CN116207280A

CN116207280A - Carbon-coated platinum-nickel alloy nano material and preparation method and application thereof

Info

Publication number: CN116207280A
Application number: CN202111456261.0A
Authority: CN
Inventors: 张云阁; 荣峻峰; 张家康; 吴耿煌; 谢婧新; 夏庆山
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2021-12-01
Filing date: 2021-12-01
Publication date: 2023-06-02

Abstract

The invention relates to the field of electrocatalysis, and discloses a carbon-coated platinum-nickel alloy nanomaterial, and a preparation method and application thereof. The method comprises the following steps: (1) precursor preparation: removing the solvent in the homogeneous solution containing the metal precursor, the carbon source and the solvent to obtain a precursor material; (2) roasting: carrying out high-temperature pyrolysis on the precursor material obtained in the step (1) in an inert atmosphere to obtain a pyrolysis product; (3) annealing: cooling the pyrolysis product obtained in the step (2) to 20-60 ℃, and then carrying out annealing treatment in an inert atmosphere or a reducing atmosphere at 400-1100 ℃ or in an oxidizing atmosphere at 200-400 ℃; (4) acid washing: and (3) carrying out contact reaction on the annealing product obtained in the step (3) and an acid solution, and then sequentially carrying out solid-liquid separation, washing and drying. The carbon-coated platinum-nickel alloy nanomaterial has good electrocatalytic performance.

Description

Carbon-coated platinum-nickel alloy nano material and preparation method and application thereof

Technical Field

The invention relates to the field of electrocatalysis, in particular to a carbon-coated platinum-nickel alloy nanomaterial and a preparation method thereof, a catalyst and a preparation method thereof, and application of the carbon-coated platinum-nickel alloy nanomaterial and the catalyst in fuel cells.

Background

In recent years, energy crisis and environmental pollution are becoming one of the main obstacles restricting the development of human society, so that the development of renewable clean energy technology is imperative. The fuel cell is a device for directly converting chemical energy of fuel into electric energy through electrochemical reaction, and is considered as an ideal clean energy technology because of the advantages of high energy conversion efficiency, quick start, small pollution and the like. The fuel cell mainly comprises the following reactions: anodic oxidation reactions (e.g. hydrogen oxidation of HOR, H ₂ →2H ⁺ +2e ^- Methanol oxidation MOR, etc.) and cathodic oxygen reduction reactions (ORR, O) ₂ +4H ⁺ +4e ^- →2H ₂ O). Since cathodic oxygen reduction involves multiple electrons, the kinetic reaction rate is much slower than that of anodic oxidation. Thus, the rate of the cathodic oxygen reduction reaction is a critical factor affecting the performance of the fuel cell. At present, the high-efficiency cathode catalyst mainly depends on noble metal platinum, but the price of platinum is high, so that the catalyst cost accounts for about 40% of the total cost of the fuel cell; in addition, during the long circulation process, the electrochemical active area of platinum is obviously reduced with time due to the agglomeration and dissolution of platinum, and the service life of the fuel cell is influenced.

At present, one of the research directions of the cathode catalyst is to adopt carbon to coat a platinum-nickel alloy nano material, on one hand, the platinum-nickel alloy catalyst can improve the intrinsic activity and the utilization rate of platinum, and reduce the dosage of noble metal platinum; on the other hand, the carbon cage coating can inhibit agglomeration and dissolution of metals during long cycles, thereby improving stability. Zou Shouzhong et al (ACS appl. Energy Mater.2019,2, 2769-2778) report that 2-methylimidazole is used as an organic ligand and a carbon source, a 2-methylimidazole-Pt-Ni composite material with a MOF-like structure is formed by a solvothermal method first, and then a thermal annealing treatment is carried out, so that a carbon-coated platinum-nickel nanomaterial is prepared. CN 112467155a reports that the liquid phase reduction method is adopted to synthesize oleylamine coated platinum nanoparticles, then the platinum nanoparticles are mixed with ketjen black, and the carbon coated platinum catalyst is prepared through high-temperature pre-crosslinking, carbonization and activation, and the preparation process is still complicated. Therefore, it is necessary to develop a method for preparing the carbon-coated platinum-nickel alloy catalyst, which has the advantages of simple process, low cost and convenient industrial production.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide a carbon-coated platinum-nickel alloy nanomaterial, a preparation method thereof, a catalyst and a preparation method thereof, and application of the carbon-coated platinum-nickel alloy nanomaterial and the catalyst in a fuel cell.

In order to achieve the above object, the present invention provides a method for preparing a carbon-coated platinum-nickel alloy nanomaterial, the method comprising the steps of:

(1) Precursor preparation: removing the solvent in a homogeneous solution containing a metal precursor, a carbon source and a solvent to obtain a precursor material, wherein the metal precursor comprises a platinum source and a nickel source, and the carbon source is an acidic organic reducing agent;

(2) Roasting: carrying out high-temperature pyrolysis on the precursor material obtained in the step (1) in an inert atmosphere to obtain a pyrolysis product, wherein the temperature of the high-temperature pyrolysis is 400-1000 ℃;

(3) Annealing: cooling the pyrolysis product obtained in the step (2) to 20-60 ℃, and then carrying out annealing treatment in an inert atmosphere or a reducing atmosphere at 400-1100 ℃ or in an oxidizing atmosphere at 200-400 ℃;

(4) Acid washing: and (3) carrying out contact reaction on the annealing product obtained in the step (3) and an acid solution, and then sequentially carrying out solid-liquid separation, washing and drying.

Preferably, in step (1), the carbon source is one or more of citric acid, ascorbic acid, ethylenediamine tetraacetic acid, 2, 5-pyridinedicarboxylic acid, benzoic acid, and terephthalic acid.

Preferably, in the step (1), the platinum source is one or more of chloroplatinic acid, tetraamineplatinum acetate, platinum acetylacetonate, chloroplatinate and platinum chloride.

Preferably, in the step (1), the nickel source is one or more of nickel acetate, nickel dichloride hexahydrate, nickel acetylacetonate, basic nickel carbonate, nickel carbonate and nickel sulfate.

