CN111408369A - A kind of nano-gold platinum bimetal@carbon material oxygen reaction catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a nano gold-platinum bimetallic @ carbon material oxygen reaction catalyst and a preparation method thereof. Preparing a nano gold-platinum bimetal @ carbon material oxygen reaction catalyst by using a carbon material as a carrier and using an organic ligand-terminated nano gold-platinum bimetal as an active center through a one-step reduction method; the carbon material is one or more of carbon nano tube, graphene and carbon black, and the end-capping reagent is one or more of tetrakis hydroxymethyl phosphonium chloride, mercaptosuccinic acid and triphenylphosphine. The average grain diameter of the nano-Au-Pt bimetal is 2.8-3.2 nm, the loading capacity of the nano-Au-Pt bimetal is 10-15 wt.%, and the molar ratio of Au to Pt is 0.5-1.7. The catalyst has the advantages of controllable structure, mild reaction conditions, simple operation and low cost; compared with commercial 20wt.% Pt/C, the prepared nano gold-platinum bimetallic @ carbon material oxygen reaction catalyst has better oxygen reduction and oxygen evolution catalytic activity and stability.

Description

A kind of nano-gold platinum bimetal@carbon material oxygen reaction catalyst and preparation method thereof

technical field

The invention relates to the field of oxygen reaction catalysis, in particular to a nano-gold platinum bimetal@carbon material oxygen reaction catalyst and a preparation method thereof.

Background technique

The development of the electric vehicle field has higher requirements for the energy density of the battery (>300 Wh/kg). At present, the theoretical energy density of widely used lithium-ion batteries is low, only 150-200Wh/kg, which is far from meeting the battery life requirements of electric vehicles. Metal-air batteries, such as zinc-air batteries, magnesium-air batteries, aluminum-air batteries, lithium-air batteries, etc., have high energy density and can meet the development needs of electric vehicles. Metal-air battery cathodes involve oxygen reduction and oxygen evolution reactions, but oxygen electrode reaction kinetics are sluggish, reducing the energy efficiency of metal-air batteries.

The use of catalysts can improve the reaction kinetics of oxygen electrodes. At present, commercial platinum-carbon catalysts (20wt.%Pt/C) have high catalytic activity for oxygen reactions. However, due to the scarcity of platinum resources, the catalyst prices are high, resulting in an increase in the cost of metal-air batteries. . In addition, platinum may dissolve or fall off during the battery cycle, and the catalyst has poor stability, which is not conducive to maintaining high energy efficiency of the battery during long-term operation. Therefore, the development of oxygen reaction catalysts with high catalytic activity, high stability and low cost has become an urgent problem to be solved.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a nano-gold platinum bimetal@carbon material oxygen reaction catalyst and a preparation method thereof.

The nano-gold-platinum bimetallic@carbon material oxygen reaction catalyst involved in the present invention uses the nano-gold-platinum bimetallic catalyst as the active center with the carbon material as the carrier and the organic ligand as the capping agent. The average particle size of the nano-Au-Pt bimetal is 2.8 nm ~ 3.2 nm, the nano-Au-Pt bi-metal loading is 10wt.% ~ 15wt.%, and the gold/platinum molar ratio is 0.5 ~ 1.7.

The specific steps of the preparation method of the nano-gold platinum bimetal@carbon material oxygen reaction catalyst involved in the present invention are:

(1) Put 40 to 80 mg of carbon material in a 150 mL conical flask, and add 100 mL of deionized water.

(2) Incubate the product obtained in step (1) in a super constant temperature water bath at 60 ~ 95°C for 5 minutes, then add 0.5 ~ 1.5 mL of chlorine with a concentration of 2.0 × 10 ^-4 ~ 3.0 × 10 ^-4 mol/L to the bottle Gold acid and 0.6 ~ 1.9 mL of chloroplatinic acid with a concentration of 2.0 × 10 ^-4 ~ 3.0 × 10 ^-4 mol/L were stirred and ultrasonically treated to obtain a stable dispersion at a constant temperature.

