Metal-modified platinum-palladium core-shell structure catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemistry, in particular to a metal-modified platinum-palladium core-shell structure catalyst and a preparation method and application thereof.The catalyst comprises carrier carbon and active components loaded on the surface of the carrier carbon, and the active components comprise platinum, palladium and modified metal; in the catalyst, based on the total weight of the catalyst, the content of the carrier carbon is 60.0 wt.%-80.0 wt.%; the content of platinum is 9.0 wt.% to 18.0 wt.%; the content of palladium is 9.0 wt.% to 18.0 wt.%; the content of the modified metal is 0.5 wt.%-4.0 wt.%; the structure of the active component is a metal-modified platinum-palladium core-shell structure, palladium serves as an inner core, platinum serves as a shell layer, and modified metal is located on the surface and near the surface of the core-shell structure; the modification metal is selected from at least one of IB group metal, VB group metal, VIB group metal and VIIB group metal. According to the catalyst provided by the invention, the platinum-palladium core-shell structure is subjected to surface and near-surface modification by adopting metal, so that the catalytic activity of precious metal platinum is improved.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, and in particular to a metal-modified platinum-palladium core-shell structure catalyst and a preparation method and application thereof. Background Art

[0002] With the extensive use of fossil energy, environmental issues have become a hot topic of concern to people. Environmental pollution has seriously affected people's daily lives.

[0003] It is particularly important to find new clean energy and energy storage conversion devices. Fuel cells, as energy conversion devices, can directly convert the chemical energy of fuel and oxidant into electrical energy through electrochemical reactions, which has attracted people's attention. Moreover, it has the advantages of high energy conversion efficiency, high current density and low pollution.

[0004] At present, precious metal platinum (Pt) catalyst is the main catalyst for fuel cells. However, precious metal platinum (Pt) has low reserves on the earth and is in short supply, which makes it expensive. At the same time, its activity and stability are insufficient under high pressure and high acid conditions. These reasons have restricted the commercial development of fuel cells.

[0005] Therefore, it is very important to research and develop fuel cell catalysts with low platinum (Pt) loading, high activity and high stability.

[0006] Based on this background, the present application studies and develops a metal-modified platinum-palladium core-shell structure catalyst and a preparation method thereof. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a metal-modified platinum-palladium core-shell structure catalyst and a preparation method and application thereof. The platinum and palladium in the catalyst present a core-shell structure arrangement at the atomic level, and the surface and near-surface of the platinum-palladium core-shell structure are modified by metal, which greatly improves the catalytic activity and utilization rate of the precious metal platinum. The preparation method of the catalyst uses deionized water and ethylene glycol as reaction solvents, which is safe and environmentally friendly. At the same time, low-priced metal salts are used as reaction raw materials, which reduces the synthesis cost of the catalyst.

[0008] In order to achieve the above object, the first aspect of the present invention provides a metal-modified platinum-palladium core-shell structure catalyst, the catalyst comprising a carrier carbon and an active component supported on the surface of the carrier carbon, the active component comprising platinum, palladium and a modified metal;

[0009] In the catalyst, the content of the carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%, based on the total weight of the catalyst;

[0010] The content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%;

[0011] The content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%;

[0012] The content of the modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%;

[0013] The structure of the active component is a metal-modified platinum-palladium core-shell structure, wherein palladium is the core, platinum is the shell, and the modified metal is located on the surface and near the surface of the core-shell structure;

[0014] The modifying metal is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals.

