Metal nanostructure and method for manufacturing same

Abstract

The present invention relates to a metal nanostructure and a method for manufacturing same. Provided is a method for manufacturing a metal nanostructure, the method comprising a step for reacting a precursor aqueous solution including a metal salt, glycerol, and oxalic acid.

Description

Metal nanostructure and method for manufacturing the same

[0001] The present invention relates to a metal nanostructure and a method for manufacturing the same.

[0002]

[0003] As a method for manufacturing metal nanostructures, the “polyol method” is known.

[0004] In the above “polyol method,” a polyol is used as a reducing agent, a metal salt precursor is reduced to produce a metal nanostructure, and the produced metal nanostructure is supported on a carbon-based carrier.

[0005]

[0006] A representative example of the "polyol" used in the above polyol method is ethylene glycol, which performs a dual function as a solvent and a reducing agent.

[0007] The above ethylene glycol, despite its advantages of low viscosity and good reactivity, has the disadvantages of being difficult to handle due to its strong toxicity and high water solubility, and its ability to uniformly control the shape and size of metal nanostructures and ensure even dispersion is limited.

[0008]

[0009] One embodiment is to solve the problem of using ethylene glycol as a “polyol”.

[0010]

[0011] One embodiment uses glycerol instead of ethylene glycol as the "polyol", while using oxalic acid as the "reducing aid" for the polyol reaction.

[0012]

[0013] One implementation example can easily control the shape and size of metal nanostructures under conditions where glycerol and oxalic acid coexist.

[0014]

[0015] Figure 1 schematically illustrates a reaction formula for a method for manufacturing a metal nanostructure according to one embodiment.

[0016]

[0017] The advantages and features of the technology described below, and the methods for achieving them, will become clearer with reference to the detailed implementation examples described below, along with the accompanying drawings. However, the form of implementation is not limited to the implementation examples disclosed below.

[0018]

[0019] (Definition of terms)

[0020] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in their common sense to those of ordinary skill in the relevant technical field. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0021] When a part of a specification is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated. Furthermore, the singular includes the plural unless specifically stated otherwise.

[0022]

[0023] In this specification, “particle size” or “average particle size” can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope photograph or a scanning electron microscope photograph.

[0024]

[0025] (Method for manufacturing metal nanostructures)

[0026] In the commonly known polyol method, metal nanostructures are manufactured using ethylene glycol.

[0027] However, the ethylene glycol exhibits strong toxicity and high water solubility, making it difficult to handle, and the ability to control the shape and size of the metal nanostructure is limited. The latter is particularly problematic when the metal nanostructure is used as a metal nanostructure for fuel cells or water electrolysis.

[0028] Specifically, if the shape and size of the metal nanostructure are uneven or large, the metal nanostructure may be eluted from the catalyst including the same, damaging the polymer electrolyte membrane and reducing the performance and durability of the fuel cell or water electrolysis device.

[0029]

[0030] One embodiment uses glycerol instead of ethylene glycol as the "polyol", while using oxalic acid as the "reducing aid" for the polyol reaction.

[0031] Specifically, one embodiment provides a method for preparing a metal nanostructure, comprising the step of reacting a precursor aqueous solution comprising a metal salt, glycerol, and oxalic acid.

[0032] More specifically, one embodiment facilitates the manufacture of metal nanostructures of varying shapes and sizes under conditions in which glycerol and oxalic acid coexist. The manufacturing process of the metal nanostructures and the process of supporting them on a carbon-based carrier are performed in situ.

[0033] As a result, one embodiment can provide a metal nanostructure with excellent durability. In particular, the metal nanostructure is suitable for use as a metal nanostructure for a fuel cell or a metal nanostructure for water electrolysis.

[0034]

[0035] Hereinafter, raw materials for metal nanostructures according to one embodiment and a manufacturing method using the same will be described in more detail.

[0036]

[0037] metal salts

[0038] The above metal salt is a precursor of a metal nanostructure.

[0039] The metal constituting the metal salt may be a noble metal, a transition metal, an alloy thereof, or a mixture thereof. Specifically, the noble metal may include platinum (Pt), ruthenium (Ru), osmium (Os), iridium (Ir), palladium (Pd), an alloy thereof, or a mixture thereof, and may be, for example, platinum. In addition, the transition metal may include cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), tin (Sn), manganese (Mn), copper (Cu), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), yttrium (Y), niobium (Nb), an alloy thereof, or a mixture thereof.

[0040] Meanwhile, the metal salt is in the form of salts and may include nitrate, sulfate, acetate, chloride, oxide, or a combination thereof of the metal.

