Pt-Pd composite electrode and preparation method and application thereof

Abstract

The invention relates to a Pt-Pd composite electrode and a preparation method and application thereof. The preparation method comprises the following steps: placing a conductive substrate in an electro-deposition liquid, taking the conductive substrate as a working electrode, sequentially carrying out first electro-deposition and second electro-deposition, and forming a Pt-Pd composite catalyst layer on the surface of the conductive substrate to prepare the Pt-Pd composite electrode, the electro-deposition liquid comprises a platinum source, a palladium source and a supporting electrolyte. The Pt-Pd composite electrode is prepared through cooperation of Pt and Pb, the structural stability of the electrode is remarkably improved, meanwhile, layer-by-layer growth of catalytic particles is achieved in the mode that first electrodeposition and second electrodeposition are combined, it is guaranteed that catalytic active sites are fully exposed, it is also guaranteed that the binding force between a plating layer and a substrate is extremely high, and the service life of the plating layer is prolonged. The electrode is used for electrochemically synthesizing ammonia, has relatively high Faraday efficiency, is particularly suitable for long-term operation under high current density, and has a good industrial application prospect.

Description

Technical Field

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

[0002] Anode catalysts are crucial for the hydrogen oxidation reaction (HOR) in the electrochemical ammonia synthesis process. However, the high cost of traditional anode catalysts like PtAu limits the commercialization of electrochemical ammonia production. Therefore, exploring novel, efficient, and low-cost anodes is a significant bottleneck for the commercialization of battery-based ammonia production.

[0003] CN109126782A discloses a porous PdRu alloy catalyst for electrochemical ammonia synthesis and its preparation method. The method involves dissolving potassium chloride and ruthenium chloride in deionized water, controlling their concentrations between 10 and 40 mM; then dissolving sodium borohydride in deionized water, controlling the concentration between 5 and 50 mM; and then rapidly adding the freshly synthesized sodium borohydride solution to a noble metal precursor solution under stirring. After reacting for 1-5 minutes, the catalyst is washed, centrifuged, and dried to obtain a PdRu alloy catalyst with controllable structure and composition. This invention features a simple preparation process, extremely short reaction time, and the resulting material exhibits excellent electrochemical ammonia synthesis performance under ambient temperature and pressure.

[0004] CN116855999A discloses a sponge-like copper tellurium electrocatalyst for electrochemical ammonia synthesis and its preparation method. The catalyst preparation includes the following steps: (1) preparation of the reaction solution; (2) preparation of the porous copper tellurium nanomesh catalyst; and (3) electrocatalytic reduction reaction performance testing. The organic-inorganic composite catalyst preparation method provided by this invention is simple to operate, low in cost, and environmentally friendly, making it suitable for large-scale production. The porous structure provides abundant channels for molecular penetration, increasing the reachable active sites between reactants and catalysts. In addition, the amorphous structure provides abundant unsaturated structural active sites, thereby improving catalytic performance.

[0005] CN118026173A discloses a three-dimensional open porous doped carbon material and its preparation. Using a heterocyclic polymer as the carbon and dopant source, a dipotassium salt (potassium chloride and potassium bicarbonate) as the activator, and an acetylacetone salt as the metal source, a three-dimensional open porous doped carbon material with a highly developed pore structure is obtained through steps such as ball milling, high-temperature carbonization, acid washing, and drying. The resulting product exhibits high heteroatom doping, high specific surface area, excellent pore size distribution characteristics, and superior electrochemical performance. Based on its unique electrochemical nitrate reduction mechanism, the electrocatalytic synthesis of ammonia from nitrate using this product not only achieves high yield and excellent Faradaic efficiency but also demonstrates good long-term operational stability.

[0006] Therefore, it is of great significance to provide a composite electrode for the electrochemical reduction of nitrogen to synthesize ammonia that has a simple preparation method and excellent stability, as well as its preparation method. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a Pt-Pd composite electrode, its preparation method, and its applications. This invention uses a combination of Pt and Pb to prepare a Pt-Pd composite electrode, significantly improving the electrode's structural stability. Simultaneously, by combining first and second electrodeposition, layer-by-layer growth of catalytic particles is achieved, ensuring both sufficient exposure of catalytic active sites and extremely strong adhesion between the coating and the substrate. When used in electrochemical ammonia synthesis, this electrode exhibits significantly better long-term stability than a pure Pd electrode and possesses high Faradaic efficiency. It is particularly suitable for long-term operation at high current densities and shows promising prospects for industrial application.

