Catalyst and method for producing the same, catalyst-containing electrode for metal-air secondary battery or for water electrolysis system, and metal-air secondary battery or water electrolysis system including electrode

Abstract

To provide a catalyst and a method for producing the same, the catalyst demonstrating both excellent oxygen reduction catalytic performance and excellent oxygen generation catalytic performance, and effectively utilizing biomass; a catalyst-containing electrode for a metal-air secondary battery or for a water electrolysis system; and a metal-air secondary battery or a water electrolysis system including an electrode.SOLUTION: There is provided a catalyst that includes a calcined product of a mixture of biomass-derived cellulose nanofibers and a dry substance containing proteins or amino acids; a method for producing the catalyst; a catalyst-containing electrode for a metal-air secondary battery or for a water electrolysis system; and a metal-air secondary battery or a water electrolysis system including the electrode.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst and a method for producing the same, an electrode for a metal-air secondary battery or an electrode for a water electrolysis system containing the catalyst, and a metal-air secondary battery or a water electrolysis system containing the electrode. [Background technology]

[0002] Among metal-air batteries that have high energy densities by using oxygen present in the air as the positive electrode active material and a metal as the negative electrode active material, those that can be reversibly charged and discharged are called metal-air secondary batteries, and are known to have energy densities several to ten times higher than those of lithium-ion batteries. At the positive electrode (air electrode) of these batteries, an oxygen reduction reaction occurs during discharge, and a catalyst is used to promote this reduction reaction. Carbon materials supporting rare metals such as platinum are known as typical oxygen reduction catalysts. Meanwhile, at the air electrode during charge, a reverse oxygen evolution reaction occurs, and rare metals such as iridium oxide or ruthenium oxide are generally used as catalysts to promote the oxygen evolution reaction.

[0003] However, rare metals such as platinum, iridium, and ruthenium are expensive and their resources are limited, so the development of electrode catalysts that do not use these rare metals but use less expensive, more abundant materials has become a challenge.

[0004] Furthermore, the air electrode of a metal-air secondary battery requires a catalyst that is active in both the oxygen reduction reaction and the oxygen evolution reaction. However, while platinum exhibits excellent catalytic performance in the oxygen reduction reaction, it has the problem of low catalytic activity in the oxygen evolution reaction. Conversely, iridium and ruthenium exhibit high catalytic performance in the oxygen evolution reaction, but have the problem of low catalytic activity in the oxygen reduction reaction. Therefore, a dual catalyst that has excellent activity in both the oxygen evolution reaction and the oxygen reduction reaction has been required.

[0005] Promising cathode catalyst materials that do not use rare metals such as platinum include nitrogen-doped graphene and carbon nanotubes, and metal-containing carbon materials with an M-N structure in which four nitrogen atoms (N) are coordinated on a plane around a central metal (M). For example, Patent Document 1 describes the production of an oxygen reduction electrode catalyst that can replace platinum by thermally decomposing a metal complex with an M-N structure and a carbon material. However, the technology described in Patent Document 1 requires a process for synthesizing the raw material metal complex with an M-N structure.

[0006] Meanwhile, with environmental problems becoming more serious in recent years, realizing a resource-circulating society has become an important issue. Therefore, materials that effectively utilize biomass have attracted attention as cathode catalyst materials to replace rare metals such as platinum. For example, Patent Document 2 discloses the production of an oxygen reduction catalyst using metal-containing organic natural products such as hemoglobin as raw materials. Patent Document 3 also describes the production of an oxygen reduction electrode by adding a conductive material such as carbon black to a metal-containing carbon material having an FeN structure using a metal-containing organic natural product as a raw material. Patent Documents 2 and 3 also describe the use of blood meal obtained from blood waste as a raw material containing metal-containing natural products.

[0007] However, the performance of the cathode catalyst materials in the technologies described in Patent Documents 2 and 3 as oxygen reduction catalysts is still insufficient and there is room for improvement. Furthermore, for use in metal-air secondary batteries, it is important that the materials have oxygen generation catalytic performance in addition to oxygen reduction catalytic performance. Furthermore, in order to achieve more complete resource circulation, it is desirable to not use rare metals, and to use carbon materials derived from biomass rather than expensive nanocarbons such as graphene and carbon nanotubes. Therefore, there has been a need to develop catalysts that have better catalytic performance while still effectively utilizing biomass. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-183743 [Patent Document 2] Patent No. 4555897 [Patent Document 3] Patent No. 6178968 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the problems of the conventional art described above, and aims to provide a high-performance catalyst that uses biomass as an alternative to rare metals such as platinum, iridium, and ruthenium, a method for producing the same, an electrode for a metal-air secondary battery or an electrode for a water electrolysis system that includes the catalyst, and a metal-air secondary battery or a water electrolysis system that includes the electrode. [Means for solving the problem]

[0010] As a result of extensive research into the above-mentioned problems, the inventors unexpectedly discovered that a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers and a dried material containing protein or amino acids has excellent oxygen reduction catalytic performance and oxygen generation catalytic performance, as well as excellent hydrogen generation catalytic performance, and further has catalytic performance comparable to that of carbon catalysts using rare metals such as platinum, iridium, and ruthenium, thereby arriving at the present invention.

[0011] Furthermore, as a result of extensive research into the above-mentioned problems, the inventors unexpectedly discovered that when the catalyst contains a calcined product of a mixture containing a cobalt complex in addition to a dried material containing biomass-derived cellulose nanofibers, proteins or amino acids, the oxygen generation catalytic performance of the catalyst is significantly improved, resulting in excellent oxygen reduction catalytic performance and oxygen generation catalytic performance, as well as excellent hydrogen generation catalytic performance, and thus arrived at the present invention.

[0012] The object of the present invention is to This is achieved by a catalyst comprising a calcined mixture containing biomass-derived cellulose nanofibers and a dried material containing protein or amino acids.

[0013] The cellulose nanofibers are preferably derived from marine biomass.

[0014] The cellulose nanofibers are preferably derived from sea squirt shells or seaweed.

[0015] The protein or amino acid-containing dry matter is preferably a dry matter of blood waste having an FeN4 structure.

[0016] The catalyst preferably contains 0.1 to 30 mass % of iron based on the total mass of the catalyst.

[0017] The catalyst preferably contains 0.1 to 40 mass % of phosphorus relative to the total mass of the catalyst.

[0018] The mass ratio of the protein- or amino acid-containing dry material to the cellulose nanofibers contained in the mixture is preferably 1:1 to 20:1.

[0019] The mixture preferably further contains a cobalt complex.

[0020] The cobalt complex is a vitamin B 12 It is preferable that it is a type.

[0021] Vitamin B 12 Preferably, the species is derived from biomass.

[0022] Vitamin B 12 Preferably, the species is derived from seaweed and / or oysters.

[0023] The catalyst preferably contains 0.1 to 30 mass % of cobalt relative to the total mass of the catalyst.

[0024] The mass ratio of the cellulose nanofibers, the dried material containing protein or amino acid, and the cobalt complex contained in the mixture (cellulose nanofibers: dried material containing protein or amino acid: cobalt complex) is preferably 1:1-20:0.1-10.

[0025] The catalyst is preferably a catalyst for oxygen generation, oxygen reduction, or hydrogen generation.