(3) Add 500-700 μL of alkali source with a concentration of 1 mol/L and 1.9-2.4 mL of a capping agent with a concentration of 50 mmol/L into the stable dispersion at constant temperature obtained in step (2) to obtain an alkaline mixed solution. If the capping agent is mercaptosuccinic acid, then add 3.8 to 4.8 mL of sodium borohydride with a concentration of 50 mmol/L.

(4) The product obtained in step (3) was stirred and reacted in a constant temperature water bath for 3 hours to obtain a mixed solution with the reaction product; immediately after the reaction was completed, the conical flask was placed in an ice-water bath to stop the reaction, then taken out, and allowed to stand at air temperature Overnight, centrifuge at 8000 rpm until neutral, dry, and grind thoroughly to obtain nano-gold platinum bimetal@carbon nanotube oxygen reaction catalyst powder.

The carbon material is one or more of commercially available carbon nanotubes, graphene and carbon black.

The alkali source is sodium hydroxide or potassium hydroxide.

The end-capping agent is one or more of commercially available tetrahydroxymethyl phosphorus chloride, mercaptosuccinic acid and triphenylphosphine, wherein tetrahydroxymethyl phosphorus chloride is oxidized in the reaction of step (3) to generate triphenylphosphine. Phosphorus oxyhydroxide.

The present invention has no special requirements on ultrasonic power and ultrasonic time, as long as a uniform mixed solution can be generated.

The present invention has no special requirements on the model of the super constant temperature water bath, and a commercially available instrument well known in the art can be used.

The present invention has no special requirements on the stirring speed, as long as the mixture is uniform; the present invention has no special requirements on the stirring time, as long as it can reach a constant temperature.

The present invention has no special requirements on the centrifugation method, and the product can be obtained by using methods well known in the art.

The present invention has no special requirements on the number of times of washing, as long as the solids obtained by centrifugation can be cleaned.

The present invention has no special requirements on the drying temperature and time, as long as it can ensure that the moisture of the solids after washing is removed.

The carbon material acts as a support for the catalyst to avoid agglomeration of the catalyst while providing a conductive network for the catalyst. Since the organic ligand capping agent is coordinated and complexed with nano-gold and nano-platinum, nano-gold and nano-platinum are closely combined to form nano-gold-platinum bimetal instead of nano-gold-platinum alloy. The organic ligand capping agent can prevent the growth of nano-Au-Pt bimetallic crystals and help to provide more active sites. Both nano-gold and nano-platinum can be used as oxygen reaction active sites, and the synergistic effect of the two makes the activity of nano-gold and platinum bimetals higher than that of single nano-gold or nano-platinum. The combination of nano-gold and nano-platinum can inhibit the dissolution and desorption of nano-platinum, so the stability of nano-gold-platinum bimetal is good.

The invention uses carbon material as a matrix and an organic ligand capping agent to prepare a nano-gold platinum bimetal@carbon material oxygen reaction catalyst through a one-step reduction method, the catalyst structure is controllable, the reaction conditions are mild, the operation is simple, and the cost is low; Compared with commercial 20wt.% Pt/C, the nano-gold platinum bimetal@carbon material oxygen reaction catalyst has better catalytic activity and stability for oxygen reduction and evolution.

Description of drawings

FIG. 1 is a transmission electron microscope image of Example 1. FIG.

FIG. 2 is a particle size distribution diagram of Example 1. FIG.

FIG. 3 is a high-resolution transmission electron microscope image of Example 1. FIG.

FIG. 4 is an X-ray diffraction pattern of Example 1. FIG.

FIG. 5 is a distribution diagram of gold, platinum and carbon elements of nano-gold and platinum bimetals in Example 1. FIG.

