Catalyst for hydrogen evolution reaction and preparing method thereof

Abstract

A catalyst for a hydrogen generation reaction is provided that improves the performance of the catalyst while minimizing the amount of Pt loaded. According to one aspect of the present invention, a catalyst for a hydrogen generation reaction is provided, comprising: a conductive substrate; and a catalyst layer disposed on at least one surface of the conductive substrate; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak.

Description

Technology Field

[0001] The present invention relates to a catalyst for a hydrogen generation reaction, and more specifically, to a catalyst for a hydrogen generation reaction and a method for manufacturing the same. Background Technology

[0002] Green hydrogen, one of the eco-friendly energies, faces difficulties in commercialization due to the problem of high production costs. To solve this, it is necessary to reduce the cost of the catalyst used in the water electrolysis reaction or to reduce the overpotential required for the water electrolysis reaction.

[0003] Platinum (Pt), a catalyst element primarily used in the Hydrogen Evolution Reaction (HER), possesses excellent electrical conductivity, chemical stability, and optimal metal-H bond energy, allowing it to exhibit superior activity. Nevertheless, because platinum is an expensive precious metal, using Pt / C as a commercial catalyst for battery stacks or water electrolysis has resulted in high manufacturing costs. Consequently, research on reducing the amount of Pt or using other metal elements in the field of catalysts for the hydrogen evolution reaction is continuously being conducted. The problem to be solved

[0004] The objective of the present invention is to provide a catalyst for a hydrogen generation reaction that can improve the performance of the catalyst despite lowering the loading amount of Pt.

[0005] Another objective of the present invention is to provide a catalyst for a hydrogen generation reaction with improved durability by exhibiting long-term oxidation-reduction cycle stability.

[0006] Another objective of the present invention is to provide a method for manufacturing the catalyst for the hydrogen generation reaction that is rapidly synthesized in a one-pot at room temperature.

[0007] Another objective of the present invention is to provide an electrode for a hydrogen fuel cell comprising the catalyst for the hydrogen generation reaction.

[0008] Another objective of the present invention is to provide an electrode for a water decomposition device comprising the catalyst for the hydrogen generation reaction.

[0009] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. means of solving the problem

[0010] According to a first aspect of the present invention for achieving the above objective, a catalyst for a hydrogen generation reaction is provided, comprising: a conductive substrate; and a catalyst layer disposed on at least one surface of the conductive substrate; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak.

[0011] According to a second aspect of the present invention, in the first aspect, the catalyst layer may include a first structure, a second structure different from the first structure, and an anion between the first structure and the second structure. Here, the anion may be interlayer-intercalated between the first structure and the second structure.

[0012] According to a third aspect of the present invention, in the second aspect, the first structure comprises platinum oxide (PtO2) nanoparticles, and the second structure may comprise the Pt-O peak.

[0013] According to the fourth aspect of the present invention, in the second or third aspect, the anion may include one or more of chloride ions and nitrate ions.

[0014] According to the fifth aspect of the present invention, in any one of the second to fourth aspects, the anion may include chloride ions and nitrate ions.

[0015] According to the sixth aspect of the present invention, in any one of the first to fifth aspects, the amount of Pt loaded on the catalyst for the hydrogen generation reaction may be 2.47 weight% or less based on the total weight of the catalyst for the hydrogen generation reaction.

[0016] According to the seventh aspect of the present invention, a method for manufacturing a catalyst for a hydrogen generation reaction can be provided, comprising: (S1) a step of preparing a conductive substrate from which an oxide layer has been removed; and (S2) a step of forming a catalyst layer on at least one surface of the conductive substrate by an electrodeposition method, wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak.

[0017] According to the eighth aspect of the present invention, the electrodeposition method in the seventh aspect may be a method performed at a voltage of -0.5 to -2.0 V relative to a reference electrode using a three-electrode device containing an electrolyte.

[0018] According to the ninth aspect of the present invention, in the seventh or eighth aspect, the electrolyte may include one or more of chloride ions and nitrate ions.

[0019] According to the 10th aspect of the present invention, in any one of the 7th to 9th aspects, the electrolyte may include chloride ions and nitrate ions.

[0020] The means for solving the above problem do not enumerate all the features of the present invention. Various features of the present invention and the resulting advantages and effects can be understood in more detail by referring to the specific embodiments below. Effects of the invention

[0021] According to one aspect of the present invention, a catalyst for a hydrogen generation reaction can be realized that can increase the activity and reaction rate of the catalyst even when the loading amount of Pt is lowered.

[0022] According to another aspect of the present invention, the overvoltage required to reach a specific current density is significantly reduced, and at the same time, low charge transfer resistance is exhibited, thereby enabling the effect of rapid charge transfer on the catalyst surface.