[0026] The present invention also provides a method for producing a catalyst comprising a calcined product of a mixture comprising biomass-derived cellulose nanofibers and a dried material containing a protein or amino acid, The present invention also relates to a production method, which includes the steps of preparing a mixture containing the protein- or amino acid-containing dry material and the cellulose nanofibers, and firing the mixture.

[0027] The mixture preferably further contains a cobalt complex.

[0028] The production method preferably includes a step of extracting the cellulose nanofibers from biomass.

[0029] The production method preferably includes a step of concentrating and drying the blood waste to obtain a dried product of the blood waste.

[0030] The present invention also relates to an electrode for a metal-air secondary battery or a water electrolysis system, which comprises the catalyst of the present invention.

[0031] The present invention also relates to a metal-air secondary battery or a water electrolysis system comprising the electrode of the present invention.

[0032] The following are examples of aspects of the present invention.

[0033] (Aspect 1) A catalyst comprising a calcined mixture containing biomass-derived cellulose nanofibers and a dried material containing a protein or amino acid.

[0034] (Aspect 2) 2. The catalyst of claim 1, wherein the cellulose nanofibers are derived from marine biomass.

[0035] (Aspect 3) Aspect 3. The catalyst of aspect 1 or 2, wherein the cellulose nanofibers are derived from sea squirt shells or seaweed.

[0036] (Aspect 4) A catalyst according to any one of Aspects 1 to 3, wherein the protein- or amino acid-containing dry matter is a dry matter of blood waste having an FeN4 structure.

[0037] (Aspect 5) A catalyst according to any one of aspects 1 to 4, comprising 0.1 to 30% by weight of iron, based on the total weight of the catalyst.

[0038] (Aspect 6) A catalyst according to any one of aspects 1 to 5, comprising 0.1 to 40% by weight of phosphorus, based on the total weight of the catalyst.

[0039] (Aspect 7) 7. The catalyst according to any one of aspects 1 to 6, wherein the mass ratio of the protein- or amino acid-containing dry material to the cellulose nanofibers contained in the mixture is 1:1 to 20:1.

[0040] (Aspect 8) 8. The catalyst of any one of aspects 1 to 7, wherein the mixture further comprises a cobalt complex.

[0041] (Aspect 9) The cobalt complex is a vitamin B 12 9. The catalyst of embodiment 8, wherein the catalyst is a

[0042] (Aspect 10) Vitamin B 12 10. The catalyst of embodiment 9, wherein the species is biomass-derived.

[0043] (Aspect 11) Vitamin B 12 11. The catalyst according to aspect 9 or 10, wherein the species is derived from seaweed and / or oysters.

[0044] (Aspect 12) 12. The catalyst of any one of aspects 8 to 11, comprising 0.1 to 30 wt. % cobalt, based on the total weight of the catalyst.

[0045] (Aspect 13) A catalyst according to any one of aspects 8 to 12, wherein the mass ratio of the cellulose nanofibers, the dried material containing protein or amino acid, and the cobalt complex contained in the mixture (cellulose nanofibers:dried material containing protein or amino acid:cobalt complex) is 1:1 to 20:0.1 to 10.

[0046] (Aspect 14) Aspect 14. The catalyst of any one of aspects 1 to 13, wherein the catalyst is for oxygen evolution, oxygen reduction, or hydrogen evolution.

[0047] (Aspect 15) A method for producing a catalyst comprising a calcined product of a mixture comprising biomass-derived cellulose nanofibers and a dried material containing a protein or amino acid, A production method comprising the steps of preparing a mixture containing the biomass-derived cellulose nanofibers and the dried material containing the protein or amino acid, and firing the mixture.

[0048] (Aspect 16) 16. The method of claim 15, wherein the mixture further comprises a cobalt complex.

[0049] (Aspect 17) 17. The method according to aspect 15 or 16, comprising extracting the cellulose nanofibers from biomass.

[0050] (Aspect 18) 18. The method according to any one of aspects 15 to 17, comprising concentrating and drying blood waste to obtain a dried product containing the protein or amino acid.

[0051] (Aspect 19) Aspect 19. The method of any of aspects 15 to 18, wherein the cellulose nanofibers are derived from marine biomass.

[0052] (Aspect 20) Aspect 20. The method according to any one of aspects 15 to 19, wherein the cellulose nanofibers are derived from sea squirt shells or seaweed.

[0053] (Aspect 21) The cobalt complex is a vitamin B 12 21. The method of any one of aspects 16 to 20, wherein the method is of the same type.

[0054] (Aspect 22) Vitamin B 12 22. The method of claim 21, wherein the species is derived from biomass.

[0055] (Aspect 23) Vitamin B 12 23. The method according to claim 21 or 22, wherein the hydroxyl group is derived from seaweed and / or oysters.

[0056] (Aspect 24) 15. An electrode for a metal-air secondary battery or a water electrolysis system, comprising the catalyst according to any one of aspects 1 to 14.

[0057] (Aspect 25) A metal-air secondary battery or a water electrolysis system comprising the electrode according to embodiment 24. [Effects of the Invention]

[0058] According to the present invention, it is possible to provide a catalyst that effectively utilizes biomass and has excellent catalytic performance in both oxygen reduction catalytic performance and oxygen generation catalytic performance, and also has excellent catalytic performance in hydrogen generation catalytic performance. [Brief explanation of the drawings]

[0059] [Figure 1]1 is a graph showing the results of an oxygen reduction catalyst performance and oxygen generation catalyst performance evaluation test for a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex. [Figure 2] 1 is a graph showing the results of a hydrogen generation catalyst performance evaluation test for a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex. [Figure 3] 1 is a graph showing the results of an IV characteristic evaluation test for a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing a protein or amino acid, and a cobalt complex. DETAILED DESCRIPTION OF THE INVENTION

[0060] [catalyst] The catalyst of the present invention comprises a calcined product of a mixture containing biomass-derived cellulose nanofibers and a dried material containing a protein or an amino acid. By including a calcined product of a mixture containing biomass-derived cellulose nanofibers and a dried material containing a protein or an amino acid, it is possible to obtain a catalyst that is endowed with excellent catalytic ability for both oxygen reduction and oxygen generation, as well as catalytic performance for hydrogen generation.

[0061] [Biomass-derived cellulose nanofiber] The cellulose nanofibers of the present invention are obtained from biomass. Preferably, the cellulose nanofibers are not derived from wood. More preferably, the cellulose nanofibers are derived from marine biomass. Even more preferably, the cellulose nanofibers are derived from urochordates or seaweed.

[0062] In a preferred embodiment, the cellulose nanofibers of the present invention are derived from urochordates. In a more preferred embodiment, the cellulose nanofibers of the present invention are derived from sea squirt shells. Sea squirts are known as the only animals capable of producing cellulose. However, sea squirt shells, which are inedible parts of sea squirts, are generated in large quantities as industrial waste. Therefore, when the cellulose nanofibers of the present invention are derived from sea squirt shells, catalysts can be produced that more effectively utilize waste biomass. Furthermore, cellulose derived from sea squirt shells has higher tensile strength and excellent crystallinity than cellulose derived from wood. Therefore, when the cellulose nanofibers of the present invention are derived from sea squirt shells, a highly conductive carbon material can be obtained by calcining the cellulose.