[0041] Specifically, the metal salt is a metal salt containing platinum (Pt), and may be dinitrodiamineplatinum nitrate, chloroplatinic acid, potassium chloroplatinate, platinum oxalate, monoethanolamineplatinum hydroxide, triethanolamineplatinum hydroxide, or a combination thereof.

[0042] For example, the metal salt may be dinitrodiamineplatinum nitrate. For more specific examples, the dinitrodiamineplatinum nitrate may be a basic platinum precursor such as (TEA)-2Pt(OH)6, (MEA)-2Pt(OH)6, [Pt(NH3)4]Cl2, [Pt(NH3)4](NO3)2, [Pt(NH3)4](OH)2, Pt(NH3)2Cl2, (NH4)2[PtCl4].

[0043]

[0044] glycerol

[0045] The above glycerol is a type of polyol compound and is represented by the following chemical formula 1:

[0046] [Chemical Formula 1]

[0047]

[0048] The above glycerol is a by-product of biodiesel and can be easily and inexpensively purchased in the industry. It is less toxic than ethylene glycol and can be used as a food additive.

[0049]

[0050] Theoretically, since the glycerol is a type of polyol compound, it can function as a solvent and a reducing agent to reduce the metal salt.

[0051] However, the polyol used in the above "polyol method" must have low viscosity. In the case of the above glycerol, its viscosity is relatively higher than that of the above ethylene glycol, and thus it has not been handled in the "polyol method" so far.

[0052] In one embodiment, to lower the viscosity of the glycerol, the glycerol is dissolved in water and used in the form of an aqueous solution. Specifically, a precursor aqueous solution containing a metal salt, glycerol, and oxalic acid is reacted. This will be described in more detail below.

[0053]

[0054] Meanwhile, the glycerol acts as a template, allowing the metal salt to have a uniform shape and size during the process of being converted into a metal nanostructure. As a result, the use of the glycerol allows for even dispersion of the metal nanostructure.

[0055]

[0056] oxalic acid

[0057] The above oxalic acid can assist the reducing function of glycerol during the conversion of the metal salt into a metal nanostructure, while maintaining the pH of the reaction between the metal salt and the glycerol. In this sense, the oxalic acid acts as a "reducing agent."

[0058] Specifically, the precursor aqueous solution comprising the metal salt, glycerol, and oxalic acid may further comprise formic acid. Here, the formic acid may be converted from a portion of the oxalic acid.

[0059]

[0060] The molar ratio of the metal salt and the oxalic acid may be 1:0.5 to 1:12, specifically 1:3 to 1:10, more specifically 1:4 to 1:9, for example 1:5 to 1:7. In this range, the pH control and reduction aid role of the oxalic acid may be improved.

[0061]

[0062] Manufacturing process of metal nanostructures

[0063] Figure 1 schematically illustrates the reaction of a precursor aqueous solution containing the metal salt, glycerol, oxalic acid, and water.

[0064] Specifically, when some or all of the oxalic acid is converted into formic acid by reacting with some or all of the glycerol, some of the glycerol reacts with some or all of the oxalic acid to produce 2-(2,3-dihydroxypropoxy)-2-oxoacetic acid ((2-(2,3-dihydroxypropoxy)-2-oxoacetic acid or glycerol mono oxalate); through a carbon dioxide removal reaction of the 2-(2,3-dihydroxypropoxy)-2-oxoacetic acid, 2,3-dihydroxypropyl formate (or glycerol mono format) is produced; through a hydrolysis reaction of the 2,3-dihydroxypropyl formate, formic acid can be produced. Here, together with the formic acid Glycerol can be regenerated.

[0065] Accordingly, the reaction between the oxalic acid and glycerol, the reaction between the metal salt and glycerol, etc. can be performed in-situ.

[0066]

[0067] The step of reacting the precursor aqueous solution containing the above metal salt, glycerol, and oxalic acid can be performed under heat treatment conditions.

[0068] The above heat treatment may be carried out at a temperature range of 60°C or more to 150°C or less, specifically 80°C or more to 100°C or less, for 1 hour or more to 24 hours or less, specifically 3 hours or more to 10 hours or less, for example 5 hours or more to 8 hours or less.

[0069] The above heat treatment can be performed in a non-oxidizing atmosphere, for example, in a reducing atmosphere (such as a hydrogen gas atmosphere).

[0070]

[0071] In the step of reacting the precursor aqueous solution containing the metal salt, glycerol, and oxalic acid, the pH can be maintained within a range of 1 to 9, specifically, 2 to 5, for example, 2 to 3, by formic acid converted from a portion of the oxalic acid and the remainder of the oxalic acid. Here, in order to more precisely control the pH within a desired range, a pH adjusting agent such as nitrate, sulfate, acetate, NaOH, or NH4OH can be further used.