[0023] According to another aspect of the present invention, a catalyst for a hydrogen generation reaction with improved durability can be provided by maintaining the stability of the catalyst even after long-term oxidation-reduction cycling.

[0024] In addition to the effects described above, the specific effects of the present invention are described together with the following explanation of the specific details for implementing the invention. Brief explanation of the drawing

[0025] FIG. 1 is a schematic diagram showing a method for manufacturing and a structure of a catalyst for a hydrogen generation reaction according to one embodiment of the present invention. FIG. 2(a) is a TEM image of the catalyst according to Comparative Example 1, FIG. 2(b) is a HAADF (High-angle annular dark-field)-EDS mapping image of the catalyst according to Comparative Example 1, FIG. 2(c) is a high-resolution image using a JEM-ARM200F instrument, and FIG. 2(d) is a SAED (Selected area electron diffraction) pattern of the catalyst according to Comparative Example 1. FIG. 2(e) is a TEM image of the catalyst according to Example 1-2, FIG. 2(f) is a HAADF-EDS mapping image of the catalyst according to Example 1-2, FIG. 2(g) is a high-resolution image using a JEM-ARM200F instrument, and FIG. 2(h) is a SAED (Selected area electron diffraction) pattern of the catalyst according to Example 1-2. Figures 3(a) to 3(c) are the X-ray photoelectron spectroscopy (XPS) analysis results of Ni 2p, Fe 2p, and Pt 4f + Ni3p of the catalyst according to Comparative Example 1, respectively. Figures 3(d) to 3(f) are the XPS analysis results of Ni 2p, Fe 2p, and Pt 4f + Ni3p of the catalyst according to Examples 1-2, respectively. Figure 4(a) shows the linear sweep voltammetry (LSV) analysis results of the catalysts according to each Bare nickel foam, Comparative Example 4 (Pt / C), Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Example 1-2 (NiFePt_Cl LDH). Figure 4(b) shows the bar graph comparison of the overpotentials of the catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Example 1-2 (NiFePt_Cl LDH). Figure 4(c) shows the overpotentials of the catalysts according to previously reported catalysts for hydrogen evolution reactions (Ref

[24] ,

[34] ,

[37] ~

[43] ) and Example 1-2 (NiFePt_Cl LDH). FIG. 4(d) is the Tafel slope of the catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), Examples 1-2 (NiFePt_Cl LDH), and Comparative Example 4 (Pt / C). FIG. 4(e) is the Electrochemical Impedance Spectroscopy (EIS) graph of the catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Examples 1-2 (NiFePt_Cl LDH). FIG. 4(f) is an enlarged graph of the red rectangular area in FIG. 4(e). Figure 5(a) shows the results of the durability evaluation of the catalyst according to Comparative Example 1 (NiFePt LDH). Figure 5(b) shows the results of the durability evaluation of the catalyst according to Example 1-2 (NiFePt_Cl LDH). Figure 5(c) is 10 mA / cm 2 This is a chronopotentiometry (CP) graph showing the activity of the catalysts according to Comparative Example 1 (NiFePt LDH), Comparative Example 4 (Pt / C), and Examples 1-2 (NiFePt_Cl LDH) for 24 hours at a current density. Figures 6(a) and 6(b) are the results of the durability evaluation of catalysts for hydrogen generation reaction according to Comparative Examples 5 (NiFePt_CO3LDH) and 6 (NiFePt_SO4LDH), respectively. Specific details for implementing the invention

[0026] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0027] In this specification, a numerical range indicated by the term 'to' represents a numerical range that includes the values ​​listed before and after the term as the lower and upper limits, respectively. Where multiple numerical values ​​are disclosed for the upper and lower limits of an arbitrary numerical range, the numerical range disclosed in this specification may be understood as an arbitrary numerical range in which any one of the multiple lower limits and any one of the multiple upper limits are set as the lower and upper limits, respectively.

[0028] According to one aspect of the present invention, a catalyst for a hydrogen generation reaction is provided, comprising: a conductive substrate; and a catalyst layer disposed on at least one surface of the conductive substrate; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak. According to one aspect of the present invention, by forming Pt-O bonds in the nanosheets included in the layered double hydroxide (LDH) structure comprising at least one nanosheet, the overpotential required to reach a specific current density is significantly lowered, and at the same time, low charge transfer resistance is exhibited, thereby enabling the effect of rapid charge transfer on the catalyst surface. According to another aspect of the present invention, a Pt-O bond is formed in the nanosheets included in the layered double hydroxide (LDH) structure, thereby maintaining the stability of the catalyst even after long-term redox cycling, and thus providing a catalyst for a hydrogen generation reaction with improved durability. According to yet another aspect of the present invention, the activity and durability of the catalyst can be increased even when the loading amount of Pt is lowered.

