Pt-Au catalytic electrode and preparation method and application thereof

Abstract

The invention relates to a Pt-Au catalytic electrode and a preparation method and application thereof. The preparation method comprises the following steps: (1) placing a conductive substrate in a nickel plating solution, and electroplating to obtain a nickel-plated conductive substrate; (2) placing the nickel-plated conductive substrate in a replacement liquid containing gold ions and platinum ions, and carrying out a replacement reaction to obtain a Pt-Au catalytic electrode precursor; (3) putting the Pt-Au catalytic electrode precursor into an acid solution, and carrying out acid pickling on the Pt-Au catalytic electrode precursor; (4) carrying out heat treatment on the pickled Pt-Au catalytic electrode precursor in a reducing atmosphere; and (5) putting the Pt-Au catalytic electrode precursor subjected to heat treatment into an electrolyte, and carrying out cyclic voltammetry scanning to obtain the Pt-Au catalytic electrode. The Pt-Au catalytic electrode which is high in crystallinity, good in stability, good in surface state and excellent in catalytic performance is obtained by adopting a nickel layer pre-deposition and replacement deposition strategy, and the use amount of precious metal is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of catalytic synthesis technology, specifically to the electrochemical synthesis of ammonia, and more particularly to a Pt-Au catalytic electrode, its preparation method, and its application. Background Technology

[0002] Pt-Au catalytic electrodes are crucial for the HOR reaction in the electrochemical synthesis of ammonia; however, their high cost is a disadvantage in practical industrial applications. Therefore, reducing the loading of precious metals in the catalytic electrode to lower costs has become a key research focus.

[0003] CN120717487A discloses a method for synthesizing ammonia based on osmium-platinum catalyst and nitrogen oxides. The method includes: preparing NO, H2, and inert gases according to preset requirements; weighing the osmium-platinum catalyst and adding it to a tubular reactor containing quartz wool; introducing H2 into the tubular reactor and heating the reactor to 200-400°C to pretreat the osmium-platinum catalyst at this temperature, followed by cooling the catalyst to room temperature under H2 purging; simultaneously introducing NO, H2, and inert gases into the reactor to form a mixed gas, and then raising the temperature of the tubular reactor to a preset temperature and maintaining this temperature, allowing the mixed gas to react under the action of the osmium-platinum catalyst to synthesize ammonia. This method has lower energy consumption and higher yield, and uses a lower-cost and better-performing catalyst.

[0004] CN119877029A discloses a method for preparing a low-loading RuPdPt ternary noble metal electrocatalyst, including Ni x Fe y Cu z An OOH substrate is immersed in a mixed solution of noble metals, and the immersion is carried out under stirring and heating conditions for 1-6 hours. The resulting product is washed with water and dried to obtain RuPdPt-Ni. x Fe y Cu z OOH composite catalyst. In this invention, noble metals Ru, Pd, and Pt are combined with a Ni substrate. x Fe y Cu z OOH nanosheets are bonded together by M1-M2-O bonds, effectively anchoring the single-atom cluster sites of noble metals Ru, Pd, and Pt, which greatly improves the stability of the catalyst at high current densities.

[0005] CN120099562A discloses a low-loading noble metal catalyst for industrial water electrolysis and its preparation method. The method uses a thin-layer two-dimensional layered hydrogen hydroxide (LDH) as the substrate material, loads noble metals via a hydrothermal reaction under specific temperature and pressure, and then washes with water to remove impurity ions. After drying, the target product is obtained. The resulting electrocatalyst is an ultra-low-loading noble metal-supported LDH, with the noble metal loading percentage being 0.1wt%-0.5wt%. The prepared electrocatalyst can achieve highly efficient and stable water splitting at industrial-grade current densities. The obtained electrocatalyst exhibits high catalytic activity and durability under industrial conditions; moreover, the preparation process is simple, reproducible, and significantly reduces the noble metal loading.

