Electrode material, hydrogen peroxide production device, and hydrogen peroxide production method

Abstract

This electrode material 2 is characterized by containing a porous polymer having at least one of a triphenylamine residue and a thiophene residue in each repeating unit. This hydrogen peroxide production device 1 is characterized by comprising a cathode member 2, an anode member 3, and a power supply 4 for generating electromotive force between the cathode member 2 and the anode member 3, the cathode member 2 containing a porous polymer having at least one of a triphenylamine residue and a thiophene residue in each repeating unit.

Description

Electrode material, hydrogen peroxide production apparatus, and method for producing hydrogen peroxide

[0001] The present invention relates to an electrode material, a hydrogen peroxide production apparatus, and a method for producing hydrogen peroxide.

[0002] Hydrogen peroxide is widely used in various industries, water treatment, and sanitation fields, and its use worldwide is on the rise. Conventionally, two methods for producing hydrogen peroxide are known: the auto-oxidation method and the direct synthesis method. The auto-oxidation method involves hydrogenating 2-alkylanthraquinone in benzene to synthesize anthrahydroquinone, and recovering the hydrogen peroxide produced when the anthrahydroquinone is oxidized in air as the product. The direct synthesis method involves directly reacting oxygen and hydrogen in a pressure vessel to synthesize hydrogen peroxide. Prior art related to the auto-oxidation method is disclosed in Japanese Patent Application Publication No. 2022-90478 (Patent Document 1), and prior art related to the direct synthesis method is disclosed in Japanese Patent Application Publication No. 2024-68380 (Patent Document 2), among others.

[0003] Japanese Patent Publication No. 2022-90478 Japanese Patent Publication No. 2024-68380

[0004] Conventional methods for producing hydrogen peroxide, either by auto-oxidation or direct synthesis, use high-pressure hydrogen as a raw material. Therefore, producing hydrogen peroxide using these conventional technologies required meeting requirements such as location, equipment, and raw material supply capable of handling high-pressure hydrogen. Consequently, it was difficult to produce hydrogen peroxide in the required quantity at the required location.

[0005] Therefore, there is a need for a hydrogen peroxide production apparatus and a method for producing hydrogen peroxide that can produce hydrogen peroxide in the required amount at the required location, as well as electrode materials that can be applied to various devices such as hydrogen peroxide production apparatuses, hydrogen generators, and carbon dioxide reduction apparatuses.

[0006] The electrode material according to the present invention is characterized by containing a porous polymer having at least one triphenylamine residue and a thiophene residue in its repeating units.

[0007] The hydrogen peroxide production apparatus according to the present invention comprises a cathode member, an anode member, and a power source for generating an electromotive force between the cathode member and the anode member, wherein the cathode member contains a porous polymer having at least one triphenylamine residue and a thiophene residue in a repeating unit.

[0008] The present invention relates to a hydrogen peroxide production apparatus comprising an anode member, a cathode member, and a power source for generating an electromotive force between the cathode member and the anode member, wherein the cathode member contains a porous polymer having at least one triphenylamine residue and a thiophene residue in a repeating unit, and the method for producing hydrogen peroxide is characterized by comprising reducing oxygen in the cathode member to obtain hydrogen peroxide.

[0009] With these configurations, hydrogen peroxide can be produced through an electrochemical reaction using oxygen as a raw material. Therefore, hydrogen peroxide can be produced where and in the required quantity.

[0010] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

[0011] In one embodiment of the electrode material according to the present invention, it is preferable that each repeating unit of the porous polymer is bonded to other repeating units at three or more locations.

[0012] This configuration results in a porous polymer with a three-dimensional network molecular structure and a high specific surface area, leading to high activity as an electrode catalyst. Therefore, it tends to have high performance as an electrode material.

[0013] In one embodiment, the electrode material according to the present invention preferably contains at least one porous polymer selected from the group consisting of poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine), poly(1,3,5-tri(2-thienyl)benzene), and poly(benzo[1,2-b:3,4-b':5,6-b'']trithiophene).

[0014] This configuration results in a π-electron conjugated system throughout the entire repeating unit, which tends to improve the performance of the electrode material.

[0015] In one embodiment, the electrode material according to the present invention is preferably an aromatic amine polymer synthesized by a synthesis method that includes contacting at least one monomer which is a tertiary aromatic amine with iodine.

[0016] This configuration uses porous polymers that are superior in homogeneity and purity compared to porous polymers obtained by conventional methods, thus tending to improve performance as electrode materials.

[0017] In one embodiment, the electrode material according to the present invention further comprises a substrate, wherein the aromatic amine polymer forms a film containing the monomer on the conductive substrate, and is preferably synthesized by a synthesis method in which the monomer and iodine are brought into contact by bringing the film into contact with the vapor of iodine.

