CN110676469A - Carbon-supported platinum-based nanomaterials - Google Patents

Abstract

The invention provides a carbon-supported platinum-based nanomaterial for a catalyst of a methanol fuel cell, wherein the carbon-supported platinum-based nanomaterial comprises a carbon-supported material and a platinum-based material, the platinum-based material comprises platinum and a single metal, and the single metal is iron or gold; when the single metal is iron, the mass ratio of platinum to iron is 1: 1/40; when the single metal is gold, the mass ratio of platinum to gold is 1: 1/2.

Description

Carbon-supported platinum-based nanomaterials

technical field

The invention relates to a carbon-supported platinum-based nanomaterial, in particular to a carbon-supported platinum-based nanomaterial for methanol fuel cells.

Background technique

As a new type of battery, methanol fuel cell has attracted much attention due to its advantages of low fuel price, low toxicity, liquid state at room temperature, small size, portability, and easy storage. At present, the commercialized methanol fuel cell catalytic materials with the best electrocatalytic performance are platinum group materials. Among them, platinum group catalysts supported by platinum black and highly dispersed carbon black are the hot spots in the research and application development of fuel cell catalysts. However, in practical applications, the cost, efficiency and stability of platinum group catalysts limit their application. The development of catalysts with high catalytic efficiency and stable performance is an urgent problem to be solved in methanol fuel cells. In a series of developed and improved platinum-based nanocatalytic materials, binary platinum-based metal nanomaterials composed of two different metal elements have become a new class of materials that have attracted much attention. In most cases, binary metal nanoparticles are widely used in optics, biology and catalysis due to the synergistic effect between metals, which greatly improves their physical and chemical properties.

SUMMARY OF THE INVENTION

The invention provides a binary platinum-based metal nanometer material, which exhibits good methanol catalytic activity and stability.

The present invention is realized in this way:

A carbon-supported platinum-based nanomaterial for a catalyst for a methanol fuel cell, wherein the carbon-supported platinum-based nanomaterial includes a carbon-supported material and a platinum-based material, the platinum-based material includes platinum and a single metal, and the The single metal is iron or gold; when the single metal is iron, the mass ratio of platinum and iron is 1:1/40; when the single metal is gold, the mass ratio of platinum and gold is 1:1/2.

As a further improvement, the size of the carbon particles ranges from 20 to 50 nm.

As a further improvement, the single metal is iron, and the diameter of platinum particles is less than 10 nm.

As a further improvement, the single metal is gold, and the diameter of the platinum particles is less than 10 nm.

The beneficial effects of the present invention are: using carbon-supported platinum nanomaterials with a platinum-iron ratio of 1:1/40 and carbon-supported platinum nanomaterials with a platinum-to-metal ratio of 1:1/2, compared with a single platinum metal nanomaterial supported by carbon, All of them have high electrocatalytic performance for methanol and high stability.

Description of drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is a scanning electron microscope image of carbon-supported platinum nanomaterials provided by the present invention.

2 is a scanning electron microscope image of the carbon-supported platinum nanomaterial provided by the present invention.

3 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different ratios of platinum and iron provided by the present invention in 0.5mol/LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution.

FIG. 4 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios in a 0.5MH ₂ SO ₄ solution when nitrogen gas is introduced.

FIG. 5 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios in 0.5MH ₂ SO ₄ solution when oxygen is introduced.

6 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum ratios provided by the present invention in 0.5mol/LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution.

FIG. 7 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum ratios provided by the present invention in a 0.5MH ₂ SO ₄ solution when nitrogen gas is introduced.

FIG. 8 is a cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum ratios provided by the present invention when oxygen is introduced into a 0.5MH ₂ SO ₄ solution.

FIG. 9 is a stable curve of electrocatalytic performance of carbon-supported platinum nanomaterial catalysts with different ratios of platinum and iron provided by the present invention in 0.5MH ₂ SO ₄ +0.5 MCH ₃ OH solution.

Fig. 10 is the electrocatalytic performance stability curve of the carbon-supported platinum nanomaterial catalysts with different platinum ratios provided by the present invention in 0.5MH ₂ SO ₄ +0.5M CH ₃ OH solution.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, the terms "first" and "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

The invention provides a carbon-supported platinum-based nanomaterial, the carbon-supported platinum-based nanomaterial includes a carbon-supported material and a platinum-based material, and the platinum-based material includes platinum and a single metal. The single metal may be iron or gold. When the single metal is iron, preferably, the mass ratio of platinum and iron is 1:1/40; when the single metal is gold, preferably, the mass ratio of platinum and gold is 1:1/2.

The carbon-supported material is circular or oval carbon particles. The carbon particles have a size range of 20-50 nm. When the single metal is iron, the diameter of the platinum particles is less than 10 nm, and iron is the doped metal. When the single metal is gold, the diameter of platinum particles is less than 10 nm, and gold is one of the main components of platinum nanomaterials.