[0029] The configuration of the present invention will be described in more detail below.

[0030] 1. Catalyst for hydrogen generation reaction

[0031] The catalyst for a hydrogen generation reaction according to the present invention comprises a conductive substrate and a catalyst layer.

[0032] conductive substrate

[0033] The conductive substrate according to the present invention can increase the reaction rate of a catalyst for hydrogen generation reaction and simultaneously improve electrical efficiency due to its high surface area and electrical conductivity characteristics.

[0034] The conductive substrate according to the present invention may be any one selected from the group consisting of metal foam materials such as nickel foam, copper foam, stainless steel foam, and titanium foam, and specifically may be nickel foam. Meanwhile, nickel foam is a material manufactured into a foam form by processing nickel metal at high temperatures, and has a larger reaction surface area compared to other conductive substrates, which can increase the reaction rate of the catalyst.

[0035] For example, the thickness of the conductive substrate may be 0.8 to 3.0 mm. However, the technical concept of the present invention is not limited thereto, and the thickness range may be varied depending on the field of application.

[0036] catalyst layer

[0037] The catalyst layer according to the present invention not only induces a hydrogen generation reaction but can also achieve excellent durability even after a long-term oxidation-reduction cycle.

[0038] The catalyst layer according to the present invention is a layered double hydroxide (LDH) structure comprising at least one nanosheet. Specifically, the double hydroxide structure may be a structure formed of a compound having a two-dimensional lattice structure in which metal ions and hydroxides are intersected, and may have an interlayer intercalation of anions. According to one embodiment of the present invention, by forming the catalyst layer with a double hydroxide structure, the reaction surface area of ​​the catalyst is increased, thereby effectively increasing the activity and reaction rate of the hydrogen evolution reaction catalyst.

[0039] The BET specific surface area of ​​individual nanosheets constituting at least one nanosheet according to the present invention is 1 to 600 m² 2 / g, 5 to 500 m 2 / g, 10 to 400 m 2 / g, 90 to 350 m 2 / g, or 100 to 300 m 2 / g. Specifically, by satisfying the BET specific surface area of ​​the individual nanosheets within the above numerical range, the reaction surface area of ​​the catalyst is increased, thereby effectively increasing the activity and reaction rate of the hydrogen evolution reaction catalyst.

[0040] At least one nanosheet according to the present invention includes a Pt-O peak when analyzed by X-ray photoelectron spectroscopy (XPS). According to one aspect of the present invention, by forming Pt-O bonds in nanosheets included in a layered double hydroxide (LDH) structure comprising at least one nanosheet, the overpotential required to reach a specific current density is significantly lowered, and at the same time, low charge transfer resistance is exhibited, thereby enabling the effect of rapid charge transfer on the catalyst surface. According to another aspect of the present invention, by forming Pt-O bonds in nanosheets included in the layered double hydroxide (LDH) structure, the stability of the catalyst is maintained even after long-term redox cycling, thereby providing a catalyst for hydrogen evolution with improved durability. For example, the XPS analysis can be performed under monochromatic Al Kα (1486.6 eV) conditions.

[0041] According to one embodiment of the present invention, the catalyst layer may include a first structure, a second structure different from the first structure, and an anion between the first structure and the second structure. Specifically, the first structure and the second structure may be spaced apart from each other or arranged side by side to form a layered structure. In this case, the anion may be interlayer-intercalated between the first and second structures.

[0042] The anion according to the present invention can inhibit the reduction of metal ions to promote the growth of nanosheets and increase the specific surface area of ​​the catalyst, as well as improve the activity and durability of the hydrogen evolution reaction catalyst by forming a Pt-O peak. Here, the anion may exist in an ionic state together with water in the empty region between the first and second structures. Specifically, the anion may be derived from the electrolyte used in the electrodeposition method.

[0043] Specifically, the first structure comprises platinum oxide (PtO2) nanoparticles, and the second structure may include a Pt-O peak according to XPS analysis. Here, platinum oxide nanoparticles and the Pt-O peak are distinct concepts, and the Pt-O peak may refer to a chemical bond formed by the substitution of a specific cation (e.g., nickel ion) with a platinum ion. According to one embodiment of the present invention, by including a Pt-O peak in the second structure, the overpotential required to reach a specific current density is significantly lowered, and at the same time, a low charge transfer resistance is exhibited, thereby enabling the effect of rapid charge transfer on the catalyst surface. Furthermore, the stability of the catalyst is maintained even after long-term oxidation-reduction cycling, thereby providing a catalyst for hydrogen generation reaction with improved durability.

