating decomposition is difficult to proceed by heating in the calcination step, and the aggregation of nickel is suppressed. In addition, it is considered that the aggregation of nickel can also be suppressed by shortening the calcination time to 1 hour or less. As a result, it is considered that the supported amount of nickel that is not aggregated on the support can be increased.

[0039] Hereinafter, the mixing step and the calcination step described in the embodiments of the present disclosure are described in detail, and then, the cathode, the ion exchange membrane-electrode assembly, and the electrolytic device are sequentially described.

[0040] First, the mixing step is described.

[0041] 〔Mixing step〕 In the mixing step (1), a support containing carbon; a nickel compound; and a nitrogen-containing compound containing 1 to 6 heterocycles having 5 to 14 ring-forming atoms, and containing at least 2 nitrogen atoms [nitrogen-containing heterocyclic compound (1)] are mixed.

[0042] In the mixing step (2), a support containing carbon; and a nitrogen-containing compound containing 1 to 6 heterocycles having 5 to 14 ring-forming atoms, and containing at least 2 nitrogen atoms, and containing a nickel ion [nitrogen-containing heterocyclic compound (2)] are mixed.

[0043] In the mixing step described in the embodiments of the present disclosure, a solvent can be further used in order to efficiently mix the components.

[0044] [Support] The support described in the embodiments of the present disclosure contains carbon.

[0045] Carbon generally has electrical conductivity, and thus the support described in the embodiments of the present disclosure is an electrically conductive support.

[0046] The support containing carbon is not limited as long as it is an electrically conductive material that can be used as a gas diffusion layer in an electrode provided in a device for reducing carbon dioxide, and examples thereof include carbon black (furnace black, acetylene black, ketjen black, and medium heat black), activated carbon, graphite, carbon nanotube, carbon nanofiber, carbon nanohorn, graphene nanoplatelet, and nanoporous carbon. From the viewpoint of increasing the density of active sites, carbon black is preferred.

[0047] The primary particle diameter of the carbon black is preferably 5 to 200 nm, more preferably 10 to 100 nm, and further preferably 10 to 50 nm, from the viewpoint of increasing the density of active sites and increasing the current density. The primary particle diameter of the carbon black can be measured using a transmission electron microscope. The primary particle diameter can be measured by measuring the length in the longest direction of the particle that appears under a microscope as the major axis, and calculating the average of the major axes obtained.

[0048] From the same viewpoint, the secondary particle diameter (aggregate particle diameter) of the carbon black is preferably small, and preferably the carbon black is one having a large amount of functional groups.

[0049] The carbon black can be a commercially available product, and examples thereof include Vulcan (registered trademark) XC-72 (manufactured by Cabot Corporation), BLACK PEARL 2000 (manufactured by Cabot Corporation), and the like.

[0050] The support can be used alone or in combination with two or more kinds.

[0051] From the viewpoint of dispersing the support in the solution, the amount of the support to be mixed in the mixing step according to the present embodiment is preferably 0.1 to 100 parts by mass, and more preferably 0.1 to 50 parts by mass, relative to 100 parts by mass of the solvent.

[0052] [Nickel compound] The nickel compound to be mixed in the mixing step (1) can be a chloride salt, a nitrate salt, a sulfate salt, or the like containing a nickel ion, and can also be a hydrate.

[0053] Specific examples thereof include nickel (II) chloride hexahydrate, nickel (II) nitrate hexahydrate, and the like.

[0054] In the mixing step according to the present embodiment, one kind of nickel compound can be used alone, or two or more kinds can be used in combination.

[0055] The amount of the nickel compound to be mixed in the mixing step according to the present embodiment is preferably 1 to 80 parts by mass, and more preferably 3 to 60 parts by mass, relative to 100 parts by mass of the support.

[0056] [Nitrogen-containing compound] In the nitrogen-containing compound according to the present embodiment (the nitrogen-containing heterocyclic compound according to the present embodiment of the present disclosure), the nitrogen-containing heterocyclic compound (1) contains 1 to 6 heterocycles having 5 to 14 ring-forming atoms, and contains at least two nitrogen atoms. The nitrogen-containing heterocyclic compound (2) contains 1 to 6 heterocycles having 5 to 14 ring-forming atoms, contains at least two nitrogen atoms, and contains a nickel ion.

[0057] The nitrogen-containing heterocyclic compound (1) and the nitrogen-containing heterocyclic compound (2) differ in that the former (1) does not contain a nickel ion, and the latter (2) contains a nickel ion, but are the same in terms of the structure containing 1 to 6 heterocycles having 5 to 14 ring-forming atoms, and containing at least two nitrogen atoms.

[0058] The nitrogen-containing heterocyclic compound (2) can be used as a complex in which a nickel ion is bonded to the nitrogen-containing heterocyclic compound (1) by a coordination bond.

[0059] "containing at least 2 nitrogen atoms" means that the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure contains 2 or more nitrogen atoms as a whole.

[0060] It can be (a) a form having 1 heterocycle containing 2 or more nitrogen atoms as a ring-forming heteroatom, (b) a form having a plurality of heterocycles each containing 1 nitrogen atom as a ring-forming heteroatom, or (c) a form in which the heterocycle contains a heteroatom other than a nitrogen atom, and has 2 or more nitrogen-containing groups such as an amino group as a substituent in the heterocycle, or has 1 nitrogen-containing group such as an azo group containing 2 or more nitrogen atoms.