[0015] A second aspect of the present invention provides a method for preparing the above catalyst, the preparation method comprising the following steps:

[0016] (1) mixing and dispersing carbon powder, deionized water, a palladium salt precursor and a reducing agent under stirring conditions to obtain a first mixed solution;

[0017] (2) adjusting the first mixed solution to alkalinity and stirring to obtain a carbon-supported palladium catalyst;

[0018] (3) mixing and dispersing the carbon-supported palladium catalyst, polyol, modified metal salt and platinum salt precursor under stirring conditions to obtain a second mixed solution;

[0019] (4) adjusting the second mixed solution to a weak alkaline state, stirring, and microwave heating to obtain a metal-modified platinum-palladium core-shell structure catalyst;

[0020] The modified metal in the modified metal salt is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals;

[0021] The amount of each component used is such that in the catalyst, based on the total weight of the catalyst, the content of carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%; the content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; the content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; and the content of modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%.

[0022] The third aspect of the present invention provides a metal-modified platinum-palladium core-shell structure catalyst prepared by the above-mentioned preparation method.

[0023] The fourth aspect of the present invention provides an application of the above-mentioned metal-modified platinum-palladium core-shell structure catalyst in a fuel cell.

[0024] The beneficial effects of the present invention are:

[0025] (1) The metal-modified platinum-palladium core-shell structure catalyst proposed in the present invention has a core-shell structure arrangement of platinum and palladium at the atomic level, and the surface and near-surface modification of the platinum-palladium core-shell structure is performed by metal, which greatly improves the catalytic activity and utilization rate of the precious metal platinum.

[0026] (2) The metal-modified platinum-palladium core-shell structure catalyst proposed in the present invention has the advantages of low platinum loading, high catalytic activity and high chemical stability, which will promote the further development of fuel cells.

[0027] (3) The preparation method of the metal-modified platinum-palladium core-shell structure catalyst proposed in the present invention uses deionized water and ethylene glycol as reaction solvents, which is safe and environmentally friendly. At the same time, low-cost metal salts are used as reaction raw materials, which reduces the synthesis cost of the catalyst.

[0028] (4) The method for preparing the metal-modified platinum-palladium core-shell structure catalyst proposed in the present invention adopts a microwave-assisted polyol method to reduce the catalyst, and the metal precursor is reduced to the surface and near-surface of the platinum-palladium core-shell structure to obtain a metal-modified platinum-palladium core-shell structure catalyst.

[0029] (5) The present invention proposes a method for preparing a metal-modified platinum-palladium core-shell structure catalyst. During the reaction process, the temperature and time of the microwave reaction are adjusted to synthesize a metal-modified platinum-palladium core-shell structure catalyst with a smaller particle size. The preparation process is simple and stable, and the entire process is environmentally friendly, which promotes the further development of core-shell structure catalysts.

[0030] (6) The preparation method of the metal-modified platinum-palladium core-shell structure catalyst proposed in the present invention has a simple and efficient entire preparation process, the materials are simple and easy to obtain, the preparation method is simple, and it is easy to scale up the preparation.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

[0033] Figure 1They are respectively the XRD patterns of the carbon-supported palladium catalyst (Pd / C) obtained in step (3) of Example 1 of the present invention and the chromium-modified platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5).

[0034] Figure 2-1 This is a high-resolution electron microscope image of the palladium catalyst (Pd / C) obtained in step (3) of Example 1 of the present invention.

[0035] Figure 2-2 yes Figure 2-1 A partial enlarged view of .

[0036] Figure 3-1 This is a high-resolution electron microscope image of the chromium-modified platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5) of Example 1 of the present invention.

[0037] Figure 3-2 yes Figure 3-1 A partial enlarged view of . DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0039] The present invention provides a metal-modified platinum-palladium core-shell structure catalyst, which comprises a carrier carbon and an active component loaded on the surface of the carrier carbon, wherein the active component of the catalyst comprises platinum, palladium and a modified metal;

[0040] In the catalyst, the content of the carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%, based on the total weight of the catalyst;

[0041] The content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%;

[0042] The content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%;

[0043] The content of the modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%;

[0044] The structure of the active component of the catalyst is a metal-modified platinum-palladium core-shell structure, wherein palladium is the core, platinum is the shell, and the modified metal is located on the surface and near the surface of the core-shell structure;

[0045] The catalyst modifying metal is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals.