[0006] Therefore, it is of great significance to provide a Pt-Au catalytic electrode with low noble metal loading and excellent catalytic performance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a Pt-Au catalytic electrode, its preparation method, and its applications. This invention employs a pre-deposited nickel layer + displacement deposition strategy, utilizing nickel as a "sacrificial layer" to spontaneously form an ultrathin Pt-Au alloy or Pt-Au mixed layer on its surface through a displacement reaction. By subjecting the Pt-Au alloy or Pt-Au mixed layer to heat treatment and cyclic voltammetry, a Pt-Au catalytic electrode with high crystallinity, good stability, excellent surface condition, and superior catalytic performance is obtained, significantly reducing the amount of precious metals used.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a Pt-Au catalytic electrode, the method comprising:

[0010] (1) Place the conductive substrate in a nickel plating solution and electroplate to obtain a nickel-plated conductive substrate.

[0011] (2) The nickel-plated conductive substrate is placed in a displacement solution containing gold ions and platinum ions to undergo a displacement reaction, thereby obtaining a Pt-Au catalytic electrode precursor.

[0012] (3) Place the Pt-Au catalytic electrode precursor in an acid solution and acid wash the Pt-Au catalytic electrode precursor;

[0013] (4) The acid-washed Pt-Au catalytic electrode precursor was heat-treated under a reducing atmosphere;

[0014] (5) The heat-treated Pt-Au catalytic electrode precursor was placed in an electrolyte and subjected to cyclic voltammetry to obtain the Pt-Au catalytic electrode.

[0015] This invention employs a pre-deposited nickel layer + displacement deposition strategy. First, nickel is electroplated on the surface of a conductive substrate, using nickel as a "sacrificial layer." Through a displacement reaction, an ultrathin Pt-Au alloy or Pt-Au mixed layer is spontaneously formed on the surface of the conductive substrate. Through further geothermal treatment and electrochemical cyclic voltammetry scanning, a Pt-Au catalytic electrode with high crystallinity, good stability, good surface condition, and excellent catalytic performance is obtained, significantly reducing the amount of precious metals used.

[0016] Preferably, the solute in the nickel plating solution in step (1) includes any one or a combination of at least two of nickel chloride, nickel acetate, nickel sulfate, or nickel nitrate.

[0017] Preferably, the concentration of nickel ions in the nickel plating solution in step (1) is 0.1 mol / L to 0.4 mol / L.

[0018] Preferably, the electroplating voltage in step (1) is 4V~8V.

[0019] Preferably, the electroplating time in step (1) is 1 min to 8 min.

[0020] Preferably, the thickness of the nickel plating layer in the nickel-plated conductive substrate in step (1) is 50 μm to 300 μm.

[0021] Preferably, the molar ratio of gold ions to platinum ions in the replacement solution in step (2) is 1:(0.8~1.25).

[0022] Preferably, the total concentration of gold ions and platinum ions in the replacement solution in step (2) is 10 mmol / L to 30 mmol / L.

[0023] Preferably, the displacement reaction time in step (2) is 1 min to 8 min.

[0024] Preferably, the acid solution in step (3) includes any one of dilute sulfuric acid, dilute hydrochloric acid, or dilute nitric acid.

[0025] Preferably, the pickling time in step (3) is 10s to 60s.

[0026] Preferably, the temperature of the heat treatment in step (4) is 300℃~500℃.

[0027] Preferably, the heat treatment time in step (4) is 0.5h to 1.5h.

[0028] Preferably, the reducing atmosphere in step (4) includes an Ar / H2 mixture.

[0029] Preferably, in the Ar / H2 mixture described in step (4), the volume percentage of H2 is 3 vol% to 10 vol%.

[0030] Preferably, the voltage range of the cyclic voltammetry scan in step (5) is -0.2V to 1.0V vs. REH.

[0031] Preferably, the number of cyclic voltammetric scans in step (5) is 10 to 50.

[0032] Preferably, the conductive substrate in step (1) includes any one of carbon paper, carbon paper, iron mesh, titanium mesh, nickel mesh or stainless steel mesh.

[0033] Preferably, before the conductive substrate in step (1) is placed in the nickel plating solution, and after steps (1), (2) and (3) are completed, each step independently includes cleaning and drying.

[0034] Preferably, the drying process includes drying in an inert gas stream or vacuum drying.