The carbon-supported platinum-based nanomaterial is prepared by a hydrothermal synthesis method. When the single metal is iron, the carbon-supported platinum-based nanomaterial is a carbon-supported platinum nanomaterial, and iron is a doped metal; when the single-metal is gold, the carbon-supported platinum-based nanomaterial is a carbon-supported nanomaterial Platinum nanomaterials, gold is one of the main components of platinum nanomaterials.

The preparation process of the carbon-supported platinum nanomaterial is as follows: take 100 mg of trisodium citrate dihydrate, dissolve in 1 mL of water, add 10 mL of ethylene glycol, shake well, and then add a certain proportion of potassium chloroplatinate and chlorine to it. Iron, add 10 mg of carbon powder after mixing evenly, ultrasonicate for 30 min with an ultrasonic cleaner, take out and put it into a vacuum desiccator for decompression and degassing, adjust the pH to 10 with 2% NaOH solution, and transfer the solution to a hydrothermal synthesis reactor, The reaction was carried out at 120°C for 4 hours. After the reaction, the samples were subjected to suction filtration, ethanol cleaning, and low-temperature drying to obtain carbon-supported platinum nanomaterials with different platinum-iron ratios, as shown in Table 1. Please refer to Figure 1, (A) (B) (C) (D) are the scanning electron microscope images of each sample in Table 1, (A) (B) (C) (D) 4 sub-images with diameters of 20-50nm The spherical or ellipsoidal particles are carbon-supported materials. In sample (A), a series of platinum particles with a diameter of less than 10 nm can be clearly observed on the surface of the carbon support, in which the platinum particles are dispersed and a small number of particles are agglomerated; The platinum particles were supported on the surface of the carbon support in agglomerated or partially dispersed form, and the increase of iron content did not change the shape, size and loading of the platinum particles to a great extent.

Table 1 Carbon-supported platinum nanomaterials with different platinum-iron ratios

Sample serial number Platinum iron ratio Platinum content/% Iron content/% (A) C-Pt-1 1:0 20 0 (B) C-Pt-2 1:1/80 20 0.25 (C)C-Pt-3 1:1/40 20 0.5 (D)C-Pt-4 1:1/8 20 2.5

The preparation process of the carbon-supported platinum nanomaterial is as follows: take 100 mg of trisodium citrate dihydrate, dissolve in 1 mL of water, add 10 mL of ethylene glycol, shake well, and then add a certain proportion of potassium chloroplatinate and chlorine to it. Gold acid, mix well, add 10 mg of carbon powder, ultrasonicate with an ultrasonic cleaner for 30 min, take it out and put it in a vacuum desiccator for decompression and degassing, adjust the pH to 10 with 2% NaOH solution, and transfer the solution to a hydrothermal synthesis reactor, The reaction was carried out at 120°C for 4 hours. After the reaction, the samples were subjected to suction filtration, ethanol cleaning, and low-temperature drying to obtain carbon-supported platinum nanomaterials with different platinum ratios, as shown in Table 2. Please refer to Figure 2, (A) (B) (C) (D) are the scanning electron microscope images of each sample in Table 2, (A) (B) (C) (D) 4 sub-images with diameters of 20-50nm The spherical or ellipsoidal particles are carbon-supported materials. In samples (A) (C) (D), it can be clearly observed that a series of platinum particles with diameters less than 10 nm are agglomerated or partially dispersed on the surface of the carbon support. In sample (B), the platinum ions supported on the surface of the carbon support are many The platinum particles smaller than 10 nm are dispersed or a small part of the agglomerated particles exist in the form of particles smaller than 20 nm. In platinum nanomaterials, the change of gold content changes the dispersion morphology of nanoparticles to a certain extent.

Table 2 Nanomaterials of carbon-supported platinum with different platinum ratios

Sample serial number Platinum Ratio Platinum content/% Gold content/% (A) C-Pt-Au-1 1:1/4 20 5 (B) C-Pt-Au-2 1:1/2 20 10 (C)C-Pt-Au-3 1:1 20 20 (D)C-Pt-Au-4 1:2 20 40

The carbon-supported platinum-based nanomaterial provided by the present invention is a catalyst for methanol fuel cells. In order to illustrate the effect of carbon-supported platinum-based nanomaterials on the electrocatalytic performance of methanol, electrochemical tests were performed on the samples in Table 1 and Table 2, respectively.

The electrochemical test steps of the sample include: taking 2 mg of the sample and dispersing it in 0.5 mL of absolute ethanol, adding 10 uLNafion solution, and placing it in an ultrasonic cleaner for 30-60 min to form a uniform suspension. Take 10uL of suspension solution and apply it on the surface of the polished glassy carbon electrode with a diameter of 5mm, and wait for the solvent to evaporate for use; the graphite electrode is used as the counter electrode, the saturated calomel electrode is used as the reference electrode, and the platinum-based nanomaterial electrode is used as the working electrode. The electrochemical tests of the samples were carried out in a solution system with 0.5mol/L H ₂ SO ₄ as an acidic medium.