[0046] According to the present invention, the particle size of the catalyst active component is 5 to 10 nm.

[0047] According to the present invention, the catalyst carrier carbon is at least one of carbon black, carbon nanotubes, and graphene, preferably conductive carbon black, and more preferably XC-72 conductive carbon black.

[0048] Preferably, the catalyst modifying metal is at least one of gold, chromium, manganese, molybdenum and vanadium.

[0049] In the present invention, the metal-modified platinum-palladium core-shell structure catalyst has a core-shell structure arrangement of platinum and palladium at the atomic level, and the surface and near-surface modification of the platinum-palladium core-shell structure is performed by metal, which greatly improves the catalytic activity and utilization rate of the precious metal platinum.

[0050] In the present invention, the metal-modified platinum-palladium core-shell structure catalyst has the advantages of low platinum loading, high catalytic activity and high chemical stability, which will promote the further development of fuel cells.

[0051] The present invention also provides a method for preparing the above catalyst, which comprises the following steps:

[0052] (1) mixing and dispersing carbon powder, deionized water, a palladium salt precursor and a reducing agent under stirring conditions to obtain a first mixed solution;

[0053] (2) adjusting the first catalyst mixed solution to alkalinity and stirring to obtain a carbon-supported palladium catalyst;

[0054] (3) mixing and dispersing the catalyst carbon-supported palladium catalyst, polyol, modified metal salt and platinum salt precursor under stirring conditions to obtain a second mixed solution;

[0055] (4) adjusting the second catalyst mixed solution to a weak alkalinity, stirring, and microwave heating to obtain a metal-modified platinum-palladium core-shell structure catalyst;

[0056] The modified metal in the catalyst modified metal salt is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals;

[0057] The amount of each component used is such that in the catalyst, based on the total weight of the catalyst, the content of carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%; the content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; the content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; and the content of modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%.

[0058] In the present invention, the preparation method of the metal-modified platinum-palladium core-shell structure catalyst uses deionized water and ethylene glycol as reaction solvents, which is safe and environmentally friendly. At the same time, low-priced metal salts are used as reaction raw materials, which reduces the synthesis cost of the catalyst.

[0059] In the present invention, the preparation method of the metal-modified platinum-palladium core-shell structure catalyst adopts microwave-assisted polyol method to reduce the catalyst, and the metal precursor is reduced to the surface and near the surface of the platinum-palladium core-shell structure to obtain the metal-modified platinum-palladium core-shell structure catalyst.

[0060] According to the present invention, in step (1), the catalyst carbon powder is at least one of carbon black, carbon nanotubes, and graphene, preferably conductive carbon black, and more preferably XC-72 conductive carbon black; the catalyst palladium salt precursor is at least one of potassium chloropalladate, sodium chloropalladate, and palladium nitrate; and the catalyst reducing agent is at least one of sodium borohydride, hydrazine hydrate, and ascorbic acid;

[0061] For every 1 mg of carbon powder, the amount of deionized water added is 0.2-1 mL.

[0062] Preferably, in step (1), the catalyst is dispersed by ultrasonic dispersion, the catalyst dispersion temperature is 20-30° C., and the time is 1 to 1.5 h;

[0063] The catalyst was stirred for 5-10 min.

[0064] Preferably, in step (2), an alkaline solution is added to adjust the first catalyst mixed solution to alkalinity, the catalyst alkalinity is pH 8.5-10, and the catalyst alkaline solution is preferably a sodium hydroxide solution;

[0065] The catalyst is stirred at a temperature of 10-30°C for 8-16 hours.