[0072]

[0073] In the step of reacting the precursor aqueous solution containing the above metal salt, glycerol, and oxalic acid, the viscosity needs to be controlled.

[0074] The viscosity of the above precursor aqueous solution may be in the range of 10 cP or more to 1000 cP or less, specifically 100 cP or more to 500 cP or less, for example 150 cP or more to 300 cP or less.

[0075] For the above viscosity control, the water content in 100 wt% of the precursor aqueous solution may be 10 wt% or more and 99 wt% or less, specifically 30 wt% or more and 70 wt% or less, for example 40 wt% or more and 60 wt% or less.

[0076] Here, the need for viscosity control is as described above.

[0077]

[0078] (Specific method for manufacturing the catalyst)

[0079] Below, the manufacturing method of the above-described embodiment is described in more detail.

[0080]

[0081] The step of reacting the precursor aqueous solution containing the metal salt, glycerol, and oxalic acid may include a first step of preparing a glycerol aqueous solution; a second step of reacting the glycerol aqueous solution prepared in the first step with a metal salt aqueous solution; and a third step of reacting the reaction product of the second step with an oxalic acid aqueous solution.

[0082]

[0083] Step 1

[0084] As mentioned above, in one embodiment, in order to lower the viscosity of the glycerol, the glycerol is dissolved in water and used in the form of an aqueous solution.

[0085] In this regard, the glycerol aqueous solution of the first step may contain glycerol and water in a weight ratio of 10:90 to 80:20, specifically 40:60 to 60:40.

[0086]

[0087] Step 2

[0088] The metal salt aqueous solution of the second step may contain the metal salt and water in a weight ratio of 30:70 to 90:10, specifically 50:50 to 70:30.

[0089] The reaction of the slurry prepared in the first step and the metal salt aqueous solution can be performed under heat treatment conditions.

[0090] The above heat treatment may be carried out at a temperature range of 60°C or more to 150°C or less, specifically 80°C or more to 110°C or less, for 0.1 hour or more to 24 hours or less, specifically 3 hours or more to 10 hours or less, for example 5 hours or more to 8 hours or less.

[0091] The above heat treatment can be performed in a non-oxidizing atmosphere, for example, in a reducing atmosphere (such as a hydrogen gas atmosphere).

[0092]

[0093] Step 3

[0094] The oxalic acid aqueous solution of the third step may contain oxalic acid and water in a weight ratio of 1:1 to 1:10, specifically 1:3 to 1:8.

[0095] When reacting the reaction product of the second step with an oxalic acid aqueous solution, the molar ratio of the metal salt and oxalic acid may be 1:0.5 to 1:12, specifically 1:3 to 1:10, more specifically 1:4 to 1:9, for example 1:5 to 1:7. In this range, the pH control and reduction aid role of the oxalic acid may be improved.

[0096] In the third step, the oxalic acid aqueous solution can be supplied at a temperature range of 50 to 90°C, specifically 60 to 80°C, at a rate of 10 to 100 ml / min, specifically 30 to 80 ml / min, and mixed with the reaction product of the second step.

[0097] After the above supply is completed, the temperature of the mixture of the reaction product of the second step and the oxalic acid aqueous solution is within the range of 90 to 120°C, specifically 100 to 110°C, and the mixture is mixed for 5 to 10 hours while maintaining this temperature range, thereby enabling uniform nucleation and dispersion of the metal nanostructure.

[0098]

[0099] Step 4

[0100] After the above third step, a fourth step may be further included, sequentially performing maturation, filtration, washing, and drying. This can be viewed as a post-processing step to increase the purity of the final metal nanostructure obtained.

[0101]

[0102] Step 5

[0103] The metal nanostructures obtained after the third or fourth step can be dispersed on a support to increase the activated surface area. Specifically, a carbon material, a metal oxide, or a combination thereof can be used as the support. For example, a high surface area carbon material having a size of 5 μm or less can be dispersed in water, and then a dispersion of the high surface area carbon material can be added to the metal nanostructure solution, thereby obtaining a material in which the metal nanostructures are supported on the high surface area carbon material. The obtained product can be used as a catalyst for a fuel cell or a catalyst for water electrolysis.

[0104] Meanwhile, after adding the high surface area carbon material dispersion to the metal nanostructure solution, nanomilling can be performed so that the size of the solid particles becomes less than 1 μm.

[0105]

[0106] (metal nanostructure)

[0107] In one embodiment, a metal nanostructure is provided that inevitably further comprises glycerol in an amount greater than 0 ppm and less than 40 ppm.

[0108] The metal nanostructure of one embodiment may be manufactured using the method described above and may be in an active state. The activated metal nanostructure strongly adsorbs the materials used during its manufacturing process. Accordingly, analyzing the metal nanostructure of one embodiment can detect the materials used during its manufacturing process.