[0018] This configuration uses a porous polymer film uniformly formed on the substrate, which tends to result in particularly high performance as an electrode material.

[0019] In one embodiment, the electrode material according to the present invention has a BET specific surface area of ​​100 m² of the porous polymer. ２ g －１ It is preferable that the above conditions are met.

[0020] With this configuration, the pores of the porous polymer can easily function as a reaction field, resulting in particularly high performance as an electrode material.

[0021] In one embodiment, the electrode material according to the present invention preferably has a metal content of the porous polymer determined by energy-dispersive X-ray spectroscopy of 0.1 atm% or less.

[0022] This configuration makes it less susceptible to the influence of metals, which tends to result in particularly high performance as an electrode material.

[0023] In one embodiment, the hydrogen peroxide production apparatus according to the present invention further comprises a tank for housing the anode member and the cathode member, wherein the tank preferably has a receiving port for receiving water and oxygen, and a discharge port for discharging an aqueous solution containing hydrogen peroxide generated at least in the cathode member.

[0024] This configuration makes it easy to continuously produce hydrogen peroxide.

[0025] Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments, with reference to the drawings.

[0026] This is a schematic diagram of a hydrogen peroxide production apparatus according to an embodiment. This is the mass spectrum of the product of Example 1. This is the SEM-EDX spectrum of the product of Example 1. This is the mass spectrum of the product of Example 2. This is the mass spectrum of the product of Example 3. This is the mass spectrum of the product of Example 5. This is the SEM-EDX spectrum of the product of Example 5. This is the mass spectrum of the product synthesized by solution polymerization. This is the SEM-EDX spectrum of the product synthesized by solution polymerization. This is the voltammogram of the cathode member of Example 1. This is the voltammogram of the cathode member of Example 2. This is the voltammogram of the cathode member of Example 3. This is the voltammogram of the cathode member of Example 4. This is the voltammogram of the cathode member of Example 5.

[0027] Embodiments of the electrode material, hydrogen peroxide production apparatus, and hydrogen peroxide production method according to the present invention will be described with reference to the drawings. Below, a hydrogen peroxide production apparatus 1, which is an example of a hydrogen peroxide production apparatus according to the present invention, will be described. Here, the cathode member 2 provided in the hydrogen peroxide production apparatus 1 is an example of the electrode material according to the present invention. Furthermore, the method of producing hydrogen peroxide using the hydrogen peroxide production apparatus 1 is an example of a hydrogen peroxide production method according to the present invention.

[0028] [Configuration of Hydrogen Peroxide Production Apparatus] The hydrogen peroxide production apparatus 1 according to this embodiment comprises a cathode member 2, an anode member 3, a power supply 4, and a tank 5 (Figure 1). The power supply 4 is connected between the cathode member 2 and the anode member 3 and generates an electromotive force between the two electrodes. The tank 5 is a tank capable of containing a liquid such as water, and the cathode member 2 and the anode member 3 are housed in the tank 5. Although Figure 1 shows one cathode member 2 and one anode member 3, multiple cathode members 2 and anode members 3, or both, may be provided.

[0029] The cathode member 2 includes a catalyst layer 21 containing a porous polymer having at least one triphenylamine residue and a thiophene residue in repeating units, and a conductive substrate 22 made of a conductor. The conductor constituting the conductive substrate 22 is not particularly limited and may be, for example, conductive glass (e.g., transparent glass surface coated with indium tin (ITO)), glassy carbon, carbon paper, or conductive plastic film (e.g., polyethylene terephthalate film surface coated with poly(3,4-ethylenedioxythiophene) doped with conductive poly(4-styrenesulfonic acid)). The thickness of both the catalyst layer 21 and the conductive substrate 22 is not particularly limited.

[0030] The porous polymer in the catalyst layer 21 has at least one triphenylamine residue and a thiophene residue in its repeating units. The porous polymer may be a homopolymer with a single monomer as the repeating unit, or a copolymer with multiple monomers as the repeating unit, but a homopolymer is preferred. Examples of porous polymers having a triphenylamine residue in the repeating unit include, but are not limited to, poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine). Examples of porous polymers having repeating thiophene residues in their units include, but are not limited to, poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(1,3,5-tri(2-thienyl)benzene), and poly(benzo[1,2-b:3,4-b':5,6-b'']trithiophene).

[0031] In porous polymers, it is preferable that each repeating unit is bonded to other repeating units at three or more locations. Examples of porous polymers that satisfy this requirement include, but are not limited to, poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), poly(1,3,5-tri(2-thienyl)benzene), and poly(benzo[1,2-b:3,4-b':5,6-b'']trithiophene).