Preferably, in step (1), the molar ratio of the metal precursor to the carbon source in terms of metal element is 1:0.5-5;

preferably, the molar ratio of the platinum source in terms of platinum to the nickel source in terms of nickel is 1:0.5-20, preferably 1:1-10.

Preferably, in step (1), the solvent is one or more of water, an alcoholic solvent and N, N-Dimethylformamide (DMF).

Preferably, in step (1), the alcohol solvent is ethanol.

Preferably, in the step (1), the reducing atmosphere includes hydrogen or carbon monoxide, preferably a mixed atmosphere of hydrogen or carbon monoxide and an inert gas, more preferably a mixed atmosphere of hydrogen and nitrogen; preferably, the hydrogen or carbon monoxide comprises 5-30% by volume of the total gas.

Preferably, in step (1), the oxidizing atmosphere comprises oxygen, preferably air or a mixed atmosphere of oxygen and an inert gas; preferably, the oxygen comprises 10-100% by volume of the total gas.

Preferably, in the step (2), the heating rate of the pyrolysis is 2-10 ℃/min.

Preferably, in the step (2), the constant temperature time of the pyrolysis is 1-10h.

Preferably, in the step (3), the heating rate of the annealing treatment is 2-10 ℃/min.

Preferably, in the step (3), the constant temperature time of the annealing treatment is 1-10h.

Preferably, in the step (4), the acid solution is one or more of sulfuric acid solution, nitric acid solution and hydrochloric acid solution.

Preferably, in the step (4), the acid solution is used in an amount of H based on 1mol of nickel element in the annealed product obtained in the step (3) ⁺ The content is more than 2 mol.

Preferably, in the step (4), when the acid solution is sulfuric acid solution, the acid concentration is 0.5-2mol/L, and the temperature of the contact reaction is 25-90 ℃; when the acid solution is nitric acid solution, the acid concentration is 0.5-15mol/L, and the contact reaction temperature is 25-60 ℃; when the acid solution is hydrochloric acid solution, the acid concentration is 0.5-2mol/L, and the contact reaction temperature is 25-90 ℃.

Preferably, in step (4), the contact reaction time is 3 to 50 hours, preferably 3 to 24 hours.

The second aspect of the invention provides the carbon-coated platinum-nickel alloy nanomaterial obtained by the preparation method of the invention.

Preferably, in the nanomaterial, the carbon content is 5-70 wt%, the platinum content is 10-70 wt%, the nickel content is 1-70 wt%, the hydrogen content is 0.1-3 wt%, the oxygen content is 0.5-20 wt%, and the nitrogen content is 0-15 wt%.

Preferably, the carbon-coated platinum-nickel alloy nanomaterial has a core-shell structure with platinum-nickel alloy particles as a core and a carbon layer as a shell.

Preferably, the platinum nickel alloy particles have a particle size of 3-200nm, more preferably 3-100nm.

Preferably, at least one platinum nickel alloy peak is present in the XRD spectrum of the nanomaterial in the range of 39.7 ° to 44.7 °.

Preferably, the specific surface area of the nanomaterial is 100-500m ² Preferably 100-300m ² /g。

Preferably, the carbon shell of the nanomaterial is at least partially graphitized, preferably I in Raman spectroscopy _D /I _G In the range of 0.5 to 1.5, more preferably 0.5 to 1.

The third aspect of the present invention provides a catalyst comprising the carbon-coated platinum-nickel alloy nanomaterial of the present invention described above and conductive carbon black.

Preferably, the weight ratio of the carbon-coated platinum-nickel alloy nanomaterial to the conductive carbon black is 1:0.1-5.

In a fourth aspect, the present invention provides a process for the preparation of the catalyst of the present invention, which comprises: the carbon-coated platinum-nickel alloy nanomaterial of the present invention is mixed with conductive carbon black in the presence of a solvent, and then the solvent in the resulting mixture is removed and dried.

Preferably, the mixing comprises one or more of ultrasound, mechanical agitation and milling, preferably for a period of time of from 0.5 to 2 hours, preferably for a period of time of from 8 to 24 hours, preferably the milling conditions comprise: ball milling is carried out in inert atmosphere at the rotating speed of 100-500rpm for 2-24h.

In a fifth aspect, the present invention provides another process for preparing the catalyst of the present invention, which comprises: the carbon-coated platinum-nickel alloy nanomaterial of the present invention is solid-phase mixed with conductive carbon black.

Preferably, the conditions of the solid phase mixing include: ball milling is carried out in inert atmosphere at the rotating speed of 100-500rpm for 2-24h.

The sixth aspect of the present invention provides the use of the carbon-coated platinum-nickel alloy nanomaterial, the catalyst of the present invention described above, or the catalyst obtained by the preparation method of the present invention described above in a fuel cell.

According to the technical scheme, the preparation method provided by the invention takes the acidic organic reducing agent as a carbon source, the catalyst precursor is pyrolyzed in an inert atmosphere, the nickel salt is used as a template and a catalyst of a carbon cage in the process of being reduced to generate a coated carbon cage in situ, and then annealing treatment is carried out to improve the alloying degree of metal and the graphitization degree of the carbon cage and enhance the electrocatalytic activity of the material, so that the carbon-coated platinum-nickel alloy nano material with high activity and good stability is prepared.

The carbon-coated cage can inhibit agglomeration and dissolution of metal in the electrochemical long-cycle process, and the obtained carbon-coated platinum-nickel alloy nanomaterial has good stability of electrochemical active area (ECSA). The carbon-coated platinum-nickel alloy nano material has good electrocatalytic activity, and can be directly used as an oxygen reduction catalyst of a fuel cell or used as the oxygen reduction catalyst of the fuel cell after being uniformly mixed with conductive carbon black in proportion.

The invention provides a novel material containing carbon-coated platinum-nickel alloy nanoparticle core-shell structure through the technical scheme.