[0044] For example, the average size of the platinum oxide nanoparticles may be 1 to 9 nm, 2 to 8 nm, 3 to 7 nm, 4 to 6 nm, or 4 to 5 nm. Factors affecting the average size of the platinum oxide nanoparticles may include the molar concentration of the platinum precursor, the molar concentration of chloride ions, and the magnitude of the voltage applied during electrodeposition.

[0045] According to one embodiment of the present invention, the anion may include one or more of chloride ions and nitrate ions, specifically, chloride ions and nitrate ions. Here, the anion may vary depending on the type of metal precursor solution contained in the electrolyte. Specifically, by including both chloride ions and nitrate ions in the anion, the growth of nanosheets can be promoted and the specific surface area of ​​the catalyst can be increased, as well as the activity and durability of the hydrogen evolution reaction catalyst can be improved by forming a Pt-O peak.

[0046] According to another embodiment of the present invention, the molar ratio of chloride ions and nitrate ions (chloride ions: nitrate ions) may be 1:0.44 to 1:11, and specifically 1:4 to 1:5. When the molar ratio of chloride ions and nitrate ions satisfies the above numerical range, not only can the growth of nanosheets be promoted and the specific surface area of ​​the catalyst be increased, but the activity and durability of the hydrogen evolution reaction catalyst can also be improved by forming a Pt-O peak. Specifically, the molar ratio of chloride ions and nitrate ions is set based on the amount added to the electrolyte.

[0047] According to another embodiment of the present invention, the thickness of the catalyst layer may be 50 to 2000 nm, and specifically 200 to 600 nm.

[0048] According to another embodiment of the present invention, the Pt loading amount of the catalyst for a hydrogen generation reaction may be 2.47 wt% or less, 1.57 wt% or less, or 1.30 wt% or less, specifically 1.0 wt% to 1.57 wt% based on the total weight of the catalyst for a hydrogen generation reaction. According to one embodiment of the present invention, the performance of the catalyst can be improved while minimizing the loading amount of expensive Pt. For example, an ICP-OES (Inductively coupled plasma optical emission spectroscopy) analysis method may be used to analyze the Pt loading amount based on the final product, the catalyst specimen for a hydrogen generation reaction.

[0049] 2. Method for manufacturing a catalyst for hydrogen generation reaction

[0050] According to another aspect of the present invention, a method for manufacturing a catalyst for a hydrogen generation reaction is provided, comprising: (S1) preparing a conductive substrate from which an oxide layer has been removed; and (S2) forming a catalyst layer on at least one surface of the conductive substrate by electrodeposition; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and the at least one nanosheet comprises a Pt-O peak according to X-ray photoelectron spectroscopy (XPS) analysis.

[0051] A method for manufacturing a catalyst for a hydrogen generation reaction according to the present invention includes the step (S1) of preparing a conductive substrate from which an oxide layer has been removed in order to remove an oxide layer formed on the surface of a conductive substrate.

[0052] For example, the above step (S1) may include the step of immersing a conductive substrate in an acidic solution and then performing ultrasonic treatment. Specifically, the acidic solution may be a strong acid solution and, for example, an HCl solution.

[0053] A method for manufacturing a catalyst for a hydrogen generation reaction according to the present invention includes the step (S2) of forming a catalyst layer on at least one surface of the conductive substrate by electrodeposition. According to one embodiment of the present invention, when using the electrodeposition method, the efficiency of the manufacturing process can be increased by rapidly forming a catalyst layer in a single pot at room temperature.

[0054] The configuration of the present invention will be explained in more detail below with reference to FIG. 1.

[0055] FIG. 1 is a schematic diagram showing a method for manufacturing and a structure of a catalyst for a hydrogen generation reaction according to one embodiment of the present invention.

[0056] Referring to FIG. 1, a three-electrode device commercially available in the relevant technical field may be used as a means to implement the above electrodeposition method. For example, the three-electrode device may be a device comprising a reference electrode (RE), a counter electrode (CE), a working electrode (WE), and an electrolyte.

[0057] According to some embodiments of the present invention, the electrodeposition method may be a method performed at a voltage of -0.5 to -2V relative to a reference electrode using a three-electrode device containing an electrolyte. Specifically, when the voltage satisfies the above numerical range, the activity and durability of the hydrogen activation reaction catalyst may be improved.

[0058] Specifically, a catalyst layer according to the present invention may be formed at one end of the above-mentioned working electrode.

[0059] Specifically, the electrolyte may contain one or more of nitrate ions and chloride ions, and more specifically, may contain nitrate ions and chloride ions. Meanwhile, if the electrolyte contains ions other than nitrate ions and chloride ions, the long-term oxidation-reduction cycle stability of the catalyst may not be sufficiently improved. The nitrate ions and chloride ions included in the electrolyte according to the present invention can promote the growth of nanosheets and increase the specific surface area of ​​the catalyst, as well as improve the activity and durability of the hydrogen evolution reaction catalyst by forming a Pt-O peak. Here, the electrolyte may be in an aqueous solution state. Therefore, water in the aqueous solution may be reduced to generate hydrogen gas.