[0032] Porous polymers are more advantageous the larger the π-electron conjugation system in each repeating unit. Therefore, it is preferable that the repeating unit satisfies structural requirements such as having a bond at the ortho or para position of the phenyl group, or having a bond at the α position of the thienyl group. Among the porous polymers exemplified above, poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) are preferred because they have a π-electron conjugation system throughout almost the entire repeating unit. Therefore, it is preferable that the catalyst layer 21 contains at least one porous polymer selected from the group consisting of poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine).

[0033] The porous polymer monomers exemplified above are all available as commercially available reagents sold by companies such as Tokyo Chemical Industry Co., Ltd. (Japan) and Merck KGaA (Germany), or as products obtained by known synthesis methods using commercially available reagents as starting materials.

[0034] The porous polymer is preferably an aromatic amine polymer, that is, a polymer in which monomers that are tertiary aromatic amines are repeated units.

[0035] As an example of an aromatic amine polymer, poly(triphenylamine) is shown by the following formula. Poly(triphenylamine) is a homopolymer having triphenylamine as a monomer. Poly(triphenylamine) has a structure in which each phenyl group of the triphenylamine unit is bonded to a phenyl group of another triphenylamine unit at the para-position. This is due to the fact that the para-position of each phenyl group of triphenylamine has a higher substitution activity than the ortho- and meta-positions.

[0036] In poly(triphenylamine), each triphenylamine unit is bonded to another triphenylamine unit at three positions. As a result, poly(triphenylamine) has a three-dimensional network molecular structure and tends to exhibit the properties of an amorphous porous polymer. Since an amorphous porous polymer has high chemical stability and thermal stability and a high specific surface area, it has high activity as an electrode catalyst. When each repeating unit is bonded to another repeating unit at three or more positions like the above poly(triphenylamine), it tends to exhibit the properties of an amorphous porous polymer, so the catalytic ability of the catalyst layer 21 tends to be high.

[0037] In the present embodiment, it is preferable that the BET specific surface area of the porous polymer is 100 m ２ g －１ or more. When this requirement is satisfied, the pores of the porous polymer tend to effectively function as reaction fields, so the catalytic ability of the catalyst layer 21 tends to be high.

[0038] In the present embodiment, it is preferable that the metal content of the porous polymer is 0.1 atm% or less. Even when this requirement is satisfied, since it is hardly affected by the metal, the catalytic ability of the catalyst layer 21 tends to be high. The metal content of the porous polymer can be determined by energy dispersive X-ray spectroscopy.

[0039] The method for synthesizing the porous polymer is not particularly limited, but it is preferably synthesized by a synthesis method including contacting at least one monomer which is a tertiary aromatic amine with iodine. The tertiary aromatic amine is oxidized by iodine to generate radicals, and radical polymerization using the radicals as active species proceeds. Before contacting the monomer with iodine, the monomer may be purified by a known method. Further, the method for synthesizing the aromatic amine polymer according to the present embodiment may optionally purify the crude product obtained by contacting the monomer with iodine.

[0040] More preferably, a film-like porous polymer is synthesized on the conductor substrate 22 by a gas-phase polymerization method, and the film may be used as the catalyst layer 21. The gas-phase polymerization method herein is a polymerization method in which iodine is contacted with the monomer in the form of vapor. After forming a film containing the monomer on the conductor substrate 22, the film is contacted with iodine vapor to effect contact between the monomer and iodine.

[0041] First, the conductor substrate 22 before forming the catalyst layer 21 is prepared, and a film of the monomer is formed on the conductor substrate 22. The method for forming a film on the conductor substrate 22 may be a known method, such as spin coating, bar coating, flow coating, drop casting, etc., but is not limited thereto. Also, the monomer may be dissolved in a solvent when forming the film. Such a solvent is not limited as long as the monomer is soluble therein, and may be, for example, 1,2-dichloroethane, chlorobenzene, chloroform, etc.

[0042] Contact between the monomer film formed on the conductive substrate 22 and iodine can be carried out by any method. For example, one method involves placing the conductive substrate 22 with the film formed on it into a sealed container filled with iodine vapor. The temperature at which the monomer film and iodine are brought into contact is not particularly limited, as in the case of solution polymerization, and can be, for example, 80°C to 120°C. From the viewpoint of facilitating the polymerization reaction, a temperature of 90°C or higher is preferable. From the viewpoint of increasing the options for usable substrates and containers, a temperature of 100°C or lower is preferable, and 90°C or lower is more preferable. In the case of the method using a sealed container as exemplified above, for example, the monomer film and iodine vapor can be brought into contact at a predetermined temperature by placing the sealed container into an electric furnace or the like maintained at a predetermined temperature.