[0061] From the viewpoint of further inhibiting the aggregation of nickel, the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure is preferably 1 or more selected from the group consisting of a compound having 1 heterocycle containing 2 or more nitrogen atoms as a ring-forming heteroatom and a compound having a plurality of heterocycles each containing 1 nitrogen atom as a ring-forming heteroatom.

[0062] From the viewpoint of further inhibiting the aggregation of nickel, the number of nitrogen atoms in the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure is preferably 20 or less, more preferably 15 or less, and further preferably 10 or less. In addition, from the viewpoint of further increasing the supported amount of nickel that has not aggregated on the support, the number of nitrogen atoms in the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure is preferably 2 or more, more preferably 3 or more, and further preferably 4 or more.

[0063] "the heterocycle having 5 to 14 ring-forming atoms" means a ring having 5 to 14 ring-forming atoms, which contains carbon atoms as ring-forming atoms, and nitrogen atoms, oxygen atoms, sulfur atoms, silicon atoms, and the like as heteroatoms. The heterocycle can be a fused ring.

[0064] For example, phenanthroline is a fused ring of two pyridine rings and one benzene ring, and is a heterocycle having 14 ring-forming atoms. In addition, bipyridine is a compound containing two heterocycles each having 6 ring-forming atoms, which are connected by a single bond.

[0065] The heteroatom constituting the heterocycle preferably contains at least a nitrogen atom.

[0066] The heterocycle can have substituents such as alkyl groups, aryl groups, and halogen atoms.

[0067] In the case where the heterocycle has substituents, the number of substituents is preferably 1 to 5, and more preferably 1 to 3. In addition, the number of carbon atoms of the alkyl group is preferably 1 to 5, and more preferably 1 to 3. The number of carbon atoms of the aryl group is preferably 5 to 10, and more preferably 6 to 8.

[0068] The heterocycle having 5 to 14 ring-forming atoms includes, specifically, for example, a ring having only nitrogen atoms as heteroatoms such as a pyridine ring, a pyrrole ring, an isoindole ring, a pyrazole ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a quinoline ring, an isoquinoline ring, a carbazole ring, a phenanthridine ring, and the like; a ring having only sulfur atoms as heteroatoms such as a thiophene ring, a thianthrene ring, and the like; a ring having only oxygen atoms as heteroatoms such as a furan ring, an isobenzofuran ring, a pyran ring, a chromene ring, a xanthene ring, and the like; a ring having only silicon atoms as heteroatoms such as a silane ring, a silabenzene ring, and the like; a ring having a plurality of heteroatoms as heteroatoms such as an isothiazole ring, a phenoxazine ring, a phenothiazine ring, and the like; and the like.

[0069] The nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure can have a plurality of heterocycles, which can be the same or different.

[0070] Among the above, the heterocycle having 5 to 14 ring-forming atoms is preferably a ring having only nitrogen atoms as heteroatoms, and more preferably a pyridine ring, a pyrrole ring, and an isoindole ring.

[0071] In other words, the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure more preferably contains a pyridine ring, a pyrrole ring, or an isoindole ring.

[0072] As the nitrogen-containing heterocyclic compound (1) containing a pyridine ring, for example, 1,10-phenanthroline, 4,4'-dimethyl-2,2'-bipyridine, 2,2'-bipyridine, and the like can be given.

[0073] As the nitrogen-containing heterocyclic compound (1) containing a pyrrole ring, for example, 5,10,15,20-tetraphenyl-21H,23H-porphine, and the like can be given.

[0074] As the nitrogen-containing heterocyclic compound (1) containing an isoindole ring, for example, phthalocyanine, and the like can be given.

[0075] As the nitrogen-containing heterocyclic compound (2) containing a pyrrole ring, for example, 5,10,15,20-tetraphenyl-21H,23H-porphine nickel (II), and the like can be given.

[0076] As the nitrogen-containing heterocyclic compound (2) containing an isoindole ring, for example, phthalocyanine nickel (II), and the like can be given.

[0077] In the mixing step according to the embodiment of the present disclosure, the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure can be used alone or in combination of two or more, but is preferably used alone.

[0078] The amount of the nitrogen-containing heterocyclic compound (1) used in the mixing step (1) is preferably 5 to 300 parts by mass, and more preferably 10 to 200 parts by mass, relative to 100 parts by mass of the support, from the viewpoint of sufficiently forming a nitrogen ligand on the support.

[0079] The amount of the nitrogen-containing heterocyclic compound (2) to be mixed in the mixing step (2) is preferably 1 to 150 parts by mass, and more preferably 30 to 130 parts by mass, relative to 100 parts by mass of the support, from the viewpoint of sufficiently forming the nitrogen ligand on the support.

[0080] [Solvent] The solvent is preferably a solvent that does not react with the support, the nickel compound, and the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure, and specifically, alcohols, water, hexane, toluene, dimethyl sulfoxide, tetrahydrofuran, and the like can be given.

[0081] The solvent can be used alone or in combination of two or more.

[0082] Among them, an alcohol containing ethanol is preferably used.

[0083] In the mixing step (1), the support, the nickel compound, and the nitrogen-containing heterocyclic compound (1) are mixed to produce a catalyst precursor as a mixture.

[0084] In the mixing step (2), the support and the nitrogen-containing heterocyclic compound (2) are mixed to produce a catalyst precursor as a mixture.

[0085] In the case where a solvent is used in the mixing step described in the embodiments of the present disclosure, the solvent dispersion of the catalyst precursor can also be subjected to ultrasonic irradiation for degassing.

[0086] [Calcination Step] In the calcination step described in the present embodiment, the mixture (catalyst precursor) obtained in the mixing step is calcined for a calcination time of 10 seconds or more and 1 hour or less.