[0060] According to one embodiment of the present invention, a reaction for forming PtO2 nanoparticles can proceed in the first structure, and nickel ions (Ni) in the second structure 2+ ) platinum ions (Pt 2+ It can be substituted with ) to form a Pt-O peak.

[0061] 3. Applications

[0062] According to another aspect of the present invention, either an electrode for a hydrogen fuel cell or an electrode for a water decomposition device may be provided, comprising the catalyst for the hydrogen generation reaction. For example, by including the catalyst for the hydrogen generation reaction in the electrode for the hydrogen fuel cell, the efficiency of the hydrogen generation reaction can be maximized to improve the performance of the fuel cell, and by including the catalyst for the hydrogen generation reaction in the electrode for the water decomposition device, the water decomposition efficiency can be further increased.

[0063] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the present invention; however, this is merely an example, and the scope of the present invention is not limited by the following.

[0064] [Preparation Example 1: Preparation of a catalyst for hydrogen generation reaction]

[0065] <Examples 1-1 to 1-4: Synthesis of NiFePt_Cl LDH>

[0066] Step for pre-treating nickel foam:

[0067] A piece of nickel foam (NF, 2 cm x 2 cm, Wellcos Corporation) was rinsed in an ultrasonic bath with ethanol for 15 minutes. Then, to remove the surface oxide layer of the nickel foam, ultrasonic treatment was performed in a 3M HCl solution for 20 minutes. Subsequently, the nickel foam from which the surface oxide layer had been removed was rinsed under ultrasonic treatment with deionized water and ethanol for 15 minutes to prepare a pretreated nickel foam.

[0068] Preparation of electrolytes:

[0069] The electrolyte contains 3 mmol nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O, Junsei Chemicals, Tokyo, Japan, 97%), 3 mmol iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O, Sigma Aldrich, Burlington, Massachusetts, USA, 98%), 0.15 mmol chloroplatinic acid hexahydrate (H2PtCl6·6H2O, Sigma Aldrich Co., Burlington, Ma, USA, 37.5%), and sodium chloride (NaCl, Sigma Aldrich Co., Burlington, Ma, USA, 99%) in various molar concentrations. Specifically, Example 1-1 contains 0.5 mmol of sodium chloride, Example 1-2 contains 2.5 mmol of sodium chloride, Example 1-3 contains 5 mmol of sodium chloride, and Example 1-4 contains 25 mmol of sodium chloride.

[0070] Preparation of a catalyst for hydrogen generation reaction by performing an electrodeposition method:

[0071] Using an electrodeposition apparatus (VSP-Potentiostat of BioLogic) equipped with Hg / HgO (saturated with 20% KOH) as a reference electrode, a Pt coil as a counter electrode, a working electrode, and the above electrolyte, the pretreated nickel foam was immersed in each electrolyte, and then electrostatic deposition was performed at -1.0 (vs Ag / AgCl) for 1 minute at room temperature. Then, the pretreated nickel foam was recovered from the above electrolyte and rinsed several times with deionized water to remove residual salts, thereby producing a catalyst for hydrogen evolution reaction (hereinafter referred to as 'NiFePt_Cl LDH').

[0072] <Comparative Example 1: Synthesis of NiFePt LDH>

[0073] A catalyst for a hydrogen generation reaction was prepared in the same manner as in Example 1, but sodium chloride was excluded from the electrolyte.

[0074] <Comparative Example 2: Synthesis of NiFe_Cl LDH>

[0075] A catalyst for a hydrogen generation reaction was prepared in the same manner as in Example 1, but the platinum precursor was excluded from the electrolyte.

[0076] <Comparative Example 3: Synthesis of NiFe LDH>

[0077] A catalyst for a hydrogen generation reaction was prepared in the same manner as in Example 1, but the platinum precursor and sodium chloride were excluded from the electrolyte.

[0078] <Comparative Example 4: Preparation of a catalyst (Pt / C) for hydrogen evolution reaction coated with catalyst ink on nickel foam>

[0079] A Pt / C ink was prepared by sonicating commercial Pt / C (5 mg; Alfa Aesar, Haverhill, MA, USA, 20 wt.%) in a mixture of 950 μL ethanol (OCI, Seoul, South Korea, 99.9%) and 50 μL Nafion solution (Alfa Aesar, Haverhill, MA, USA, 5 wt%) for 30 minutes. The prepared Pt / C ink (150 μL) was dropped onto a nickel foam (1 cm x 1 cm) and dried overnight in a vacuum oven at 60°C to prepare the catalyst for the hydrogen evolution reaction of Comparative Example 4.