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

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

[0010] A conductive substrate is placed in an electrodeposition solution, and a first electrodeposition and a second electrodeposition are performed sequentially using the conductive substrate as the working electrode to form a Pt-Pd composite catalytic layer on the surface of the conductive substrate, thereby preparing the Pt-Pd composite electrode. The electrodeposition solution includes a platinum source, a palladium source, and a supporting electrolyte. The first electrodeposition and the second electrodeposition satisfy any one of the following conditions (a) or (b): (a) the current of the first electrodeposition is less than the current of the second electrodeposition; (b) the voltage of the first electrodeposition is less than the voltage of the second electrodeposition.

[0011] In this invention, a two-electrode system is constructed using a conductive substrate as the working electrode. The material of the electrode is not particularly limited; for example, it can be a platinum electrode or graphite.

[0012] This invention prepares a Pt-Pd composite electrode using platinum and palladium. The stabilizing effect of platinum effectively improves the morphology of the pure palladium electrode, preventing pulverization or detachment during long-term high-current operation and significantly enhancing the electrode's structural stability. Simultaneously, by combining first and second electrodeposition, layer-by-layer growth of catalytic particles is achieved, ensuring both sufficient exposure of catalytic active sites and extremely strong adhesion between the coating and the substrate. When used in electrochemical ammonia synthesis, this electrode exhibits significantly better long-term stability than the pure palladium electrode and possesses high Faradaic efficiency. It is particularly suitable for long-term operation at high current densities and shows promising prospects for industrial application.

[0013] Preferably, the platinum source includes any one or a combination of at least two of potassium chloroplatinate, sodium chloroplatinate, ammonium chloroplatinate, or chloroplatinic acid.

[0014] Preferably, the palladium source includes any one or a combination of at least two of potassium chloropalladium, sodium chloropalladium, ammonium chloropalladium, or chloropalladic acid.

[0015] Preferably, the supporting electrolyte includes any one of sulfuric acid, hydrochloric acid, or perchloric acid, with sulfuric acid being the most preferred.

[0016] Preferably, the conductive substrate comprises any one of stainless steel cloth, nickel foam, carbon paper, or carbon cloth.

[0017] Preferably, in the electrodeposition solution, the molar ratio of platinum to palladium, based on the content of platinum in the platinum source and palladium in the palladium source, is (0.5~8):(2~9.5), more preferably (1~3):(7~9).

[0018] Preferably, in the electrodeposition solution, the total concentration of platinum and palladium, based on the content of platinum in the platinum source and palladium in the palladium source, is 5 mmol / L to 50 mmol / L.

[0019] Preferably, the concentration of the supporting electrolyte is 1 mol / L to 5 mol / L, and more preferably 1 mol / L to 4 mol / L.

[0020] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the first electrodeposition is 2A~6A.

[0021] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (a), the time for the first electrodeposition is 50s to 150s.

[0022] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the second electrodeposition is 6A~10A.

[0023] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (a), the time for the second electrodeposition is 20s to 100s.

[0024] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the first electrodeposition is 1V~4V.

[0025] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (b), the time for the first electrodeposition is 50s to 150s.

[0026] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the second electrodeposition is 4V~10V.

[0027] Preferably, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the second electrodeposition is 20s~100s.

[0028] Preferably, the first and second electrodeposition processes further include stirring the electrodeposition solution.

[0029] Preferably, the preparation method further includes pretreatment of the conductive substrate, the pretreatment including placing the conductive substrate in an acid solution and performing cyclic voltammetry treatment.

[0030] Preferably, the acid solution includes any one of sulfuric acid solution, hydrochloric acid solution, or nitric acid solution.

[0031] Preferably, the concentration of the acid solution is 0.05 mol / L to 1 mol / L.

[0032] Preferably, the scanning voltage range of the cyclic voltammetry process is -0.5V to 1.5V.

[0033] Preferably, the scan rate of the cyclic voltammetry process is 0.01V / s to 0.5V / s.

[0034] Preferably, the number of scans in the cyclic voltammetry process is 5 to 50.