[0035] Secondly, the present invention provides a Pt-Au catalytic electrode, which is prepared by the preparation method described in the first aspect; the total loading of Pt and Au in the Pt-Au catalytic electrode is 0.03 mg / cm³. 2 ~0.07mg / cm 2 .

[0036] Thirdly, the present invention provides an application of the Pt-Au catalytic electrode as described in the second aspect in the electrochemical ammonia synthesis reaction.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention employs a pre-deposited nickel layer + displacement deposition strategy, using nickel as a "sacrificial layer" to spontaneously form an ultrathin Pt-Au alloy or Pt-Au mixed layer on its surface through a displacement reaction. By subjecting the Pt-Au alloy or Pt-Au mixed layer to heat treatment and cyclic voltammetry scanning, a Pt-Au catalytic electrode with high crystallinity, good stability, good surface condition, and excellent catalytic performance is obtained, significantly reducing the amount of precious metals used. Attached Figure Description

[0039] Figure 1 This is a 200x magnified SEM image of the nickel plating layer on the surface of the nickel-plated stainless steel mesh prepared in Example 1.

[0040] Figure 2 This is a 1000x magnified SEM image of the nickel plating layer on the surface of the nickel-plated stainless steel mesh prepared in Example 1.

[0041] Figure 3 This is a Ni distribution map on the surface of the Pt-Au catalytic electrode prepared in Example 1.

[0042] Figure 4 This is a Pt distribution map on the surface of the Pt-Au catalytic electrode prepared in Example 1.

[0043] Figure 5 This is a map showing the Au distribution on the surface of the Pt-Au catalytic electrode prepared in Example 1.

[0044] Figure 6 The open-circuit voltage curve is shown when the Pt-Au catalytic electrode prepared in Example 1 is used as the counter electrode.

[0045] Figure 7 The image shows the electrochemical impedance spectroscopy of the Pt-Au catalytic electrode prepared in Example 1 as the counter electrode.

[0046] Figure 8 The image shows the cyclic voltage curve when the Pt-Au catalytic electrode prepared in Example 1 is used as the counter electrode.

[0047] Figure 9 The chronopotential curves are obtained when the Pt-Au catalytic electrode prepared in Example 1 is used as the counter electrode.

[0048] Figure 10 This is a Faraday efficiency diagram when the Pt-Au catalytic electrode prepared in Example 1 is used as the counter electrode. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0050] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0051] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0053] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0054] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0055] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0056] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0057] In this invention, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0058] In this invention, unless otherwise specified, the operation is assumed to be performed at room temperature or a temperature conventionally set in the art. "Room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this invention, room temperature refers to 20°C to 30°C.

[0059] In one specific embodiment, the present invention provides a method for preparing a Pt-Au catalytic electrode, the method comprising:

[0060] (1) Place the conductive substrate in a nickel plating solution and electroplate to obtain a nickel-plated conductive substrate.

[0061] (2) The nickel-plated conductive substrate is placed in a displacement solution containing gold ions and platinum ions to undergo a displacement reaction, thereby obtaining a Pt-Au catalytic electrode precursor.

[0062] (3) Place the Pt-Au catalytic electrode precursor in an acid solution and acid wash the Pt-Au catalytic electrode precursor;

[0063] (4) The acid-washed Pt-Au catalytic electrode precursor was heat-treated under a reducing atmosphere;

[0064] (5) The heat-treated Pt-Au catalytic electrode precursor was placed in an electrolyte and subjected to cyclic voltammetry to obtain the Pt-Au catalytic electrode.

[0065] This invention employs a pre-deposited nickel layer + displacement deposition strategy. First, nickel is electroplated on the surface of a conductive substrate, using nickel as a "sacrificial layer." Through a displacement reaction, an ultrathin Pt-Au alloy or Pt-Au mixed layer is spontaneously formed on the surface of the conductive substrate. Through further geothermal treatment and electrochemical cyclic voltammetry scanning, a Pt-Au catalytic electrode with high crystallinity, good stability, good surface condition, and excellent catalytic performance is obtained, significantly reducing the amount of precious metals used.

[0066] In some embodiments, the solute in the nickel plating solution in step (1) includes any one or a combination of at least two of nickel chloride, nickel acetate, nickel sulfate, or nickel nitrate.