[0109]

[0110] Residual amount of glycerol

[0111] According to the method described above, since glycerol is used as a solvent and reducing agent, glycerol inevitably remains on the surface of the metal nanostructure finally obtained.

[0112] In one embodiment of the metal nanostructure, the residual amount of glycerol can be measured by the LC-MS method. Specifically, a 10 g sample is treated with 100 g of water (H2O) and 5 g of ethanol, and then heated at approximately 90°C for 4 hours. During this process, the glycerol remaining on the surface of the metal nanostructure is released by the water and ethanol.

[0113] The above-mentioned released glycerol is measured by LC-MS and HPLC. Here, a nonpolar dimethyl-polysiloxane column is used, a toluene standard solution with a concentration of 4 g / L is used, and the amount of toluene to be injected is standardized to 4 μg, and the peak of the organic compound is measured. Among the chromatograms obtained above, the areas between n-hexane and n-hexadecane are added, converted to the mass unit of toluene, and the amount of glycerol is calculated, and the amount of glycerol (μg) is expressed based on the amount (g) of the sample used in the experiment, and expressed in ppm, ppb, or weight%.

[0114] As a result of the LC-MS measurement as described above, in the metal nanostructure of one embodiment, the residual amount of glycerol may be more than 0 ppm and less than 50 ppm, specifically more than 0 ppm and less than 40 ppm, and more specifically 0 ppm or more and 30 ppm or less.

[0115]

[0116] Residual amount of reactants

[0117] According to the above-described method, in addition to the glycerol, metal salts, oxalic acid, formic acid, etc. are used as reactants. Accordingly, according to the above-described method, the reactants may inevitably or selectively remain on the surface of the metal nanostructure ultimately obtained.

[0118] The residual amounts of the above reaction substances can also be measured by LC-MS. The specific LC-MS measurement method is as described above, except that only the "glycerol" is replaced with each of the above reaction substances.

[0119] Specifically, in the metal nanostructure of one embodiment, the residual amount of oxalic acid may be 0 ppb or more and less than 20 ppb, specifically 0 ppb or more and 15 ppb or less, or 0 ppb or more and 10 ppb or less.

[0120]

[0121] Residual amount of pH adjuster

[0122] According to the above-described method, since pH regulators such as nitrate, sulfate, acetate, NaOH, and NH4OH can be further used, the pH regulator can also optionally remain. The remaining amount of the pH regulator can also be measured by the LC-MS method. The specific LC-MS measurement method is as described above, except that only the "glycerol" is replaced with the pH regulator.

[0123]

[0124] Residual amount of nitrogen compounds

[0125] When using the above ethylene glycol according to the generally known "polyol" method, when using basic platinum precursors such as (TEA)-2Pt(OH)6, (MEA)-2Pt(OH)6, [Pt(NH3)4]Cl2, [Pt(NH3)4](NO3)2, [Pt(NH3)4](OH)2, Pt(NH3)2Cl2, (NH4)2[PtCl4], an excess of nitrogen compounds may inevitably remain on the surface of the final obtained metal nanostructure.

[0126] However, when using glycerol instead of ethylene glycol according to the method described above, the content of nitrogen compounds remaining in the final obtained metal nanostructure may be reduced even when using the basic platinum precursor.

[0127] As a result, in the metal nanostructure of one embodiment, the maximum residual amount of nitrogen compound may be 0 ppm or more and 50 ppm or less.

[0128] The maximum residual amount of the above nitrogen compound can be measured by the N2-TPD method. For example, by loading a 0.1 g sample into a vertical gas flow reactor using quartz wool, then sending 2 L of N2 gas into the reactor at a ramp rate of 10 °C / min until the temperature reaches 400 °C, and then measuring the exhaust gas using an MKS FT-IR analyzer, the maximum residual amount of the nitrogen compound can be determined.

[0129]

[0130] Shape and size of metal nanostructures

[0131] When using the ethylene glycol and polyvinylpyrrolidone according to the generally known "polyol" method, it is difficult to uniformly control the shape and size of the final obtained metal nanostructure and to evenly disperse it.

[0132]

[0133] However, when using the glycerol and oxalic acid according to the method described above, the shape and size of the final metal nanostructure can be uniformly controlled to ensure even dispersion. As a result, the metal nanostructure of one embodiment can be a spherical metal nanoparticle.

[0134]

[0135] When performing XRD analysis on a metal nanostructure of one embodiment, the crystallite diameter of the (111) plane may be 0.1 nm or more and 20 nm or less, specifically 0.5 nm or more and 15 nm or less, for example 1 nm or more and 10 nm or less.