Fig. 6 is the oxygen reduction reaction catalytic activity control curve of Example 2, the dotted line is the commercial platinum/carbon catalyst, and the solid line is the nano-gold platinum bimetal@carbon material catalyst.

Figure 7 is a comparative curve of the catalytic activity of the oxygen evolution reaction in Example 2, the dotted line is a commercial platinum/carbon catalyst, and the solid line is a nano-gold platinum bimetal@carbon material catalyst.

Figure 8 is the stability control curve of Example 2, the dotted line is the commercial platinum/carbon catalyst, and the solid line is the nano-gold platinum bimetal@carbon material catalyst.

Fig. 9 is the oxygen reduction reaction catalytic activity control curve of Example 3, the dotted line is the commercial platinum/carbon catalyst, and the solid line is the nano-gold platinum bimetal@carbon material catalyst.

Figure 10 is the oxygen evolution reaction catalytic activity control curve of Example 3, the dotted line is the commercial platinum/carbon catalyst, and the solid line is the nano-gold platinum bimetal@carbon material catalyst.

Figure 11 is the stability comparison curve of Example 3, the dotted line is the commercial platinum/carbon catalyst, and the solid line is the nano-gold platinum bimetal@carbon material catalyst.

Detailed ways

Example 1:

(1) Place 45 mg of commercially available carbon nanotubes in a 150 mL conical flask and add 100 mL of deionized water.

(2) Incubate the product obtained in step (1) in a super constant temperature water bath at 70°C for 5 minutes, and then add 1.5 mL of chloroauric acid with a concentration of 2.43×10 ^-4 mol/L and 0.625 mL of a concentration of 2.0×10 to the bottle. ^-4 mol/L chloroplatinic acid, stirring, and ultrasonic treatment to obtain a stable dispersion at a constant temperature.

(3) Add 550 μL of 1 mol/L sodium hydroxide and 1.9 mL of 50 mmol/L tetrahydroxymethyl phosphorus chloride to the stable dispersion at constant temperature obtained in step (2) to obtain an alkaline solution. mixture.

(4) The product obtained in step (3) was stirred and reacted in a constant temperature water bath for 3 hours to obtain a mixed solution with the reaction product; immediately after the reaction was completed, the conical flask was placed in an ice-water bath to stop the reaction, then taken out, and allowed to stand at air temperature Overnight, centrifuge at 8000 rpm until neutral, dry, and grind thoroughly to obtain nano-gold platinum bimetal@carbon nanotube oxygen reaction catalyst powder.

The TEM of the nano-gold-platinum bimetal@carbon nanotube prepared in this example is shown in Figure 1, and it can be seen from Figure 1 that the nano-gold-platinum bimetal is uniformly distributed on the carbon nanotube. The particle size distribution of the nano-gold-platinum bimetal in this embodiment is shown in FIG. 2 , and it can be seen from FIG. 2 that the average size of the nano-gold-platinum bimetal is 3.02 nm. The high-resolution TEM morphology of the nano-Au-Pt bimetal in this example is shown in Figure 3. It can be seen from Figure 3 that the interplanar spacing is 0.236 nm is nano-gold (111), and the interplanar spacing is 0.225 nm is nanometer Platinum (111), nano-gold and nano-platinum combine but do not form an alloy. The XRD of this example is shown in Figure 4. The XRD peaks of gold nanoparticles and platinum nanoparticles are located at 38.1°, 44.3°, 64.5° and 39.5°, 45.9°, and 67.0°, respectively, which proves that gold nanoparticles and platinum nanoparticles do not form alloys. . The distribution of gold and platinum elements of the nano-gold-platinum bimetal in this example is shown in FIG. 5 , the gold and platinum elements are overlapped together, which proves that the nano-gold and the nano-platinum are combined together.

Example 2:

(1) Put 50 mg of commercially available carbon nanotubes in a 150 mL conical flask and add 100 mL of deionized water.