[0063] In one embodiment, the cellulose nanofibers of the present invention are derived from seaweed. Examples of seaweed include wakame (Undaria pinnatifida), kombu (kelp), agar, and ulva (Ulva). Among these, the cellulose nanofibers are preferably derived from wakame (Undaria pinnatifida), and more preferably from the core stem of wakame (Undaria pinnatifida).

[0064] The cellulose nanofiber of the present invention may be a combination of one or more types of cellulose nanofibers. The cellulose nanofiber of the present invention may use only cellulose nanofibers derived from sea tuna shells. Alternatively, the cellulose nanofiber of the present invention may use only cellulose nanofibers derived from seaweed. The cellulose nanofiber of the present invention may use a combination of cellulose nanofibers derived from sea tuna shells and cellulose nanofibers derived from seaweed. In one embodiment, it is preferable that the cellulose nanofiber of the present invention use only cellulose nanofibers derived from sea tuna shells.

[0065] The cellulose nanofibers of the present invention preferably have a diameter of less than 200 nm, more preferably less than 100 nm, and even more preferably less than 50 nm. When the diameter of the cellulose nanofibers is less than the above upper limit, the specific surface area increases and the conductivity can be increased. In one embodiment, the cellulose nanofibers of the present invention are derived from sea squirt shells, and therefore have a smaller fiber diameter than cellulose nanofibers derived from wood. Therefore, the increased surface area of ​​the cellulose nanofibers allows the production of carbon materials with superior catalytic activity.

[0066] The cellulose nanofibers of the present invention preferably have a fiber length of more than 4 μm, more preferably more than 4.5 μm, and even more preferably more than 5 μm. When the fiber length of the cellulose nanofibers exceeds the upper limit, they can have excellent tensile strength.

[0067] The cellulose nanofibers of the present invention preferably have a crystal size of 7 to 14 nm, more preferably 8 to 12 nm, and even more preferably 8.5 to 11.5 nm. In one embodiment, the cellulose nanofibers are derived from marine biomass and therefore can have higher crystallinity than cellulose nanofibers derived from wood.

[0068] The cellulose nanofibers of the present invention preferably have a tensile strength of 2.5 to 7.5 GPa, more preferably 2.8 to 7.0 GPa, and even more preferably 3.0 to 6.4 GPa. In one embodiment, the cellulose nanofibers are derived from marine biomass and therefore can have a higher tensile strength than cellulose nanofibers derived from wood.

[0069] The cellulose nanofibers of the present invention preferably have a crystallinity of 80% or more, more preferably 90% or more, and even more preferably 95% or more. In one embodiment, the cellulose nanofibers are derived from marine biomass and therefore can have a higher crystallinity than cellulose nanofibers derived from wood.

[0070] [Dry products containing proteins or amino acids] Examples of the dried material containing the protein or amino acid of the present invention include dried materials derived from raw materials such as livestock meat, seafood, beans, dairy products, yeast, etc. Preferably, the dried material containing the protein or amino acid of the present invention is derived from an animal or plant source. In one embodiment, the dried material containing the protein or amino acid of the present invention is preferably derived from waste, more preferably from animal waste, plant waste, or a mixture of animal waste and plant waste. In one embodiment, the dried material containing the protein or amino acid of the present invention is most preferably derived from blood waste.

[0071] In one embodiment, the protein or amino acid of the present invention may contain a metal. When the protein or amino acid contains a metal, the type of metal may include iron, copper, manganese, cobalt, nickel, vanadium, etc. In one embodiment, the protein or amino acid of the present invention contains iron. In one embodiment, the dried material containing the protein or amino acid of the present invention is a dried material of blood waste having an FeN4 structure.

[0072] The dried blood waste material having an FeN structure can be, for example, blood waste generated in meat processing plants, seafood processing plants, etc. Preferably, the blood waste can be dried blood meal obtained by drying waste blood generated in meat processing plants. The blood waste can be, for example, dried blood meal obtained by drying waste blood from pigs, poultry, rabbits, sheep, cattle, etc. Preferably, dried blood meal obtained by drying waste blood from cattle or pigs is used.

[0073] The dried blood waste material having an FeN4 structure may contain a metal-containing organic compound having an FeN4 structure. The metal-containing organic compound having an FeN4 structure is preferably an iron protein. Examples of iron proteins include hemoglobin, catalase, peroxidase, and cytochrome. Among these, the iron protein is preferably hemoglobin.

[0074] When the dried blood waste material having an FeN structure contains iron protein, the content of the iron protein is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more, based on the total amount of the dried blood waste material. When the content of the iron protein is equal to or more than the lower limit, the FeN structure source relative to the total amount of the catalyst is abundant, and the catalyst performance is further improved.

[0075] The dried blood waste material having an FeN structure may further contain one or more proteins other than iron proteins, lysine, and sulfur-containing amino acids, in addition to iron proteins. Examples of proteins other than iron proteins include, but are not limited to, copper proteins. Examples of copper proteins include bilirubin oxidase, tyrosinase, and laccase.

[0076] The dried blood waste material having an FeN4 structure may further contain water and fat. The dried blood waste material having an FeN4 structure preferably contains less than 12% by mass of water, more preferably less than 10% by mass, and even more preferably less than 8% by mass. When the dried blood waste material having an FeN4 structure contains less than the upper limit of water content, the catalytic performance is further improved. Furthermore, the dried blood waste material having an FeN4 structure preferably contains less than 5% by mass of fat, more preferably less than 2% by mass, and even more preferably less than 1% by mass. When the dried blood waste material having an FeN4 structure contains less than the upper limit of fat content, the catalytic performance is further improved.

[0077] [Burned product of a mixture containing biomass-derived cellulose nanofibers and a dried material containing protein or amino acids] The fired product of a mixture containing the biomass-derived cellulose nanofibers of the present invention and a dried material containing a protein or amino acid can be obtained by preparing a mixture containing the biomass-derived cellulose nanofibers of the present invention and a dried material containing the protein or amino acid of the present invention, and firing the resulting mixture.

[0078] The catalyst of the present invention may contain additional components in addition to the calcined mixture containing biomass-derived cellulose nanofibers and a dried material containing proteins or amino acids. The additional components preferably include a solvent. The solvent may be one that easily dissolves the catalyst (i.e., has high solubility) or one that does not easily dissolve the catalyst (i.e., has low solubility).

[0079] The solvent is not particularly limited, and may be an inorganic solvent such as water, or may be an organic solvent. Specific examples of organic solvents include alcohols such as methanol, ethanol, propanol, isopropanol (2-propanol), and 1-hexanol; dimethyl sulfoxide; tetrahydrofuran; aprotic polar solvents such as N-methylpyrrolidone, dimethylformamide, and acetone; and nonpolar solvents such as chloroform, dichloromethane, 1,4-dioxane, benzene, and toluene. One type of solvent may be used alone, or two or more types may be used in combination.

[0080] The catalyst of the present invention is preferably a catalyst for oxygen generation, oxygen reduction, or hydrogen generation. In one embodiment, the catalyst of the present invention has the properties of oxygen generation catalytic performance, oxygen reduction catalytic performance, and hydrogen generation catalytic performance. Thus, in one embodiment, the catalyst of the present invention is a catalyst for oxygen generation, oxygen reduction, and hydrogen generation.