[0136] Here, the "crystallite diameter" refers to the size of crystals that are connected on the (111) plane of the metal nanostructure. The crystallite diameter can be calculated from the half width of the XRD peak for the metal nanostructure of the above embodiment using the Scherrer equation.

[0137]

[0138] In addition, when analyzing the metal nanostructure of one embodiment by TEM, the observed particle size may be 0.1 nm or more and 20 nm or less, specifically 0.5 nm or more and 15 nm or less, for example 1 nm or more and 10 nm or less.

[0139]

[0140] Weight retention during heat treatment of metal nanostructures

[0141] When the glycerol and oxalic acid are used according to the method described above, the weight loss of the metal nanostructure finally obtained can be suppressed.

[0142] The metal nanostructure of one embodiment may have a weight retention ratio of 97 wt% to 100 wt% according to the following mathematical formula 1 when heat-treated at 250°C:

[0143] [Mathematical Formula 1]

[0144] Weight retention of metal nanostructure = 100*(AB) / A

[0145] In the above mathematical formula 1,

[0146] A is the weight of the metal nanostructure before heat treatment,

[0147] B is the weight of the metal nanostructure after heat treatment.

[0148]

[0149] (catalyst)

[0150] The above metal nanostructure is suitable for use as a metal nanostructure for a fuel cell or a metal nanostructure for water electrolysis.

[0151]

[0152] Accordingly, as an embodiment, a catalyst including the above metal nanostructure is provided.

[0153]

[0154] carbon-based carrier

[0155] The above carrier may be a carbon-based carrier.

[0156] The carbon-based carrier may include carbon black, graphite, carbon nanofibers, graphitized carbon nanofibers, carbon nanotubes, carbon nanohorns, carbon nanowires, or a combination thereof. The carbon black may include, for example, Denka black, Ketjen black, acetylene black, channel black, furnace black, lamp black, thermal black, or a combination thereof.

[0157] The specific surface area of ​​the carbon-based carrier may be 250 m2 / g to 1200 m2 / g. When the specific surface area of ​​the carbon-based carrier is 250 m2 / g or more, the area on which the metal nanostructure is attached can be increased, thereby dispersing the metal nanostructure to a high level and increasing the effective surface area. On the other hand, when the specific surface area of ​​the carbon-based carrier exceeds 1200 m2 / g, the presence ratio of ultrafine pores (less than about 20 angstroms) into which the ion exchange resin has difficulty penetrating when forming a fuel cell electrode increases, which may lower the utilization efficiency of the catalyst.

[0158]

[0159] The catalyst of one embodiment may include the metal and the carbon-based carrier in a weight ratio of 30:70 to 95:5, 40:60 to 95:5, or 50:50 to 95:5. This can be appropriately adjusted in consideration of performance as a catalyst.

[0160]

[0161] (catalysts, electrodes for fuel cells, membrane-electrode assemblies, and fuel cells)

[0162] One embodiment provides an electrode for a fuel cell, comprising the above-described catalyst and an ionomer mixed with the catalyst.

[0163] One embodiment provides a membrane-electrode assembly comprising an anode electrode and a cathode electrode positioned opposite each other, and an ion exchange membrane positioned between the anode electrode and the cathode electrode, wherein the anode electrode, the cathode electrode, or both correspond to electrodes for a fuel cell as described above.

[0164] One embodiment provides a fuel cell comprising the membrane-electrode assembly described above.

[0165] The electrode, membrane-electrode assembly, and fuel cell are the same as those for a general fuel cell electrode, membrane-electrode assembly for a fuel cell, and fuel cell, except that they include the above-mentioned catalyst, and therefore a detailed description thereof is omitted.

[0166]

[0167] Specific embodiments of the invention are presented below. However, the embodiments described below are merely intended to specifically illustrate or explain the invention and should not be construed as limiting the scope of the invention.

[0168]

[0169] Example 1

[0170] (1) Using a high-shear dispersion mixer, a glycerol aqueous solution was prepared by mixing glycerol and water (H2O) in a weight ratio of 50:50. The glycerol aqueous solution was wet stirred.

[0171] (2) A metal salt aqueous solution was prepared by mixing metal salt and water (H2O) in a weight ratio of 50:50. The metal salt aqueous solution was added to the glycerol aqueous solution and heated to 100°C for 1 hour. When the metal salt aqueous solution was added, the weight ratio of the metal salt and glycerol was set to 60:40.

[0172] (3) An oxalic acid aqueous solution was prepared by mixing oxalic acid and water (H2O) in a weight ratio of 1:5. The oxalic acid aqueous solution was heated to 70°C, and the heated oxalic acid aqueous solution was pumped into the mixture obtained in step (2). Here, the molar ratio of the metal salt and oxalic acid was set to 1:2, taking into account the size distribution of the final metal nanostructure.