[0043] The porous polymers obtained by the above-described gas-phase polymerization method have the following advantages compared to porous polymers obtained by conventionally known electrolytic polymerization (a method of electrochemically oxidizing monomers on an electrode) and chemical polymerization (a method of bonding monomers together using metal salts or metal complexes as oxidizing agents or catalysts).

[0044] In electropolymerization, it is difficult to maintain a uniform current distribution on the electrodes while the polymerization reaction is progressing, so the polymerization reaction may proceed locally in areas where the current is concentrated on the electrodes. Therefore, when comparing porous polymers obtained by gas-phase polymerization with porous polymers obtained by electropolymerization, the porous polymer obtained by gas-phase polymerization is considered to have superior homogeneity as a material. As a result, the catalytic activity of the catalyst layer 21 tends to be higher. Here, homogeneity refers to homogeneity in terms of the molecular weight of the porous polymer and the nature of the pores.

[0045] In chemical polymerization, porous polymers have been synthesized by oxidative coupling using iron chloride or aluminum chloride as an oxidizing agent, or by named reactions (Suzuki-Miyaura coupling, Yamamoto coupling, etc.) using transition metal catalysts. In these methods, metal components used as oxidizing agents or catalysts may remain as impurities in the resulting porous polymer. Therefore, when comparing porous polymers obtained by gas-phase polymerization with those obtained by chemical polymerization, the porous polymer obtained by gas-phase polymerization has superior material purity. As a result, the catalytic activity of the catalyst layer 21 tends to be higher.

[0046] Thus, porous polymers obtained by a synthesis method involving contact between at least one monomer, which is a tertiary aromatic amine, and iodine are superior to porous polymers obtained by conventional methods, at least in terms of homogeneity and purity. Furthermore, in the examples described later, it was confirmed that porous polymers obtained by this synthesis method exhibit unique gas adsorption behavior not seen in porous polymers obtained by conventional methods. This result experimentally confirms that the catalyst layer 21 containing the porous polymer obtained by this synthesis method is a different substance from the catalyst layer containing the porous polymer obtained by conventional methods. However, at the time of filing this application, attempts to clarify the difference between the two in terms of specific physical properties of the substances themselves have been partially successful in terms of BET specific surface area and metal content, but not completely. For these reasons, it is not practical to directly identify electrode materials containing porous polymers obtained by this synthesis method based on their structure or physical properties.

[0047] The anode member 3 is not limited insofar as it is a component that can be used as an anode in an electrolysis apparatus. Therefore, electrode components such as titanium, platinum, and carbon can be used as the anode member 3. However, the material of the anode member 3 is not limited to the above examples.

[0048] Power supply 4 can be any known power supply device that can be used as a power source in an electrolysis apparatus.

[0049] Tank 5 is a tank capable of containing liquids such as water, and has a receiving port 51 and a discharge port 52. As described above, the cathode member 2 and the anode member 3 are housed in Tank 5. When water is added to Tank 5, the cathode member 2 and the anode member 3 become immersed in the water. The receiving port 51 is connected to a water and oxygen supply source (not shown). This supply source may include a biasing device such as a pump. The discharge port 52 is connected to equipment (not shown) for utilizing, storing, etc., an aqueous solution containing hydrogen peroxide.

[0050] When the hydrogen peroxide production apparatus 1 is in use, the tank 5 receives water and oxygen from the receiving port 51 and discharges an aqueous solution containing hydrogen peroxide from the discharge port 52. This hydrogen peroxide is produced by an electrochemical reaction in the cathode member 2 and the anode member 3. Details of the reaction will be described later.

[0051] [Method for Producing Hydrogen Peroxide] Next, an embodiment of a method for producing hydrogen peroxide using the hydrogen peroxide production apparatus 1 will be described. In the production method according to this embodiment, water and oxygen are introduced into the tank 5 from the receiving port 51, hydrogen peroxide is produced by an electrochemical reaction in the cathode member 2, and the aqueous solution containing the produced hydrogen peroxide is removed from the discharge port 52. In other words, in this embodiment, the electrochemical reaction in the tank 5 proceeds in a continuous process. The oxygen introduced into the tank 5 can be oxygen dissolved in water at room temperature and atmospheric pressure, but it is preferable to use water whose oxygen concentration has been increased in advance by means such as blowing in air (or oxygen).

[0052] Under conditions where the water supplied to tank 5 is neutral, the electrochemical reaction of formula (1-1) occurs in the cathode member 2, and the electrochemical reaction of formula (2-1) occurs in the anode member 3. Under conditions where the water supplied to tank 5 is basic, the electrochemical reaction of formula (1-2) occurs in the cathode member 2, and the electrochemical reaction of formula (2-2) occurs in the anode member 3.