[0066] According to the present invention, in step (3), the catalyst is dispersed by ultrasonic dispersion, the catalyst dispersion temperature is 20-30° C., and the time is 1 to 1.5 h;

[0067] For every 1 mg of carbon powder, the amount of polyol added is 0.2-1 mL;

[0068] The catalyst polyol is at least one of ethylene glycol, propylene glycol, butanediol and isopentatriol;

[0069] The catalyst modification metal is at least one of gold, chromium, manganese, molybdenum and vanadium;

[0070] The catalyst-modified metal salt is at least one of a nitrate, a sulfate, a halide, an amine complex, a hydrohalic acid, and a hydrohalic acid salt of the catalyst-modified metal;

[0071] The catalyst platinum salt precursor is at least one of chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, platinum acetylacetonate, and platinum acetylacetonate.

[0072] According to the present invention, in step (4),

[0073] Adding an alkaline solution to adjust the catalyst second mixed solution to a weak alkalinity, wherein the catalyst weak alkalinity is pH 7.5-8.5, and the catalyst alkaline solution is preferably a sodium hydroxide solution;

[0074] The catalyst is heated by microwave with a power of 200-400W, a temperature of 70-90°C and a time of 20-40min.

[0075] In the present invention, a method for preparing a metal-modified platinum-palladium core-shell structure catalyst is provided. During the reaction process, the temperature and time of the microwave reaction are adjusted to synthesize a metal-modified platinum-palladium core-shell structure catalyst with a smaller particle size. The preparation process is simple and stable, the whole process is environmentally friendly, and the further development of the core-shell structure catalyst is promoted.

[0076] In the present invention, the preparation method of the metal-modified platinum-palladium core-shell structure catalyst has the advantages of simple and efficient whole preparation process, simple and easy-to-obtain materials, simple preparation method and easy scale-up preparation.

[0077] The present invention also provides a metal-modified platinum-palladium core-shell structure catalyst prepared by the above preparation method.

[0078] The present invention also provides the use of the metal-modified platinum-palladium core-shell structure catalyst in a fuel cell.

[0079] The present invention is further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0080] In the following examples, Examples 1-9 are examples of metal-modified platinum-palladium core-shell structure catalysts, and Comparative Examples 1-3 are comparative examples of metal-modified platinum-palladium core-shell structure catalysts.

[0081] Example 1

[0082] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0083] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0084] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0085] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0086] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. by a microwave reactor with a power of 300 W under stirring, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S1, in which the mass percentages of carbon, platinum, palladium and chromium are 75.3:15:8.4:1.3.

[0087] Example 2

[0088] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0089] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0090] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0091] (4) Under stirring, 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.147 mL of gold chloride trihydrate aqueous solution (AuCl3·3H2O, 20 g / L) were added to the mixed solution obtained in step (3) to obtain a mixed solution;

[0092] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a gold-modified platinum-palladium core-shell structure catalyst S2, wherein the mass percentages of carbon, platinum, palladium and gold in S2 are 75.3:15:8.4:1.3.

[0093] Example 3

[0094] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0095] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0096] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0097] (4) under stirring, 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.209 mL of molybdenum chloride aqueous solution (MoCl5, 20 g / L) were added to the mixed solution obtained in step (3) to obtain a mixed solution;

[0098] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. by a microwave reactor with a power of 300 W under stirring, and the reaction is continued for 30 minutes to obtain a molybdenum-modified platinum-palladium core-shell structure catalyst S3, in which the mass percentages of carbon, platinum, palladium and molybdenum are 75.3:15:8.4:1.3.

[0099] Example 4

[0100] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0101] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0102] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0103] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.461 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0104] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S4, in which the mass percentages of carbon, platinum, palladium and chromium are 75.1:15:8.3:1.6.

[0105] Example 5

[0106] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0107] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0108] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0109] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.308 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0110] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S5, in which the mass percentages of carbon, platinum, palladium and chromium are 75.5:15.1:8.4:1.0.

[0111] Example 6

[0112] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 69.01 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 80:20;

[0113] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0114] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0115] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0116] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S6, in which the mass percentages of carbon, platinum, palladium and chromium are 68.2:17:13.6:1.2.