[0173] (4) The final reaction mixture was treated at 100°C for 5 hours, cooled to room temperature, and aged for 12 hours with stirring at 500 rpm. The aged metal nanostructure slurry was filtered and washed with hot water to remove water, oxalic acid, and its derivatives. The washed metal nanostructure cake reached a final pH of 6.5. The metal nanostructure cake that reached the pH was vacuum-dried at 100°C.

[0174]

[0175] Example 2

[0176] A metal nanostructure was manufactured in the same manner as in Example 1, except that the weight ratio of glycerol and water (H2O) in step (1) was changed to 40:60.

[0177]

[0178] Example 3

[0179] A metal nanostructure was manufactured in the same manner as in Example 1, except that the weight ratio of glycerol and water (H2O) in step (1) was changed to 60:40.

[0180]

[0181] Comparative Example 1

[0182] (1) An ethylene glycol aqueous solution was prepared.

[0183] (2) A metal salt aqueous solution was prepared by mixing metal salt and water (H2O) in a weight ratio of 50:50. The metal salt aqueous solution was added to the ethylene glycol aqueous solution and heated at 100°C for 1 hour.

[0184] (3) After adjusting the pH to 9.5, it was heated at 180 ℃ for 5 hours, cooled to room temperature, and aged for 12 hours with stirring at 500 rpm. The aged metal nanostructure slurry was filtered and washed with hot water to remove water, oxalic acid, and its derivatives. The washed metal nanostructure cake reached a final pH of 5. The metal nanostructure cake that reached the above pH was vacuum-dried at 100 ℃, and then further dried at 200 ℃ in an N2-purged oven dryer for 12 hours.

[0185]

[0186] [Evaluation Example 1: Performance Evaluation of Metal Nanostructures]

[0187] Evaluation Example 1-1: Residual amount of each residual substance on the surface of a metal nanostructure

[0188] For the metal nanostructures of the examples and comparative examples, the residual amount of each residual substance on the surface of the metal nanostructure was evaluated according to the following methods, and the evaluation results are shown in Table 1 below.

[0189] (1) Glycerol and oxalic acid

[0190] For the metal nanostructures of the examples and comparative examples, the residual amounts of glycerol and oxalic acid were evaluated. The residual amounts of each substance can be measured by LC-MS.

[0191] Specifically, a 10 g sample is treated with 100 g of water (H2O) and 5 g of ethanol, and then heated at approximately 90°C for 4 hours. During this process, glycerol remaining on the surface of the metal nanostructure is released by the water and ethanol.

[0192] The above-mentioned released glycerol is measured by LC-MS and HPLC. Here, a nonpolar dimethyl-polysiloxane column is used, a toluene standard solution with a concentration of 4 g / L is used, and the amount of toluene to be injected is standardized to 4 μg, and the peak of the organic compound is measured. Among the chromatograms obtained above, the areas between n-hexane and n-hexadecane are added up, converted to the mass unit of toluene, and the amount of glycerol is calculated, and the amount of glycerol (μg) is expressed based on the amount (g) of the sample used in the experiment, and expressed in ppm units.

[0193] In addition, oxalic acid was measured in the same way as glycerol, and expressed in ppb and weight%, respectively.

[0194] (2) Nitrogen compounds

[0195] Meanwhile, the maximum residual amount of nitrogen compounds was evaluated for the metal nanostructures of the examples and comparative examples.

[0196] The maximum residual amount of the above nitrogen compound can be measured by the N2-TPD method. For example, by loading a 0.1 g sample into a vertical gas flow reactor using quartz wool, then sending 2 L of N2 gas into the reactor at a ramp rate of 10°C / min until the temperature reaches 400°C, and then measuring the exhaust gas using an MKS FT-IR analyzer, the maximum residual amount of the nitrogen compound can be determined.

[0197]

[0198] Glycerol (ppm) Oxalic acid (ppb) Nitrogen compounds (Max ppm) Example 1 183.424 Example 292.121 Example 3 216.519 Comparative example 100168

[0199] Evaluation Example 1-2: Crystal diameter, particle size, and weight retention of metal nanostructures

[0200] For the metal nanostructures of the examples and comparative examples, the crystallite diameter, particle size, and weight retention were evaluated according to the following methods, and the evaluation results are shown in Table 2 below.

[0201] (1) Determinant diameter

[0202] For the metal nanostructures of the examples and comparative examples, the crystallite diameter of the (111) plane was evaluated through XRD analysis.

[0203] (2) Particle size

[0204] For the metal nanostructures of the examples and comparative examples, the particle size was evaluated through TEM analysis.