[0087] By the heat of calcination in the calcination step, the nitrogen-containing heterocyclic compound described in the embodiments of the present disclosure in the mixture is thermally decomposed, and the aggregation of nickel is suppressed. At this time, by making the calcination time 10 seconds or more and 1 hour or less, the aggregation of nickel can also be suppressed.

[0088] In the case where a solvent is used in the mixing step described in the embodiments of the present disclosure, the calcination step can be performed in two stages. That is, the solvent in the solvent dispersion of the catalyst precursor is evaporated by heating to dry the catalyst precursor, and then the catalyst precursor is put into a calcination furnace to be calcined.

[0089] When the mixture is calcined, the mixture is preferably put into a quartz tube, and the inside of the quartz tube is replaced with an inert gas such as argon to be calcined.

[0090] The calcination time is preferably 20 seconds or more and 45 minutes or less, more preferably 30 seconds or more and 45 minutes or less, further preferably 30 seconds or more and 30 minutes or less. The calcination time can be 20 minutes or less, 10 minutes or less, or 1 minute or less. By shortening the calcination time, the aggregation of nickel can be further inhibited.

[0091] In addition, the calcination temperature is preferably 500°C or higher and 1400°C or lower, more preferably 700°C or higher and 1200°C or lower, further preferably 700°C or higher and less than 1000°C, more further preferably 800°C or higher and less than 1000°C.

[0092] 〔Cleaning step〕 The cleaning step is a step of cleaning the catalyst obtained in the calcination step with water, inorganic acid, or the like.

[0093] Water can be ion-exchange water, pure water, or the like. The inorganic acid is preferably sulfuric acid. The inorganic acid is preferably 1 to 3 mol / L (mol / L is sometimes written as M below), and in addition, the inorganic acid can be heated to 60 to 90°C.

[0094] In the cleaning step, the catalyst is preferably cleaned with water, then cleaned with an inorganic acid, and finally cleaned again with water.

[0095] The cleaning step can be repeated multiple times. For example, a first cleaning step can be performed before the pulverization step, and a second cleaning step can be performed after the pulverization step.

[0096] 〔Pulverization step〕 The pulverization step is a step of pulverizing the catalyst obtained in the calcination step.

[0097] In the method for manufacturing a catalyst according to the embodiment of the present disclosure, by using the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure to manufacture a catalyst precursor, the aggregation of nickel can be inhibited, but by performing the pulverization step, the active site density of the catalyst can be increased.

[0098] Note that in the present disclosure, the active site density refers to the content (mass %) of nickel ions coordinated with nitrogen atoms in the catalyst.

[0099] The pulverization of the calcined product can be performed using, for example, zirconia balls or alumina balls. The diameter of the balls is preferably 0.05 to 5 mm, and in addition, the pulverization conditions are preferably set to 400 to 1100 rpm for 2 minutes to 20 hours.

[0100] 〔Coating step〕 The coating step is a step of coating the catalyst manufactured in the calcination step with an ionomer.

[0101] By coating the catalyst with ionomer, an ion conduction path between the coated catalyst and the solid electrolyte described later is easily formed, ion movement by reaction is facilitated, and electrolysis efficiency can be improved.

[0102] Details of the ionomer are described below.

[0103] The nickel ion contained in the catalyst manufactured by the catalyst manufacturing method according to the embodiment of the present disclosure is preferably present in a monatomic state, coordinates with a nitrogen atom, and is thereby supported on the carrier.

[0104] The content of the nickel ion coordinated with the nitrogen atom can be calculated as follows.

[0105] The composition ratio (Ni / C) of the nickel ion bonded to (coordinated with) the nitrogen atom and carbon in the catalyst can be measured by X-ray photoelectron spectroscopy (XPS). Each element can be measured by narrow scan measurement, and the composition ratio can be calculated from the area of each peak.

[0106] Note that the nickel fine particles do not become active sites, and the nickel exists in an aggregated state.

[0107] < Cathode > The cathode (cathode) according to the embodiment of the present disclosure has a catalyst layer containing an electrode catalyst manufactured by the catalyst manufacturing method according to the embodiment of the present disclosure, and a gas diffusion layer.

[0108] The cathode (cathode) according to the embodiment of the present disclosure has a catalyst layer containing an electrode catalyst manufactured by the catalyst manufacturing method according to the embodiment of the present disclosure, and a gas diffusion layer.

[0109] [ Catalyst layer ] The catalyst layer contains at least an electrode catalyst manufactured by the catalyst manufacturing method according to the embodiment of the present disclosure, and can further contain an ionomer.

[0110] The ionomer functions as a binder resin in the catalyst layer, and also has the following functions: as a matrix resin (continuous phase) that can disperse and immobilize the catalyst according to the embodiment of the present disclosure, and also conducts ions generated by electrolysis, improving CO2 electrolysis efficiency. Furthermore, from the viewpoint of improving the transmission efficiency of ions generated by electrolysis, the ionomer is preferably electrically conductive, and more preferably a polymer electrolyte. The polymer electrolyte is further preferably an ion exchange resin. The ion exchange resin can be a cation exchange resin or an anion exchange resin, and is preferably an anion exchange resin.

[0111] In particular, when an anion exchange resin is used, the anion exchange resin itself has carbon dioxide adsorption capacity, ion conduction of the anion exchange resin is facilitated, and the electrolysis efficiency of carbon dioxide can be greatly improved.