[0053] Furthermore, the hydrogen peroxide ion (HO) produced in formula (1-2) ２ － ) automatically becomes hydrogen peroxide through the neutralization reaction shown in equation (3).

[0054] While the oxidation-reduction potential of formula (1-1) is -0.21V (value with a silver / silver chloride electrode as the reference electrode; the same applies hereinafter), the oxidation-reduction potential of formula (1-2) is -0.15V. Therefore, the electrochemical reaction in the cathode member 2 proceeds more easily when the water supplied to the tank 5 is basic than when the water is neutral. Accordingly, in this embodiment, it is preferable to introduce basic water into the tank 5, for example, to have a pH of 12 or higher. The method for adjusting the water to be basic may be a known method, for example, adding salts such as sodium hydroxide, sodium carbonate, or sodium bicarbonate to the water introduced into the tank 5 is an example.

[0055] As will be shown in the examples described later, the inventors have discovered that a porous polymer having at least one triphenylamine residue and a thiophene residue in its repeating unit exhibits a non-zero current density at least at -0.4 V in linear sweep voltammetry using a silver / silver chloride electrode as the reference electrode. This result means that these porous polymers have properties suitable for use as cathode material 2 when generating the electrochemical reaction of formula (1-1) with a redox potential of -0.21 V and the electrochemical reaction of formula (1-2) with a redox potential of -0.15 V.

[0056] The electrochemical reaction in the cathode member 2 (formula (1-1) or formula (1-2)) is a reaction that reduces oxygen. That is, the oxygen atom needs to accept electrons. In the hydrogen peroxide production apparatus 1 according to this embodiment, it is thought that the electron-density portion of the porous polymer contained in the catalyst layer 21 of the cathode member 2 (such as the ortho and para positions of the phenyl group and the α position of the thienyl group) acts as a catalyst to transfer electrons to the oxygen atom, thereby facilitating the progress of the above electrochemical reaction.

[0057] In the previous research of the present inventors (K. Oka, et. al., Adv. Sci. 2021, 2003077), it has been observed that when a voltage is applied to poly(1,4-phenylene-alt-(2,2'-bithiophene)-5,5'-diyl), the following changes (i) to (iii) occur. (i) A peak (1191 cm －１ ) attributed to the stretching vibration of the C-C bond between the α-position of thiophene and the phenylene group disappears. (ii) A peak (881 cm －１ ) attributed to the stretching vibration of the O-O bond appears. (iii) A peak (1600 cm －１ ) attributed to the stretching vibration of the C=C double bond of the phenylene group attenuates.

[0058] From the above observation facts (i) to (iii), the present inventors presume that electron transfer to oxygen occurs at the para-position (carbon bonded to the thienyl group) of the phenylene group. Due to the similarity in the molecular structures of poly(1,4-phenylene-alt-(2,2'-bithiophene)-5,5'-diyl) and the porous polymer according to the present embodiment, it is considered that the catalytic action is exhibited in the porous polymer according to the present embodiment by the same mechanism as in the previous research.

[0059] As described above, it is preferable that each repeating unit of the porous polymer is bonded to other repeating units at three or more positions. Since the porous polymer satisfying the above requirements has a three-dimensional molecular structure of the repeating unit, it is considered that the total surface area of the pores is larger than that of the porous polymer not satisfying the above requirements. Since the electrochemical reaction in the cathode member 2 occurs with the pores of the porous polymer as the reaction field, it is advantageous to use a porous polymer having a large total surface area of the pores. The reason why the BET specific surface area of the porous polymer is preferably 100 m ２ g －１ or more is similarly explained.

[0060] As mentioned above, the porous polymer is preferably synthesized by a synthesis method that includes contacting at least one monomer, which is a tertiary aromatic amine, with iodine. The porous polymer synthesized by this method is superior to porous polymers obtained by conventional methods, at least in terms of homogeneity and purity. Although the detailed mechanism is not clear, it is thought that factors such as the relatively low metal content work advantageously in the electrochemical reaction in the cathode member 2.

[0061] [Examples] The present invention will be further described below with reference to examples. However, the following examples are not limiting to the present invention.