[0080] <Comparative Example 5: Case where sodium carbonate was used instead of sodium chloride, unlike Examples 1-2>

[0081] To confirm the effect of Pt-O formation in the catalyst, a catalyst for a hydrogen evolution reaction was prepared in the same manner as in Examples 1-2, but 2.5 mmol of sodium carbonate (Na2CO3, Junsei Chemicals, Tokyo, Japan, 99%) was used instead of 2.5 mmol of sodium chloride. As a result, the catalyst for a hydrogen evolution reaction of Comparative Example 5 (NiFePt_CO3LDH) was prepared.

[0082] <Comparative Example 6: Case where anhydrous sodium sulfate was used instead of sodium chloride, unlike Examples 1-2>

[0083] To confirm the effect of Pt-O formation in the catalyst, a catalyst for a hydrogen evolution reaction was prepared in the same manner as in Examples 1-2, but 2.5 mmol of sodium anhydride (Na2SO4, Shinyo Pure Chemical, Osaka, Japan, 99%) was used instead of 2.5 mmol of sodium chloride. As a result, the catalyst for a hydrogen evolution reaction of Comparative Example 5 (NiFePt_SO4LDH) was prepared.

[0084] [Experimental Example 1: Morphological and structural analysis of catalysts according to Comparative Example 1 and Examples 1-2]

[0085] FIGS. 2(a) to 2(d) are the results of the morphology and structural analysis of the catalyst according to Comparative Example 1. Specifically, FIG. 2(a) is a TEM image of the catalyst according to Comparative Example 1, FIG. 2(b) is a HAADF (High-angle annular dark-field)-EDS mapping image of the catalyst according to Comparative Example 1, FIG. 2(c) is a high-resolution image taken using a JEM-ARM200F instrument, and FIG. 2(d) is a SAED (Selected area electron diffraction) pattern of the catalyst according to Comparative Example 1.

[0086] Referring to Fig. 2(a), it can be seen that in the catalyst (NiFePt LDH) according to Comparative Example 1, Pt exists in an aggregated form rather than being evenly dispersed in the double-layer hydroxide structure. Referring to Fig. 2(b), it can be seen that Pt exists in an aggregated form on the double-layer hydroxide structure. Referring to Fig. 2(c), it can be seen that some Pt ​​forms nanoparticles on the double-layer hydroxide structure, and that the material is PtO2. Referring to Fig. 2(d), it can be seen that crystallization of PtO2 occurs.

[0087] Figures 2(e) to 2(h) show the results of the morphology and structural analysis of the catalyst according to Example 1-2. Specifically, Figure 2(e) is a TEM image of the catalyst according to Example 1-2, Figure 2(f) is a HADDF-EDS mapping image of the catalyst according to Example 1-2, Figure 2(g) is a high-resolution image taken using a JEM-ARM200F instrument, and Figure 2(h) is a Selected Area Electron Diffraction (SAED) pattern of the catalyst according to Example 1-2.

[0088] Referring to Fig. 2(e), it can be seen that Pt is evenly dispersed in the double-layer hydroxide structure. Referring to Fig. 2(f), some Pt ​​forms nanoparticles in part of the double-layer hydroxide structure, while other Pt forms Pt in other parts of the double-layer hydroxide structure. 2+ It can be confirmed that Pt-O is formed by replacing the nickel ion sites of NiFe. Referring to Fig. 2(g), it can be confirmed that the catalyst according to Example 1-2, similar to Comparative Example 1, forms nanoparticles of some Pt ​​on the double-layer hydroxide structure, and that the material is PtO2. Referring to Fig. 2(h), the catalyst according to Example 1-2 exhibited crystallized PtO2, similar to Comparative Example 1.

[0089] [Experimental Example 2: XPS analysis results of catalysts according to Comparative Example 1 and Examples 1-2]

[0090] FIGS. 3(a) to 3(c) show the X-ray photoelectron spectroscopy (XPS) analysis results of Ni 2p, Fe 2p, and Pt 4f + Ni 3p of the catalyst according to Comparative Example 1, respectively. FIGS. 3(d) to 3(f) show the XPS analysis results of Ni 2p, Fe 2p, and Pt 4f + Ni 3p of the catalyst according to Examples 1-2, respectively. Specifically, the XPS analysis was performed under monochromatic Al Kα (1486.6 eV) conditions.

[0091] Referring to Figures 3(a) to 3(f), the catalyst for the hydrogen evolution reaction according to Example 1-2, treated with chloride ions, showed that the Ni 2p and Fe 2p peaks shifted to overall higher binding energies compared to Comparative Example 1, which was not treated with chloride ions. Specifically, in the case of Example 1-2, a new Pt-O peak appeared at Pt 4f, and Ni 2+ The seat is Pt 2+ It can be confirmed that it is substituted. In addition, when comparing Example 1-2 with Comparative Example 1, it can be confirmed that the intensity of the PtO2 peak of the catalyst according to Example 1-2 becomes stronger.