[0035] In a second aspect, the present invention provides a Pt-Pd composite electrode, which is prepared by the preparation method described in the first aspect.

[0036] Thirdly, the present invention provides an application of the Pt-Pd composite electrode as described in the second aspect, wherein the Pt-Pd composite electrode is used for the electrochemical reduction of nitrogen to synthesize ammonia.

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

[0038] This invention prepares a Pt-Pd composite electrode by combining Pt and Pb, which significantly improves the structural stability of the electrode. At the same time, by combining the first electrodeposition and the second electrodeposition, the catalytic particles are grown layer by layer, which not only ensures the full exposure of the catalytic active sites, but also ensures a very strong bond between the coating and the substrate. When this electrode is used for electrochemical ammonia synthesis, it exhibits long-term stability far superior to that of a pure Pd electrode and has a high Faradaic efficiency. It is particularly suitable for long-term operation at high current densities and has good prospects for industrial application. Attached Figure Description

[0039] Figure 1 This is a SEM image of the Pt-Pb composite electrode prepared in Example 1.

[0040] Figure 2This is a SEM image of the catalyst layer on the surface of the Pt-Pb composite electrode prepared in Example 1.

[0041] Figure 3 The time-potential curves of the nitrogen reduction reaction of the Pt-Pd composite electrode prepared in Example 1 are shown.

[0042] Figure 4 This is a Faraday efficiency diagram of the nitrogen reduction reaction of the Pt-Pd composite electrode prepared in Example 1.

[0043] Figure 5 This is a SEM image of the Pb electrode prepared in Comparative Example 1.

[0044] Figure 6 This is a SEM image of the catalyst layer on the surface of the Pb electrode prepared in Comparative Example 1.

[0045] Figure 7 This is the chronopotential curve of the Pb electrode prepared in Comparative Example 1 undergoing nitrogen reduction reaction.

[0046] Figure 8 This is a Faraday efficiency diagram of the nitrogen reduction reaction of the Pb electrode prepared in Comparative Example 1. Detailed Implementation

[0047] 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 in any way.

[0048] 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.

[0049] 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] 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.

[0052] 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.

[0053] 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."

[0054] 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.

[0055] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth 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," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0056] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0057] In this invention, unless otherwise specified, it is assumed that the experiments are conducted 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.

[0058] In one specific embodiment, the present invention provides a method for preparing a Pt-Pd composite electrode, the method comprising:

[0059] A conductive substrate is placed in an electrodeposition solution, and a first electrodeposition and a second electrodeposition are performed sequentially using the conductive substrate as the working electrode to form a Pt-Pd composite catalytic layer on the surface of the conductive substrate, thereby preparing the Pt-Pd composite electrode. The electrodeposition solution includes a platinum source, a palladium source, and a supporting electrolyte. The first electrodeposition and the second electrodeposition satisfy any one of the following conditions (a) or (b): (a) the current of the first electrodeposition is less than the current of the second electrodeposition; (b) the voltage of the first electrodeposition is less than the voltage of the second electrodeposition.

[0060] In this invention, a two-electrode system is constructed using a conductive substrate as the working electrode. The material of the electrode is not particularly limited; for example, it can be a platinum electrode or graphite.

[0061] This invention prepares a Pt-Pd composite electrode using platinum and palladium. The stabilizing effect of platinum effectively improves the morphology of the pure palladium electrode, preventing pulverization or detachment during long-term high-current operation and significantly enhancing the electrode's structural stability. Simultaneously, by combining first and second electrodeposition, layer-by-layer growth of catalytic particles is achieved, ensuring both sufficient exposure of catalytic active sites and extremely strong adhesion between the coating and the substrate. When used in electrochemical ammonia synthesis, this electrode exhibits significantly better long-term stability than the pure palladium electrode and possesses high Faradaic efficiency. It is particularly suitable for long-term operation at high current densities and shows promising prospects for industrial application.

[0062] In some embodiments, the platinum source includes any one or a combination of at least two of potassium chloroplatinate, sodium chloroplatinate, ammonium chloroplatinate, or chloroplatinic acid. Typical but non-limiting combinations include a combination of potassium chloroplatinate and sodium chloroplatinate, or a combination of ammonium chloroplatinate and chloroplatinic acid.