[0067] In some embodiments, the concentration of nickel ions in the nickel plating solution in step (1) is 0.1 mol / L to 0.4 mol / L, for example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L or 0.4 mol / L.

[0068] In some embodiments, the electroplating voltage in step (1) is 4V~8V, for example, it can be 4V, 4.5V, 5V, 5.5V, 6V, 6.5V, 7V, 7.5V or 8V.

[0069] In some embodiments, the electroplating time in step (1) is 1 min to 8 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min or 8 min.

[0070] In some embodiments, the thickness of the nickel plating layer in the nickel-plated conductive substrate in step (1) is 50μm to 300μm, for example, it can be 50μm, 100μm, 150μm, 200μm, 250μm or 300μm.

[0071] In some embodiments, the molar ratio of gold ions to platinum ions in the replacement solution in step (2) is 1:(0.8~1.25), for example, it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2 or 1:1.25.

[0072] In some embodiments, the total concentration of gold ions and platinum ions in the replacement solution in step (2) is 10 mmol / L to 30 mmol / L, for example, it can be 10 mmol / L, 12 mmol / L, 14 mmol / L, 16 mmol / L, 18 mmol / L, 20 mmol / L, 22 mmol / L, 24 mmol / L, 26 mmol / L, 28 mmol / L or 30 mmol / L.

[0073] In some embodiments, the displacement reaction time in step (2) is 1 min to 8 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min or 8 min.

[0074] In some embodiments, the acid solution in step (3) includes any one of dilute sulfuric acid, dilute hydrochloric acid, or dilute nitric acid.

[0075] In some implementations, the pickling time in step (3) is 10s to 60s.

[0076] The dilute sulfuric acid mentioned in this invention refers to an aqueous solution of sulfuric acid with a solute molar concentration of less than 2 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, or 2 mol / L. The dilute hydrochloric acid refers to an aqueous solution of hydrochloric acid with a solute molar concentration of less than 2 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, or 2 mol / L. The dilute nitric acid refers to an aqueous solution of nitric acid with a solute molar concentration of less than 1 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or 1 mol / L.

[0077] In some embodiments, the temperature of the heat treatment in step (4) is 300°C to 500°C, for example, it can be 300°C, 350°C, 400°C, 450°C or 500°C.

[0078] In some embodiments, the heat treatment time in step (4) is 0.5h to 1.5h, for example, it can be 0.5h, 0.75h, 1h, 1.25h or 1.5h.

[0079] In some embodiments, the reducing atmosphere in step (4) includes an Ar / H2 mixture in which the volume percentage of H2 is 3 vol% to 10 vol%, for example, it can be 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, or 10 vol%.

[0080] In this invention, the composition of the electrolyte in step (5) is not particularly limited. For example, the electrolyte in step (5) may include HAuCl4, H2PtCl6 and sulfuric acid, or the electrolyte in step (5) may include a lithium tetrafluoroborate diethylene glycol dimethyl ether electrolyte.

[0081] In some embodiments, when the electrolyte in step (5) includes HAuCl4, H2PtCl6 and sulfuric acid, the molar ratio of HAuCl4 to H2PtCl6 in the electrolyte is 1:(0.8~1.25), for example, it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2 or 1:1.25.

[0082] In some embodiments, when the electrolyte in step (5) includes HAuCl4, H2PtCl6 and sulfuric acid, the total concentration of HAuCl4 and H2PtCl6 in the electrolyte is 5 mmol / L to 15 mmol / L, for example, it can be 5 mmol / L, 7.5 mmol / L, 10 mmol / L, 12.5 mmol / L or 15 mmol / L.

[0083] In some embodiments, when the electrolyte in step (5) includes HAuCl4, H2PtCl6 and sulfuric acid, the concentration of sulfuric acid in the electrolyte is 2.5 mol / L to 3.5 mol / L, for example, it can be 2.5 mol / L, 2.75 mol / L, 3 mol / L, 3.25 mol / L or 3.5 mol / L.

[0084] In some embodiments, when the electrolyte is a lithium tetrafluoroborate in diethylene glycol dimethyl ether electrolyte, the concentration of lithium tetrafluoroborate in the electrolyte is 0.5 mol / L to 2 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0085] In some implementations, the voltage range of the cyclic voltammetry scan in step (5) is -0.2V to 1.0V vs. REH.