[0092] Considering the above experimental results comprehensively, platinum oxides PtO and PtO2 are platinum in the metallic state Pt 0 Compared to, it can be inferred that it has excellent hydrogen generation reaction activity and high bond energy, resulting in excellent durability.

[0093] [Experimental Example 3: Evaluation of Electrical Properties of the Catalyst]

[0094] Figure 4(a) shows the linear sweep voltammetry (LSV) analysis results of the catalysts according to each Bare nickel foam, Comparative Example 4 (Pt / C), Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Examples 1-2 (NiFePt_Cl LDH).

[0095] Referring to FIG. 4(a), it can be seen that the catalyst according to Example 1-2 (NiFePt_Cl LDH) has a significantly lower overpotential required for the hydrogen evolution reaction compared to other types of bare nickel foam, Comparative Example 4 (Pt / C), Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), and Comparative Example 1 (NiFePt LDH). This can be presumed to be because a large amount of platinum oxide was generated in the catalyst of Example 1-2.

[0096] Meanwhile, the commercial catalyst of Comparative Example 4 supports 20 wt% of Pt, whereas the catalyst according to Example 1-2 supports 1.57 wt% of Pt. Therefore, in the case of Example 1-2, by supporting a lower amount of Pt, it is possible to secure economic feasibility while simultaneously achieving the effect of lowering the overpotential required for the hydrogen generation reaction.

[0097] Figure 4(b) is a bar graph showing the results of comparing the overpotentials of catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Examples 1-2 (NiFePt_Cl LDH).

[0098] Referring to Fig. 4(b), 50 mA / cm 2 and 100mA / cm 2 Regarding the overpotential value required to reach the current density, it can be confirmed that the catalyst according to Example 1-2 (NiFePt_Cl LDH) exhibits a significantly lower overpotential compared to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), and Comparative Example 1 (NiFePt LDH).

[0099] Figure 4(c) shows the overpotential of catalysts according to previously reported catalysts for hydrogen evolution reactions (Ref

[24] ,

[34] ,

[37] ~

[43] ) and Examples 1-2 (NiFePt_Cl LDH).

[0100] Referring to Fig. 4(c), 100 mA / cm 2Regarding the overpotential value required to reach the current density, the catalyst according to Example 1-2 (NiFePt_Cl LDH) exhibited a lower overpotential compared to previously reported catalysts for hydrogen evolution reactions.

[0101] FIG. 4(d) is the Tafel slope of the catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), Examples 1-2 (NiFePt_Cl LDH), and Comparative Example 4 (Pt / C).

[0102] Referring to Fig. 4(d), it can be seen that the Tafel slope of the catalyst according to Example 1-2 is 50 mV / dec, which is significantly lower compared to other types of catalysts. In addition, it can be seen that the reaction rate of the catalyst according to Example 1-2 is significantly faster than that of the catalysts according to Comparative Examples 2 and 3.

[0103] Figure 4(e) is an Electrochemical Impedance Spectroscopy (EIS) graph of the catalysts according to Comparative Example 3 (NiFe LDH), Comparative Example 2 (NiFe_Cl LDH), Comparative Example 1 (NiFePt LDH), and Examples 1-2 (NiFePt_Cl LDH). Figure 4(f) is an enlarged graph of the red square area in Figure 4(e). Solution resistance (Rs) was measured at a high frequency of 100 kHz, and charge transfer resistance (Rct) was measured at a low frequency of 0.01 Hz.

[0104] Meanwhile, when the solution resistance (Rs) is the same, the lower the charge transfer resistance (Rct), the faster the charge transfer on the catalyst surface.

[0105] Referring to Figures 4(e) and 4(f), Example 1-2 (NiFePt_Cl LDH) exhibited the lowest charge transfer resistance at 1.79 Ω, and it can be seen that the charge transfer resistance increased in the order of Comparative Example 1 (NiFePt LDH), Comparative Example 2 (NiFe Cl LDH), and Comparative Example 3 (NiFe LDH). Through this, it can be inferred that the catalyst according to Example 1-2 exhibited the fastest charge transfer at the surface of the catalyst, which is due to the increased specific surface area of ​​the catalyst.

[0106] [Experimental Example 4-1: Evaluation of Durability of Catalyst for Hydrogen Generation Reaction]

[0107] Figure 5(a) shows the results of the durability evaluation of the catalyst according to Comparative Example 1 (NiFePt LDH). Figure 5(b) shows the results of the durability evaluation of the catalyst according to Example 1-2 (NiFePt_Cl LDH). Specifically, the LSV curves before and after 1,000 redox cycles are shown for the catalysts according to Comparative Example 1 and Example 1-2, respectively. Here, the CV cycling test was performed at a scan rate of 50 mV / s for 1,000 cycles.