[0117] Example 7

[0118] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 48.71 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions is 85:15;

[0119] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0120] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0121] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0122] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S7, in which the mass percentages of carbon, platinum, palladium and chromium are 71.8:14.4:12.7:1.1.

[0123] Example 8

[0124] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0125] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0126] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0127] (4) under stirring, adding 53.13 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium chloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0128] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S8, in which the mass percentages of carbon, platinum, palladium and chromium are 74.1:16.5:8.2:1.2.

[0129] Example 9

[0130] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0131] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0132] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0133] (4) under stirring, adding 42.5 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0134] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst S9, in which the mass percentages of carbon, platinum, palladium and chromium are 76.6:13.6:8.5:1.3.

[0135] Comparative Example 1

[0136] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and ultrasonically disperse for 1 h to mix them evenly to obtain a mixed solution, in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0137] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0138] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0139] (4) Under stirring, 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) was added to the mixed solution obtained in step (3) to obtain a mixed solution;

[0140] (5) To the mixed solution obtained in step (4), sodium hydroxide solution was added dropwise to adjust the pH value of the solution to 8, and then the system was heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction was continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst D1, in which the mass percentages of carbon, platinum and palladium in D1 were 76.3:15.3:8.4.

[0141] Comparative Example 2

[0142] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0143] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0144] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0145] (4) adding 0.376 mL of an aqueous solution of chromium chloride hexahydrate (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) under stirring to obtain a mixed solution;

[0146] (5) To the mixed solution obtained in step (4), sodium hydroxide solution is added dropwise to adjust the pH value of the solution to 8, and then the system is heated to 80° C. in a microwave reactor at a power of 300 W under stirring conditions, and the reaction is continued for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst D2, in which the mass percentages of carbon, palladium and chromium are 88.7:9.9:1.4.

[0147] Comparative Example 3

[0148] (1) Weigh 90 mg of XC-72 carbon black into a beaker, add 40 ml of deionized water to evenly disperse the XC-72 carbon black in the water, then stir magnetically for 8 min, add 30.67 mg of potassium chloropalladate (K2PdCl4) and 10.78 mg of sodium borohydride (NaBH4), and mix them evenly by ultrasonication for 1 h to obtain a mixed solution in which the mass percentage of carbon and palladium ions in the mixed solution is 90:10;

[0149] (2) under continuous stirring, adding NaOH solution dropwise to the mixed solution of step (1) to adjust the pH of the mixed system to 9, and stirring at room temperature for 12 h to obtain a carbon-supported palladium catalyst;

[0150] (3) placing the carbon-supported palladium catalyst obtained in step (2) in a three-necked flask, adding 40 mL of ethylene glycol, ultrasonically dispersing for 1 h, and magnetically stirring for 5 min to obtain a mixed solution;

[0151] (4) under stirring, adding 47.78 mg of chloroplatinic acid (H2PtCl6·6H2O) and 0.376 mL of chromium trichloride hexahydrate aqueous solution (CrCl3·6H2O, 20 g / L) to the mixed solution obtained in step (3) to obtain a mixed solution;

[0152] (5) Adding sodium hydroxide solution dropwise to the mixed solution obtained in step (4) to adjust the pH value of the solution to 8, then heating the system to 80° C. under stirring conditions, and continuing the reaction for 30 minutes to obtain a chromium-modified platinum-palladium core-shell structure catalyst D3, wherein the mass percentages of carbon, platinum, palladium and chromium in D3 are 75.3:15:8.4:1.3.

[0154] Test Example 1

[0155] 10 mg of catalysts S1-S9 in the examples and catalysts D1-D3 in the comparative examples were used to obtain different catalyst evaluation results, as shown in Table 1.