[0062] (1) Manufacturing of cathode material (Example 1) Triphenylamine was dissolved in 1,2-dichloroethane to obtain a solution with a concentration of 10 mg / mL. 0.4 mL of this solution was applied by spin coating onto a glassy carbon substrate (conductive substrate 22 in the above embodiment) to form a triphenylamine film. The spin coating conditions were a rotation speed of 1500 rpm and a time of 30 seconds. Subsequently, the substrate on which the triphenylamine film was formed was sealed in a sealed container that had been pre-filled with iodine vapor. When this sealed container was heated at 80°C for 1 hour, a dark red film-like crude product was obtained on the substrate. The substrate was removed from the sealed container, washed with ethanol, and then immersed in ethanol and left overnight. The substrate was removed from the ethanol, washed again with ethanol, and then dried in air at 80°C. The film-like product after washing and drying was colorless.

[0063] Mass spectrometry of the obtained product was performed using a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOFMS) (MALDI-8030, Shimadzu Corporation). The obtained mass spectrum (Figure 2) showed fragment peaks at m / z intervals of 245.3 that can be attributed to triphenylamine units, confirming that a poly(triphenylamine) film (the catalyst layer 21 in the above embodiment) was formed on the substrate. In this embodiment, peaks that can be attributed to di- to hexamers of triphenylamine were detected.

[0064] Energy-dispersive X-ray spectroscopy (SEM-EDX) of the obtained product was performed using a scanning electron microscope (SU6600, Hitachi High-Tech Corporation). The obtained SEM-EDX spectrum (Figure 3) showed no peaks in the region corresponding to the L-line of iodine, indicating that the residual amount of iodine in the product was below the detection limit (0.1 atm%). Furthermore, the absence of peaks originating from metal elements in the spectrum indicated that the metal content of the product was below the detection limit (0.1 atm%).

[0065] (Example 2) Tris[4-(2-thienyl)phenyl]amine was dissolved in chlorobenzene to obtain a solution with a concentration of 10 mg / mL. 0.4 mL of this solution was applied by drop casting onto a glassy carbon substrate to form a film of tris[4-(2-thienyl)phenyl]amine. Subsequently, the substrate with the tris[4-(2-thienyl)phenyl]amine film was sealed in a sealed container that had been pre-filled with iodine vapor. When this sealed container was heated at 90°C for 1 hour, a yellow film-like crude product was obtained on the substrate. The substrate was removed from the sealed container, washed with chlorobenzene and ethanol, and then immersed in ethanol overnight. The substrate was removed from the ethanol, washed again with ethanol, and then dried in air at 90°C. The film-like product after washing and drying was yellow.

[0066] Mass spectrometry was performed using the same method as in Example 1. The mass spectrum is shown in Figure 4. From the mass spectrum, it was confirmed that a poly(tris[4-(2-thienyl)phenyl]amine) film was formed on the substrate.

[0067] (Example 3) Tris[4'-(2-thienyl)-4-biphenylyl]amine was dissolved in chlorobenzene to obtain a solution with a concentration of 10 mg / mL. 0.4 mL of this solution was drop-cast onto a glassy carbon substrate to form a film of tris[4'-(2-thienyl)-4-biphenylyl]amine. Subsequently, the substrate with the tris[4'-(2-thienyl)-4-biphenylyl]amine film was sealed in a sealed container that had been pre-filled with iodine vapor. When this sealed container was heated at 90°C for 1 hour, a yellow film-like crude product was obtained on the substrate. The substrate was removed from the sealed container, washed with chlorobenzene and ethanol, and then immersed in ethanol overnight. The substrate was removed from the ethanol, washed again with ethanol, and then dried in air at 90°C. The film-like product after washing and drying was yellow.

[0068] Mass spectrometry was performed using the same method as in Example 1. The mass spectrum is shown in Figure 5. From the mass spectrum, it was confirmed that a poly(tris[4'-(2-thienyl)-4-biphenylyl]amine) film was formed on the substrate.

[0069] (Example 4) N,N,N',N'-tetraphenylbenzidine was dissolved in chlorobenzene to obtain a solution with a concentration of 10 mg / mL. 0.4 mL of this solution was applied by spin coating onto a glassy carbon substrate to form a film of N,N,N',N'-tetraphenylbenzidine. Subsequently, the substrate with the N,N,N',N'-tetraphenylbenzidine film was sealed in a sealed container that had been pre-filled with iodine vapor. When this sealed container was heated at 90°C for 2 hours, a reddish-brown film-like crude product was obtained on the substrate. The substrate was removed from the sealed container, washed with chlorobenzene, and then immersed in ethanol and left to stand overnight. The substrate removed from the ethanol was dried in air at 80°C. The film-like product after washing and drying was colorless.