[0112] Examples of the cation exchange resin include fluorinated resins having a sulfonic group and styrene-divinylbenzene copolymers having a sulfonic group. Commercially available products may also be used, such as Nafion (manufactured by Chemours), Aquivion (manufactured by Solvay Specialty Polymers), DIAION (manufactured by Mitsubishi Chemical Corporation), and Fumasep (manufactured by Fumatech).

[0113] Examples of anion exchange resins include resins having one or more ion exchange groups selected from quaternary ammonium groups, primary amino groups, secondary amino groups, and tertiary amino groups. Commercially available products may also be used, such as Sustainion (manufactured by Dioxide Materials), Fumasep (manufactured by FUMATECH), PENTION (manufactured by Xergy), DURION (manufactured by Xergy), NEOSEPTA (manufactured by ASTOM), and TOYOPEARL (manufactured by Tosoh Corporation).

[0114] From the viewpoint of improving conductivity, the base site density of the anion exchange resin in a dry state is preferably 2.0 to 5.0 mmol / L. 3 , more preferably 2.5 mmol / 3 Above and less than 4.5mmol / 3 , more preferably 2.9 mmol / 3 Above and less than 4.5mmol / 3 .

[0115] The base point density of anion exchange resin can be determined by 1 It can be obtained by integrating the signal during H NMR measurement.

[0116] In addition, regarding the anion exchange resin, the dry state refers to a state in which the anion exchange resin does not contain free water. For example, the anion exchange resin can be made into a dry state by heating in a vacuum.

[0117] When the cathode according to the embodiment of the present disclosure is used in the ion exchange membrane-electrode assembly and solid electrolyte electrolysis device described below, the ionomer is preferably the same resin as that of the solid electrolyte (ion exchange membrane) from the viewpoint of improving conductivity.

[0118] From the viewpoint of further improving the electrolytic activity and the CO2 reduction reaction rate, the content of the catalyst according to the embodiment of the present disclosure in the catalyst layer is preferably 50 to 99% by mass, more preferably 75 to 97% by mass, and even more preferably 90 to 95% by mass.

[0119] Gas diffusion layer The gas diffusion layer is made of, for example, carbon paper, nonwoven fabric, or metal mesh, and examples thereof include graphite carbon, glassy carbon, titanium, and SUS steel.

[0120] <Ion Exchange Membrane-Electrode Assembly> The ion exchange membrane-electrode assembly according to the embodiment of the present disclosure includes the cathode according to the embodiment of the present disclosure, a solid electrolyte, and an anode.

[0121] The ion exchange membrane-electrode assembly according to the embodiment of the present disclosure includes a cathode containing a catalyst produced by the method for producing a catalyst according to the embodiment of the present disclosure, and therefore has high electrolytic activity.

[0122] Figure 1 This is a schematic diagram of an ion exchange membrane-electrode assembly preferably used in this embodiment. Figure 1 1 shows an ion exchange membrane-electrode assembly 50 having a gas diffusion layer 10, a catalyst layer 20, a solid electrolyte 30, and an anode 40. The catalyst layer 20 includes a plurality of catalysts 24 and an ionomer 22 according to embodiments of the present disclosure. The combination of the gas diffusion layer 10 and the catalyst layer 20 constitutes a cathode according to embodiments of the present disclosure.

[0123] like Figure 1 As shown, carbon dioxide (CO 2 ) is supplied to the catalyst layer 20 through the gas diffusion layer 10 , and generates carbon monoxide (CO) through a reduction reaction.

[0124] Below, in Figure 1 Symbols are omitted for explanation.

[0125] Solid electrolyte The ion exchange membrane-electrode assembly according to the embodiment of the present disclosure includes a solid electrolyte.

[0126] A polymer membrane can be used as the solid electrolyte. The polymer can be various ionomers, which can be cation exchange resins or anion exchange resins, preferably anion exchange resins. That is, the solid electrolyte is preferably an anion exchange membrane. Furthermore, it is more preferable to use the same anion exchange resin as the ionomer used in the catalyst layer.

[0127] As the solid electrolyte, a commercially available cation exchange membrane or anion exchange membrane can be used.

[0128] Further, in the case of using an anion exchange membrane, the alkali point density of the solid electrolyte is preferably 0.5 to 5.0 mmol / cm 3 , more preferably 2.5 mmol / cm 3 , and further preferably 2.9 mmol / cm 3 , and more preferably 2.9 mmol / cm 3 , and further preferably 2.9 mmol / cm 3 .

[0129] As the cation exchange membrane, for example, a strong acid cation exchange membrane in which a sulfonic group is introduced into a fluororesin base, Nafion 117, Nafion 115, Nafion 212, Nafion 350 (manufactured by Chemours Corporation); a strong acid cation exchange membrane in which a sulfonic group is introduced into a styrene-divinylbenzene copolymer base, NeoSepha CSE (manufactured by Asahi Kasei Corporation), and the like can be used.

[0130] As the anion exchange membrane, for example, an anion exchange membrane having one or more ion exchange groups selected from a quaternary ammonium group, a primary amino group, a secondary amino group, and a tertiary amino group can be listed. Specifically, for example, NeoSepha (registered trademark) ASE, AHA, ACS, AFX (manufactured by Asahi Kasei Corporation); Celgard (registered trademark) AMVN, DSVN, AAV, ASVN, AHO (manufactured by Asahi Glass Company Limited), and the like can be listed.

[0131] Regarding the reduction reaction of carbon dioxide, the reduction reaction at the cathode described in the embodiments of the present disclosure varies depending on the kind of the solid electrolyte. In the case of using a cation exchange membrane as the solid electrolyte, the reduction reaction of the following reaction formula (1) and reaction formula (2) occurs, and in the case of using an anion exchange membrane as the solid electrolyte, the reduction reaction of the following reaction formula (3) and reaction formula (4) occurs.