[0156] Table 1 Evaluation results of catalysts

[0157]

[0158] By comparing the data in Table 1, it can be seen that the catalytic activity of the catalyst can be improved by using microwave heating, coating the core with a Pt shell, and modifying the surface and near-surface of the core-shell structure with metals, and the best catalytic activity is obtained when the mass percentage of carbon, platinum, palladium and chromium added is 75.3:15:8.4:1.3. The best effect is achieved by modifying the surface and near-surface with chromium elements, which has the highest catalytic activity.

[0159] Test Example 2

[0160] The carbon-supported palladium catalyst (Pd / C) obtained in step (2) of Example 1 of the present invention and the chromium-modified platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5) were subjected to X-ray diffraction, respectively, and their diffraction patterns were analyzed.

[0161] like Figure 1 , which are XRD patterns of the carbon-supported palladium catalyst (Pd / C) obtained in step (2) of Example 1 of the present invention and the chromium-modified platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5), Figure 1 The XRD patterns of Cr-Pd@Pt / C and Pd / C are shown. The broad peak at around 2θ=25° corresponds to the peak of the carbon support. Pd and Pt have the same crystal structure and very close lattice constants, so the characteristic diffraction peaks at about 2θ=39.8°, 46.9°, 67.8° and 81.3° are attributed to the Pd face-centered cubic structure planes (111), (200), (220) and (311), indicating that the synthesized catalyst conforms to the face-centered cubic (fcc) structure. When the Pt shell is deposited on the core Pd / C, the four peaks of Pd shift to higher 2θ angles. The shift is due to the increase in the lattice parameter, which indicates that the atomic radius of Pt atoms is larger than that of Pd, and when Pt atoms enter the Pd lattice, the lattice shrinks. This change can also confirm the emergence of the core-shell structure from another aspect.

[0162] By characterizing the structure of the chromium-modified platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) prepared in Example 1, it was proved that it is based on carbon as a carrier and the active components are loaded on the carbon surface. The active component is a chromium-modified structural core-shell platinum-palladium catalyst (Cr-Pd@Pt / C) with a particle size of 5 to 10 nm. Electron microscopy observation showed that the distribution is uniform.

[0163] Test Example 3

[0164] The carbon-supported palladium catalyst (Pd / C) obtained in step (2) of Example 1 of the present invention and the chromium-modified carbon-supported platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5) were analyzed by electron microscopy.

[0165] like Figure 2-1 , which is a high-resolution electron micrograph of the carbon-supported palladium catalyst (Pd / C) obtained in step (2) of Example 1 of the present invention. Analysis shows that the active ingredient has good dispersion on the carbon carrier, and the particles are relatively uniform, with a particle size of about 5 nm; there is only a small amount of agglomeration. Figure 2-2 yes Figure 2-1 A partial enlarged view of .

[0166] like Figure 3-1 As shown, it is a high-resolution electron micrograph of the chromium-modified carbon-supported platinum-palladium core-shell structure catalyst (Cr-Pd@Pt / C) obtained in step (5) of Example 1 of the present invention. Analysis shows that the active components are evenly distributed and the particle size is uniform, without obvious agglomeration. The particle size is about 6 nm. It can be seen that the particle size has increased significantly after loading Pt, which also indirectly proves the successful loading of Pt atoms. Figure 3-2 yes Figure 3-1 A partial enlarged view of .

[0167] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0168] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A metal-modified platinum-palladium core-shell catalyst, characterized in that: The catalyst comprises a carrier carbon and an active component loaded on the surface of the carrier carbon, wherein the active component comprises platinum, palladium and a modified metal; In the catalyst, the content of the carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%, based on the total weight of the catalyst; The content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; The content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; The content of the modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%; The structure of the active component is a metal-modified platinum-palladium core-shell structure, wherein palladium is the core, platinum is the shell, and the modified metal is located on the surface and near the surface of the core-shell structure; The modifying metal is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals.

2. The catalyst according to claim 1, characterized in that The particle size of the active component is 5 to 10 nm.

3. The catalyst according to claim 1, characterized in that The carrier carbon is at least one of carbon black, carbon nanotubes, and graphene, preferably conductive carbon black, and more preferably XC-72 conductive carbon black.

