Coordination compound and preparation method thereof, carbon-coated platinum-based alloy nano-material and preparation method and application of carbon-coated platinum-based alloy nano-material

Abstract

The invention relates to the technical field of electro-catalysis, and discloses a coordination compound and a preparation method thereof, and a carbon-coated platinum-based alloy nano-material and a preparation method and application thereof, the coordination compound comprises a coordination cation as shown in a formula (1) and a coordination anion as shown in a formula (2), and M is selected from at least one of Ni, Co and Zn. The coordination compound is used as a precursor to prepare the carbon-coated platinum-based alloy nano material through pyrolysis, and the carbon-coated platinum-based alloy nano material shows good catalytic activity during catalytic oxygen reduction reaction.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a coordination compound and its preparation method, carbon-coated platinum-based alloy nanomaterials and their preparation method and applications. Background Technology

[0002] Energy is the foundation of human societal development. While the use of fossil fuels has accelerated this progress, it has also brought about a series of environmental and climate problems. With these problems becoming increasingly prominent, the development of inexpensive, sustainable, and clean energy technologies is urgently needed. Among numerous energy technologies, fuel cells possess advantages such as high energy conversion efficiency, environmental friendliness, and high power density, making them a hot research topic in the field of new energy. However, the oxygen reduction reaction kinetics at the fuel cell cathode are extremely slow, a key factor affecting fuel cell performance. Currently, commercial fuel cell cathode catalysts primarily rely on the precious metal platinum. On the one hand, platinum resources are limited and expensive, increasing the cost of fuel cells; on the other hand, platinum undergoes aggregation and dissolution during catalysis, resulting in poor fuel cell lifespan. Therefore, developing low-cost, highly active, and highly stable oxygen reduction catalysts is of great significance to the development of fuel cells.

[0003] In recent years, one of the research hotspots in oxygen reduction reaction catalysts has been the formation of alloys between platinum and non-precious metals. Platinum-based alloys can not only improve the catalytic activity of catalysts through inductive and strain effects, but also reduce the platinum loading, improve platinum utilization, and thus reduce the cost of catalysts. However, maintaining the high activity of platinum-based alloy catalysts for extended periods under harsh catalytic conditions remains a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of insufficient activity and stability of platinum-based alloy catalysts in the prior art, and to provide a coordination compound and its preparation method, carbon-coated platinum-based alloy nanomaterials and their preparation method and applications. The coordination compound has a novel composition and structure, and when used as a precursor to prepare carbon-coated platinum-based alloy nanomaterials, it exhibits good catalytic activity and stability in the catalytic oxygen reduction reaction.

[0005] To achieve the above objectives, the present invention provides a coordination compound comprising a cation as shown in formula (1) and an anion as shown in formula (2).

[0006]

[0007] M is selected from at least one of Ni, Co and Zn.

[0008] A second aspect of the present invention provides a method for preparing a coordination compound, comprising:

[0009] Under stirring conditions, tetraammineplatinum acetate, M metal acetate and citric acid were mixed and subjected to a coordination reaction to obtain a precipitate product.

[0010] M is selected from at least one of Ni, Co and Zn.

[0011] A third aspect of this invention provides a method for preparing carbon-coated platinum-based alloy nanomaterials, the method comprising:

[0012] (1) Under an inert atmosphere, the coordination compound described in the first aspect or the coordination compound prepared by the preparation method provided in the second aspect is subjected to high-temperature pyrolysis.

[0013] (2) The product obtained in step (1) is contacted with acid, and then solid-liquid separation, washing and drying are performed.

[0014] The fourth aspect of the present invention provides carbon-coated platinum-based alloy nanomaterials prepared by the above-mentioned method for preparing carbon-coated platinum-based alloy nanomaterials.

[0015] The fifth aspect of this invention provides the application of the carbon-coated platinum-based alloy nanomaterials described in the fourth aspect in the oxygen reduction reaction at the cathode of a fuel cell.

[0016] This invention provides a novel coordination compound with tetraammineplatinum as the coordinating cation and a chelate of metal M and citric acid as the coordinating anion. Carbon-coated platinum-based alloy nanomaterials are prepared by pyrolysis using this coordination compound as a precursor. These nanomaterials exhibit excellent catalytic activity in the oxygen reduction reaction, with a half-wave potential above 0.80 V and a specific activity of 0.10 A / mg at 0.9 V. Pt Furthermore, after 5000 cyclic scans, the catalyst exhibited a half-wave potential decrease of less than 10 mV, and its mass-specific activity and ECSA retention rate remained above 90%, demonstrating excellent stability. This is likely due to the use of tetraammineplatinum as the coordinating cation and the chelate of metal M and citric acid as the coordinating anion to form a coordination compound. During pyrolysis, this compound promotes the alloying of platinum and metal M, while simultaneously forming a carbon shell on the alloy surface, thereby improving platinum utilization. This can enhance catalytic activity through inductive and strain effects. Additionally, the presence of the carbon shell can inhibit the dissolution of metal elements and the aggregation of alloy nanoparticles, thus improving catalyst stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the precursor material A1 prepared in Example 1;

[0018] Figure 2 This is the XRD pattern of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0019] Figure 3This is a TEM image of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0020] Figure 4 The image shows the LSV curves of the catalyst obtained by using the carbon-coated platinum-nickel alloy nanomaterial prepared in Example 1 before and after 5000 cyclic scans.