(2) Incubate the product obtained in step (1) in a super constant temperature water bath at 75°C for 5 minutes, and then add 1 mL of chloroauric acid with a concentration of 2.43 × 10 ^-4 mol/L and 1.25 mL of 2.0 × 10 chloroauric acid into the bottle. ^-4 mol/L chloroplatinic acid, stirring, and ultrasonic treatment to obtain a stable dispersion at a constant temperature.

(3) Add 600 μL of 1 mol/L sodium hydroxide and 2.1 mL of 50 mmol/L tetramethylolphosphorus chloride to the stable dispersion at constant temperature obtained in step (2) to obtain an alkaline solution. mixture.

(4) The product obtained in step (3) was stirred and reacted in a constant temperature water bath for 3 hours to obtain a mixed solution with the reaction product; immediately after the reaction was completed, the conical flask was placed in an ice-water bath to stop the reaction, then taken out, and allowed to stand at air temperature Overnight, centrifuge at 8000 rpm until neutral, dry, and grind thoroughly to obtain nano-gold platinum bimetal@carbon nanotube oxygen reaction catalyst powder.

Taking commercial platinum/carbon catalyst (20wt.%Pt/C) as a control, the oxygen reduction reaction catalytic performance and oxygen evolution reaction of the nano-gold-platinum bimetallic@carbon nanotubes (denoted as AuPt-1/MWNTs) prepared in this example The catalytic performance and stability were tested respectively, and the test results are shown in Figure 6, Figure 7 and Figure 8. The dotted line in Figure 6 represents 20 wt.% Pt/C, and the solid line represents AuPt-1/MWNTs; it can be seen from Figure 6 that the oxygen reduction catalytic activity of AuPt-1/MWNTs is comparable to that of 20 wt.% Pt/C. The dotted line in Figure 7 represents 20 wt.% Pt/C, and the solid line represents AuPt-1/MWNTs; it can be seen from Figure 7 that the oxygen evolution catalytic activity of AuPt-1/MWNTs is comparable to that of 20 wt.% Pt/C. The dotted line in Figure 8 represents 20wt.%Pt/C, and the solid line represents AuPt-1/MWNTs; it can be seen from Figure 8 that the stability of AuPt-1/MWNTs is comparable to that of 20wt.%Pt/C.

Example 3:

(1) Put 55 mg of commercially available carbon nanotubes in a 150 mL conical flask and add 100 mL of deionized water.

(2) Incubate the product obtained in step (1) in a super constant temperature water bath at 80°C for 5 minutes, and then add 0.5 mL of chloroauric acid with a concentration of 2.43×10 ^-4 mol/L and 1.875 mL of a concentration of 2.0×10 to the bottle. ^-4 mol/L chloroplatinic acid, stirring, and ultrasonic treatment to obtain a stable dispersion at a constant temperature.

(3) Add 650 μL of 1 mol/L sodium hydroxide and 2.3 mL of 50 mmol/L mercaptosuccinic acid to the stable dispersion at constant temperature obtained in step (2), and then add 4.6 mL of 50 mmol/L of sodium borohydride to obtain an alkaline mixed solution.

(4) The product obtained in step (3) was stirred and reacted in a constant temperature water bath for 3 hours to obtain a mixed solution with the reaction product; immediately after the reaction was completed, the conical flask was placed in an ice-water bath to stop the reaction, then taken out, and allowed to stand at air temperature Overnight, centrifuge at 8000 rpm until neutral, dry, and grind thoroughly to obtain nano-gold platinum bimetal@carbon nanotube oxygen reaction catalyst powder.