[0070] (Example 5) 1,3,5-tri(2-thienyl)benzene was dissolved in chlorobenzene to obtain a solution with a concentration of 10 mg / mL. 0.4 mL of this solution was applied to a glassy carbon substrate by spin coating to form a chlorobenzene film of 1,3,5-tri(2-thienyl)benzene. Subsequently, the substrate with the chlorobenzene film of 1,3,5-tri(2-thienyl)benzene was sealed in a sealed container that had been pre-filled with iodine vapor. When this sealed container was heated at 90°C for 1 hour, a dark green film-like crude product was obtained on the substrate. The substrate was removed from the sealed container, washed with chlorobenzene and ethanol, and then immersed in ethanol overnight. The substrate was removed from the ethanol, washed again with ethanol, and then dried in air at 90°C. The film-like product after washing and drying was yellow.

[0071] Mass spectrometry and energy-dispersive X-ray spectroscopy (SEM-EDX) were performed using the same method as in Example 1. The mass spectrum is shown in Figure 6, and the SEM-EDX spectrum is shown in Figure 7. From the mass spectrum, it was confirmed that a poly(1,3,5-tri(2-thienyl)benzene) film was formed on the substrate. From the SEM-EDX spectrum, it was confirmed that both the residual iodine and metal content were below the detection limit (0.1 atm%).

[0072] (2) BET specific surface area of ​​porous polymer (Preparation of measurement sample) 496.0 mg (2.02 mmol) of triphenylamine and 2570 mg (10.1 mmol, 5 equivalents) of iodine were added to 30 mL of 1,2-dichloroethane, and the mixture was stirred at 80°C for 20 hours. After cooling, the mixture was added to ethanol. The resulting precipitate was collected by filtration and washed with methanol and acetone until the filtrate was no longer colored. The washed solid was dried at 80°C for 22 hours to obtain 186.8 mg of product. The product was a pale green powder.

[0073] The obtained product was subjected to mass spectrometry using a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOFMS) (MALDI-8030, Shimadzu Corporation). The obtained mass spectrum (Figure 8) showed fragment peaks with m / z intervals of 245.3 that can be attributed to triphenylamine units, confirming that the product is poly(triphenylamine).

[0074] Energy-dispersive X-ray spectroscopy (SEM-EDX) of the obtained product was performed using a scanning electron microscope (SU6600, Hitachi High-Tech Corporation). The obtained SEM-EDX spectrum (Figure 9) showed no peak in the region corresponding to the L-line of iodine, indicating that the residual amount of iodine in the product was below the detection limit (0.1 atm%). Furthermore, the absence of peaks originating from metal elements in the spectrum indicated that the metal content of the product was below the detection limit (0.1 atm%).

[0075] From the above, it was confirmed that the product obtained by the above synthesis method is equivalent to the porous polymer obtained in Example 1 in terms of composition and metal content.

[0076] (Measurement of BET specific surface area) The BET specific surface area of ​​the sample obtained by the above synthesis method was measured using a high-precision gas / vapor adsorption amount measuring device (BELSORP® MAX X, manufactured by Microtrac-Bell Co., Ltd.). The measured value was 302.37 m². ２ g －１ The BET specific surface area of ​​conventional poly(triphenylamine) obtained by chemical polymerization was 5 m². ２ g －１ Considering the extent of this (Z. Chen et al., J. Polym. Sci, Part A : Polym. Chem. 2018, 56, 2574-2583), it can be said that it exhibited a BET specific surface area value exceeding that of porous polymers obtained by conventional techniques.

[0077] (3) Evaluation of cathode materials Linear sweep voltammetry was performed on the cathode materials of Examples 1 to 5 using a silver / silver chloride electrode as the reference electrode. A Hokuto Denko HZ-7000 was used as the measuring device, and a 0.01 M sodium chloride aqueous solution adjusted to pH 12 with sodium hydroxide was used as the electrolyte. The voltammograms of Examples 1 to 5 are shown in Figures 10 to 14. The current density values ​​at -0.4 V that could be read from each voltammogram are shown in Table 1.

[0078] Table 1: Current density at -0.4V

[0079] In all of the examples, a non-zero current density was observed at -0.4V. This indicates that the cathode materials of Examples 1 to 7 can be used to produce the electrochemical reaction of equation (1-2) with a redox potential of -0.15V. Therefore, it is considered that hydrogen peroxide can be produced using the cathode materials of Examples 1 to 7. It can also be inferred that a similar electrochemical reaction can be produced when the electrolyte is neutral.

[0080] (4) For the cathode component of hydrogen peroxide production example 3, chronoamperometry was performed using a silver / silver chloride electrode as the reference electrode, and the amount of hydrogen peroxide generated during measurement was quantified. A Hokuto Denko HZ-7000 was used as the measuring device, and a 0.01 M sodium chloride aqueous solution adjusted to pH 12 with sodium hydroxide was used as the electrolyte. The measurement voltage was kept constant at -0.4 V, and the measurement was performed for 30 minutes. During the measurement, the sample was kept out of the light.