[0021] Figure 5 The image shows the CV curves of the catalyst obtained by using the carbon-coated platinum-nickel alloy nanomaterial prepared in Example 1 before and after 5000 cyclic scans. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] A first aspect of the present invention provides a coordination compound comprising a cation as shown in formula (1) and an anion as shown in formula (2).

[0024]

[0025] M is selected from at least one of Ni, Co and Zn.

[0026] This invention provides a novel coordination compound with tetraammineplatinum as the coordinating cation and a chelate of metal M and citric acid as the coordinating anion. This coordination compound can be used as a precursor to prepare carbon-coated platinum-based alloy nanomaterials, exhibiting good catalytic activity and stability in the oxygen reduction reaction. This is likely because the coordination compound promotes the alloying of platinum and metal M during pyrolysis, simultaneously forming a carbon shell on the alloy surface, thereby improving platinum utilization. The catalytic activity can be enhanced through inductive and strain effects. Furthermore, the presence of the carbon shell can inhibit the dissolution of metal elements and the aggregation of alloy nanoparticles, thus improving catalyst stability.

[0027] In this invention, the molecular structure of the coordination compound was determined by single-crystal X-ray diffraction. The testing equipment used was Rigaku Corporation, Japan, XtaLAB PRO 007HF, and the testing conditions were: radiation: Mo Kα (0.71037 × 10⁻⁶). - 1 nm), voltage: 50kV, current: 24mA, ambient temperature: 24℃, ambient humidity: 40%.

[0028] According to some preferred embodiments of the present invention, in formula (2), M is Ni and / or Zn.

[0029] A second aspect of the present invention provides a method for preparing a coordination compound, comprising:

[0030] Under stirring conditions, tetraammineplatinum acetate, M metal acetate, citric acid and solvent were mixed and subjected to a coordination reaction to obtain a precipitate product.

[0031] M is selected from at least one of Ni, Co and Zn.

[0032] The inventors of this invention discovered in experiments that tetraammineplatinum acetate, metal M acetate, and citric acid can promote a coordination reaction between tetraammineplatinum, metal M, and citric acid, resulting in the precipitation of the coordination compound.

[0033] In this invention, tetraammineplatinum acetate, M metal acetate, and citric acid are all commercially available. The M metal acetate and / or citric acid may also contain water of crystallization, as is well known to those skilled in the art.

[0034] According to some preferred embodiments of the present invention, the molar ratio of tetraammineplatinum acetate (calculated as platinum) to metal acetate (calculated as element M) is 1:(1-20), preferably 1:(4-12).

[0035] According to some preferred embodiments of the present invention, the total molar amount of tetraammineplatinum acetate and M metal acetate, calculated as metal elements, to the molar ratio of citric acid is 1:(0.1-5), preferably 1:(0.3-2).

[0036] According to the present invention, the coordination reaction is carried out in the presence of a solvent. The present invention does not particularly limit the type of solvent, but the solvent should be capable of sufficiently dissolving and dispersing tetraammineplatinum acetate, M metal acetate, and citric acid. Preferably, the solvent is water. The present invention also does not particularly limit the amount of solvent used, but the amount should also be capable of sufficiently dissolving and dispersing the reactants. Those skilled in the art can select the appropriate amount based on actual needs.

[0037] This invention does not impose particular limitations on the stirring rate or the specific conditions of the coordination reaction, as long as the three components can react sufficiently. Preferably, the conditions for the coordination reaction include: a temperature of 40-100℃, more preferably 60-80℃, and a time of 3-12 hours, more preferably 6-10 hours. Adopting the above preferred embodiments is beneficial for the formation of coordination compounds.

[0038] In this invention, the precipitate can be separated from the product of the coordination reaction by any solid-liquid separation method, such as filtration, vacuum filtration, centrifugation, etc., which can be selected by those skilled in the art as needed.

[0039] According to the present invention, the method for preparing the complex optionally further includes drying the precipitated product. The present invention does not particularly limit the drying method and conditions, and conventional methods in the art can be used. Preferably, the drying is vacuum drying, the drying temperature is 50-100°C, and the drying time is 6-14 hours.