The preparation method of the invention has the following advantages: firstly, the preparation process is simple, the cost is low, and the raw material selection range is wide; and secondly, when catalyzing the oxygen reduction reaction, the electrochemical active area (ECSA) of the catalyst has good stability.

Drawings

FIG. 1 is a TEM image of the carbon-coated platinum-nickel alloy nanomaterial obtained in example 1;

FIG. 2 is an XRD pattern of the carbon-coated platinum-nickel alloy nanomaterial obtained in example 1;

FIG. 3 is a Raman spectrum of the carbon-coated platinum-nickel alloy nanomaterial obtained in example 3;

FIG. 4 is an XPS full spectrum of the carbon-coated platinum-nickel alloy nanomaterial obtained in example 1;

FIG. 5 is a LSV graph of the carbon coated platinum nickel alloy catalyst obtained in example 1A before and after 5000 cycles of cyclic scanning as ORR catalyst;

FIG. 6 is an ECSA graph of the carbon coated platinum nickel alloy catalyst obtained in example 1A before and after 5000 cycles of cyclic scanning as ORR catalyst;

FIG. 7 is a LSV plot of the catalyst of comparative example 1 before and after 5000 cycles of cyclic scanning as an ORR catalyst;

FIG. 8 is an ECSA graph of the catalyst of comparative example 1 before and after 5000 cycles of cyclic scanning as ORR catalyst;

FIG. 9 is a LSV comparison of the carbon coated platinum nickel alloy catalysts obtained in example 1A and comparative example 2A as ORR catalysts;

fig. 10 is a graph comparing ECSA of carbon coated platinum nickel alloy catalysts obtained in example 1A and comparative example 2A as ORR catalysts.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The invention provides a preparation method of a carbon-coated platinum-nickel alloy nanomaterial, which comprises the following steps:

According to the preparation method of the carbon-coated platinum-nickel alloy nanomaterial, an acidic organic reducing agent is used as a carbon source, a catalyst precursor is pyrolyzed in an inert atmosphere and is further annealed, nickel salt is used as a template and a catalyst of a carbon cage in the process of being reduced, and the coated carbon cage is generated in situ, so that the carbon-coated platinum-nickel alloy nanomaterial is prepared.

According to the present invention, in the step (1), the carbon source may be used as the reducing agent at the same time, and may be any acidic organic compound having a reducing property, preferably a reducing organic acid, a reducing polyhydroxy compound, or the like, and specifically, one or more of citric acid, ascorbic acid, ethylenediamine tetraacetic acid, 2, 5-pyridinedicarboxylic acid, benzoic acid, and terephthalic acid may be used.

According to the present invention, in the step (1), the platinum source may be any platinum-containing compound soluble in the solvent, and may be, for example, an inorganic acid salt, or an organic acid salt containing platinum, and may be, for example, one or more of chloroplatinic acid, tetraamineplatinum acetate, platinum acetylacetonate, chloroplatinic acid salt, and platinum chloride, and preferably chloroplatinic acid, tetraamineplatinum acetate, and the like.

According to the present invention, in the step (1), the nickel source may be any nickel-containing compound soluble in the solvent, and may be, for example, an organic acid salt or an inorganic acid salt containing nickel, and may be, for example, one or more of nickel acetate, nickel dichloride hexahydrate, nickel acetylacetonate, basic nickel carbonate, and nickel sulfate, and is preferably.

According to the present invention, preferably, in the step (1), the molar ratio of the metal precursor to the carbon source in terms of metal element may be 1:0.5 to 5, preferably 1:0.5-3.

According to the present invention, the platinum source and the nickel source may be appropriately adjusted according to the desired platinum nickel alloy composition, and preferably, the molar ratio of the platinum source in terms of platinum to the nickel source in terms of nickel is 1:0.5-20, preferably 1:1-10, for example, can be 1:1. 1:1.2, 1: 2. 1: 3. 1:4.5, 1: 5. 1: 6. 1:7.5, 1: 8. 1:9 or 1:10, etc.

In the production method of the present invention, it is preferable that other metal sources are not used in addition to the above-mentioned platinum source and nickel source. The other metal source may be other metal salts, such as alkali metal salts or alkaline earth metal salts.

According to the present invention, in the step (1), the precursor material is obtained by dissolving a metal precursor and a carbon source in a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution. The kind of the solvent is not particularly limited as long as it can form a homogeneous solution, and it is preferable that the solvent is one or more of water, an alcoholic solvent such as ethanol, and N, N-Dimethylformamide (DMF), and it is more preferable that the solvent is water or a mixture of ethanol and water (the volume ratio of ethanol and water may be, for example, 0.1 to 10:1, and preferably 1 to 5:1). The amount of the solvent used in the present invention is not particularly limited, and is also sufficient to form a homogeneous solution.

In the present invention, in the step (1), the formation method of the homogeneous solution is not particularly limited, and for example, the homogeneous solution may be formed by stirring. The stirring rate and time are not particularly limited in the present invention, and the homogeneous solution can be formed. In addition, in order to form the homogeneous solution, the dissolution may be further accelerated by heating.

As a method for removing the solvent in the homogeneous solution, the solvent in the homogeneous solution may be removed by direct evaporation, and the temperature and process of evaporation may be the same as those known in the art, for example, the solvent in the homogeneous solution may be removed by heat evaporation or spin evaporation. According to a specific embodiment of the present invention, the solvent in the homogeneous solution may be removed by drying in a vacuum oven at 60-120 ℃ for 12-24 hours.

According to the present invention, the catalyst precursor material is preferably suitably ground to obtain a catalyst precursor powder prior to performing the high temperature pyrolysis of step (2), in order to facilitate the pyrolysis. The manner and degree of grinding may be appropriately selected.

According to the present invention, preferably, in the step (2), pyrolysis is performed under an inert atmosphere to obtain a pyrolysis product. The inert atmosphere may be at least one of nitrogen, argon, neon and helium. Pyrolysis may be carried out in any apparatus that provides the pyrolysis conditions described above, for example in a tube furnace.