[0132] CO2+ 2H + + 2e - → CO + H2O (1) 2H + + 2e - → H2 (2) H2O + CO2+ 2e - → CO + 2OH - (3) 2H2O + 2e - → H2 + 2OH - (4) [Anode] The oxidation reaction at the anode differs depending on the type of solid electrolyte. In the case where a cation exchange membrane is used as the solid electrolyte, the oxidation reaction of the following reaction formula (5) occurs, and in the case where an anion exchange membrane is used as the solid electrolyte, the oxidation reaction of the following reaction formula (6) occurs.

[0133] 2H2O→O2+4H + +4e - (5) 4OH - →O2+2H2O+4e - (6) The anode is a gas diffusion electrode including a gas diffusion layer.

[0134] The gas diffusion layer includes, for example, a metal mesh. The electrode material of the anode can be exemplified by, for example, Ir, IrO2, Ru, RuO2, Co, CoOx, Cu, CuOx, Fe, FeOx, FeOOH, FeMn, Ni, NiOx, NiOOH, NiCo, NiCe, NiC, NiFe, NiCeCoCe, NiLa, NiMoFe, NiSn, NiZn, SUS, Au, and Pt.

[0135] <solid electrolyte type electrolytic device> The solid electrolyte type electrolytic device according to the embodiment of the present disclosure has the cathode according to the embodiment of the present disclosure described above, an anode that constitutes a pair of electrodes with the cathode, a solid electrolyte that is sandwiched between the cathode and the anode in a contact state, and a voltage application unit that applies a voltage between the cathode and the anode.

[0136] The solid electrolyte type electrolytic device according to the embodiment of the present disclosure has the cathode including the catalyst manufactured by the manufacturing method of the catalyst according to the embodiment of the present disclosure, and thus has high electrolytic activity.

[0137] Figure 2 is a schematic view of the solid electrolyte type electrolytic device suitable for use in the embodiment of the present disclosure.

[0138] Figure 2 The solid electrolyte type electrolytic device 800 is shown in FIG. 8, which has the cathode 200 according to the embodiment described above, an anode 400 that constitutes a pair of electrodes with the cathode 200, a solid electrolyte 300 that is sandwiched between the cathode 200 and the anode 400 in a contact state, and a voltage application unit 700 that applies a voltage between the cathode 200 and the anode 400.

[0139] Figure 2 The solid electrolyte type electrolytic device 800 shown in FIG. 8 further has a cathode current collector 100, an anode current collector 500, and an electrolyte 600.

[0140] The cathode described in the above-described embodiment of the present disclosure is used as a cathode 200. It is further preferable that the solid electrolyte 300 be the same as the solid electrolyte 30 in Figure 1 Figure 1 The anode 400 is the same as the anode 40 in

[0141] Details of the cathode 200, the solid electrolyte 300, and the anode 400 are as described above.

[0142] Hereinafter, the description of each element other than the cathode 200, the solid electrolyte 300, and the anode 400 is omitted.

[0143] [Cathode Current Collector] As the cathode current collector (cathode current collector), a metal material such as copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, brass, or the like can be exemplified, and from the viewpoints of ease of processing and cost, copper is preferable. In the case where the material is a metal material, the shape of the cathode current collector can be exemplified by a metal foil, a metal plate, a metal film, an expanded metal, a punched metal, a foamed metal, or the like.

[0144] The cathode current collector can be provided with a gas supply hole for supplying a raw material gas containing carbon dioxide to the cathode and a gas recovery hole for recovering a generated gas containing carbon monoxide. By having the gas supply hole and the gas recovery hole, it is possible to uniformly and efficiently feed the raw material gas to the cathode and discharge the generated gas (containing unreacted raw material gas). The gas supply hole and the gas recovery hole can each independently exist only one or two or more. In addition, the shape, position, size, and the like of the gas supply hole and the gas recovery hole are not limited and can be appropriately set. Furthermore, in the case where the cathode current collector has air permeability, the gas supply hole and the gas recovery hole are not necessarily required.

[0145] Note that in the case where the cathode has a function of conducting electrons, the cathode current collector is not necessarily required.

[0146] [Anode Current Collector] The anode current collector (anode current collector) is preferably electrically conductive in order to receive electrons from the anode and has rigidity to support the anode. From this viewpoint, a metal material such as titanium (Ti), copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, brass, or the like can be appropriately used for the anode current collector.

[0147] The anode current collector can be provided with a gas flow path for feeding a raw material gas (H2O or the like) to the anode. By having the anode current collector with the gas flow path, it is possible to uniformly and efficiently feed the raw material gas to the anode. Note that the number, shape, position, size, and the like of the gas flow path are not limited and can be appropriately set.​

[0148] voltage application unit The voltage application unit functions to apply a voltage between the cathode and the anode by applying a voltage to the cathode current collector and the anode current collector. Here, both the current collectors are conductive, and thus, electrons are supplied from the cathode and received from the anode. In addition, the voltage application unit can be electrically connected to a control unit not shown in order to apply an appropriate voltage.

[0149] electrolyte solution The electrolyte solution is preferably an aqueous solution having a pH of 5 or more.

[0150] Examples of the electrolyte solution include an aqueous carbonate solution, an aqueous bicarbonate solution (e.g., an aqueous KHC03 solution), an aqueous sulfate solution, an aqueous borate solution, an aqueous NaOH solution, an aqueous KOH solution, and an aqueous NaCl solution.