[0040] A third aspect of this invention provides a method for preparing carbon-coated platinum-based alloy nanomaterials, the method comprising:

[0041] (1) Under an inert atmosphere, the coordination compound described in the first aspect or the coordination compound prepared by the preparation method described in the second aspect is subjected to high-temperature pyrolysis.

[0042] (2) The product obtained in step (1) is contacted with acid, and then solid-liquid separation, washing and drying are performed.

[0043] According to the present invention, the coordination compound provided by the present invention can promote the alloying of platinum and metal M during pyrolysis, and form a carbon shell on the alloy surface to form carbon-coated platinum-based alloy nanomaterials. The above preparation method can improve the utilization rate of platinum, and can improve the catalytic activity of carbon-coated platinum-based alloy nanomaterials in electrocatalytic oxygen reduction reaction through induction effect and strain effect. In addition, the presence of carbon shell can inhibit the dissolution of metal elements and the agglomeration of alloy nanoparticles, thereby improving stability.

[0044] In this invention, in step (1), the inert gas refers to any non-reactive gas that does not participate in the reaction. Preferably, the inert gas is nitrogen and / or argon.

[0045] Preferably, the flow rate of the inert gas is 20-120 mL / min, and more preferably 60-100 mL / min.

[0046] According to some preferred embodiments of the present invention, the pyrolysis temperature is 400-1000℃, for example, it can be a specific but not limiting pyrolysis temperature such as 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, or any range between the two. Preferably, the pyrolysis temperature is 500-800℃.

[0047] In this invention, the high-temperature pyrolysis is performed by heating to the above-mentioned pyrolysis temperature through a program, and then maintaining the temperature. Preferably, the heating rate of the high-temperature pyrolysis is 2-10℃ / min, and more preferably 2-8℃ / min.

[0048] Preferably, the isothermal time for the high-temperature pyrolysis is 1-6 hours, and more preferably 2-5 hours.

[0049] After the above-mentioned high-temperature pyrolysis, it is preferable to let the pyrolysis product cool naturally in an inert atmosphere, then grind it appropriately, and then perform subsequent acid washing.

[0050] According to the present invention, in step (2), the purpose of contacting the product obtained in step (1) with acid is to remove the uncoated metal in the pyrolysis product. The acid can be an acid conventionally used in the art, as long as it can properly remove the uncoated metal in the pyrolysis product. Preferably, the acid can be an inorganic acid and / or an organic acid, and more preferably at least one of sulfuric acid, nitric acid and hydrochloric acid.

[0051] Preferably, the amount of acid used is 40-100 mL, more preferably 40-80 mL, relative to 1 g of the pyrolysis product obtained in step (1).

[0052] According to some preferred embodiments of the present invention, in step (2), the acid is provided by an aqueous solution of an acid. Preferably, the acid is provided by a sulfuric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C; or, the acid is provided by a nitric acid solution with a concentration of 0.5-15 mol / L and a contact temperature of 25-60°C; or, the acid is provided by a hydrochloric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C.

[0053] Preferably, in step (2), the contact time is 3-50 hours, more preferably 3-24 hours.

[0054] According to the present invention, in step (2), the purpose of washing is to remove the acid remaining on the pyrolysis products during the pickling process. Therefore, various water washing methods that can wash the pyrolysis products to neutrality are applicable to the present invention. Preferably, washing is performed until the pH of the washing solution is neutral.

[0055] According to the present invention, in step (2), the purpose of drying is to remove water from the pickling product. Therefore, drying can be carried out under normal pressure or reduced pressure, preferably under vacuum, at a temperature of 60-80°C for 4-12 hours.

[0056] The fourth aspect of the present invention provides carbon-coated platinum-based alloy nanomaterials prepared by the above-mentioned method for preparing carbon-coated platinum-based alloy nanomaterials.

[0057] Preferably, the carbon-coated platinum-based alloy nanomaterial has a core-shell structure with platinum-metal M alloy particles as the core and a carbon layer as the shell, wherein M is selected from at least one of Ni, Co and Zn.

[0058] In this invention, the surface morphology of the material is characterized by high-resolution transmission electron microscopy (HRTEM, JEM-2100, NEC Corporation) and scanning electron microscopy (SEM, model: S-4800, Hitachi), wherein the accelerating voltage of HRTEM is 200kV and the accelerating voltage of SEM is 3kV.

[0059] According to the present invention, in the carbon-coated platinum-based alloy nanomaterials prepared by the above preparation method, Pt and metallic M exist in alloy form, which can be characterized by X-ray diffraction. X-ray diffraction was performed on an Empyrean instrument from Malvern Panaco GmbH, Netherlands, under the following conditions: Cu target, Kα rays, tube voltage 40 kV, tube current 40 mA, and scan rate 2° / min.