[0063] In some embodiments, the palladium source includes any one or a combination of at least two of potassium chloropalladium, sodium chloropalladium, ammonium chloropalladium, or chloropalladic acid. Typical but non-limiting combinations include a combination of potassium chloropalladium and sodium chloropalladium, or a combination of ammonium chloropalladium and chloropalladic acid.

[0064] In some embodiments, the supporting electrolyte includes any one of sulfuric acid, hydrochloric acid, or perchloric acid, preferably sulfuric acid.

[0065] In some embodiments, the conductive substrate includes any one of stainless steel cloth, nickel foam, carbon paper, or carbon cloth.

[0066] In some embodiments, the molar ratio of platinum to palladium in the electrodeposition solution is (0.5~8):(2~9.5), based on the content of platinum in the platinum source and palladium in the palladium source. For example, it can be 0.5:9.5, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 or 8:2, preferably (1~3):(7~9).

[0067] In some embodiments, the total concentration of platinum and palladium in the electrodeposition solution is 5 mmol / L to 50 mmol / L, based on the content of platinum in the platinum source and palladium in the palladium source. For example, it can be 5 mmol / L, 10 mmol / L, 15 mmol / L, 20 mmol / L, 25 mmol / L, 30 mmol / L, 35 mmol / L, 40 mmol / L, 45 mmol / L, or 50 mmol / L.

[0068] In some embodiments, the concentration of the supporting electrolyte is 1 mol / L to 5 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, preferably 1 mol / L to 4 mol / L.

[0069] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the first electrodeposition is 2A to 6A, for example, it can be 2A, 2.5A, 3A, 3.5A, 4A, 4.5A, 5A, 5.5A or 6A.

[0070] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (a), the time for the first electrodeposition is 50s to 150s, for example, it can be 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s or 150s.

[0071] In some implementations, when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the second electrodeposition is 6A to 10A, for example, it can be 6A, 7A, 8A, 9A or 10A.

[0072] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (a), the time for the second electrodeposition is 20s to 100s, for example, it can be 20s, 40s, 60s, 70s, 80s, 90s or 100s.

[0073] In some implementations, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the first electrodeposition is 1V to 4V, for example, it can be 1V, 1.5V, 2V, 2.5V, 3V, 3.5V, or 4V.

[0074] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (b), the time for the first electrodeposition is 50s to 150s, for example, it can be 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s or 150s.

[0075] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the second electrodeposition is 4V to 10V, for example, it can be 6V, 6.5V, 7V, 7.5V, 8V, 8.5V, 9V, 9.5V, or 10V.

[0076] In some embodiments, when the first electrodeposition and the second electrodeposition satisfy condition (b), the time for the second electrodeposition is 20s to 100s, for example, it can be 20s, 40s, 60s, 70s, 80s, 90s or 100s.

[0077] In some embodiments, the first and second electrodeposition processes also include stirring the electrodeposition solution.

[0078] In some embodiments, the preparation method further includes pretreatment of the conductive substrate, the pretreatment including placing the conductive substrate in an acid solution and performing cyclic voltammetry treatment.

[0079] In some embodiments, the acid solution includes any one of sulfuric acid solution, hydrochloric acid solution, or nitric acid solution.

[0080] In some embodiments, the concentration of the acid solution is 0.05 mol / L to 1 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L.

[0081] In some embodiments, the scanning voltage range of the cyclic voltammetry treatment is -0.5V to 1.5V. In this invention, a suitable scanning voltage range can be selected within the above range depending on the type of conductive substrate, for example, it can be -0.5V to 1.5V, -0.3V to 1.2V, or 0V to 1.2V.

[0082] In some embodiments, the scan rate of the cyclic voltammetry process is 0.01V / s to 0.5V / s, for example, it can be 0.01V / s, 0.05V / s, 0.1V / s, 0.2V / s, 0.3V / s, 0.4V / s or 0.5V / s.

[0083] In some implementations, the number of scans in the cyclic voltammetry process is 5 to 50 times, for example, 5, 10, 20, 30, 40 or 50 times.

[0084] In another specific embodiment, the present invention provides a Pt-Pd composite electrode, which is prepared by the preparation method described in one of the preceding specific embodiments.

[0085] In yet another embodiment, the present invention provides an application of the Pt-Pd composite electrode as described in the previous embodiment, wherein the Pt-Pd composite electrode is used for the electrochemical reduction of nitrogen to synthesize ammonia.