[0081] The catalyst of the present invention is preferably a catalyst for oxygen generation or oxygen reduction at the positive electrode of a battery. The catalyst of the present invention is more preferably a catalyst for oxygen generation or oxygen reduction at the positive electrode (air electrode) of a metal-air secondary battery. Alternatively, the catalyst of the present invention is preferably a catalyst for oxygen generation in a water electrolysis system. The catalyst of the present invention is more preferably a catalyst for oxygen generation at the anode of a water electrolysis system.

[0082] The catalyst of the present invention can also be used preferably as a catalyst for generating hydrogen in a water electrolysis system, more preferably as a catalyst for generating hydrogen at the cathode of a water electrolysis system.

[0083] The catalyst of the present invention preferably contains 0.1 to 30 mass %, more preferably 0.2 to 10 mass %, and even more preferably 0.5 to 10 mass %, of iron relative to the total mass of the catalyst. By containing iron in this range, the catalyst of the present invention can have better catalytic activity.

[0084] The catalyst of the present invention contains phosphorus in an amount of preferably 0.1 to 40 mass%, more preferably 0.2 to 20 mass%, and even more preferably 0.5 to 10 mass%, based on the total mass of the catalyst. By containing phosphorus in the above range, the catalyst of the present invention can have better catalytic activity.

[0085] The catalyst of the present invention preferably contains 0.1 to 40 mass %, more preferably 0.2 to 20 mass %, and even more preferably 0.5 to 10 mass % of nitrogen relative to the total mass of the catalyst. By containing nitrogen in this range, the catalyst of the present invention can have better catalytic activity.

[0086] In the catalyst of the present invention, the mass ratio of the protein- or amino acid-containing dried material to the cellulose nanofibers contained in the mixture is preferably 0.1:1 to 50:1, more preferably 1:1 to 30:1, and even more preferably 1:1 to 20:1. By having the mass ratio of the protein- or amino acid-containing dried material to the cellulose nanofibers in the above range, better conductivity and catalytic activity can be achieved. When the protein- or amino acid-containing dried material of the present invention includes a dried blood waste product, the mass ratio of the dried blood waste product to the cellulose nanofibers contained in the mixture of the present invention is preferably 0.1:1 to 50:1, more preferably 1:1 to 30:1, and even more preferably 1:1 to 20:1. By having the mass ratio of the dried blood waste product to the cellulose nanofibers in the above range, better conductivity and catalytic activity can be achieved.

[0087] The oxygen evolution (OER) catalyst of the present invention preferably has an onset potential E of 1.5 V [vs. RHE] or less, more preferably 1.45 V [vs. RHE] or less, and even more preferably 1.4 V [vs. RHE] or less. on-set / OER When the oxygen generating catalyst of the present invention has an onset potential equal to or lower than the upper limit, it can have oxygen generating (OER) catalytic activity comparable to that of rare metals such as iridium.

[0088] The oxygen generating catalyst of the present invention is 2 When the potential E reaches j-10(OER) is preferably 2.0 V [vs. RHE] or less, more preferably 1.9 V [vs. RHE] or less, and even more preferably 1.8 V [vs. RHE] or less, E j-10(OER) The oxygen generating catalyst of the present invention has an E j-10(OER) By having this, it is possible to have oxygen generating catalytic activity comparable to that of rare metals such as iridium.

[0089] The oxygen reduction (ORR) catalyst of the present invention has an onset potential E of preferably 0.8 V [vs. RHE] or more, more preferably 0.9 V [vs. RHE] or more, even more preferably 0.98 V [vs. RHE] or more, and particularly preferably 1.0 V [vs. RHE] or more. on-set / ORR When the oxygen reduction catalyst of the present invention has an onset potential equal to or higher than the lower limit, it can have oxygen reduction catalytic activity comparable to that of rare metals such as platinum.

[0090] The oxygen reduction catalyst of the present invention has a half-wave potential E of preferably 0.75 V [vs. RHE] or more, more preferably 0.80 or more, even more preferably 0.82 or more, and particularly preferably 0.85 V [vs. RHE]. half(ORR) When the oxygen reduction catalyst of the present invention has a half-wave potential equal to or greater than the lower limit, it can have oxygen reduction catalytic activity comparable to that of rare metals such as platinum.

[0091] [Catalyst containing a calcined product of biomass-derived cellulose nanofibers, a dried material containing protein or amino acid, and a cobalt complex] In one embodiment, the mixture prepared to obtain the calcined product contained in the catalyst of the present invention contains a cobalt complex in addition to a dried material containing biomass-derived cellulose nanofibers and a protein or amino acid. By containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing a protein or amino acid, and a cobalt complex, the catalyst of the present invention has significantly improved activity in the oxygen generation reaction, and is excellent in both oxygen reduction catalytic performance and oxygen generation catalytic performance, and furthermore, can be obtained with a catalyst that has even improved hydrogen generation catalytic performance.

[0092] [Cobalt complexes] In one embodiment, the cobalt complexes of the present invention are vitamin B 12 Vitamin B 12 Vitamin B 12 (cyanocobalamin), its derivatives, and their salts. Vitamin B 12Derivatives of cyanocobalamin include compounds in which the ligand on the cobalt in cyanocobalamin is substituted, and compounds in which the functional group in cyanocobalamin is substituted, and more specifically, methylcobalamin, hydroxocobalamin, adenosylcobalamin, aquacobalamin, etc. are included. In addition, vitamin B 12 Examples of salts of vitamin B and derivatives thereof include carboxylates such as acetate, trifluoroacetate, butyrate, palmitate, stearate, fumarate, maleate, succinate, malonate, lactate, tartrate, and citrate; organic sulfonates such as methanesulfonate, toluenesulfonate, and tosylate; inorganic acid salts such as hydrochloride, sulfate, nitrate, and phosphate; organic amine salts such as methylamine, triethylamine, and triethanolamine; alkali metal salts such as sodium and potassium salts; alkaline earth metal salts such as calcium and magnesium; and ammonium salts. 12 The cobalt complex of the present invention may be used alone or in combination of two or more thereof. 12 (cyanocobalamin).

[0093] In one embodiment, vitamin B 12 Vitamin B12 derived from biomass. 12 By using these compounds, it is possible to produce catalysts that utilize biomass more effectively. 12 Vitamin B12 derived from seafood, seaweed, or meat is one example. 12 More preferably, the vitamin B 12 The vitamins are derived from fish and shellfish and / or seaweed. Examples of fish and shellfish include oysters, clams, salmon roe, saury, and herring. Examples of seaweed include laver, wakame seaweed, kelp, agar, and sea lettuce. Among these, the vitamin B 12 The vitamin B of the present invention is preferably derived from oysters and / or seaweed. 12 Vitamin B12 derived from oysters 12 You can also use only the vitamin B12 You can also use only oysters, and vitamin B 12 Vitamin B from seaweed and seaweed 12 Vitamin B of the present invention may be used in combination. 12 Vitamin B derived from oysters and / or seaweed 12 By using a cobalt complex containing a cobalt complex of the present invention, the activity of the oxygen generating reaction is further improved, and a catalyst having excellent catalytic performance in both oxygen reduction and oxygen generating reactions and improved catalytic performance in hydrogen generation can be obtained. 12 (cyanocobalamin).

[0094] In one embodiment, the catalyst of the present invention contains preferably 0.1 to 30 mass %, more preferably 0.1 to 20 mass %, and even more preferably 0.5 to 10 mass % of cobalt relative to the total mass of the catalyst. By containing cobalt in this range, the catalyst of the present invention can have better oxygen generation catalytic performance and better hydrogen generation catalytic performance.