As the conditions of the pyrolysis, preferably, the temperature of the pyrolysis may be 400 to 1000 ℃, preferably 500 to 900 ℃, and the constant temperature time may be 1 to 10 hours, preferably 2 to 5 hours. The heating rate of the pyrolysis is preferably 2 to 10 ℃/min, more preferably 2 to 5 ℃/min.

According to the invention, in step (3), the degree of alloying of the metal and/or the degree of graphitization of the carbon cage is increased by annealing the pyrolysis product. After the pyrolysis, the pyrolysis product is preferably naturally cooled to 20-60 ℃ (preferably 20-30 ℃, more preferably room temperature) in an inert atmosphere, and then subjected to an annealing treatment.

The alloying degree of the metal in the carbon-coated platinum-nickel alloy nano material can be further improved by high-temperature annealing treatment in an inert atmosphere or a reducing atmosphere, and meanwhile, the graphitization degree of the carbon shell layer can be increased. Preferably, when the annealing treatment is performed under an inert atmosphere or a reducing atmosphere, the annealing temperature is 400 to 1100 ℃, preferably 600 to 1000 ℃.

The inert atmosphere may be at least one of nitrogen, argon, neon and helium.

The reducing atmosphere preferably includes hydrogen or carbon monoxide, more preferably a mixed atmosphere of hydrogen or carbon monoxide and an inert gas, and particularly may be a mixed atmosphere of hydrogen and nitrogen. Preferably, the hydrogen or carbon monoxide comprises 5-30% by volume of the total gas.

By annealing treatment in an oxidizing atmosphere, amorphous carbon in the carbon-coated platinum-nickel alloy nanomaterial can be partially oxidized and decomposed, so that the proportion of graphitized carbon is increased, and nickel which is not tightly coated can be oxidized and is easier to be removed by acid washing. Preferably, when the annealing treatment is performed under an oxidizing atmosphere, the annealing temperature is 200 to 400 ℃, preferably 300 to 400 ℃.

The oxidizing atmosphere preferably includes oxygen, more preferably air or a mixed atmosphere of oxygen and an inert gas, and the inert gas may be at least one of nitrogen, argon, neon and helium, and particularly may be a mixed atmosphere of oxygen and nitrogen. Preferably, the oxygen comprises 10-100% by volume of the total gas.

According to the invention, the constant temperature time of the annealing treatment may be preferably 1 to 10 hours, preferably 2 to 6 hours. The heating rate of the annealing treatment is preferably 2 to 10℃per minute, more preferably 5 to 10℃per minute.

In the present invention, the annealing treatment may be performed in any apparatus that provides the above annealing treatment conditions, for example, may be performed in a tube furnace. The annealed product is preferably subjected to subsequent pickling after being suitably ground as needed.

According to the present invention, in the step (4), the acid solution may be an acid conventionally used in the art, as long as the nickel element in the pyrolysis product can be properly removed. Preferably, the acid is an inorganic acid solution and/or an organic acid solution, preferably one or more of sulfuric acid solution, nitric acid solution and hydrochloric acid solution, further preferably sulfuric acid solution; preferably, the concentration of the acid solution is 0.5-2moL/L.

According to the present invention, preferably, the acid solution is used in an amount of H based on 1mol of nickel element in the annealed product obtained in the step (3) ⁺ It is preferably not less than 2mol, more preferably 4 to 20mol. In the present invention, the excess acid solution means 1mol relative to nickel element in the annealed product obtained in the step (3), and the acid solution is used in an amount of H ⁺ The content is more than 2 mol.

According to a preferred embodiment of the invention, when the acid solution is sulfuric acid solution, the acid concentration is 0.5-2mol/L, and the contact reaction temperature is 25-90 ℃; when the acid solution is nitric acid solution, the acid concentration is 0.5-15mol/L, and the contact reaction temperature is 25-60 ℃; when the acid solution is hydrochloric acid solution, the acid concentration is 0.5-2mol/L, and the contact reaction temperature is 25-90 ℃.

According to the invention, preferably, the pyrolysis product is contacted with the acid solution for a reaction time of 3 to 50 hours, preferably 3 to 24 hours.

According to the present invention, the washing is used to remove acid remaining on the annealed product caused by the acid washing process, and thus, various water washing methods capable of washing the pyrolysis product to neutrality are applicable to the present invention. Preferably, the washing is carried out until the pH of the washing solution is neutral.

According to the invention, the drying is used to remove water from the acid-washed product. The drying may be carried out under normal pressure or reduced pressure, and preferably vacuum drying is carried out. The drying conditions may include: the temperature is 60-80 ℃ and the time is 2-10h.

The second aspect of the present invention provides a carbon-coated platinum-nickel alloy nanomaterial obtained by the preparation method of the first aspect of the present invention.

In the nanomaterial, preferably, the carbon content is 5 to 70 wt%, more preferably 5 to 40 wt%, the platinum content is 10 to 70 wt%, more preferably 30 to 70 wt%, and the nickel content is 1 to 70 wt%, more preferably 5 to 40 wt%. In addition, small amounts of hydrogen (e.g., 0.1-3 wt%), oxygen (e.g., 0.5-20 wt%) and nitrogen (e.g., 0-15 wt%) are present in the nanomaterial.

The carbon-coated platinum-nickel alloy nano material obtained by the preparation method disclosed by the invention has a core-shell structure with platinum-nickel alloy particles as cores and a carbon layer as a shell. The carbon layer is a carbon cage, preferably an at least partially graphitized carbon cage.

According to the invention, the platinum nickel alloy particles may preferably have a particle size of 3-200nm, preferably 3-100nm.

According to the present invention, preferably, at least one platinum nickel alloy peak, more preferably 1 to 2 platinum nickel alloy peaks, are present in the range of 39.7 ° to 44.7 ° 2θ in the XRD spectrum of the nanomaterial.