[0060] Preferably, when M is Ni, the XRD spectrum of the carbon-coated platinum-based alloy nanomaterial has characteristic diffraction peaks at 2θ of 42.5±1°, 49.6±1°, and 72.6±1°, and does not have characteristic diffraction peaks of Pt and / or Ni elements.

[0061] Preferably, when M is Co, the XRD spectrum of the carbon-coated platinum-based alloy nanomaterial has characteristic diffraction peaks at 2θ of 40.0±0.5°, 46.6±0.5°, and 67.9±0.5°, and does not have characteristic diffraction peaks of Pt and / or Co elements.

[0062] Preferably, the average particle size of the platinum-metal M alloy particles is 3-6 nm.

[0063] In this invention, the average particle size of the alloy particles is measured by electron microscopy statistical method, with no less than 200 particles counted, and then the average particle size is calculated.

[0064] Preferably, in the carbon-coated platinum-based alloy nanomaterial, the carbon content is 5-20% by weight, preferably 10-20% by weight; the platinum content is 40-65% by weight, preferably 50-65% by weight; the content of metallic M is 10-30% by weight, preferably 15-25% by weight; the hydrogen content is 0.5-1.5% by weight, preferably 0.7-1.3% by weight; and the oxygen content is 1-15% by weight, preferably 5-12% by weight.

[0065] The carbon, hydrogen, and oxygen content was measured using an Elementar Vario EL Cube elemental analyzer. The specific procedure was as follows: Approximately 5 mg of sample was weighed into a tin cup, placed in the autosampler tray, and introduced into the combustion tube via a ball valve. Combustion was performed at 1000℃ (helium purging was used to eliminate atmospheric interference during injection). The carbon and hydrogen in the sample were converted into carbon dioxide and water, respectively. The mixed gas was separated by a chromatographic column and finally detected by a thermal conductivity cell. For oxygen determination, the sample was pyrolyzed in a high-temperature pyrolysis tube containing carbon powder. The oxygen in the sample was converted into carbon monoxide. The carrier gas carried the pyrolysis products into a series of scrubbers to remove acid gases and water vapor, and finally detected by an infrared detector.

[0066] The content of metal elements was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The specific method is as follows: (1) Nitration: 10 mg of catalyst sample was placed in a flask, 16 mL of freshly prepared aqua regia was added, a magnetic stir bar was added, the flask was placed in an oil bath, refluxed at 120 °C for 12 h, and after cooling to room temperature, the solution was drawn up with a glass syringe and filtered with a disposable filter with a pore size of 0.22 μm. The filtrate was added to a 500 mL volumetric flask and diluted with ultrapure water. (2) Content test: 10 mL of the solution after nitration and dilution was taken and the metal content was tested using an Agilent 5110 instrument.

[0067] The fifth aspect of this invention provides the application of the carbon-coated platinum-based alloy nanomaterials described in the fourth aspect in the oxygen reduction reaction at the cathode of a fuel cell.

[0068] In this invention, the carbon-coated platinum-based alloy nanomaterial can be used as a catalyst for the oxygen reduction reaction in the battery cathode, exhibiting good catalytic activity and stability.

[0069] The present invention does not particularly limit the composition of the catalyst. In addition to carbon-coated platinum-based alloy nanomaterials, it may also contain other conventional catalyst compositions in the art. For example, the catalyst may include the carbon-coated platinum-based alloy nanomaterials and conductive carbon black.

[0070] In this invention, there is no particular limitation on the conductive carbon black, which can be obtained commercially. Any conductive carbon black that can be used for oxygen reduction reaction at the cathode of a fuel cell can be used in this invention, such as Ketjen black (e.g., ECT-600JD), Cabot carbon black (e.g., Vulcan XC 72), etc.

[0071] According to some preferred embodiments of the present invention, the weight ratio of the carbon-coated platinum-based alloy nanomaterial to the conductive carbon black is 1:0.1-5, preferably 1:0.1-1.

[0072] The present invention will be described in detail below through embodiments.

[0073] In the following examples, unless otherwise specified, all reagents used in this invention are of analytical grade and are commercially available.

[0074] The molecular structure of the coordination compound was determined by single-crystal X-ray diffraction. The testing equipment used was Rigaku Corporation XtaLAB PRO 007HF, and the testing conditions were: radiation: Mo Kα (0.71037×10-1nm), voltage: 50kV, current: 24mA, ambient temperature: 24℃, and ambient humidity: 40%.

[0075] The surface morphology of the material was characterized by high-resolution transmission electron microscopy (HRTEM, JEM-2100, NEC Corporation) and scanning electron microscopy (SEM, model: S-4800, Hitachi). The accelerating voltage of HRTEM was 200 kV and the accelerating voltage of SEM was 5 kV.

[0076] The crystal structure of the material was characterized by X-ray diffraction (XRD, Malvern Panaco GmbH, Netherlands, Empyrean). The test conditions were: Cu target, Kα rays, tube voltage 40 kV, tube current 40 mA, and scan rate 2° / min.