[0086] In some implementations, the number of cyclic voltammetric scans in step (5) is 10 to 50, for example, 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0087] In some embodiments, the conductive substrate in step (1) includes any one of carbon paper, carbon paper, iron mesh, titanium mesh, nickel mesh or stainless steel mesh.

[0088] In some embodiments, cleaning and drying are independently included before the conductive substrate in step (1) is placed in the nickel plating solution, and after steps (1), (2) and (3) are completed.

[0089] In this invention, before the conductive substrate is placed in the nickel plating solution in step (1), the cleaning of the conductive substrate specifically includes immersing the conductive substrate in dilute acid for 1 min to 10 min. When the conductive substrate is carbon paper or carbon cloth, it is repeatedly cleaned with ultrapure water until neutral after immersion. When the conductive substrate is a metal wire mesh gas diffusion electrode, after immersion, it also includes polishing the conductive substrate and ultrasonic cleaning to remove the oxide layer and oil stains.

[0090] The cleaning after steps (1), (2) and (3) includes rinsing with ultrapure water until no soaking solution remains.

[0091] In some embodiments, the drying includes drying in an inert gas stream or vacuum drying.

[0092] In another specific embodiment, the present invention provides a Pt-Au catalytic electrode, which is prepared by the preparation method described in one of the foregoing specific embodiments; in the Pt-Au catalytic electrode, the total loading of Pt and Au is 0.03 mg / cm³. 2 ~0.07mg / cm 2 For example, it could be 0.03 mg / cm³. 2 0.04 mg / cm 2 0.05 mg / cm 2 0.06 mg / cm 2 Or 0.07 mg / cm 2 .

[0093] In yet another specific embodiment, the present invention provides an application of the Pt-Au catalytic electrode as described in another specific embodiment above in the electrochemical ammonia synthesis reaction.

[0094] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0095] Example 1

[0096] This embodiment provides a method for preparing a Pt-Au catalytic electrode, the method comprising:

[0097] (1) Cut a 62mm×62mm stainless steel mesh using a standard mold, activate it by acid washing with 0.5mol / L sulfuric acid solution, polish it with fine sandpaper, ultrasonically clean it, and vacuum dry it; then place the cleaned stainless steel mesh in a 0.1mol / L nickel chloride solution, set the electroplating voltage to 8V, electroplat for 2.5min, and obtain a nickel-plated stainless steel mesh with a nickel plating layer thickness of 100μm. Rinse the nickel-plated stainless steel mesh with ultrapure water until there is no residue of nickel plating solution, and vacuum dry it. Figure 1 and Figure 2 SEM image of the nickel plating layer;

[0098] (2) The nickel-plated stainless steel mesh was placed in a displacement solution with a total concentration of gold ions and platinum ions of 20 mmol / L and a molar ratio of 1:1. The displacement reaction was carried out for 3 min to obtain the Pt-Au catalytic electrode precursor. The Pt-Au catalytic electrode precursor was rinsed with ultrapure water until there was no residue in the displacement solution and then vacuum dried.

[0099] (3) Place the Pt-Au catalytic electrode precursor in 0.1 mol / L dilute sulfuric acid, acid wash the Pt-Au catalytic electrode precursor for 30s, then rinse with ultrapure water until no acid residue remains, and blow dry in an argon flow.

[0100] (4) The acid-washed Pt-Au catalytic electrode precursor was subjected to heat treatment at 400℃ for 1h in an Ar / H2 mixture with a volume percentage of 5 vol% H2.

[0101] (5) The heat-treated Pt-Au catalytic electrode precursor was placed in an electrolyte containing HAuCl4 and H2PtCl6 in a molar ratio of 1:1 and a total concentration of 20 mmol / L, and 3 mol / L H2SO4. Cyclic voltammetry was performed for 30 cycles within a voltage range of -0.2V to 1.0V vs. REH to obtain the Pt-Au catalytic electrode. The total loading of Pt and Au in the Pt-Au catalytic electrode was 0.04 mg / cm³. 2 .