[0151] reaction gas supply unit In the solid electrolyte-type electrolytic device according to the embodiment of the present disclosure, a reaction gas supply unit not shown can be provided outside the solid electrolyte-type electrolytic device. That is, as long as CO2 as a reaction gas is supplied to the catalyst layer provided in the cathode, the reaction gas can be supplied from the reaction gas supply unit to the gas supply hole by means of a pipe or the like not shown, and the reaction gas supply unit can be provided so as to blow the reaction gas to the surface of the cathode current collector opposite to the surface in contact with the cathode. In addition, from the environmental aspect, the reaction gas is preferably a plant exhaust gas discharged from a factory.

[0152] CO generation method Next, a CO generation method using the solid electrolyte-type electrolytic device according to the embodiment of the present disclosure will be described.

[0153] First, a reaction gas CO2 as a raw material is supplied to the solid electrolyte-type electrolytic device in a gaseous state by means of a reaction gas supply unit not shown. At this time, the CO2 is supplied to the cathode by means of, for example, a gas supply hole provided in the cathode current collector.

[0154] Next, the CO2 supplied to the cathode is supplied to the catalyst layer provided in the cathode, and thus, in the case where a cation exchange membrane is used as the solid electrolyte, the reduction reactions of the above reaction formulae (1) and (2) occur, and in the case where an anion exchange membrane is used as the solid electrolyte, the reduction reactions of the above reaction formulae (3) and (4) occur, and thus, a synthesis gas containing at least CO and H2 is generated.

[0155] Next, the synthesis gas containing CO and H2 generated is sent to a gas recovery device not shown by means of, for example, a gas recovery hole provided in the cathode current collector, and each of the predetermined gases is recovered. Example

[0156] Next, the technology of the present disclosure will be specifically described by examples, but the technology of the present disclosure is not at all limited to these examples.

[0157] <Manufacture of catalyst> [Example 1] (Mixing step (a)) In a beaker, in 15 mL of ethanol, carbon black [VULCAN (XC-72) (manufactured by Cabot Corporation)] (0.4 g) having a primary particle diameter of 30 nm as an electrically conductive carrier; 4,4'-dimethyl-2,2'-bipyridine (3.3 mmol) as the nitrogen-containing heterocyclic compound (1); and nickel (II) chloride hexahydrate (0.7 mmol) as the nickel compound were mixed, and the obtained ethanol dispersion liquid was irradiated with ultrasonic waves for 10 minutes. Then, the ethanol dispersion liquid was dried by heating to evaporate ethanol, and a powder of a mixture was obtained.

[0158] Note that the primary particle diameter of the carbon black was obtained by laser diffraction type particle size distribution measurement.

[0159] (Calcination step (a)) The obtained powder of the mixture was heated at 900°C for 45 seconds in an inert gas using an electric furnace to perform calcination.

[0160] (Washing step 1) The calcined substance taken out from the quartz tube was dispersed in pure water using a homogenizer, and then the calcined substance was washed in 2M sulfuric acid at 80°C for 3 hours. After the calcined substance was further washed with pure water, the calcined substance was dried.

[0161] (Pulverization step) The calcined substance subjected to the washing step 1 was pulverized using alumina balls having a diameter of 0.5 mm at 800 rpm for 40 minutes.

[0162] (Washing step 2) The calcined substance subjected to the pulverization step was dispersed in pure water using a homogenizer, and then the calcined substance was washed in 2M sulfuric acid at 80°C for 3 hours. After the calcined substance was further washed with pure water, the calcined substance was dried to obtain the catalyst of Example 1.

[0163] [Example 2] In the manufacture of the catalyst of Example 1, instead of 4,4'-dimethyl-2,2'-bipyridine, 2,2'-bipyridine was used as the nitrogen-containing heterocyclic compound (1), and the catalyst of Example 2 was manufactured in the same manner as that of Example 1.

[0164] [Example 3] Instead of 4,4'-dimethyl-2,2'-bipyridine, as the nitrogen-containing heterocyclic compound (1), 1,10-phenanthroline was used in the production of the catalyst of Example 1, and the catalyst of Example 3 was produced in the same manner except for this.

[0165] [Example 4] Instead of 4,4'-dimethyl-2,2'-bipyridine (3.3 mmol) and nickel (II) chloride hexahydrate (0.7 mmol), as the nitrogen-containing heterocyclic compound (2), nickel (II) phthalocyanine (0.7 mmol) was used in the production of the catalyst of Example 1, and the catalyst of Example 4 was produced in the same manner except for this.

[0166] [Example 5] Instead of 4,4'-dimethyl-2,2'-bipyridine (3.3 mmol) and nickel (II) chloride hexahydrate (0.7 mmol), as the nitrogen-containing heterocyclic compound (2), 5,10,15,20-tetraphenyl-21H,23H-porphine nickel (II) (0.7 mmol) was used in the production of the catalyst of Example 1, and the catalyst of Example 5 was produced in the same manner except for this.

[0167] [Example 6] In the production of the catalyst of Example 1, the mixing step (a) was changed to the following mixing step (b), and the catalyst of Example 6 was produced in the same manner except for this.

[0168] (Mixing step (b)) In a beaker, carbon black having a primary particle size of 30 nm [VULCAN (XC-72) (manufactured by Cabot Corporation)] (0.4 g) as the electrically conductive carrier; 1,10-phenanthroline (0.7 mmol) as the nitrogen-containing heterocyclic compound (1); and nickel (II) chloride hexahydrate (0.1 mmol) as the nickel compound were mixed in 15 mL of ethanol, and the resulting ethanol dispersion liquid was irradiated with ultrasonic waves for 10 minutes. Then, the ethanol dispersion liquid was dried by heating to evaporate the ethanol, and a powder of the mixture was obtained.