[0077] The carbon, hydrogen, and oxygen content was measured using an Elementar Vario EL Cube elemental analyzer. The specific procedure was as follows: Approximately 5 mg of sample was weighed into a tin cup, placed in the autosampler tray, and introduced into the combustion tube via a ball valve. Combustion was performed at 1000℃ (helium purging was used to eliminate atmospheric interference during injection). The carbon and hydrogen in the sample were converted into carbon dioxide and water, respectively. The mixed gas was separated by a chromatographic column and finally detected by a thermal conductivity cell. For oxygen determination, the sample was pyrolyzed in a high-temperature pyrolysis tube containing carbon powder. The oxygen in the sample was converted into carbon monoxide. The carrier gas carried the pyrolysis products into a series of scrubbers to remove acid gases and water vapor, and finally detected by an infrared detector.

[0078] The content of platinum and nickel was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The specific method is as follows: (1) Nitration: 10 mg of catalyst sample was placed in a flask, 16 mL of freshly prepared aqua regia was added, a magnetic stir bar was added, the flask was placed in an oil bath, refluxed at 120 °C for 12 h, and after cooling to room temperature, the solution was drawn up with a glass syringe and filtered with a disposable filter with a pore size of 0.22 μm. The filtrate was added to a 500 mL volumetric flask and diluted with ultrapure water. (2) Content test: 10 mL of the solution after nitration and dilution was taken and the metal content was tested using an Agilent 5110 instrument.

[0079] The following preparation examples illustrate the preparation of coordination compounds in this invention.

[0080] Preparation Example 1

[0081] 1.0 g of tetraammineplatinum acetate, 7.6 g of nickel acetate tetrahydrate, and 4.2 g of citric acid monohydrate were added to 200 mL of deionized water. The mixture was refluxed in an oil bath at 80 °C and stirred for 10 h to allow the three compounds to react fully and form a light green precipitate. The precipitate was separated by filtration and dried in a vacuum drying oven at 60 °C for 10 h to obtain precursor material A1. The yield of the coordination compound was calculated to be 82.97%.

[0082] The yield (%) of the coordination compound is calculated as: (mass of recovered precipitate / theoretical yield of the coordination compound based on tetraammineplatinum acetate) × 100%.

[0083] Single-crystal X-ray diffraction analysis was performed on precursor material A1 to determine its crystal structure as follows: Figure 1 As shown, a coordination compound comprising a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0084] Preparation Example 2

[0085] 2.0 g of tetraammineplatinum acetate, 8.6 g of nickel acetate tetrahydrate, and 3.4 g of citric acid monohydrate were added to 200 mL of deionized water. The mixture was refluxed in an oil bath at 80 °C and stirred for 10 h to allow the three compounds to react fully and form a light green precipitate. The precipitate was separated by filtration. The precipitate was dried in a forced-air drying oven at 60 °C for 12 h to obtain precursor material A2. The yield of the coordination compound was calculated to be 91.50%.

[0086] Single-crystal X-ray diffraction analysis was performed on precursor material A2 to determine that the crystal structure of precursor material A2 is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0087] Preparation Example 3

[0088] 2.0 g of tetraammineplatinum acetate, 6.3 g of nickel acetate tetrahydrate, and 11.3 g of citric acid monohydrate were added to 150 mL of deionized water. The mixture was stirred under constant reflux in an oil bath at 60 °C for 12 h to allow the three compounds to react fully and form a light green precipitate. The precipitate was separated by centrifugation and dried in a forced-air drying oven at 80 °C for 8 h to obtain precursor material A3. The yield of the coordination compound was calculated to be 61%.

[0089] Single-crystal X-ray diffraction analysis was performed on precursor material A3 to determine that the crystal structure of precursor material A3 is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0090] Preparation Example 4

[0091] 1.0 g tetraammineplatinum acetate, 2.8 g zinc acetate, and 3.9 g citric acid monohydrate were mixed and added to 150 mL deionized water. The mixture was stirred under constant reflux in an oil bath at 70 °C for 8 h to allow the three compounds to react fully and form a white precipitate. The precipitate was separated by filtration and dried in a vacuum oven at 60 °C for 12 h to obtain precursor material A4. The yield of the coordination compound was calculated to be 85.84%.

[0092] Single-crystal X-ray diffraction analysis was performed on precursor material A4 to determine that the crystal structure of precursor material A4 is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Zn.

[0093] Preparation Example 5

[0094] 1.0 g tetraammineplatinum acetate, 2.6 g cobalt acetate, and 4.0 g citric acid monohydrate were mixed and 150 mL of deionized water was added. The mixture was stirred under constant reflux in an oil bath at 70 °C for 8 h to allow the three compounds to react fully and form a red precipitate. The precipitate was separated by filtration and dried in a vacuum oven at 60 °C for 12 h to obtain precursor material A5. The yield of the coordination compound was calculated to be 69.57%.