[0102] The surface of the prepared Pt-Au catalytic electrode was subjected to SEM-EDS analysis, and the Ni distribution pattern is shown in the figure below. Figure 3 As shown, the distribution diagram of Pt is as follows: Figure 4 As shown in the figure, the distribution of Au is as follows: Figure 5 As shown.

[0103] Example 2

[0104] This embodiment provides a method for preparing a Pt-Au catalytic electrode, the method comprising:

[0105] (1) Cut a 60mm×60mm Ti mesh using a standard mold, activate it by acid washing with 0.3mol / L sulfuric acid solution, polish it with fine sandpaper, ultrasonically clean it, and vacuum dry it; then place the cleaned Ti mesh in a 0.2mol / L nickel chloride solution, set the electroplating voltage to 4V, electroplat for 5min, and obtain a nickel-plated Ti mesh with a nickel plating layer thickness of 50μm. Rinse the nickel-plated Ti mesh with ultrapure water until there is no residue in the nickel plating solution, and vacuum dry it.

[0106] (2) The nickel-plated Ti mesh was placed in a displacement solution with a total concentration of gold ions and platinum ions of 18 mmol / L and a molar ratio of 1:0.8. The displacement reaction was carried out for 2 min to obtain the Pt-Au catalytic electrode precursor. The Pt-Au catalytic electrode precursor was rinsed with ultrapure water until there was no residue in the displacement solution and then vacuum dried.

[0107] (3) Place the Pt-Au catalytic electrode precursor in a 0.5 mol / L dilute hydrochloric acid solution, acid wash the Pt-Au catalytic electrode precursor for 10 s, then rinse with ultrapure water until no acid residue remains, and dry in an argon flow.

[0108] (4) The acid-washed Pt-Au catalytic electrode precursor was subjected to heat treatment at 300℃ for 0.5h in an Ar / H2 mixture with a volume percentage of 3 vol% H2.

[0109] (5) The heat-treated Pt-Au catalytic electrode precursor was placed in a 1 mol / L lithium tetrafluoroborate diethylene glycol dimethyl ether electrolyte, and cyclic voltammetry was performed for 10 cycles within a voltage range of -0.2 V to 1.0 V vs. REH to obtain the Pt-Au catalytic electrode. The total loading of Pt and Au in the Pt-Au catalytic electrode was 0.04 mg / cm³. 2 .

[0110] Example 3

[0111] This embodiment provides a method for preparing a Pt-Au catalytic electrode, the method comprising:

[0112] (1) Cut 58mm×58mm carbon cloth using a standard mold and clean it in a 1mol / L dilute hydrochloric acid solution. Rinse it with ultrapure water until there is no acid residue, and then vacuum dry it. Then place the cleaned carbon cloth in a 0.4mol / L nickel chloride solution, set the electroplating voltage to 6V, and electroplat for 4min to obtain a nickel-plated carbon cloth with a nickel layer thickness of 300μm. Rinse the nickel-plated carbon cloth with ultrapure water until there is no nickel plating solution residue, and then vacuum dry it.

[0113] (2) The nickel-plated carbon was placed in a displacement solution with a total concentration of gold ions and platinum ions of 30 mmol / L and a molar ratio of 1:1.25. The displacement reaction was carried out for 5 min to obtain the Pt-Au catalytic electrode precursor. The Pt-Au catalytic electrode precursor was rinsed with ultrapure water until there was no residue in the displacement solution and then vacuum dried.

[0114] (3) The Pt-Au catalytic electrode precursor was placed in hydrochloric acid with a concentration of 1.5 mol / L and acid-washed for 60s. Then it was rinsed with ultrapure water until no acid residue remained and dried in an argon flow.

[0115] (4) The acid-washed Pt-Au catalytic electrode precursor was subjected to heat treatment at 500℃ for 2h in an Ar / H2 mixture with a volume percentage of 10 vol% H2.

[0116] (5) The heat-treated Pt-Au catalytic electrode precursor was placed in a 1 mol / L lithium tetrafluoroborate + 0.25% vol dimethyl ether diadic acid electrolyte, and cyclic voltammetry was performed for 50 cycles within a voltage range of -0.2 V to 1.0 V vs. REH to obtain the Pt-Au catalytic electrode. The total loading of Pt and Au in the Pt-Au catalytic electrode was 0.07 mg / cm³. 2 .