[0095] In one embodiment, the mass ratio of the cellulose nanofibers, the dried material containing protein or amino acid, and the cobalt complex contained in the mixture for the calcined product contained in the catalyst of the present invention (cellulose nanofibers: dried material containing protein or amino acid: cobalt complex) is preferably 1:1-20:0.1-10, more preferably 1:1-15:0.1-5, and even more preferably 1:1-12:0.5-3. When the mass ratio of the cellulose nanofibers, the dried material containing protein or amino acid, and the cobalt complex of the present invention is within the above range, better conductivity and catalytic activity can be achieved.

[0096] In one embodiment, when the catalyst of the present invention comprises a calcined mixture containing biomass-derived cellulose nanofibers, a dried material containing a protein or an amino acid, and a cobalt complex, the current density of the oxygen evolution (OER) catalyst of the present invention is 10 mA / cm 2 When the potential E reaches j-10(OER)is preferably 1.8 V [vs. RHE] or less, more preferably 1.75 V [vs. RHE] or less, and even more preferably 1.73 V [vs. RHE] or less, E j-10(OER) The catalyst of the present invention can have an E j-10(OER) By having this, it is possible to have oxygen generating catalytic activity comparable to that of rare metals such as iridium.

[0097] The hydrogen evolution (HER) catalyst of the present invention has an onset potential E of preferably −0.7 V [vs. RHE] or higher, more preferably −0.5 V [vs. RHE] or higher, even more preferably −0.4 V [vs. RHE] or higher, and particularly preferably −0.3 V [vs. RHE] or higher. on-set / HER When the hydrogen generation catalyst of the present invention has an onset potential equal to or higher than the lower limit, it can have hydrogen catalytic activity comparable to that of rare metals such as platinum.

[0098] [Catalyst manufacturing method] In one embodiment, the present invention relates to a method for producing the catalyst of the present invention, which includes the steps of preparing a mixture containing a dried material containing a protein or amino acid and cellulose nanofibers derived from biomass, and calcining the mixture.

[0099] To produce the catalyst of the present invention, for example, a mixture containing a dried material containing protein or amino acids and biomass-derived cellulose nanofibers as a carbon source is prepared, followed by carbonization by heat treatment at a predetermined temperature under an inert atmosphere such as nitrogen or helium. The heat treatment temperature is not particularly limited as long as it is a temperature that allows carbonization; however, preferred temperatures are 350 to 1600°C, more preferably 500 to 1200°C, even more preferably 600 to 1000°C, and particularly preferably 750 to 950°C (approximately 900°C). The heat treatment time is also not particularly limited as long as it allows carbonization; however, it is preferably 30 minutes to 6 hours, more preferably 1 to 5 hours, and even more preferably 1 to 3 hours. The resulting carbonized material is then finely pulverized, for example, using a ball mill, to obtain a fired product of the mixture containing the dried material containing protein or amino acids and biomass-derived cellulose nanofibers. In one embodiment, the dried material containing protein or amino acids can be dried blood waste as a nitrogen-iron complex source.

[0100] The method for producing a catalyst of the present invention preferably further comprises a step of extracting cellulose nanofibers from biomass. In the method for producing a catalyst of the present invention, the cellulose nanofibers are preferably not derived from wood. In the method for producing a catalyst of the present invention, the cellulose nanofibers are more preferably derived from marine biomass. In the method for producing a catalyst of the present invention, the cellulose nanofibers are even more preferably derived from urochordates or seaweed. In the method for producing a catalyst of the present invention, the cellulose nanofibers are preferably derived from sea squirt shells or seaweed, and are particularly preferably derived from sea squirt shells. When the cellulose nanofibers of the present invention are derived from sea squirt shells, they can be more easily decomposed than when cellulose derived from wood, which contains a lot of lignin, and the energy and costs required for production can be reduced.

[0101] Any method can be used to extract cellulose nanofibers from biomass. When the cellulose nanofibers are derived from sea squirt shells, the method for extracting cellulose nanofibers may include, for example, treating the sea squirt shells with an alkaline solution to decompose proteins and extract cellulose. The alkaline solution is not particularly limited, but examples include a 10% potassium hydroxide solution and a sodium hydroxide solution. When the cellulose nanofibers are derived from seaweed such as wakame seaweed, the method may include a step of removing alginic acid by centrifugation or the like. Subsequently, the method for extracting cellulose from biomass may include a step of crushing the obtained cellulose to nano-size particles.

[0102] When a dried blood waste product is used as the protein- or amino acid-containing dried material of the present invention, the catalyst production method of the present invention preferably further includes a step of concentrating and drying the blood waste product to obtain a dried blood waste product. The method for concentrating and drying the blood waste product is optional. For example, the dried blood waste product can be obtained by concentrating blood obtained from meat and removing water by low-temperature vacuum drying. In one embodiment, the catalyst production method of the present invention does not require removing components other than iron proteins from the blood waste product. When the catalyst production method of the present invention does not include a step of removing components other than iron proteins from the blood waste product, catalyst production becomes easier and production costs can be reduced.

[0103] In one embodiment, when the catalyst of the present invention comprises a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex, the method for producing the catalyst of the present invention comprises the steps of preparing and calcining a mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex.

[0104] In one embodiment, when the catalyst of the present invention includes a calcined mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex, the catalyst can be produced, for example, by preparing a mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex, followed by heat treatment at a predetermined temperature in an inert atmosphere such as nitrogen or helium to carbonize the mixture. The heat treatment temperature is not particularly limited as long as it is a temperature that allows carbonization, but is preferably 350 to 1600°C, more preferably 500 to 1200°C, even more preferably 600 to 1000°C, and particularly preferably 750 to 950°C (near 900°C). The heat treatment time is not particularly limited as long as it allows carbonization, but is preferably 30 minutes to 6 hours, more preferably 1 to 5 hours, and even more preferably 1 to 3 hours. The resulting carbonized material is then finely pulverized, for example, using a ball mill, to obtain a fired mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex.

[0105] When the catalyst of the present invention comprises a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing proteins or amino acids, and a cobalt complex, the method for producing the catalyst of the present invention preferably further comprises a step of obtaining the cobalt complex from the biomass. The method for obtaining the cobalt complex from the biomass is arbitrary.

[0106] In one embodiment, the cobalt complexes of the present invention are vitamin B 12 Preferably, the cobalt complex of the present invention is a vitamin B 12 (cyanocobalamin).

[0107] In one embodiment, vitamin B 12 The vitamins are derived from biomass and preferably contain vitamin B 12 Vitamin B6 is derived from seafood and / or seaweed, and more preferably from vitamin B 12In one embodiment, the catalyst of the present invention is derived from oysters and / or seaweed. 12 For example, the method may include a step of homogenizing a biomass raw material (oysters, seaweed, etc.) in a food processor and extracting the homogenized material by heating in an acetate buffer solution containing a potassium cyanide solution to obtain a cobalt complex.

[0108] [electrode] In one embodiment, the present invention relates to an electrode comprising the catalyst of the present invention. The electrode can have a layer (i.e., a catalyst layer) comprising the catalyst of the present invention on a substrate, and can be used as a catalyst for the oxygen evolution reaction or the oxygen reduction reaction. In one embodiment, it can also be used as a catalyst for the hydrogen evolution reaction. The catalyst layer can be in direct contact with the substrate, or other layers can be present between the substrate and the catalyst.