[0095] Single-crystal X-ray diffraction analysis was performed on precursor material A5 to determine that the crystal structure of precursor material A5 is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Co.

[0096] Preparation Example 6

[0097] 2.0 g of tetraammineplatinum acetate, 3.8 g of nickel acetate tetrahydrate, and 1.2 g of citric acid monohydrate were added to 150 mL of deionized water. The mixture was refluxed in an oil bath at 80 °C and stirred for 10 h to allow the three compounds to react fully and form a light green precipitate. The precipitate was separated by filtration and dried in a vacuum drying oven at 60 °C for 10 h to obtain precursor material A6. The yield of the coordination compound was calculated to be 39.22%.

[0098] Single-crystal X-ray diffraction analysis was performed on precursor material A6 to determine that the crystal structure of precursor material A6 is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0099] Comparative Preparation Example 1

[0100] Following the method in CN116207279A, 1.0 g of tetraammineplatinum acetate, 1.8 g of basic nickel carbonate (with a Ni content of 40.33% by weight), and 4.2 g of citric acid monohydrate were mixed and 200 mL of deionized water was added. The mixture was magnetically stirred for 1 h to completely dissolve the nickel. The mixture was then heated and stirred in an oil bath at 80 °C. No precipitate was formed during the heating and stirring process, indicating that basic nickel carbonate, as a nickel source, cannot form precipitated complexes.

[0101] Continue stirring until the solvent evaporates completely, and then dry in a vacuum oven at 60°C for 12 hours to obtain the precursor material DA1.

[0102] Comparative Preparation Example 2

[0103] Mix 1.0g tetraammineplatinum acetate, 1.8g basic nickel carbonate (with a Ni content of 40.33% by weight), and 4.2g citric acid monohydrate, add 200mL of deionized water, and stir magnetically for 2 hours to completely dissolve the mixture. Then add 1g acetic acid and reflux in an oil bath at 80℃ for 8 hours. No precipitate was formed during the heating and stirring process.

[0104] The following examples illustrate the preparation of carbon-coated platinum-based alloy nanomaterials in this invention.

[0105] Example 1

[0106] (1) Grind the precursor material A1 into powder in a mortar, put it into a porcelain boat, transfer it to a tube furnace, and raise it to 700℃ at a nitrogen atmosphere with a nitrogen flow rate of 80 mL / min and hold it for 2 hours. After naturally cooling to room temperature, take it out.

[0107] (2) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 23h, filter, wash with deionized water until the solution pH is neutral, and put it in a vacuum drying oven at 60℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterial S1.

[0108] X-ray diffraction analysis was performed on the carbon-coated platinum-nickel alloy nanomaterial S1, such as... Figure 2 As shown, from Figure 2 It can be seen that the diffraction peaks of the carbon-coated platinum-nickel alloy nanomaterial are located between the diffraction peaks of standard platinum (PDF#04-0802) and standard nickel (PDF#04-0850), corresponding to the (111), (200) and (220) planes of the face-centered cubic structure, indicating the formation of the platinum-nickel alloy structure.

[0109] Transmission electron microscopy analysis of carbon-coated platinum-nickel alloy nanomaterial S1, such as... Figure 3 As shown, by Figure 3It can be seen that the material has a clear core-shell structure, with a carbon shell covering alloy nanoparticles, and the average particle size of the alloy nanoparticles is 4.2 nm.

[0110] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. The results are shown in Table 1.

[0111] Example 2

[0112] (1) After grinding the precursor material A2 into powder in a mortar, it was placed in a porcelain boat and transferred to a tube furnace. Under a nitrogen atmosphere, the nitrogen flow rate was 60 mL / min, and the temperature was raised to 600℃ at a rate of 4℃ / min and held for 3 hours. After naturally cooling to room temperature, it was taken out.

[0113] (2) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute nitric acid (1mol / L) at 25℃ for 10h, filter, wash with deionized water until the solution pH is neutral, and dry in a 60℃ forced-air drying oven for 12h to obtain carbon-coated platinum-nickel alloy nanomaterial S2.

[0114] The obtained carbon-coated platinum-nickel alloy nanomaterials were analyzed by X-ray diffraction and transmission electron microscopy, respectively, and compared with... Figure 2 and Figure 3 Similarly, the average particle size of the alloy nanoparticles is 4.4 nm.

[0115] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. The results are shown in Table 1.

[0116] Example 3

[0117] (1) After grinding the precursor material A3 into powder in a mortar, the temperature was raised to 500℃ at a rate of 3℃ / min under an argon atmosphere with an argon flow rate of 80mL / min. After holding for 4h, the temperature was naturally cooled to room temperature and then removed.