[0117] Example 4

[0118] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for the molar ratio of gold ions to platinum ions in the replacement solution in step (2), which is 1:0.75, the preparation method is the same as in Example 1.

[0119] Example 5

[0120] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for the molar ratio of gold ions to platinum ions in the replacement solution in step (2), which is 1:1.3, the preparation method is the same as in Example 1.

[0121] Example 6

[0122] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for step (2), where the total concentration of gold ions and platinum ions in the replacement solution is 8 mmol / L, the preparation method is the same as in Example 1.

[0123] Example 7

[0124] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for step (2), where the total concentration of gold ions and platinum ions in the replacement solution is 32 mmol / L, the preparation method is the same as in Example 1.

[0125] Example 8

[0126] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for step (5) of performing 5 cycles of cyclic voltammetry scanning, the preparation method is the same as in Example 1.

[0127] Example 9

[0128] This embodiment provides a method for preparing a Pt-Au catalytic electrode. Except for step (5) of performing 55 cyclic voltammetry scans, the preparation method is the same as in Example 1.

[0129] Comparative Example 1

[0130] This comparative example provides a method for preparing a Pt-Au catalytic electrode, which is the same as that in Example 1 except that step (4) is omitted.

[0131] Comparative Example 2

[0132] This comparative example provides a method for preparing a Pt-Au catalytic electrode, which is the same as that in Example 1 except that step (5) is omitted.

[0133] Performance testing:

[0134] The open-circuit voltage, impedance, and Faraday efficiency of the Pt-Au catalytic electrodes prepared in all the above examples and comparative examples were tested when used as counter electrodes. The specific test methods are as follows:

[0135] The battery (with a Ni-deposited PtAu electrode as the counter electrode, a dimethyl ether diisocyanate + 1 mol / L lithium tetrafluoroborate + 0.25% vol ethanol electrolyte, and a stainless steel mesh as the working electrode) was tested using EC-Lab at a current density of 6 mA / cm². 2 The flow rates of nitrogen and hydrogen were both 75 mL / min.

[0136] First, an open-circuit voltage test is performed to obtain the potentials of the counter electrode and working electrode of the battery. Then, the electrochemical impedance spectroscopy of the battery is tested to obtain the ohmic resistance of the battery. Next, the chronopotential method is used to test the change curves of the potentials of the counter electrode and working electrode over time during the electrolysis of ammonia. Finally, after the battery test is completed, ammonia in nitrogen gas, ammonia in electrolyte, and ammonia on stainless steel mesh are collected respectively, and the total Faraday efficiency of the battery with the counter electrode as the anode is calculated according to the Faraday efficiency calculation formula.

[0137] The test results are shown in Table 1.

[0138] Table 1

[0139]

[0140] The open-circuit voltage curve of the Pt-Au catalytic electrode prepared in Example 1 when used as the counter electrode is shown in the figure below. Figure 6 As shown, the electrochemical impedance spectroscopy is as follows: Figure 7 As shown, the cyclic voltage curve is as follows Figure 8 As shown, the timing potential curve is as follows Figure 9 As shown, the Faraday efficiency diagram is as follows: Figure 10 As shown, Figure 10 The ammonia ion absorption liquid mentioned above refers to a dilute sulfuric acid solution that is placed on the ammonia outlet side to absorb / fix the ammonia gas generated by the reaction.

[0141] The substitution reaction spontaneously generates an ultrathin Pt-Au alloy or Pt-Au mixed layer on its surface. By heat treatment and cyclic voltammetry scanning of the Pt-Au alloy or Pt-Au mixed layer, a Pt-Au catalytic electrode with high crystallinity, good stability, good surface condition and excellent catalytic performance is obtained, which greatly reduces the amount of precious metals used.

[0142] According to the test results of Example 1, Comparative Example 1 and Comparative Example 2, if step (4) is not performed after the replacement is completed, that is, if heat treatment is not performed in a reducing atmosphere, or if cyclic voltammetry is not performed on the heat-treated Pt-Au catalytic electrode precursor, a Pt-Au catalytic electrode with high crystallinity, good stability, good surface condition and excellent catalytic performance cannot be obtained.