[0109] The substrate is not particularly limited, and examples include aluminum alloys such as aluminum foil, electrolytic aluminum foil, aluminum mesh (expanded metal), foamed aluminum, punched aluminum, and duralumin; copper alloys such as copper foil, electrolytic copper foil, copper mesh (expanded metal), foamed copper, punched copper, and brass; brass foil, brass mesh (expanded metal), foamed brass, punched brass; nickel foil, nickel mesh, corrosion-resistant nickel, nickel mesh (expanded metal), punched nickel, foamed nickel, sponge nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), steel plate, punched steel plate, silver, and titanium. Substrates that can also be used include silicon substrates; metal substrates such as gold, iron, stainless steel, copper, aluminum, and lithium; alloy substrates containing any combination of these metals; oxide substrates such as indium tin oxide (ITO), indium zinc oxide (IZO), and antimony tin oxide (ATO); and carbon substrates such as glassy carbon, pyrolytic graphite, and carbon felt.

[0110] The method for producing the electrode is not particularly limited, and the electrode may be produced, for example, by applying a catalyst to the surface of a substrate. When removing components other than the catalyst, heat drying may be performed, or pressing may be performed after drying. Alternatively, a catalyst layer may be provided on the surface of the substrate by vacuum deposition or the like. The electrode may have a catalyst layer on only one side of the substrate, or on both sides of the substrate.

[0111] The thickness of the catalyst layer is not particularly limited, but can be, for example, 0.01 to 300 μm. When the thickness is equal to or greater than the lower limit, the electrode has excellent durability. When the thickness is equal to or less than the upper limit, the electrode performance is less likely to deteriorate.

[0112] The electrode functions as a catalyst for the oxygen evolution reaction or the oxygen reduction reaction, and functions as a catalyst for the reduction reaction shown below. (Oxygen generation reaction) 2H2O→O2+4H + +4e - (oxygen reduction reaction) O2+4H + +4e - →2H2O O2+2H2O+4e - →4OH -

[0113] [Metal-air secondary battery] In one embodiment, the present invention relates to a metal-air secondary battery comprising the electrode of the present invention. The electrode of the present invention can be used as the positive electrode (air electrode) of the metal-air secondary battery. The metal-air secondary battery can comprise a positive electrode (air electrode), a negative electrode (metal electrode), an electrolyte, and a separator. In the present invention, the positive electrode (air electrode) is an electrode that uses gaseous oxygen as the electrode active material.

[0114] The negative electrode (metal electrode) is not particularly limited, but examples thereof include simple metals such as aluminum, magnesium, calcium, lithium, zinc, and iron, and oxides of these metals.

[0115] The electrolyte is preferably an aqueous electrolyte, and is not particularly limited, but examples include alkaline aqueous solutions such as potassium hydroxide aqueous solution and sodium hydroxide aqueous solution, neutral aqueous solutions such as sodium chloride and ammonium chloride, and acidic aqueous solutions such as sulfuric acid aqueous solution. One type of electrolyte may be used alone, or two or more types may be used in combination. Inorganic solid electrolytes may also be used.

[0116] The separator is a component that separates the positive electrode (air electrode) from the negative electrode (metal electrode) and retains an electrolyte to ensure ionic conductivity between the positive electrode (air electrode) and the negative electrode (metal electrode). The separator is not particularly limited, but examples include polymers having micropores such as polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose, cellulose acetate, hydroxyalkyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, cellophane, polystyrene, polyacrylonitrile, polyacrylamide, polyvinyl chloride, polyimide, polyamide, vinylon, poly(meth)acrylic acid, gel compounds, ion exchange membranes, cyclized polymers, poly(meth)acrylate-containing polymers, sulfonate-containing polymers, quaternary ammonium salt-containing polymers, and quaternary phosphonium salt-containing polymers. The separator may be a non-porous or porous membrane. In the case of a porous membrane, the pore size is preferably 10 μm or less.

[0117] [Water electrolysis system] In one embodiment, the catalyst of the present invention has excellent catalytic activity for the oxygen generation reaction, and is therefore also useful as an oxygen generation catalyst for a water electrolysis system.

[0118] Currently practical water electrolysis systems are roughly divided into two types: alkaline water electrolysis, which uses an alkaline aqueous solution as the electrolyte, and polymer electrolyte membrane (PEM) water electrolysis, which uses a solid polymer membrane as the electrolyte. In one embodiment, the electrode of the present invention can be used in an alkaline water electrolysis system or a polymer electrolyte membrane water electrolysis system.

[0119] [Alkaline water electrolysis] The alkaline water electrolysis system may include, for example, an anode, a cathode, and a diaphragm for alkaline electrolysis disposed between the anode and the cathode.

[0120] The anode can include a conductive substrate and a catalyst layer covering the surface of the substrate. Preferably, the catalyst of the present invention is contained in the catalyst layer of the anode. The conductive substrate is not particularly limited, but examples thereof include nickel, nickel alloys, nickel-iron, vanadium, molybdenum, copper, silver, manganese, platinum group elements, graphite, chromium, or a combination thereof.

[0121] The cathode can be any cathode that can be used in an electrolytic cell for alkaline water electrolysis, without any particular limitation. The cathode can include a conductive substrate and a catalytic layer that coats the surface of the substrate. The catalytic layer is not particularly limited, but can include, for example, a noble metal oxide, nickel, cobalt, molybdenum, or manganese, or an oxide thereof, or a noble metal oxide. The conductive substrate is also not particularly limited, but examples include nickel, a nickel alloy, stainless steel, mild steel, a nickel alloy, or stainless steel or mild steel with a nickel-plated surface.

[0122] As the diaphragm for alkaline electrolysis, any diaphragm that can be used in an electrolytic cell for alkaline water electrolysis can be used without any particular limitation. The diaphragm is not particularly limited, and examples thereof include porous diaphragms such as porous membranes made of asbestos or modified asbestos, porous diaphragms using polysulfone-based polymers, cloth using polyphenylene sulfide fibers, fluorine-based porous membranes, and porous diaphragms using hybrid materials containing both inorganic and organic materials, and ion exchange membranes such as fluorine-based ion exchange membranes.

[0123] From the viewpoint of electrolysis efficiency, alkaline water used as an electrolyte for water electrolysis preferably has a pH of 10 or higher. Examples of alkaline water include an aqueous potassium hydroxide solution and an aqueous sodium hydroxide solution.

[0124] [Solid polymer water electrolysis (PEM electrolysis)] A solid polymer water electrolysis system can include, for example, two electrodes on either side of a solid polymer electrolyte membrane.

[0125] In one embodiment, the anode of the solid polymer water electrolysis system may include a conductive substrate and a catalyst layer covering the surface of the substrate. Preferably, the catalyst layer of the anode contains the catalyst of the present invention.

[0126] The cathode can include a conductive substrate and a catalytic layer covering the surface of the substrate. The catalytic layer preferably has high hydrogen generation capacity, and nickel, cobalt, iron, platinum group elements, or the like can be used. The conductive substrate is not particularly limited, but examples include nickel, a nickel alloy, stainless steel, mild steel, a nickel alloy, and stainless steel.