[0118] (2) For 1g of pyrolysis product, acid wash with 80mL of dilute hydrochloric acid (1mol / L) at 25℃ for 15h, filter, wash with deionized water until the solution pH is neutral, and dry in an 80℃ forced-air drying oven for 8h to obtain carbon-coated platinum-nickel alloy nanomaterial S3.

[0119] The obtained carbon-coated platinum-nickel alloy nanomaterials were analyzed by X-ray diffraction and transmission electron microscopy, respectively, and compared with... Figure 2 and Figure 3 Similarly, the average particle size of the alloy nanoparticles is 5.6 nm.

[0120] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. The results are shown in Table 1.

[0121] Example 4

[0122] (1) After grinding the precursor material A4 into powder in a mortar, the temperature was raised to 500℃ at a nitrogen atmosphere with a nitrogen flow rate of 60mL / min and a heating rate of 5℃ / min. After holding for 4 hours, the temperature was naturally cooled to room temperature and then removed.

[0123] (2) For 1g of pyrolysis product, acid wash with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 24h, filter, wash with deionized water until the solution pH is neutral, and dry in an 80℃ forced-air drying oven for 8h to obtain carbon-coated platinum-nickel alloy nanomaterial S4.

[0124] The obtained carbon-coated platinum-zinc alloy nanomaterials were analyzed by X-ray diffraction and transmission electron microscopy, respectively, and compared with... Figure 2 and Figure 3 Similarly, the average particle size of the alloy nanoparticles is 5.6 nm.

[0125] Example 5

[0126] (1) After grinding the precursor material A5 into powder in a mortar, it was placed in a porcelain boat and transferred to a tube furnace. Under a nitrogen atmosphere, the nitrogen flow rate was 60 mL / min, and the temperature was raised to 600℃ at a rate of 4℃ / min and held for 3 hours. After naturally cooling to room temperature, it was taken out.

[0127] (2) For 1g of pyrolysis product, acid wash with 70mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 24h, filter, wash with deionized water until the solution pH is neutral, and dry in an 80℃ forced-air drying oven for 8h to obtain carbon-coated platinum-cobalt alloy nanomaterial S5.

[0128] The obtained carbon-coated platinum-cobalt alloy nanomaterials were analyzed by X-ray diffraction and transmission electron microscopy, respectively, and compared with... Figure 2 and Figure 3 Similarly, the average particle size of the alloy nanoparticles is 5.5 nm.

[0129] Comparative Example 1

[0130] Following the method of Example 1, except that an equal mass of precursor material DA1 was used to replace A1, resulting in carbon-coated platinum-nickel nanomaterial DS1.

[0131] X-ray diffraction analysis was performed on carbon-coated platinum-nickel nanomaterial DS1. The diffraction pattern of this carbon-coated platinum-nickel alloy nanomaterial showed diffraction peaks at 2θ of 40.5° and 42.7°, 46.7° and 49.6°, and 68.0° and 73.4°, corresponding to the (111), (200) and (220) planes of the face-centered cubic structure. This indicates that the carbon-coated PtNi nanomaterial has two crystal phases: Pt-rich and Ni-rich.

[0132] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. The results are shown in Table 1.

[0133] Table 1

[0134]

[0135] Test case

[0136] The following tests used a commercially available catalyst for comparison, specifically a 40% Pt / C catalyst (brand name: HISPEC4000) purchased from JM Company.

[0137] (1) Preparation of catalyst: The carbon-coated platinum-based alloy nanomaterials prepared in the above examples and comparative examples were mixed with Ketjen black and thoroughly ground in a mortar to obtain carbon-coated platinum metal alloy catalysts CAT-1 to DCAT-1, the composition of which is shown in Table 2.

[0138] (2) Electrode preparation: Weigh a certain amount of catalyst sample and disperse it in a mixed solution of water, ethanol / isopropanol and perfluorosulfonic acid (nafion). Sonicate it in ice water for 1 hour to form a uniform ink. Use a pipette to pick up a certain amount of ink and drop it onto the glassy carbon electrode. After natural drying, it can be used for electrochemical testing.

[0139] (3) Preparation of electrolyte: 0.1M HClO4 was used as the electrolyte. The electrolyte was ventilated for half an hour before the test to obtain an oxygen-saturated or nitrogen-saturated electrolyte. The oxygen-saturated electrolyte was used for LSV test and the nitrogen-saturated electrolyte was used for CV test to determine the electrochemical active area.

[0140] (4) Electrochemical testing: A standard hydrogen electrode was used as the reference electrode, and a carbon rod as the counter electrode. For LSV testing, the potential range was 0-1.1V vs RHE, the working electrode rotation speed was 1600 rpm, and the scan rate was 10 mV / s. For CV testing, the potential range was 0-1.1V vs RHE, the working electrode rotation speed was 0, and the scan rate was 50 mV / s. The 5000-cycle electrochemical scanning conditions were under oxygen saturation, with a potential range from 0.60V to 1.0V and a scan rate of 50 mV / s. Electrochemical activity calculations were performed using the current density corresponding to 0.9V.