[0108] Referring to Figures 5(a) and 5(b), the catalyst according to Comparative Example 1 (NiFePt LDH) showed significantly lower activity after CV (Cyclic voltammetry) cycling, whereas the catalyst according to Example 1-2 (NiFePt_Cl LDH) showed almost no change even after cycling.

[0109] Fig. 5(c) is 10 mA / cm 2 This is a chronopotentiometry (CP) graph showing the activity of the catalysts according to Comparative Example 1 (NiFePt LDH), Comparative Example 4 (Pt / C), and Examples 1-2 (NiFePt_Cl LDH) for 24 hours at a current density.

[0110] Referring to Fig. 5(c), it can be seen that the potential difference between the catalysts increased further after 24 hours compared to the initial value (0 hours). It can be seen that the increase in potential of the catalysts according to Comparative Example 4 (Pt / C) and Comparative Example 1 (NiFePt LDH) corresponds to approximately 2 times and 3 times that of the catalyst according to Example 1-2 (NiFePt_Cl LDH), respectively. In other words, it can be confirmed that the catalyst according to Example 1-2 (NiFePt_Cl LDH) has superior durability compared to Comparative Example 1 (NiFePt LDH) and Comparative Example 4 (Pt / C). This can be presumed to be due to the formation of oxidized platinum in the catalyst of Example 1.

[0111] [Experimental Example 4-2: Evaluation of durability of catalysts for hydrogen evolution reaction according to Comparative Examples 5 and 6]

[0112] Figures 6(a) and 6(b) show the results of the durability evaluation of catalysts for hydrogen generation reactions according to Comparative Examples 5 and 6, respectively. Experimental Example 4-2 was measured in the same manner as Experimental Example 4-1.

[0113] Referring to Figures 6(a) and 6(b), the catalysts for hydrogen generation reactions according to Comparative Examples 5 and 6 showed significantly lower activity after CV (Cyclic voltammetry) cycling.

[0114] Considering the experimental results above, according to one aspect of the present invention, Pt-O bonds are formed in nanosheets included in a layered double hydroxide (LDH) structure comprising at least one nanosheet, thereby significantly lowering the overpotential required to reach a specific current density and exhibiting low charge transfer resistance, which enables the effect of rapid charge transfer on the catalyst surface. According to another aspect of the present invention, Pt-O bonds are formed in nanosheets included in the layered double hydroxide (LDH) structure, thereby maintaining the stability of the catalyst even after redox cycling, and thus providing a catalyst for a hydrogen evolution reaction with improved durability.

[0115] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention.

Claims

Claim 1 A catalyst for a hydrogen generation reaction comprising: a conductive substrate; and a catalyst layer disposed on at least one surface of the conductive substrate; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak, and wherein the catalyst layer comprises: a first structure and a second structure spaced apart from the first structure, and an anion is interlayer-inserted between the first and second structures, and wherein the anion comprises chloride ions and nitrate ions. Claim 2 delete Claim 3 A catalyst for a hydrogen generation reaction according to claim 1, wherein the first structure comprises platinum oxide (PtO2) nanoparticles and the second structure comprises the Pt-O peak. Claim 4 A catalyst for a hydrogen generation reaction according to claim 1, wherein the catalyst layer is formed by an electrodeposition method. Claim 5 In paragraph 4, the electrodeposition method is performed using a three-electrode device comprising an electrolyte, and the anion is derived from the electrolyte, a catalyst for a hydrogen generation reaction. Claim 6 A hydrogen generation reaction catalyst according to claim 1, wherein the Pt loading of the hydrogen generation reaction catalyst is 2.47 weight% or less based on the total weight of the hydrogen generation reaction catalyst. Claim 7 (S1) a step of preparing a conductive substrate from which an oxide layer has been removed; and (S2) a step of forming a catalyst layer on at least one surface of the conductive substrate by an electrodeposition method; wherein the catalyst layer is a layered double hydroxide (LDH) structure comprising at least one nanosheet, and wherein, by X-ray photoelectron spectroscopy (XPS) analysis, the at least one nanosheet comprises a Pt-O peak, and the electrodeposition method is performed using a three-electrode device comprising an electrolyte, and the electrolyte comprises chloride ions and nitrate ions. Claim 8 A method for manufacturing a catalyst for a hydrogen generation reaction according to claim 7, wherein the electrodeposition method is performed at a voltage of -0.5 to -2.0 V relative to a reference electrode using a three-electrode device containing an electrolyte. Claim 9 delete Claim 10 delete

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