[0086] 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.

[0087] Example 1

[0088] This embodiment provides a method for preparing a Pt-Pd composite electrode, the method comprising:

[0089] (1) Pretreatment of conductive substrate: Using a platinum electrode as a reference electrode, stainless steel was placed in a 0.1 mol / L sulfuric acid solution, and 20 cyclic voltammetric scans were performed at a scan rate of 0.1 V / s within a voltage range of 0 V to 1.2 V.

[0090] (2) Preparation of electrodeposition solution: Dissolve potassium chloroplatinate and potassium chloropalladium in 3 mol / L sulfuric acid solution according to the molar ratio of platinum to palladium of 1:1 and the total concentration of potassium chloroplatinate and chloropalladium acid of 20 mmol / L.

[0091] (3) The pretreated conductive substrate was placed in the electrodeposition solution. Using the conductive substrate as the working electrode and the platinum electrode as the counter electrode, a first electrodeposition and a second electrodeposition were performed sequentially. The first electrodeposition used a current of 4 A for 100 s, and the second electrodeposition used a current of 8 A for 50 s. The electrodeposition solution was stirred during the deposition process to form a Pt-Pd composite catalytic layer on the surface of the conductive substrate, thus preparing the Pt-Pd composite electrode. Figure 1 Here is a SEM image of the Pt-Pd composite electrode. Figure 2 The image shows an SEM image of the catalyst layer on the surface of the Pt-Pd composite electrode. It can be seen that the alloy particles on the surface of the Pt-Pd composite electrode obtained in this embodiment are more uniformly distributed, with no obvious agglomeration or cracks.

[0092] Example 2

[0093] (1) Pretreatment of conductive substrate: Using platinum electrode as reference electrode, nickel foam was placed in 0.05 mol / L nitric acid solution, and 5 cyclic voltammetric scans were performed at a scan rate of 0.01 V / s within the voltage range of -0.5 V to 1.5 V.

[0094] (2) Preparation of electrodeposition solution: Dissolve chloroplatinic acid and chloropalladium in 2 mol / L sulfuric acid solution according to the molar ratio of platinum to palladium of 1:9 and the total concentration of potassium chloroplatinate and chloropalladium acid of 5 mmol / L.

[0095] (3) The pretreated conductive substrate is placed in the electrodeposition solution. The conductive substrate is used as the working electrode and the platinum electrode is used as the counter electrode. The first electrodeposition and the second electrodeposition are performed in sequence. The current of the first electrodeposition is 2A and the time is 50s. The current of the second electrodeposition is 6A and the time is 20s. The electrodeposition solution is stirred during the deposition process to form a Pt-Pd composite catalytic layer on the surface of the conductive substrate, and the Pt-Pd composite electrode is prepared.

[0096] Example 3

[0097] This embodiment provides a method for preparing a Pt-Pd composite electrode, the method comprising:

[0098] (1) Pretreatment of conductive substrate: Using a platinum electrode as a reference electrode, carbon was placed in a 1 mol / L hydrochloric acid solution, and 50 cyclic voltammetric scans were performed at a scan rate of 0.5 V / s within a voltage range of -0.5 V to 1.5 V.

[0099] (2) Preparation of electrodeposition solution: Sodium chloroplatinate and sodium chloropalladium are dissolved in 4 mol / L hydrochloric acid solution according to the molar ratio of platinum to palladium of 3:7 and the total concentration of potassium chloroplatinate and chloropalladium acid of 50 mmol / L.

[0100] (3) The pretreated conductive substrate is placed in the electrodeposition solution. The conductive substrate is used as the working electrode and the platinum electrode is used as the counter electrode. The first electrodeposition and the second electrodeposition are performed in sequence. The current of the first electrodeposition is 6A and the time is 150s. The current of the second electrodeposition is 10A and the time is 100s. The electrodeposition solution is stirred during the deposition process to form a Pt-Pd composite catalytic layer on the surface of the conductive substrate, and the Pt-Pd composite electrode is prepared.

[0101] Example 4

[0102] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for step (2), in which potassium chloroplatinate and potassium chloropalladate are dissolved in a 1 mol / L sulfuric acid solution according to the molar ratio of platinum to palladium of 0.5:9.5, the preparation method is the same as in Example 1.