[0205] (3) Weight retention during heat treatment

[0206] For the metal nanostructures of the examples and comparative examples, the weight retention rate was evaluated according to the following mathematical formula 1 by heat treatment at 250°C:

[0207] [Mathematical Formula 1]

[0208] Weight retention = 100*(AB) / A

[0209] In the above mathematical formula 1,

[0210] A is the weight of the metal nanostructure before heat treatment,

[0211] B is the weight of the metal nanostructure after heat treatment.

[0212]

[0213] (111) Diameter of crystal particle (nm) Particle size (nm) Weight retention during heat treatment (wt%) Example 14.9 5.8 98.1 Example 26.5 5.5 99.2 Example 33.5 2.7 97.5 Comparative example 15.8 6.4 99.1

[0214] Evaluation Example 1-3: Manufacturing Process Change Example and Its Evaluation (1)

[0215] A metal nanostructure was manufactured using the same method as Example 1, but the molar ratio of the metal salt and oxalic acid in the precursor aqueous solution was changed according to Table 3 below.

[0216] In the same manner as Evaluation Example 2, the (111) plane crystallite diameter of the metal nanostructure was evaluated and is listed in Table 3 below.

[0217]

[0218] Manufacturing process: Molar ratio of metal salt and oxalic acid Metal nanostructure: (111) plane crystallite diameter (nm) Reference example 11: 12.1 Reference example 21. 22.2 Reference example 31: 64.5 Reference example 41: 129.8 Reference example 51: 05.4

[0219] Evaluation Example 1-4: Manufacturing Process Change Example and Its Evaluation (2)

[0220] A metal nanostructure was manufactured using the same method as Example 1, but the weight ratio of oxalic acid / metal in the precursor aqueous solution and the metal were changed according to Table 4 below.

[0221] In the same manner as Evaluation Example 2, the (111) plane crystallite diameter of the metal nanostructure was evaluated, and the particle size of the nanostructure was confirmed through SEM, and is listed in Table 4 below.

[0222]

[0223] Manufacturing process: Molar ratio of metal salt and oxalic acid Metal type of metal salt Particle size (nm) of metal nanostructure Reference example 61:2Ru4.9 Reference example 71:6Ir3.8 Reference example 81:6Ni6.3 Reference example 91:6Co3.1 Reference example 101:1Ag4.4

[0224] [Evaluation Example 2: Performance Evaluation of Metal Nanostructures for Fuel Cell Applications]

[0225] For the metal nanostructure of the example, the performance was measured when applied as a catalyst for a fuel cell, and the results are shown in Table 5 below.

[0226] (1) Fuel cell manufacturing method

[0227] The catalyst loading of the anode electrode is 0.1 mg / cm based on Pt. 2, and is manufactured using a decal method. Nafion ionomer (5 wt% Nafion Dispersion, DuPont Co., USA) is used, and the ionomer / carbon ratio is 0.9.

[0228] The catalyst loading of the cathode electrode was 0.35 mg / cm based on Pt. 2 , and is manufactured using a decal method. Nafion ionomer (5 wt% Nafion Dispersion, DuPont Co., USA) is used, and the ionomer / carbon ratio is 0.9.

[0229] In each of the anode electrode and the cathode electrode, the catalyst is a mixture of each nanostructure of the examples and comparative examples:carbon-based carrier = 70:30 in weight ratio.

[0230] For the manufacture of membrane-electrode assemblies (MEAs), the electrolyte membrane used is NRE211 (Dupont).

[0231] After positioning the anode and cathode electrodes on both sides of the electrolyte membrane, a membrane-electrode assembly (MEA) is manufactured by pressing at 150°C for 10 minutes under a pressure of 30 bar.

[0232] (2) Fuel cell evaluation method

[0233] A 5cm x 5cm single cell is connected to a voltmeter and an ammeter. The voltmeter and ammeter are used to measure the voltage and current at different points on the IV curve. The voltage and current measurements are recorded at each point on the IV curve and plotted on a graph to create an IV curve with voltage on the y-axis and current on the x-axis. Here, RH100% means 100% relative humidity.

[0234] Meanwhile, to measure the open-circuit voltage (OCV), a voltmeter is first connected to the fuel cell without any load. The voltmeter reads the highest voltage the cell can generate.

[0235]

[0236] Battery manufacturing method Evaluation results at RH100%I / CCathode(mg / cm 2 )OCV(V)Max power(W)Example 21.00.350.95318.561.10.340.93616.36Example 31.00.350.96520.251.10.360.94617.88

[0237] synthesis

[0238] According to Tables 1 to 5, one embodiment represented by the embodiment easily controls the shape and size of the metal nanostructure under conditions in which glycerol and oxalic acid coexist.