[0169] [Example 7] In the production of the catalyst of Example 6, the calcination step (a) was changed to the following calcination step (b), and the catalyst of Example 7 was produced in the same manner except for this.

[0170] (Calcination step (b)) The powder of the resulting mixture was heated at 900°C for 30 minutes in an inert gas using an electric furnace to perform calcination.

[0171] [Example 8] In the production of the catalyst of Example 6, the calcination step (a) was changed to the following calcination step (c), and otherwise the same operation was performed to produce the catalyst of Example 8.

[0172] (Calcination step (c)) The powder of the resulting mixture was heated at 900°C for 1 hour in an inert gas using an electric furnace to perform calcination.

[0173] (Comparative Example 1) In the production of the catalyst of Example 1, the mixing step (a) was changed to the following mixing step (c), and otherwise the same operation was performed to produce the catalyst of Comparative Example 1.

[0174] (Mixing step (c)) In a beaker, 30 nm primary particle size carbon black [VULCAN (XC-72) (manufactured by Cabot Corporation)] (0.4 g) as the electrically conductive carrier; pentaethylenehexamine (1.1 mmol) as the comparative nitrogen-containing compound; and nickel (II) chloride hexahydrate (0.7 mmol) as the nickel compound were mixed in 15 mL of ethanol, and the resulting ethanol dispersion liquid was irradiated with ultrasonic waves for 10 minutes. Then, the ethanol dispersion liquid was dried by heating to evaporate the ethanol, and a powder of the mixture was obtained.

[0175] (Comparative Example 2) In the production of the catalyst of Example 1, ethylenediamine was used instead of 4,4'-dimethyl-2,2'-bipyridine as the comparative nitrogen-containing compound, and otherwise the same operation was performed to produce the catalyst of Comparative Example 2.

[0176] (Comparative Example 3) In the production of the catalyst of Example 1, the mixing step (a) was changed to the following mixing step (d), and otherwise the same operation was performed to produce the catalyst of Comparative Example 3.

[0177] (Mixing step (d)) In a beaker, 30 nm primary particle size carbon black [VULCAN (XC-72) (manufactured by Cabot Corporation)] (0.4 g) as the electrically conductive carrier; pentaethylenehexamine (1.1 mmol) as the comparative nitrogen-containing compound; and nickel (II) chloride hexahydrate (0.7 mmol) as the nickel compound were mixed in 15 mL of ethanol, and the resulting ethanol dispersion liquid was irradiated with ultrasonic waves for 10 minutes. Then, the ethanol dispersion liquid was dried by heating to evaporate the ethanol, and a powder of the mixture was obtained.

[0178] (Comparative Example 4) In the production of the catalyst of Example 6, the calcination step (a) was changed to the following calcination step (d), and otherwise the same operation was performed to produce the catalyst of Comparative Example 4.

[0179] (calcination step (d)) The powder of the resulting mixture was heated at 600°C for 2 hours in an inert gas using an electric furnace to perform calcination.

[0180] [Comparative Example 5] In the production of the catalyst of Example 6, the calcination step (a) was changed to the following calcination step (e), and otherwise the same operation was performed to produce the catalyst of Comparative Example 5.

[0181] (calcination step (e)) The powder of the resulting mixture was heated at 900°C for 1.5 hours in an inert gas using an electric furnace to perform calcination.

[0182] The calcination conditions (calcination temperature and calcination time) and the amount of nickel added to the support containing carbon (Ni / C) [atom %] of the catalysts produced in Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

[0183] <Evaluation of Catalyst> The composition ratio (Ni / C) of nickel ions bonded to (coordinated with) nitrogen atoms to carbon in the catalyst was measured by X-ray photoelectron spectroscopy (XPS). The composition ratio was calculated from the area of each peak by performing narrow scan measurement on each element using an XPS measurement device (Axis Ultra Dld, manufactured by Kratos Analytical).

[0184] The content of nickel ions coordinated to nitrogen atoms was calculated from the measurement results, and the supported amount of nickel (Ni) with respect to the support containing carbon (C) (Ni / C) [atom %] was calculated.

[0185] The supported amount of Ni (Ni / C) [atom %] is shown in Table 1.

[0186] The allowable range is a supported amount of Ni (Ni / C) of 2.3 [atom %] or more.

[0187] As can be seen from Table 1, the supported amount of nickel on the support that is not aggregated is greater in the catalysts of the examples in which the mixture is calcined according to the calcination step of the embodiment of the present disclosure using the nitrogen-containing heterocyclic compound (1) or (2) obtained in the mixing step according to the embodiment of the present disclosure than in the catalysts of any of the comparative examples.

[0188] On the other hand, the supported amount of Ni (Ni / C) of the catalysts of Comparative Examples 1 to 3 in which the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure is not used and Comparative Examples 4 to 5 in which the nitrogen-containing heterocyclic compound according to the embodiment of the present disclosure is used but the calcination step according to the embodiment of the present disclosure is not performed is less than 2.1 [atom %].

[0189] Note that "trace" in Comparative Example 2 means that it was difficult to perform quantification below the detection limit of the analysis device.