[0103] Example 5

[0104] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for step (2), in which potassium chloroplatinate and potassium chloropalladate are dissolved in a 5 mol / L sulfuric acid solution according to a platinum to palladium molar ratio of 4:6, the preparation method is the same as in Example 1.

[0105] Example 6

[0106] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for the first electrodeposition current of 1.5A in step (3), the preparation method is the same as in Example 1.

[0107] Example 7

[0108] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for the first electrodeposition current of 6.5A in step (3), the preparation method is the same as in Example 1.

[0109] Example 8

[0110] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for the second electrodeposition current of 5.5A in step (3), the preparation method is the same as in Example 1.

[0111] Example 9

[0112] This embodiment provides a method for preparing a Pt-Pd composite electrode. Except for the second electrodeposition current of 10.5A in step (3), the preparation method is the same as in Example 1.

[0113] Comparative Example 1

[0114] This comparative example provides a method for preparing a Pd electrode. The method is identical to that in Example 1, except that in step (2), the electrodeposition solution contains only potassium chloropalladate and no potassium chloroplatinate is added. Figure 5 Here is a SEM image of the Pd electrode. Figure 6 The image shows an SEM image of the catalyst layer on the surface of the Pd electrode. It can be seen that the alloy particles on the surface of the pure Pb electrode have poor uniformity, and there are agglomerations and cracks.

[0115] Comparative Example 2

[0116] This comparative example provides a method for preparing a Pt electrode. The preparation method is the same as in Example 1, except that the electrodeposition solution in step (2) contains only potassium chloroplatinate and no potassium chloropalladate is added.

[0117] Comparative Example 3

[0118] This comparative example provides a method for preparing a Pt-Pd composite electrode. Except for step (3), in which only the first deposition is performed and the time for the first deposition is extended to 150s, the preparation method is the same as in Example 1.

[0119] Comparative Example 4

[0120] This comparative example provides a method for preparing a Pt-Pd composite electrode. Except for step (3), in which only the second deposition is performed and the time for the second deposition is extended to 150s, the preparation method is the same as in Example 1.

[0121] Performance testing:

[0122] The electrodes prepared in all the above embodiments and comparative examples were used as working electrodes, and in an electrolyte filled with N2, at 6 mA / cm². 2 Electrolysis was performed at a constant current density, and the change in potential over time and the Faraday efficiency were tested. The test results are shown in Table 1.

[0123] The chronopotential curves and Faraday efficiency diagrams of the Pt-Pd composite electrode prepared in Example 1 during the nitrogen reduction reaction are shown below. Figure 3 and Figure 4 As shown, the chronopotential curve and Faraday efficiency diagram of the Pd electrode prepared in Comparative Example 1 undergoing nitrogen reduction reaction are respectively shown in the figures below. Figure 7 and Figure 8 As shown, the ammonia ion absorbent refers to a dilute sulfuric acid solution located on the nitrogen outlet side, used to absorb / fix the ammonia gas generated by the reaction.

[0124] Table 1

[0125]

[0126] In summary, this invention utilizes a combination of Pt and Pb to prepare a Pt-Pd composite electrode, significantly improving the electrode's structural stability. Furthermore, by combining first and second electrodeposition, layer-by-layer growth of catalytic particles is achieved, ensuring both sufficient exposure of the catalytic active sites and extremely strong adhesion between the coating and the substrate. When used in electrochemical ammonia synthesis, this electrode exhibits significantly better long-term stability than a pure Pd electrode and possesses high Faradaic efficiency. It is particularly suitable for long-term operation at high current densities and shows promising prospects for industrial application.

[0127] Based on the test results of Examples 1, 4, and 5, the present invention effectively improves the morphology of the pure palladium electrode by adjusting the molar ratio between platinum and palladium and utilizing the stabilizing effect of platinum, preventing it from pulverizing or falling off during long-term high-current operation, and significantly improving the structural stability of the electrode.

[0128] Based on the test results of Example 1 and Comparative Example 1, such as Figure 3 and Figure 4 As shown, the potential of the Pt-Pb composite electrode prepared in Example 1 remained stable during the 1.8h test, with a total charge flux of 3800C. Meanwhile, as... Figure 7 and Figure 8 As shown, the pure Pd electrode prepared in Comparative Example 1 had a high working potential and a low resting potential during the 3.25h test, with a total charge flux of only 880C, indicating weak catalytic performance.