Taking commercial platinum/carbon catalyst (20wt.%Pt/C) as a control, the oxygen reduction reaction catalytic performance and oxygen evolution reaction of the nano-gold platinum bimetallic@carbon nanotubes (denoted as AuPt-2/MWNTs) prepared in this example The catalytic performance and stability were tested respectively, and the test results are shown in Figure 9, Figure 10 and Figure 11. The dotted line in Figure 9 represents 20 wt.% Pt/C, and the solid line represents AuPt-2/MWNTs; it can be seen from Figure 9 that the oxygen reduction catalytic activity of AuPt-2/MWNTs is comparable to that of 20 wt.% Pt/C. The dotted line in Figure 10 represents 20 wt.% Pt/C, and the solid line represents AuPt-2/MWNTs; it can be seen from Figure 10 that the oxygen evolution catalytic activity of AuPt-2/MWNTs is comparable to that of 20 wt.% Pt/C. The dotted line in Figure 11 represents 20wt.%Pt/C, and the solid line represents AuPt-2/MWNTs; it can be seen from Figure 11 that the stability of AuPt-2/MWNTs is comparable to that of 20wt.%Pt/C.

Claims (2)

1. A nanometer gold platinum bimetal @ carbon material oxygen reaction catalyst is characterized in that the nanometer gold platinum bimetal @ carbon material oxygen reaction catalyst takes a carbon material as a matrix, and nanometer gold platinum bimetal with an organic ligand as a capping reagent as an oxygen reaction catalyst with an active center;

the carbon material is one or more of commercially available carbon nanotubes, graphene and carbon black;

the end-capping reagent is one or more of market-available tetrakis (hydroxymethyl) phosphonium chloride, mercaptosuccinic acid and triphenylphosphine, wherein the tetrakis (hydroxymethyl) phosphonium chloride is oxidized to generate trihydroxy phosphonium oxide;

the average grain diameter of the nano-Au-Pt bimetal is 2.8-3.2 nm, the loading capacity of the nano-Au-Pt bimetal is 10-15 wt.%, and the gold/Pt molar ratio is 0.5-1.7.

2. The preparation method of the nano-Au-Pt bimetallic @ carbon material oxygen reaction catalyst as claimed in claim 1, is characterized by comprising the following specific steps:

(1) putting 40-80 mg of carbon material into a 150 m L conical flask, and adding 100 m L deionized water;

(2) preserving the heat of the product obtained in the step (1) in a super constant temperature water bath at the temperature of 60-95 ℃ for 5 minutes, and then adding 0.5-1.5 m L with the concentration of 2.0 × 10^-4~ 3.0×10^-4The concentration of chloroauric acid in mol/L and 0.6-1.9 m L is 2.0 × 10^-4~3.0×10^-4Stirring and ultrasonically treating chloroplatinic acid of mol/L to obtain stable dispersion liquid with constant temperature;

(3) adding an alkali source with the concentration of 1 mol/L and an end-capping reagent with the concentration of 50 mmol/L of 1.9-2.4 m L into the stable dispersion liquid with the constant temperature obtained in the step (2) to obtain an alkaline mixed solution, and adding sodium borohydride with the concentration of 50 mmol/L of 3.8-4.8 m L if the end-capping reagent is mercaptosuccinic acid;

(4) stirring the product obtained in the step (3) in a constant-temperature water bath for reaction for 3 hours to obtain a mixed solution of reaction products; immediately placing the conical flask into an ice-water bath to stop reaction after the reaction is finished, then taking out the conical flask, standing the conical flask overnight at an air temperature, centrifuging the conical flask at 8000 rpm to be neutral, drying the conical flask, and fully grinding the conical flask to obtain nano gold-platinum bimetallic @ carbon nanotube oxygen reaction catalyst powder;

the carbon material is one or more of commercially available carbon nanotubes, graphene and carbon black;

the alkali source is sodium hydroxide or potassium hydroxide;

the end-capping reagent is one or more of commercial tetrakis hydroxymethyl phosphonium chloride, mercaptosuccinic acid and triphenylphosphine, wherein the tetrakis hydroxymethyl phosphonium chloride is oxidized in the reaction of the step (3) to generate trihydroxy phosphonium oxide.

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