[0190] <Manufacture of solid electrolyte-type electrolytic device> [Example 3] The catalyst of Example 3 was added to and dispersed in ethanol, and further, as an ionomer, "Nafion (registered trademark)" (cation exchange resin) manufactured by Sigma Aldrich Corporation was added to obtain a catalyst dispersion liquid containing the ionomer. This catalyst dispersion liquid was coated on carbon paper to produce a cathode. The cathode had a coating film of the catalyst dispersion liquid as a catalyst layer, and had carbon paper as a gas diffusion layer.

[0191] An anion exchange membrane (alkali point density: 2.8 mmol / cm 3 ) having a film thickness of about 30 μm was attached to the obtained cathode, and an anode produced by supporting iridium oxide on a titanium mesh (manufactured by Taihei Kikai Kogyo Co., Ltd., opening ratio: 56%) was attached to produce an ion exchange membrane-electrode assembly.

[0192] The anode was produced in a structure in contact with an electrolyte solution (0.5 mol / L of an aqueous KHCO3 solution) tank.

[0193] [Examples 6 to 7 and Comparative Examples 1 to 4] In the manufacture of the solid electrolyte-type electrolytic device of Example 3, the catalyst was changed from the catalyst of Example 3 to each of the catalysts of Examples 6 to 7 and Comparative Examples 1 to 4, and otherwise, the same operation was performed to manufacture the solid electrolyte-type electrolytic devices of Examples 6 to 7 and Comparative Examples 1 to 4.

[0194] <Evaluation of solid electrolyte-type electrolytic device> [Examples 3, 6 to 7 and Comparative Examples 1 to 4] Using each of the solid electrolyte-type electrolytic devices of Examples 3, 6 to 7 and Comparative Examples 1 to 4, pure CO2 having a flow rate of 100 sccm was supplied to the cathode, and the applied potential of the cathode was set to -1.8 V with respect to a silver / silver chloride reference electrode, and CO2 was electrolyzed to measure the current density [mA / cm 2 ] at the time of generation of CO and the CO selectivity [%].

[0195] The results are shown in Table 2.

[0196] Note that in Table 2, the nitrogen-containing compound, the calcination condition and the Ni support amount, which are also shown in Table 1, are shown for reference.

[0197] As is apparent from Table 2, the solid electrolyte-type electrolytic devices produced using the catalysts of Examples 3, 6, and 7, which have a larger amount of a source of a supported catalyst, have a higher current density and a higher electrolytic activity than the solid electrolyte-type electrolytic devices of Comparative Examples 1 to 4.

[0198] Industrial applicability According to the present embodiment, for a solid electrolyte-type electrolytic device, using, for example, CO2 gas discharged from a factory as a raw material, a renewable energy source such as a solar cell for a voltage application section, it is possible to produce a synthesis gas containing at least CO and H2 at a desired production ratio. The synthesis gas produced by such an operation can be used to produce a fuel base material, a chemical raw material, or the like by a method such as FT synthesis (Fischer-Tropsch synthesis) or methanation.

[0199] Explanation of reference numerals 10 gas diffusion layer 20 catalyst layer 22 ionomer 24 catalyst 30 solid electrolyte (ion exchange membrane) 40 anode 50 ion exchange membrane-electrode assembly 100 cathode current collector 200 cathode 300 solid electrolyte (ion exchange membrane) 400 anode 500 anode current collector 600 electrolyte 700 voltage application section 800 solid electrolyte-type electrolytic device

Claims

1. A method for producing a catalyst, comprising producing an electrode catalyst comprising a nitrogen-containing carbon material, the method comprising: a support that will contain carbon; Nickel compounds; a mixing step of mixing with a nitrogen-containing compound containing 1 to 6 heterocycles having 5 to 14 ring atoms and at least 2 nitrogen atoms; and A calcination step is performed in which the mixture obtained in the mixing step is calcined for a calcination time of 10 seconds to 1 hour.

2. A method for producing a catalyst, comprising producing an electrode catalyst comprising a nitrogen-containing carbon material, the method comprising: a support that will contain carbon; a mixing step of mixing the precipitate with a nitrogen-containing compound containing 1 to 6 heterocycles having 5 to 14 ring atoms, at least 2 nitrogen atoms, and nickel ions; and a calcining step of calcining the mixture obtained in the mixing step for a calcination time of 10 seconds to 1 hour.

3. The method for producing a catalyst according to claim 1 or 2, wherein: In the calcination step, the mixture is calcined at a temperature of 750°C or higher and lower than 1000°C.

4. The method for producing a catalyst according to any one of claims 1 to 3, wherein The nitrogen-containing compound contains a pyridine ring, a pyrrole ring, or an isoindole ring.

5. The method for producing a catalyst according to any one of claims 1 to 4, wherein The calcination time is 30 minutes or less.

6. The method for producing a catalyst according to any one of claims 1 to 5, wherein The calcination time is 1 minute or less. 7 . A cathode comprising a catalyst layer and a gas diffusion layer, wherein the catalyst layer comprises an electrode catalyst produced by the method for producing a catalyst according to claim 1 .

8. An ion exchange membrane-electrode assembly comprising the cathode according to claim 7, a solid electrolyte, and an anode.

9. The ion exchange membrane-electrode assembly according to claim 8, wherein The aforementioned solid electrolyte is an anion exchange membrane.

10. A solid electrolyte electrolysis device comprising: The cathode according to claim 7; an anode forming a pair of electrodes with the aforementioned cathode; a solid electrolyte sandwiched between the cathode and the anode in a contact state; and A voltage applying unit applies a voltage between the cathode and the anode.

11. The solid electrolyte electrolysis device according to claim 10, wherein: The aforementioned solid electrolyte is an anion exchange membrane.

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