[0129] Based on the test results of Example 1 and Comparative Example 2, the working voltage of the pure platinum electrode is relatively high, and the Faraday efficiency is also reduced.

[0130] Based on the test results of Examples 1, 6 to 9, and Comparative Examples 3 and 4, the present invention adopts a deposition mode of first mild and then enhanced, which realizes the layer-by-layer growth of catalytic particles, ensuring both the full exposure of catalytic active sites and the extremely strong adhesion between the coating and the substrate, making it particularly suitable for long-term operation under high current density.

[0131] 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-Pd composite electrode, characterized by, The preparation method comprises: placing the conductive substrate in an electrodeposition solution, taking the conductive substrate as a working electrode, sequentially performing first electrodeposition and second electrodeposition, and forming a Pt-Pd composite catalytic layer on the surface of the conductive substrate to obtain the Pt-Pd composite electrode; the electrodeposition solution comprises a platinum source, a palladium source and a supporting electrolyte; the first electrodeposition and the second electrodeposition satisfy any one of conditions (a) or (b): (a) the current of the first electrodeposition is less than that of the second electrodeposition; (b) the voltage of the first electrodeposition is less than that of the second electrodeposition.

2. The production method according to claim 1, wherein the platinum source comprises any one or a combination of at least two of potassium chloroplatinate, sodium chloroplatinate, ammonium chloroplatinate or chloroplatinic acid; and / or, the palladium source comprises any one or a combination of at least two of potassium chloropalladate, sodium chloropalladate, ammonium chloropalladate or chloropalladic acid; and / or, the supporting electrolyte comprises any one of sulfuric acid, hydrochloric acid or perchloric acid; and / or, the conductive substrate comprises any one of stainless steel cloth, foamed nickel, carbon paper or carbon cloth.

3. The production method according to claim 1 or 2, characterized by, in the electrodeposition solution, the molar ratio of platinum to palladium is (0.5-8):(2-9.5) in terms of the content of platinum in the platinum source and the content of palladium in the palladium source; and / or, in the electrodeposition solution, the total concentration of platinum and palladium is 5 mmol / L-50 mmol / L in terms of the content of platinum in the platinum source and the content of palladium in the palladium source; and / or, the concentration of the supporting electrolyte is 1 mol / L-5 mol / L.

4. The production method according to claim 3, wherein in the electrodeposition solution, the molar ratio of platinum to palladium is (1-3):(7-9) in terms of the content of platinum in the platinum source and the content of palladium in the palladium source; and / or, the concentration of the supporting electrolyte is 1 mol / L-4 mol / L.

5. The production method according to any one of claims 1 to 4, wherein when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the first electrodeposition is 2 A-6 A and the time is 50 s-150 s; and / or, when the first electrodeposition and the second electrodeposition satisfy condition (a), the current of the second electrodeposition is 6 A-10 A and the time is 20 s-100 s.

6. The production method according to any one of claims 1 to 4, wherein when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the first electrodeposition is 1 V-4 V and the time is 50 s-150 s; and / or, when the first electrodeposition and the second electrodeposition satisfy condition (b), the voltage of the second electrodeposition is 4 V-10 V and the time is 20 s-100 s.

7. The production method according to any one of claims 1 to 6, wherein The preparation method further comprises pretreating the conductive substrate, and the pretreatment comprises placing the conductive substrate in an acid solution and performing cyclic voltammetry treatment.

8. The production method according to claim 7, wherein the acid solution comprises any one of a sulfuric acid solution, a hydrochloric acid solution or a nitric acid solution; and / or, the concentration of the acid solution is 0.05 mol / L-1 mol / L; and / or, the scanning voltage range of the cyclic voltammetry treatment is -0.5 V-1.5 V; and / or, the scanning rate of the cyclic voltammetry treatment is 0.01 V / s-0.5 V / s; and / or, the cyclic voltammetry treatment is performed for 5-50 times.

9. A Pt-Pd composite electrode, characterized by, The Pt-Pd composite electrode is prepared by the preparation method according to any one of claims 1-8.

10. Use of a Pt-Pd composite electrode according to claim 9, characterized in that The Pt-Pd composite electrode is used for electrochemical reduction of nitrogen to synthesize ammonia.

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