[0127] Water electrolysis can be performed using a solid polymer ion exchange membrane as the electrolyte membrane. The electrolyte membrane is not limited as long as it can provide the effects of the present invention, and an example of the electrolyte membrane is a fluorine-based sulfonic acid ion exchange membrane. [Example]

[0128] The present invention will be described in more detail below using examples and comparative examples, but the scope of the present invention is not limited to the examples.

[0129] [Creating a catalyst] Example 1 Cellulose nanofibers (CNF) derived from sea squirt shells as biomass-derived cellulose nanofibers and dried blood waste (BM) with an FeN structure as a dried material containing proteins or amino acids were mixed in a weight ratio of 1:10 and calcined at 900°C in a nitrogen atmosphere to prepare a calcined product. The resulting calcined product was used as the catalyst of Example 1.

[0130] Example 2 Cellulose nanofibers derived from sea squirt shells as biomass-derived cellulose nanofibers and dried blood waste material with an FeN structure as a dried material containing proteins or amino acids were mixed in a weight ratio of 1:5 and calcined at 900°C in a nitrogen atmosphere to prepare a calcined product. The resulting calcined product was used as the catalyst for Example 2.

[0131] Example 3 Cellulose nanofibers derived from sea squirt shells as biomass-derived cellulose nanofibers and dried blood waste material with an FeN structure as a dried material containing proteins or amino acids were mixed in a weight ratio of 1:2 and fired at 900°C in a nitrogen atmosphere to prepare a fired product. The resulting fired product was used as the catalyst for Example 3.

[0132] (Comparative Example 1) Only the cellulose nanofibers derived from sea squirt shells were calcined in a nitrogen atmosphere at 900° C. to prepare a calcined product. The resulting calcined product was used as the catalyst of Comparative Example 1.

[0133] [Electrode preparation] (Electrode of Example 1) 2 mg of the catalyst of Example 1 and 1 mg of Milli-Q water were mixed using an ultrasonic agitator and applied to a glassy carbon electrode. 5 μL of a 0.5% by mass Nafion aqueous solution was then applied to the glassy carbon electrode to obtain the electrode of Example 1.

[0134] (Electrode of Example 2) An electrode of Example 2 was obtained in the same manner as the electrode of Example 1, except that the catalyst of Example 2 was used instead of the catalyst of Example 1.

[0135] (Electrode of Example 3) An electrode of Example 3 was obtained in the same manner as the electrode of Example 1, except that the catalyst of Example 3 was used instead of the catalyst of Example 1.

[0136] (Electrode of Comparative Example 1) The electrode of Comparative Example 1 was obtained in the same manner as the electrode of Example 1, except that the catalyst of Comparative Example 1 was used instead of the catalyst of Example 1.

[0137] (Electrode of Comparative Example 2) An electrode of Comparative Example 2 was obtained in the same manner as the electrode of Example 1, except that Pt / C was used instead of the catalyst of Example 1.

[0138] (LSV measurement) Linear Sweep Voltammetry (LSV) curves were obtained using a rotating ring-disk electrode (BAS Corporation, RRDE-3A) at a sweep rate of 5 mV / s with an oxygen-saturated 0.1 M potassium hydroxide solution as the electrolyte. The rotating disk was rotated at 1600 rpm, with a platinum wire as the counter electrode and an Ag / AgCl electrode as the reference electrode. The LSV measurements were performed using a rotating ring-disk electrode (BAS Corporation, RRDE-3A) at a sweep rate of 5 mV / s with an oxygen-saturated 0.1 M potassium hydroxide solution as the electrolyte. The rotating disk was rotated at speeds of 0 rpm, 400 rpm, 800 rpm, 1200 rpm, 1600 rpm, 2000 rpm, and 2400 rpm. A platinum counter electrode and an Ag / AgCl reference electrode were used.

[0139] (starting potential) In the LSV curve, the potential at which current generation begins is defined as the onset potential (the point where the oxidation-reduction current rapidly increases in the voltammogram is extrapolated to derive the intersection with the residual current, and the potential at this intersection). The onset potential of the oxygen evolution reaction is E on-set / OER The onset potential of the oxygen reduction reaction is E on-set / ORR It was written as follows.

[0140] (half-wave potential) In the LSV curve of the oxygen reduction reaction, the potential corresponding to half the limiting current value was defined as the half-wave potential in the oxygen reduction reaction. The half-wave potential of the oxygen reduction reaction is E half(ORR) It was written as follows.

[0141] (Comparison of oxygen generation catalyst performance) Using the electrodes of Examples 1 to 3 and Comparative Examples 1 and 2, the onset potential E of the oxygen evolution reaction was measured. on-set / OER The results are shown in Table 1.

[0142] [Table 1]

[0143] As shown in Table 1, the electrodes of Examples 1 to 3, which used a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers and a dried material containing protein or amino acids, had a lower onset potential and were found to have superior oxygen generation catalytic ability than the electrode of Comparative Example 1, which used a catalyst containing a calcined product of cellulose nanofibers alone. Furthermore, the electrodes of Examples 1 and 2 were found to have superior oxygen generation catalytic ability than a Pt / C electrode, and the electrode of Example 3 was found to have oxygen generation catalytic ability comparable to that of a Pt / C electrode.

[0144] (Comparison of oxygen reduction catalyst performance) Using the electrodes of Examples 1 to 3 and the electrode of Comparative Example 1, the onset potential E of the oxygen reduction reaction was measured. on-set / ORR and half-wave potential E half(ORR) The results are shown in Table 2.

[0145] [Table 2]

[0146] As shown in Table 2, the electrodes of Examples 1 to 3, which used a catalyst containing a calcined mixture of biomass-derived cellulose nanofibers and a dried material containing proteins or amino acids, had higher onset potentials and half-wave potentials than the electrode of Comparative Example 1, which used a catalyst containing only calcined cellulose nanofibers, and were found to have excellent oxygen reduction catalytic ability.

[0147] Next, a mixture containing a dried material containing biomass-derived cellulose nanofibers, proteins, or amino acids, and a cobalt complex was calcined, and the electrochemical performance of a catalyst containing the resulting calcined material was evaluated.

[0148] [Creating a catalyst] Example 4 The biomass-derived cellulose nanofibers were cellulose nanofibers (CNF) derived from sea squirt shells, dried blood waste (BM) with an FeN4 structure was used as a dried material containing proteins or amino acids, and vitamin B was used as a cobalt complex. 12 (VB12) were mixed in a weight ratio of 1:9:1, and purified water was added to prepare a dispersion. Next, this dispersion was dried in small portions on a hot plate maintained at 60°C, and then calcined at 900°C in a nitrogen atmosphere to obtain a calcined product. The calcined product was used as the catalyst of Example 4.

[0149] Example 5 The biomass-derived cellulose nanofibers were cellulose nanofibers derived from sea squirt shells, dried blood waste with an FeN4 structure was used as a dried material containing proteins or amino acids, and vitamin B was used as a cobalt complex. 12 A calcined product was obtained in the same manner as in Example 4, except that the above were mixed in a weight ratio of 1:9:0. The calcined product obtained was used as the catalyst of Example 5.

[0150] [Creating electrodes] (Electrode of Example 4) 2 mg of the catalyst of Example 4 and 1 mg of Milli-Q water were kneaded using an ultrasonic agitator and applied to a glassy carbon electrode. 5 μL of a 0.5% by mass Nafion aqueous solution was then applied to the glassy carbon electrode to obtain the electrode of Example 4.