According to the present invention, preferably, the specific surface area of the nanomaterial is 100 to 500m ² Preferably 100-300m ² /g。

According to the invention, preferably, the carbon shell of the nanomaterial is at least partially graphitized, preferably I in Raman spectroscopy _D /I _G In the range of 0.5 to 1.5, more preferably 0.5-1。

The third aspect of the present invention provides a catalyst comprising the carbon-coated platinum-nickel alloy nanomaterial of the second aspect of the present invention described above and conductive carbon black.

In a fourth aspect, the present invention provides a process for the preparation of the catalyst of the present invention, which comprises: after mixing the carbon-coated platinum-nickel alloy nanomaterial of the second aspect of the present invention with conductive carbon black in the presence of a solvent, the solvent in the resulting mixture is removed and dried.

In a fifth aspect, the present invention provides another process for preparing the catalyst of the present invention, which comprises: the carbon-coated platinum-nickel alloy nanomaterial of the second aspect of the present invention is solid phase mixed with conductive carbon black.

According to the catalyst and the preparation method of the catalyst, the catalyst for the cathode oxygen reduction reaction of the fuel cell can be prepared by mixing the carbon-coated platinum-nickel alloy nanomaterial of the invention with conductive carbon black. The method of mixing is not particularly limited, and may be liquid phase mixing or solid phase mixing as long as uniform mixing is possible.

According to the present invention, the conductive carbon black is not particularly limited as long as it can be used for the cathode oxygen reduction reaction of a fuel cell, and for example, ketjen black (for example, ECT-600 JD), cabot black (for example, vulcan XC 72), and the like can be used.

According to a preferred embodiment of the present invention, preferably, the weight ratio of the carbon-coated platinum nickel alloy nanomaterial to the conductive carbon black may be 1:0.1 to 5, preferably 1:0.2-2. In addition, the content of the conductive carbon black in the catalyst is preferably 10 to 80% by weight, and more preferably 15 to 65% by weight.

As a method of liquid phase mixing, as described in the fourth aspect above, the carbon-coated platinum-nickel alloy nanomaterial may be mixed with the conductive carbon black in the presence of a solvent, and then the solvent in the resultant mixture may be removed and dried. Preferably, the mixing comprises one or more of ultrasound, mechanical agitation and grinding, preferably ultrasonic followed by agitation mixing. The conditions of the ultrasonic, mechanical agitation and grinding may be appropriately selected, preferably ultrasonic for 0.5 to 2 hours, preferably mechanical agitation for 8 to 24 hours, and preferably grinding conditions include: ball milling is carried out in inert atmosphere at the rotating speed of 100-500rpm for 2-24h.

As a method of solid phase mixing, as described in the fifth aspect above, the carbon-coated platinum-nickel alloy nanomaterial may be directly solid phase mixed with the conductive carbon black, thereby obtaining a catalyst. The method and conditions of solid phase mixing are not particularly limited, and preferably, the conditions of solid phase mixing include: ball milling is carried out in an inert atmosphere at a rotational speed of 100-500rpm, for example, 200-500rpm, and a ball milling time of 2-24 hours, for example, 2-12 hours.

A sixth aspect of the invention provides the use of the carbon-coated platinum-nickel alloy nanomaterial of the second aspect of the invention, the catalyst of the third aspect of the invention, or the catalyst obtained by the preparation method of the fourth or fifth aspect of the invention in a fuel cell.

As described above, the carbon-coated platinum-nickel alloy nanomaterial of the invention can be directly used as a catalyst for the cathode oxygen reduction reaction of a fuel cell, and can also be matched with conductive carbon black to prepare the catalyst for the cathode oxygen reduction reaction of the fuel cell. When the nano material or the catalyst is used for catalyzing the cathodic oxygen reduction reaction, the half-wave potential is more than 0.85V, the mass specific activity at 0.9V is more than 0.10A/mgPt, and the area specific activity is more than 0.30mA/cm ² The electrochemical active area (ECSA) after 5000 circles of cyclic scanning has good stability, and the change rate is not more than 20%.

The present invention will be described in detail by examples. Unless otherwise specified, all reagents used in the present invention are analytically pure and commercially available.

The surface morphology of the material was characterized by high resolution transmission electron microscopy (HRTEM, JEM-2100, japanese electronics Co., ltd.) and the acceleration voltage was 200kV.

The crystal structure of the material was characterized by X-ray diffraction (XRD, empyrean sharp shadow, malvern, netherlands).

The content and valence state of each element on the surface of the material were determined by X-ray photoelectron spectroscopy (XPS, thermo Scientific, ESCALab model 250).

The specific surface area of the material was determined by the Brunauer-Emmett-Taller method (BET, quantachrome AS-6B type analyzer).

The resistivity of the material was measured by a powder resistivity tester (semiconductor powder resistivity tester of the sozhou lattice, ST-2722 type).

The Raman test method comprises the following steps: the functional group of the sample is subjected to Raman characterization by using a 532 light source by adopting a visible laser Raman measurement method (HORIBA JY Lam 800), and a characteristic spectrogram is given.

The content test of carbon, hydrogen, oxygen and nitrogen elements is carried out on a Elementar Vario EL Cube element analyzer, and the specific operation method is as follows: the sample is weighed about 5mg in a tin cup, put into an automatic sample feeding disc, enter a combustion tube through a ball valve for combustion, and have a combustion temperature of 1000 ℃ (for eliminating atmospheric interference during sample feeding, helium purging is adopted), and C, H, N in the sample is respectively converted into carbon dioxide, water and nitrogen. And separating the mixed gas by a chromatographic column, and finally detecting by a thermal conductivity cell. When oxygen element is measured, the sample is cracked in a high-temperature cracking tube filled with carbon powder, oxygen in the sample is converted into carbon monoxide, carrier gas carries the cracked product into a series scrubber to remove acid gas and water vapor, and finally the obtained product enters an infrared detector for detection.