[0081] In the above measurement, the amount of electricity flowing through the cathode component was 46,530 μC. Furthermore, the amount of hydrogen peroxide in the electrolyte, calculated using the previously reported method (AN Baga, et. al., Analytica Chimica Acta 1988, 204, 349-354), was 214.50 × 10⁻⁶. －３The amount was μmol. From these measurements, the proportion of the amount of electricity flowing through the cathode material that was consumed in the production of hydrogen peroxide (selectivity) was calculated to be 89%. The above tests demonstrated that hydrogen peroxide can indeed be produced by the present invention, and that the efficiency is very high (89%). Furthermore, since the current density at -0.4V is not zero for the cathode materials of the other embodiments as well (see section "(3) Evaluation of Cathode Materials" above), it is understood that hydrogen peroxide can be produced in the same way as for the cathode material of Embodiment 3.

[0082] [Other Embodiments] Finally, other embodiments of the electrode material, hydrogen peroxide production apparatus, and hydrogen peroxide production method according to the present invention will be described. Note that the configurations disclosed in each of the following embodiments can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise.

[0083] In the above embodiment, an example was described in which the electrode material according to the present invention is used as the cathode member 2 of a hydrogen peroxide production apparatus 1. However, the electrode material according to the present invention can be used not only in hydrogen peroxide production apparatuses but also in hydrogen generators, carbon dioxide reduction apparatuses, and the like.

[0084] In the above embodiment, the tank 5 of the hydrogen peroxide production apparatus 1 was described as having a receiving port 51 and a discharge port 52, and a configuration in which the electrochemical reaction proceeds in a continuous process. However, the hydrogen peroxide production apparatus according to the present invention may also be configured in which the electrochemical reaction proceeds in a batch process.

[0085] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention.

[0086] This invention can be used, for example, in the production of hydrogen peroxide.

[0087] 1: Hydrogen peroxide production apparatus 2: Cathode component 21: Catalyst layer 22: Conductive substrate 3: Anode component 4: Power supply 5: Tank 51: Inlet 52: Outlet

Claims

1. An electrode material comprising a porous polymer having at least one triphenylamine residue and a thiophene residue in its repeating units.

2. The electrode material according to claim 1, wherein each repeating unit of the porous polymer is bonded to other repeating units at three or more locations.

3. The electrode material according to claim 1, comprising at least one porous polymer selected from the group consisting of poly(triphenylamine), poly(tris(4-biphenylyl)amine), poly(tris[4-(2-thienyl)phenyl]amine), poly(tris[4'-(2-thienyl)-4-biphenylyl]amine), poly(N,N,N',N'-tetraphenylbenzidine), poly(1,3,5-tris[4-(diphenylamino)phenyl]benzene), poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine), poly(1,3,5-tri(2-thienyl)benzene), and poly(benzo[1,2-b:3,4-b':5,6-b'']trithiophene).

4. The electrode material according to claim 1, wherein the porous polymer is an aromatic amine polymer synthesized by a synthesis method comprising contacting at least one monomer that is a tertiary aromatic amine with iodine.

5. The electrode material according to claim 4, further comprising a substrate, wherein the aromatic amine polymer forms a film containing the monomer on a conductive substrate, and is synthesized by a synthesis method in which the monomer and the iodine are brought into contact by contacting the film with the vapor of iodine.

6. The BET specific surface area of ​​the porous polymer is 100 m². ２ g －１ The electrode material according to claim 1, wherein the above is true.

7. The electrode material according to any one of claims 1 to 6, wherein the metal content of the porous polymer determined by energy-dispersive X-ray spectroscopy is 0.1 atm% or less.

8. A hydrogen peroxide production apparatus comprising a cathode member, an anode member, and a power source for generating an electromotive force between the cathode member and the anode member, wherein the cathode member contains a porous polymer having at least one triphenylamine residue and a thiophene residue in its repeating units.

9. The hydrogen peroxide production apparatus according to claim 8, further comprising a tank for housing the anode member and the cathode member, wherein the tank has a receiving port for receiving water and oxygen, and a discharge port for discharging an aqueous solution containing hydrogen peroxide generated in at least the cathode member.

10. A method for producing hydrogen peroxide using a hydrogen peroxide production apparatus comprising an anode member, a cathode member, and a power source for generating an electromotive force between the cathode member and the anode member, wherein the cathode member comprises a porous polymer having at least one triphenylamine residue and a thiophene residue in its repeating units, the method comprising reducing oxygen in the cathode member to obtain hydrogen peroxide.

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