[0151] (Electrode of Example 5) An electrode of Example 5 was obtained in the same manner as the electrode of Example 4, except that the catalyst of Example 5 was used instead of the catalyst of Example 4.

[0152] (Electrode of Comparative Example 2) An electrode of Comparative Example 2 was obtained in the same manner as the electrode of Example 4, except that Pt / C was used instead of the catalyst of Example 4.

[0153] (Electrode of Comparative Example 3) An electrode of Comparative Example 3 was obtained in the same manner as the electrode of Example 4, except that GC was used instead of the catalyst of Example 4.

[0154] (LSV measurement by RRDE) The LSV curve was obtained using an oxygen-saturated 0.1 M potassium hydroxide aqueous solution as the electrolyte and a rotating ring-disk electrode (BAS Corporation, RRDE-3A) under the following conditions: Rotating disc speed: 1600 rpm Voltage range: 0.2 to 2.0 [VvsNHE] The results of the LSV measurements are shown in Figures 1 and 2.

[0155] As shown in Figure 1, the electrode of Example 4, which used a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex, was found to have superior oxygen generation catalytic ability compared to the electrode of Example 5, which used a catalyst containing a calcined product obtained without adding a cobalt complex.

[0156] Furthermore, as shown in Figure 1, the electrode of Example 4, which used a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex, was found to have excellent oxygen reduction catalytic performance and oxygen evolution catalytic performance.

[0157] Furthermore, as shown in Figure 1, the electrode of Example 4, which uses a catalyst containing a calcined mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex, was found to exhibit a difference between the oxygen reduction reaction potential and the oxygen evolution reaction potential that was equal to or better than that of the Pt / C electrode (Comparative Example 2).

[0158] As shown in Figure 2, the electrode of Example 4, which used a catalyst containing a calcined product of a mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex, was found to have superior hydrogen generation catalytic ability compared to the electrode of Example 5, which used a catalyst containing a calcined product obtained without adding a cobalt complex.

[0159] (IV characteristics evaluation) An air-zinc battery was fabricated using the catalyst of Example 4, which includes a mixture of biomass-derived cellulose nanofibers, a dried material containing protein or amino acid, and a calcined product of a mixture containing a cobalt complex, as a cathode catalyst of the air-zinc battery, and the IV characteristics were evaluated. The results of the IV characteristics evaluation are shown in Figure 3.

[0160] As shown in FIG. 3, in a battery using the catalyst of Example 4, which includes a calcined mixture containing biomass-derived cellulose nanofibers, a dried material containing a protein or amino acid, and a cobalt complex, as a positive electrode catalyst, the power dissipation was 189 mW / cm 2 Therefore, it was found that a high-performance battery with a high power density can be obtained by using a catalyst containing a calcined mixture containing biomass-derived cellulose nanofibers, a dried material containing protein or amino acids, and a cobalt complex.

[0161] Example 6 The biomass-derived cellulose nanofibers were derived from the seaweed wakame seaweed, the dried material containing protein or amino acid was blood waste with an FeN4 structure, and the cobalt complex was vitamin B 12 A calcined product was obtained in the same manner as in Example 4, except that the above-mentioned components were mixed in a weight ratio of 1:9:0. The calcined product obtained was used as the catalyst of Example 6. As a result, the onset potential E of the oxygen generating catalyst was on-set / OER is 1.40 V vs RHE, the onset potential E of the oxygen reduction reaction catalyst on-set / ORR The ZnO catalyst exhibited excellent catalytic activity for oxygen evolution and oxygen reduction, with a voltage of 0.965V vs. RHE. [Industrial Applicability]

[0162] The catalyst of the present invention is useful because it exhibits excellent catalytic performance when used as a catalyst for promoting the oxygen evolution reaction and the oxygen reduction reaction at the positive electrode of a metal-air secondary battery or a water electrolysis system. The catalyst of the present invention can also exhibit excellent catalytic performance when used as a catalyst for promoting the hydrogen evolution reaction. Furthermore, because the catalyst of the present invention does not use platinum, iridium, or ruthenium, production costs can be reduced and a production process suitable for mass production can be designed. Furthermore, because the catalyst of the present invention uses cellulose nanofibers derived from biomass, it can significantly contribute to waste recycling and resource recycling.

Claims

1. A catalyst comprising a calcined mixture containing biomass-derived cellulose nanofibers and a dried material containing a protein or amino acid.

2. The catalyst of claim 1 , wherein the cellulose nanofibers are derived from marine biomass.

3. The catalyst according to claim 1 , wherein the cellulose nanofibers are derived from sea squirt shells or seaweed.

4. The dried material containing the protein or amino acid is FeN ４ 10. The catalyst of claim 1, which is a dried structured blood waste product.

5. 2. The catalyst of claim 1, comprising 0.1 to 30% by weight of iron, based on the total weight of the catalyst.

6. 2. The catalyst of claim 1, comprising 0.1 to 40% by weight of phosphorus, based on the total weight of the catalyst.

7. The catalyst according to claim 1, wherein the mass ratio of the protein- or amino acid-containing dry material to the cellulose nanofibers contained in the mixture is 1:1 to 20:

1.

8. The catalyst of claim 1 , wherein the mixture further comprises a cobalt complex.

9. The cobalt complex is a vitamin B １２ The catalyst according to claim 8, which is a compound of the formula (I).

10. Vitamin B １２ 10. The catalyst of claim 9, wherein the species is derived from biomass.

11. Vitamin B １２ The catalyst according to claim 9, wherein the hydroxyl group is derived from seaweed and / or oysters.

12. 9. The catalyst of claim 8, comprising 0.1 to 30% by weight of cobalt, based on the total weight of the catalyst.

13. The catalyst according to claim 8, wherein the mass ratio of the cellulose nanofibers, the protein- or amino acid-containing dry material, and the cobalt complex contained in the mixture is 1:1 to 20:0.1 to 10.

14. The catalyst according to claim 1, which is for oxygen generation, oxygen reduction, or hydrogen generation.

15. A method for producing a catalyst comprising a calcined product of a mixture comprising biomass-derived cellulose nanofibers and a dried material containing a protein or amino acid, A production method comprising the steps of preparing a mixture containing the protein or amino acid-containing dry material and the cellulose nanofibers, and calcining the mixture.

16. The method of claim 15 , wherein the mixture further comprises a cobalt complex.

17. The production method according to claim 15, comprising a step of extracting the cellulose nanofibers from biomass.

18. The method for producing a protein or amino acid-containing dried product according to claim 15, further comprising concentrating and drying blood waste.

19. The method of claim 15, wherein the cellulose nanofibers are derived from marine biomass.

20. The method according to claim 15, wherein the cellulose nanofibers are derived from sea squirt shells or seaweed.

21. The cobalt complex is a vitamin B １２ The method of claim 16, wherein the compound is a compound of the formula (I).

22. Vitamin B １２ 22. The method of claim 21, wherein the species is derived from biomass.

23. Vitamin B １２ The method of claim 21, wherein the sesame seeds are derived from seaweed and / or oysters.

24. An electrode for a metal-air secondary battery or a water electrolysis system, comprising the catalyst according to any one of claims 1 to 14.

25. A metal-air secondary battery or a water electrolysis system comprising the electrode according to claim 24.

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