[0143] According to the test results of Examples 1, 4 and 5, if the molar ratio of gold ions to platinum ions in the replacement solution deviates from the range provided by the present invention, the surface morphology will be too sparse or too dense, resulting in the inability to obtain a Pt-Au catalytic electrode with good surface condition, high catalytic activity and large specific surface area.

[0144] Based on the test results of Examples 1, 6, and 7, if the total concentration of platinum ions and gold ions in the replacement solution is too low, Pt-Au that can sustain the reaction cannot be formed; if the total concentration of platinum ions and gold ions in the replacement solution is too high, it violates the original intention of reducing costs.

[0145] According to the test results of Examples 8 and 9, if the number of cyclic voltammetric scans is too small, a stable Pt-Au catalytic electrode cannot be formed; if the number of cyclic voltammetric scans is too large, the surface state will decrease, resulting in reduced catalytic activity.

[0146] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a Pt-Au catalytic electrode, characterized in that, The preparation method includes: (1) Place the conductive substrate in a nickel plating solution and electroplate to obtain a nickel-plated conductive substrate. (2) The nickel-plated conductive substrate is placed in a displacement solution containing gold ions and platinum ions to undergo a displacement reaction, thereby obtaining a Pt-Au catalytic electrode precursor. (3) Place the Pt-Au catalytic electrode precursor in an acid solution and acid wash the Pt-Au catalytic electrode precursor; (4) The acid-washed Pt-Au catalytic electrode precursor was heat-treated under a reducing atmosphere; (5) The heat-treated Pt-Au catalytic electrode precursor was placed in an electrolyte and subjected to cyclic voltammetry to obtain the Pt-Au catalytic electrode.

2. The preparation method according to claim 1, characterized in that, The solute in the nickel plating solution in step (1) includes any one or a combination of at least two of nickel chloride, nickel acetate, nickel sulfate, or nickel nitrate; And / or, the concentration of nickel ions in the nickel plating solution described in step (1) is 0.1 mol / L to 0.4 mol / L; And / or, the electroplating voltage in step (1) is 4V~8V, and the electroplating time is 1min~8min; And / or, the thickness of the nickel plating layer in the nickel-plated conductive substrate in step (1) is 50μm~300μm.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of gold ions to platinum ions in the replacement solution in step (2) is 1:(0.8~1.25); And / or, the total concentration of gold ions and platinum ions in the replacement solution in step (2) is 10 mmol / L to 30 mmol / L; And / or, the displacement reaction time in step (2) is 1 min to 8 min.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The acid solution mentioned in step (3) includes any one of dilute sulfuric acid, dilute hydrochloric acid, or dilute nitric acid; And / or, the pickling time in step (3) is 10s to 60s.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The heat treatment temperature in step (4) is 300℃~500℃; And / or, the heat treatment time in step (4) is 0.5h to 1.5h; And / or, the reducing atmosphere in step (4) includes an Ar / H2 mixture in which the volume percentage of H2 is 3 vol% to 10 vol%.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The voltage range for the cyclic voltammetry scan in step (5) is -0.2V to 1.0V vs. REH; And / or, the number of cycles of the cyclic voltammetric scan in step (5) is 10 to 50.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The conductive substrate in step (1) includes any one of carbon paper, carbon paper, iron mesh, titanium mesh, nickel mesh or stainless steel mesh.

8. The preparation method according to any one of claims 1 to 7, characterized in that, Before the conductive substrate in step (1) is placed in the nickel plating solution, and after steps (1), (2) and (3) are completed, each step independently includes cleaning and drying; The drying process includes drying in an inert gas stream or vacuum drying.

9. A Pt-Au catalytic electrode, characterized in that, The Pt-Au catalytic electrode is prepared by the preparation method according to any one of claims 1 to 8; In the Pt-Au catalytic electrode, the total loading of Pt and Au is 0.03 mg / cm³. 2 ~0.07mg / cm 2 .

10. The application of the Pt-Au catalytic electrode as described in claim 9 in the electrochemical synthesis of ammonia.

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