4. The catalyst according to claim 1, characterized in that The modified metal is at least one of gold, chromium, manganese, molybdenum and vanadium.

5. A method for preparing a metal-modified platinum-palladium core-shell catalyst, characterized in that: The preparation method comprises the following steps: (1) mixing and dispersing carbon powder, deionized water, a palladium salt precursor and a reducing agent under stirring conditions to obtain a first mixed solution; (2) adjusting the first mixed solution to alkalinity and stirring to obtain a carbon-supported palladium catalyst; (3) mixing and dispersing the carbon-supported palladium catalyst, polyol, modified metal salt and platinum salt precursor under stirring conditions to obtain a second mixed solution; (4) adjusting the second mixed solution to a weak alkaline state, stirring, and microwave heating to obtain a metal-modified platinum-palladium core-shell structure catalyst; The modified metal in the modified metal salt is selected from at least one of Group IB, Group VB, Group VIB and Group VIIB metals; The amount of each component used is such that in the catalyst, based on the total weight of the catalyst, the content of carrier carbon is 60.0wt.%-80.0wt.%, preferably 65.0wt.%-75.0wt.%; the content of platinum is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; the content of palladium is 9.0wt.%-18.0wt.%, preferably 10.0wt.%-17.0wt.%; and the content of modified metal is 0.5wt.%-4.0wt.%, preferably 1.0wt.%-3.0wt.%.

6. The preparation method according to claim 5, characterized in that: In step (1), the carbon powder is at least one of carbon black, carbon nanotubes, and graphene, preferably conductive carbon black, and more preferably XC-72 conductive carbon black; the palladium salt precursor is at least one of potassium chloropalladate, sodium chloropalladate, and palladium nitrate; and the reducing agent is at least one of sodium borohydride, hydrazine hydrate, and ascorbic acid; For every 1 mg of carbon powder, the amount of deionized water added is 0.2-1 mL.

7. The preparation method according to claim 5, characterized in that: In step (1), the dispersion is carried out by ultrasonic dispersion, the dispersion temperature is 20-30° C., and the dispersion time is 1 to 1.5 h; The stirring time is 5-10 min.

8. The preparation method according to claim 5, characterized in that: In step (2), an alkaline solution is added to adjust the first mixed solution to alkalinity, wherein the alkalinity is pH 8.5-10, and the alkaline solution is preferably a sodium hydroxide solution; The stirring temperature is 10-30°C and the stirring time is 8-16h.

9. The preparation method according to claim 5, characterized in that: In step (3), the dispersion is carried out by ultrasonic dispersion, the dispersion temperature is 20-30° C., and the dispersion time is 1 to 1.5 h; For every 1 mg of carbon powder, the amount of polyol added is 0.2-1 mL; The polyol is at least one of ethylene glycol, propylene glycol, butanediol and pentaerythritol; The modified metal is at least one of gold, chromium, manganese, molybdenum and vanadium; The modified metal salt is at least one of the nitrate, sulfate, halide, amine complex, hydrohalic acid and hydrohalic acid salt of the modified metal; The platinum salt precursor is at least one of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, ammonium chloroplatinate, platinum acetylacetonate, and platinum acetylacetonate.

10. The preparation method according to claim 5, characterized in that: In step (4), Adding an alkaline solution to adjust the second mixed solution to a weak alkalinity, wherein the weak alkalinity is pH 7.5-8.5, and the alkaline solution is preferably a sodium hydroxide solution; The microwave heating has a power of 200-400W, a temperature of 70-90°C and a time of 20-40min.

11. A metal-modified platinum-palladium core-shell structure catalyst prepared by the preparation method described in any one of claims 5 to 10.

12. Use of the metal-modified platinum-palladium core-shell structure catalyst according to any one of claims 1 to 4 and 11 in a fuel cell.

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