[0141] The electrocatalytic oxygen reduction performance of the above examples and comparative examples was measured using a rotating disk electrode, and the results are shown in Tables 3 and 4. The LSV and CV curves of the carbon-coated platinum-nickel alloy catalyst containing the carbon-coated platinum-nickel alloy nanomaterial prepared in Example 1 for the oxygen reduction reaction are shown in Tables 3 and 4, respectively. Figure 4 and Figure 5 As shown.

[0142] Table 2

[0143]

[0144] Table 3

[0145]

[0146] Table 4

[0147]

[0148] As shown in Table 3, the carbon-coated platinum alloy nanomaterial of the present invention exhibits good oxygen reduction catalytic activity, with a half-wave potential above 0.80 V and a mass-to-volume activity of 0.10 A / mg at 0.9 V. Pt above.

[0149] Through Tables 3 and 4 Figure 4 , Figure 5 It can be seen that the carbon-coated platinum metal alloy nanomaterials provided by this invention exhibit good catalytic activity and stability when used as catalytic oxygen reduction catalysts.

[0150] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A coordination compound, characterized in that, The complexing compounds include cations as shown in formula (1) and anions as shown in formula (2). M is selected from at least one of Ni, Co and Zn.

2. The coordination compound according to claim 1, wherein, In equation (2), M is Ni and / or Zn.

3. A method for preparing a coordination compound, comprising: Under stirring conditions, tetraammineplatinum acetate, M metal acetate, citric acid and solvent were mixed and subjected to a coordination reaction to obtain a precipitate product. M is selected from at least one of Ni, Co and Zn.

4. The preparation method according to claim 3, wherein, The molar ratio of tetraammineplatinum acetate (calculated as platinum) to metal acetate (calculated as element M) is 1:(1-20), preferably 1:(4-12); Preferably, the total molar amount of tetraammineplatinum acetate and M metal acetate, calculated as metal elements, is in a molar ratio of citric acid to 1:(0.1-5), more preferably 1:(0.3-2).

5. The preparation method according to claim 3, wherein, The conditions for the coordination reaction include: a temperature of 40-100℃, preferably 60-80℃, and a time of 3-16h, preferably 6-12h.

6. A method for preparing carbon-coated platinum-based alloy nanomaterials, characterized in that, The method includes: (1) Under an inert atmosphere, the coordination compound of claim 1 or 2 or the coordination compound prepared by any one of claims 3-5 is subjected to high-temperature pyrolysis. (2) The product obtained in step (1) is contacted with acid, and then solid-liquid separation, washing and drying are performed.

7. The method for preparing carbon-coated platinum-based alloy nanomaterials according to claim 6, wherein, In step (1), the inert gas is nitrogen and / or argon; Preferably, the flow rate of the inert gas is 20-120 mL / min; Preferably, the pyrolysis temperature is 400-1000℃; Preferably, the heating rate of the high-temperature pyrolysis is 2-10℃ / min; Preferably, the isothermal time for the high-temperature pyrolysis is 1-6 hours.

8. The method for preparing carbon-coated platinum-based alloy nanomaterials according to claim 6 or 7, wherein, In step (2), the acid is provided by an aqueous solution of an acid, preferably, the acid is at least one of sulfuric acid, nitric acid and hydrochloric acid; Preferably, for 1g of the pyrolysis product obtained in step (1), the amount of acid used is 40-100mL; Preferably, the acid is provided by a sulfuric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C; or, the acid is provided by a nitric acid solution with a concentration of 0.5-15 mol / L and a contact temperature of 25-60°C; or, the acid is provided by a hydrochloric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C. Preferably, in step (2), the contact time is 3-50 hours.

9. The carbon-coated platinum-based alloy nanomaterials prepared by the method for preparing carbon-coated platinum-based alloy nanomaterials according to any one of claims 6-8; Preferably, the carbon-coated platinum-based alloy nanomaterial has a core-shell structure with platinum-metal M alloy particles as the core and a carbon layer as the shell, wherein M is selected from at least one of Ni, Co and Zn; Preferably, the average particle size of the platinum-metal M alloy particles is 3-6 nm; Preferably, in the carbon-coated platinum-based alloy nanomaterial, the carbon content is 10-20% by weight, the platinum content is 50-65% by weight, the content of metallic M is 10-30% by weight, the hydrogen content is 1-2% by weight, and the oxygen content is 1-15% by weight.

10. The application of the carbon-coated platinum-based alloy nanomaterial as described in claim 9 in the oxygen reduction reaction at the cathode of a fuel cell.

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