The content of platinum and nickel is measured by inductively coupled plasma emission spectrometry (ICP-OES), and the specific method is as follows: (1) nitrolysis: 10mg of catalyst sample is measured and placed in a flask, 16mL of fresh aqua regia is added, a magnetic stirrer is added, the flask is placed in an oil bath, the temperature of 120 ℃ is condensed and refluxed for 12 hours, after cooling to room temperature, a glass syringe is used for sucking the solution, a disposable filter head with the aperture of 0.22 mu m is used for filtering, the filtrate is added into a 500mL volumetric flask, and ultrapure water is added for volume fixing. (2) content test: 10mL of the solution after nitrolysis and volume fixation is taken, and an instrument Agilent 5110 is adopted for metal content test.

Electrochemical testing method: (1) preparation of an electrode: weighing a certain weight of catalyst sample, dispersing into a mixed solution of water, ethanol/isopropanol and perfluorosulfonic acid (nafion), performing ultrasonic treatment in ice water for 1 hour to form uniform ink, sucking a certain amount of ink by a pipette, dripping the ink on a glassy carbon electrode, naturally drying, and then using the solution for electrochemical testing, and controlling the Pt loading capacityIs prepared at 10-30 mug/cm ² . (2) preparation of electrolyte: using 0.1M HClO ₄ As electrolyte, one half hour of aeration was performed prior to the test to obtain an oxygen-saturated or argon-saturated electrolyte, which was used for LSV testing and an argon-saturated electrolyte was used for CV testing to determine the electrochemically active area. (3) electrochemical testing: the saturated calomel electrode is used as a reference electrode, the carbon rod is used as a counter electrode, the potential range is selected to be 0.03-1.12Vvs RHE during LSV test, the rotating speed of the working electrode is 1600rpm, and the sweeping speed is 10mV/s; during CV test, the rotation speed of the working electrode is 0, and the sweeping speed is 50mV/s; the 5000-circle electrochemical cyclic scanning condition is that the rotating speed of the working electrode is 0, the potential range is from 0.60V to 1.0V, and the scanning speed is 50mV/s under the oxygen saturation state. The electrochemical activity was calculated using the corresponding current density at 0.9V.

Example 1

2.6g of chloroplatinic acid hexahydrate, 2.2g basic nickel carbonate (Ni content: 40.33% by weight) and 3.8g anhydrous citric acid were mixed, 200mL of deionized water was added, magnetically stirred for 1 hour to dissolve completely, heated and stirred in an oil bath at 80 ℃ until the solvent was evaporated, and then dried in a vacuum oven at 120 ℃ for 12 hours. Grinding the catalyst precursor powder, heating to 500 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, preserving heat for 4 hours, and naturally cooling to room temperature. Then let in H ₂ And N ₂ Is a mixed gas (H) ₂ And the temperature is increased to 600 ℃ at a heating rate of 10 ℃/min, the temperature is kept for 2 hours, the temperature is naturally cooled to room temperature, and the gas is taken out after being purged for 6 hours by nitrogen. After grinding, for 1g of annealed product, 80mL of 0.5mol/L dilute sulfuric acid is used for pickling for 12h at 90 ℃, filtering is carried out, deionized water is used for washing until the pH value of the solution is neutral, and the solution is put into a vacuum oven at 60 ℃ for 8h and dried, thus obtaining the carbon-coated platinum-nickel alloy nanomaterial.

The specific surface area of the material measured by BET method is 171.9m ² And/g, wherein the resistivity of the material measured by the powder resistivity tester is 0.22 omega.m.

Example 1A

The carbon-coated platinum nickel alloy nanomaterial of example 1 was combined with ketjen black (ECY-600 JD) in a ratio of 5:2, putting the mixture into a ball milling tank, and ball milling for 4 hours at a speed of 200rpm under the protection of nitrogen atmosphere (after each cycle is ball milling for 5min, stopping for 2 min), thereby obtaining the carbon-coated platinum-nickel alloy catalyst.

Example 2

2.6g of chloroplatinic acid hexahydrate, 2.2g basic nickel carbonate (the weight percentage of Ni contained is 40.33%) and 3.8g anhydrous citric acid are mixed, 200mL of deionized water is added, the mixture is magnetically stirred for 1h to be completely dissolved, the mixture is heated and stirred in an oil bath at 80 ℃ until the solvent is evaporated, and then the mixture is dried in a vacuum oven at 120 ℃ for 12h. Grinding the catalyst precursor powder, heating to 500 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, preserving heat for 4 hours, and naturally cooling to room temperature. Then air is introduced, the temperature is raised to 350 ℃ at a heating rate of 5 ℃/min, and the mixture is naturally cooled to room temperature after heat preservation for 2 hours. After grinding, for 1g of annealed product, 80mL of 0.5mol/L dilute sulfuric acid is used for pickling for 12h at 90 ℃, filtering, deionized water is used for washing until the pH value of the solution is neutral, and the solution is placed into a vacuum oven at 60 ℃ for 8h, and the carbon-coated platinum-nickel alloy nano material is obtained after drying.

Example 2A

A carbon-coated platinum-nickel alloy catalyst was prepared in the same manner as in example 1A using the carbon-coated platinum-nickel alloy nanomaterial of example 2.

Example 3

1.6g of tetraamineplatinum acetate, 2.1g of nickel acetate tetrahydrate and 11.1g of ascorbic acid are mixed, 200mL of deionized water is added, the mixture is magnetically stirred for 1h to be completely dissolved, and after spin evaporation, the mixture is dried in a vacuum oven at 60 ℃ for 12h. After grinding the catalyst precursor powder, the catalyst precursor powder is mixed with a catalyst precursor in a solvent mixture of N ₂ Raising the temperature to 600 ℃ at a heating rate of 5 ℃/min in the atmosphere, preserving the heat for 5 hours, and naturally cooling to room temperature. Then continue to feed N ₂ Raising the temperature to 1000 ℃ at the heating rate of 10 ℃/min, preserving the heat for 2 hours, and naturally cooling to the room temperature. After grinding, for 1g of annealed product, 80mL of 1mol/L dilute nitric acid is used for pickling for 6 hours at 25 ℃, filtering is carried out, deionized water is used for washing until the pH value of the solution is neutral, the solution is put into a vacuum oven at 60 ℃ for 8 hours, and the carbon-coated platinum-nickel alloy nano material is obtained after drying.