[0239] If the above-described metal nanostructures with controlled shape and size are supported on a carbon-based carrier, one embodiment can provide a catalyst with excellent performance and durability. In particular, the metal nanostructures are suitable for use as metal nanostructures for fuel cells or metal nanostructures for water electrolysis.

[0240]

[0241] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A method for producing a metal nanostructure, comprising the step of reacting a precursor aqueous solution containing a metal salt, glycerol, and oxalic acid.

2. In paragraph 1, The molar ratio of the above metal salt and the above oxalic acid is, A method for manufacturing a metal nanostructure having a ratio of 1:0.5 to 1:

12.

3. In paragraph 1, The precursor aqueous solution containing the above metal salt, glycerol, and oxalic acid, A method for producing a metal nanostructure further comprising formic acid.

4. In paragraph 3, A method for producing a metal nanostructure, wherein the formic acid is converted from a portion of the oxalic acid.

5. In paragraph 1, A method for producing a metal nanostructure, wherein the viscosity of the precursor aqueous solution containing the metal salt, glycerol, and oxalic acid is 10 cP or more and 1000 cP or less.

6. In paragraph 1, A method for producing a metal nanostructure, wherein the content of water in the 100 wt% precursor aqueous solution containing the metal salt, glycerol, and oxalic acid is 10 wt% or more and 99 wt% or less.

7. In paragraph 1, The step of reacting the precursor aqueous solution containing the above metal salt, glycerol, and oxalic acid is: It is performed in a temperature range of 60℃ or higher to 150℃ or lower. Method for manufacturing metal nanostructures.

8. In paragraph 1, The step of reacting the precursor aqueous solution containing the above metal salt, glycerol, and oxalic acid is: Step 1: preparing an aqueous glycerol solution; A second step of reacting the glycerol aqueous solution prepared in the first step with a metal salt aqueous solution; and A method for producing a metal nanostructure, comprising a third step of reacting the reaction product of the second step with an aqueous oxalic acid solution.

9. In paragraph 8, In the above first step, the glycerol aqueous solution, A method for producing a metal nanostructure comprising glycerol and water in a weight ratio of 10:90 to 80:

20.

10. In paragraph 8, In the second step, the metal salt aqueous solution is A method for producing a metal nanostructure comprising a metal salt and water in a weight ratio of 30:70 to 90:

10.

11. In paragraph 8, The reaction between the slurry prepared in the above first step and the metal salt aqueous solution It is performed for 0.1 to 24 hours in a temperature range of 60 to 150 ℃. Method for manufacturing metal nanostructures.

12. In paragraph 8, In the third step, the oxalic acid aqueous solution is Containing oxalic acid and water in a weight ratio of 1:1 to 1:10 Method for manufacturing metal nanostructures.

13. In paragraph 8, In the third step above, The temperature of the above oxalic acid aqueous solution is adjusted to a range of 50 to 90°C, and the mixture of the reaction product of the second step and the above oxalic acid aqueous solution is mixed for 5 to 10 hours while maintaining the temperature within a range of 90 to 120°C. Method for manufacturing metal nanostructures.

14. In paragraph 1, After the above 3rd step, A method for manufacturing a metal nanostructure further comprising a fourth step of sequentially performing maturation, filtration, washing, and drying.

15. In paragraph 1, A method for producing a metal nanostructure, further comprising a step of dispersing the metal nanostructure obtained after the third or fourth step on a support that is a carbon material, a metal oxide, or a combination thereof. A metal nanostructure that inevitably contains glycerol in an amount greater than 16.0 ppm and less than 50 ppm.

17. In paragraph 16, The above metal nanostructure is a metal nanostructure that inevitably further contains oxalic acid in an amount of 0 ppb or more and less than 20 ppb.

18. In paragraph 16, The above metal nanostructure is a metal nanostructure having a crystallite diameter of 0.1 nm or more and 20 nm or less on the (111) plane when analyzed by XRD.

19. In paragraph 16, The above metal nanostructure is, A metal nanostructure having a particle size of 0.1 nm or more and 20 nm or less when analyzed by TEM.

20. In paragraph 16, The above metal nanostructure is, A metal nanostructure having a weight retention ratio of 97 wt% to 100 wt% according to the following mathematical formula 1 when heat-treated at 250°C: [Mathematical Formula 1] Weight retention of metal nanostructure = 100*(AB) / A In the above mathematical formula 1, A is the weight of the metal nanostructure before heat treatment, B is the weight of the metal nanostructure after heat treatment.

21. The metal nanostructure of Article 16 is a metal nanostructure for a fuel cell or a metal nanostructure for water electrolysis.

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