Example 3A

Measuring 20mg of the carbon-coated platinum-nickel alloy nanomaterial of example 3, adding 10mL of a mixed solvent of ethanol and water (V/V=3/1), and performing ultrasonic treatment for 1h; simultaneously, 8mg Keqin black (ECT-600 JD) is measured, 4mL of mixed solvent of ethanol/water (V/V=3/1) is added, and ultrasonic treatment is carried out for 1h; mixing the two solutions, performing ultrasonic treatment for 1h, mechanically stirring for 24h at the rotating speed of 800rpm, performing suction filtration, and drying in a vacuum oven at the temperature of 60 ℃ for 6h to obtain the carbon-coated platinum-nickel alloy catalyst.

Example 4

2.6g of chloroplatinic acid hexahydrate, 2.2g basic nickel carbonate (the weight percentage of Ni contained is 40.33%) and 3.8g anhydrous citric acid are mixed, 200mL of deionized water is added, the mixture is magnetically stirred for 1h to be completely dissolved, the mixture is heated and stirred in an oil bath at 80 ℃ until the solvent is evaporated, and then the mixture is dried in a vacuum oven at 120 ℃ for 12h. Grinding the catalyst precursor powder, heating to 500 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, preserving heat for 4 hours, and naturally cooling to room temperature. Then continuously introducing nitrogen, heating to 800 ℃ at a heating rate of 10 ℃/min, preserving heat for 2 hours, and naturally cooling to room temperature. After grinding, for 1g of annealed product, 80mL of 0.5mol/L dilute sulfuric acid is used for pickling for 12h at 90 ℃, filtering, deionized water is used for washing until the pH value of the solution is neutral, and the solution is placed into a vacuum oven at 60 ℃ for 8h, and the carbon-coated platinum-nickel alloy nano material is obtained after drying.

Example 4A

A carbon-coated platinum-nickel alloy catalyst was prepared in the same manner as in example 1A using the carbon-coated platinum-nickel alloy nanomaterial of example 4.

Comparative example 1

JM company 40% Pt/C catalyst (brand: HISPEC 4000).

Comparative example 2

Carbon-coated platinum-nickel alloy nanomaterial was prepared as in example 1, except that no annealing treatment was performed.

Comparative example 2A

A carbon-coated platinum-nickel alloy catalyst was prepared in the same manner as in example 1A using the carbon-coated platinum-nickel alloy nanomaterial of comparative example 2.

Test example 1

The TEM and XRD patterns of the carbon-coated platinum nickel alloy nanomaterial obtained in example 1 are shown in fig. 1 and 2.

As can be seen from FIG. 1, the carbon-coated platinum-nickel alloy nanomaterial has a spheroid morphology, the shell carbon layer thickness is 0.5-5nm, the core particles have a porous/solid structure, and the diameter is 5-50nm. In fig. 1, the thickness of the carbon layer at the top arrow is about 1nm, and the thickness of the carbon layer at the right arrow is about 5nm, and the carbon-coated alloy structure is shown in the box.

As can be seen from fig. 2, the material contains two sets of alloy peaks, one set of alloy peaks biased towards the Pt unimodal and one set of alloy peaks biased towards the Ni unimodal.

The TEM and XRD patterns of the carbon-coated platinum nickel alloy nanomaterials obtained in examples 2-4 were also determined, which are similar to fig. 1 and 2, respectively.

The raman spectrum of the carbon-coated platinum-nickel alloy nanomaterial obtained in example 3 is shown in fig. 3. As can be seen from FIG. 3, the Raman shift is 1345cm ^-1 And 1587cm ^-1 A significant Raman scattering peak appears nearby, wherein 1345cm ^-1 The nearby scattering peak is attributed to the D peak of the carbon material, while 1587cm ^-1 The nearby scattering peak is assigned to the G peak. The D peak is the lattice defect of graphite or A of amorphous carbon _1g The G peak is E of the in-plane bond of the graphite structural surface generated by the vibration mode _2g Stretching vibration is generated by calculating the intensity ratio (I _D /I _G ) The degree of graphitization of the carbon material can be characterized, the smaller the ratio, the higher the degree of graphitization, example 3, I _D /I _G 0.91, indicating that the coated carbon layer is a partially graphitized carbon layer. Raman spectra of examples 1, 2, 4, which are similar to fig. 3, were determined in the same way.

Test example 2

The metal content of the material was measured by ICP-OES method, and the contents of carbon, hydrogen, oxygen and nitrogen were measured by elemental analyzer, and the results are shown in Table 1. In addition, fig. 4 shows an XPS spectrogram of the carbon-coated platinum nickel alloy nanomaterial obtained in example 1.

As can be seen from fig. 3, the carbon-coated platinum-nickel alloy nanomaterial prepared in example 1 contains Pt, ni, C, O element on the surface.

TABLE 1

Test example 3

The electrochemical properties of the nanomaterial and catalyst prepared in the above examples and comparative examples were measured, and the results are shown in table 2. The LSV curve and ECSA curve of the carbon-coated platinum nickel alloy catalyst obtained in example 1A for catalyzing the oxygen reduction reaction are shown in fig. 5 and 6, respectively, and the LSV curve and ECSA curve of the platinum carbon catalyst of comparative example 1 for catalyzing the oxygen reduction reaction are shown in fig. 7 and 8, respectively. The LSV and ECSA curves for the carbon coated platinum nickel alloy catalysts of example 1A and comparative example 2A for catalyzing the oxygen reduction reaction are shown in fig. 9 and 10, respectively.

TABLE 2

From the above results, it can be seen that the nanomaterial and catalyst of the present invention have good ORR catalytic activity. Specifically, the results of comparative example 1A and comparative example 1 are as follows, example 1A is a catalyst prepared by uniformly mixing a platinum nickel alloy coated with a carbon cage with conductive carbon black, the catalyst has good stability after being circularly scanned for 5000 circles in an acid electrolyte, the half-wave potential is reduced from 0.90V to 0.88V initially, and the mass specific activity is reduced from 0.23A/mg initially _Pt Down to 0.13A/mg _Pt The ECSA slightly rises after cyclic scanning, from the initial 34.70m ² /g _Pt Rising to 39.89m ² /g _Pt The retention rate is 115%, and the ECSA change rate is within 20%; the half-wave potential and the mass specific activity of comparative example 1 were kept unchanged before and after 5000 cycles, respectively 0.89V and 0.14A/mg _Pt But ECSA is composed of initial 68.45m ² /g _Pt Down to 53.57m ² /g _Pt The ECSA retention was only 78.3%.

As can be seen from the results of comparative example 1A and comparative example 2A, the half-wave potential of example 1A was 0.90V, and the mass specific activity was 0.23A/mg _Pt While the half-wave potential of comparative example 2A was 0.85V, the mass specific activity was 0.15A/mg _Pt Thus, the annealing treatment according to the invention is employedHas a better ORR catalytic activity than comparative example 2A, which was not annealed under the same preparation conditions.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. The preparation method of the carbon-coated platinum-nickel alloy nano material is characterized by comprising the following steps of:

2. The production method according to claim 1, wherein in the step (1), the carbon source is one or more of citric acid, ascorbic acid, ethylenediamine tetraacetic acid, 2, 5-pyridinedicarboxylic acid, benzoic acid, and terephthalic acid.

3. The production method according to claim 1 or 2, wherein in the step (1), the platinum source is one or more of chloroplatinic acid, tetraamineplatinum acetate, platinum acetylacetonate, chloroplatinate, and platinum chloride;

preferably, the nickel source is one or more of nickel acetate, nickel dichloride hexahydrate, nickel acetylacetonate, basic nickel carbonate, nickel carbonate and nickel sulfate.

4. The production method according to any one of claims 1 to 3, wherein in the step (1), a molar ratio of the metal precursor to the carbon source in terms of metal element is 1:0.5-5;

5. The production process according to any one of claims 1 to 4, wherein in the step (1), the solvent is one or more of water, an alcoholic solvent and N, N-dimethylformamide;

preferably, the alcoholic solvent is ethanol.

6. The production method according to any one of claims 1 to 5, wherein the reducing atmosphere comprises hydrogen or carbon monoxide, preferably a mixed atmosphere of hydrogen or carbon monoxide and an inert gas, more preferably a mixed atmosphere of hydrogen and nitrogen; preferably, the hydrogen or carbon monoxide comprises 5-30% by volume of the total gas;

preferably, the oxidizing atmosphere comprises oxygen, preferably air or a mixed atmosphere of oxygen and an inert gas; preferably, the oxygen comprises 10-100% by volume of the total gas.

7. The production method according to any one of claims 1 to 6, wherein in the step (2), the temperature rise rate of the high-temperature pyrolysis is 2 to 10 ℃/min;

preferably, the pyrolysis is carried out for a constant temperature of 1 to 10 hours.

8. The production method according to any one of claims 1 to 7, wherein in the step (3), the temperature rise rate of the annealing treatment is 2 to 10 ℃/min;

Preferably, the constant temperature time of the annealing treatment is 1-10h.

9. The production method according to any one of claims 1 to 8, wherein in the step (4), the acid solution is one or more of sulfuric acid solution, nitric acid solution, and hydrochloric acid solution;

preferably, the acid solution is used in an amount of H based on 1mol of nickel element in the annealed product obtained in the step (3) ⁺ Counting more than 2 mol;

preferably, when the acid solution is sulfuric acid solution, the acid concentration is 0.5-2mol/L, and the temperature of the contact reaction is 25-90 ℃; when the acid solution is nitric acid solution, the acid concentration is 0.5-15mol/L, and the contact reaction temperature is 25-60 ℃; when the acid solution is hydrochloric acid solution, the acid concentration is 0.5-2mol/L, and the contact reaction temperature is 25-90 ℃.

10. The process according to any one of claims 1 to 9, wherein in step (4), the contact reaction is carried out for a period of 3 to 50 hours, preferably 3 to 24 hours.

11. A carbon-coated platinum-nickel alloy nanomaterial obtained by the production method of any one of claims 1 to 10.

12. The carbon-coated platinum-nickel alloy nanomaterial of claim 11, wherein the nanomaterial comprises 5-70 wt% carbon, 10-70 wt% platinum, 1-70 wt% nickel, 0.1-3 wt% hydrogen, 0.5-20 wt% oxygen, and 0-15 wt% nitrogen.

13. The carbon-coated platinum-nickel alloy nanomaterial according to claim 11 or 12, wherein the carbon-coated platinum-nickel alloy nanomaterial has a core-shell structure in which platinum-nickel alloy particles are used as a core and a carbon layer is used as a shell;

preferably, the particle size of the platinum nickel alloy particles is 3-200nm, more preferably 3-100nm;

preferably, at least one platinum nickel alloy peak exists in the range of 39.7-44.7 degrees 2 theta in the XRD spectrum of the nanomaterial;

preferably, the specific surface area of the nanomaterial is 100-500m ² Preferably 100-300m ² /g；

14. A catalyst comprising the carbon-coated platinum-nickel alloy nanomaterial of any of claims 11-13 and a conductive carbon black;

15. A method for preparing a catalyst, comprising: mixing the carbon-coated platinum-nickel alloy nanomaterial of any one of claims 11-13 with conductive carbon black in the presence of a solvent, and removing and drying the solvent in the resulting mixture;

Preferably, the weight ratio of the carbon-coated platinum-nickel alloy nanomaterial to the conductive carbon black is 1:0.1-5;

16. A method for preparing a catalyst, comprising: solid phase mixing the carbon-coated platinum-nickel alloy nanomaterial of any of claims 11-13 with conductive carbon black;

17. Use of the carbon-coated platinum-nickel alloy nanomaterial according to any of claims 11 to 13, the catalyst according to claim 14, or the catalyst obtained by the preparation method according to claim 15 or 16 in a fuel cell.