Please refer to FIG. 3 , which is the cyclic voltammogram of carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios in 0.5mol/LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution, and the scanning speed is 0.05V/s. It can be seen from the figure that when the potential is swept positively, a methanol oxidation peak appears near 0.65V; when the potential is negatively swept, the peak that appears near 0.44V is the intermediate product CO _ad oxidation peak; with the increase of Fe content When the ratio of platinum to iron reaches 1:1/40, the current intensity of methanol oxidation peak reaches the maximum. However, its current intensity is compared with that of the sample with platinum to iron ratio of 1:1/80. A small increase, that is, under this condition, the increase of the ratio of platinum to iron continues to increase the efficiency of methanol oxidation peak current intensity; when the platinum to iron ratio reaches 1:1/8, the methanol oxidation peak current intensity is significantly lower than that of zero iron content. Carbon-supported platinum samples. Please refer to FIG. 4 and FIG. 5 , which are the cyclic voltammograms of carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios in 0.5MH ₂ SO ₄ solution with nitrogen gas and oxygen gas respectively. When nitrogen gas was introduced into the system (Fig. 4), it was observed that the increase of iron content enhanced the hydrogen desorption signal (-0.2V-0.0V) of carbon-supported platinum nanomaterials; The electrochemically active surface area of the catalyst can be calculated, from which it can be inferred that the increase in the iron content leads to an increase in the electrochemically active surface area of the carbon-supported platinum nanomaterials. This conclusion is verified from the negative scanning of the electrochemical curve in Fig. 4, the oxygen reduction signal on the surface of platinum metal in the potential range of 0.3-0.7V is verified; when the iron content increases, the oxygen reduction signal on the surface of platinum metal becomes stronger, and when the ratio of platinum to iron is At 1:1/40, the signal reaches the maximum, that is, the electrochemically active surface area of the sample is the largest under this condition. When oxygen is introduced into the system (Fig. 5), the catalytic activity of carbon-supported platinum can be judged from the change of the oxygen reduction peak potential of the platinum metal surface; when the iron content increases, the oxygen reduction peak potential of the platinum metal surface shifts significantly. When the iron ratio is 1:1/40, the onset potential of the oxygen reduction peak on the surface of platinum metal is the smallest during the negative scan, that is, the electrocatalytic activity of the sample is the best under this condition.

Please refer to FIG. 6 , which shows the cyclic voltammograms of carbon-supported platinum nanomaterial catalysts with different platinum ratios in 0.5mol/LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution, and the scanning speed is 0.05V/s. It can be seen from the figure that with the increase of gold content, the current intensity of methanol oxidation peak first increases and then decreases. When the platinum ratio is 1:1/2, the current intensity of methanol oxidation peak reaches the maximum. Please refer to FIG. 7 and FIG. 8 , which are the cyclic voltammograms of carbon-supported platinum nanomaterial catalysts with different platinum ratios in 0.5MH ₂ SO ₄ solution with nitrogen gas and oxygen gas respectively. When nitrogen gas was introduced into the system (Fig. 7), it can be observed that with the increase of gold content, the hydrogen desorption signal (-0.2V-0.0V) of carbon-supported platinum nanomaterials and the oxygen reduction signal (0.3V) of platinum metal surface -0.7V) first enhanced and then decreased; when the platinum ratio was 1:1/2, the signal was the largest, that is, the electrochemically active surface area of the sample was the largest under this condition. When oxygen was introduced into the system (Fig. 8), with the increase of gold content, especially the platinum ratio increased from 1:1/2 to 1:2, the oxygen reduction peak potential on the surface of platinum metal did not change significantly, so carbon-supported platinum had no obvious change. The enhanced catalytic ability of methanol is mainly through the increase of the electrochemically active area of platinum.

Please refer to Fig. 9, which is the stability curve of electrocatalytic performance of carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios in 0.5MH ₂ SO ₄ +0.5MCH ₃ OH solution, that is, the carbon-supported platinum nanomaterial catalysts with different platinum-iron ratios Cyclic voltammetry in 0.5mol/LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution, scanning potential range -0.2V-1.1V, scanning speed 0.05V/s, with methanol oxidation peak 0.65V potential condition The lower current intensity is plotted against the number of cycles. It can be seen from the figure that when the iron content is zero, the carbon-supported platinum nanomaterials maintain relatively stable electrocatalytic performance although the catalytic performance is not ideal. With the increase of the number of cycles, the signal is enhanced and then attenuated to different degrees; with the increase of the number of cycles, the signal enhancement can be attributed to the cleaning and activation of the electrochemically active surface of the catalyst in the acidic medium under the cycle test conditions; the ratio of platinum to iron is 1:1 The carbon-supported platinum nanomaterial catalyst under the synthesis condition of /40 still maintained a high catalytic activity after 1000 cycles.

Please refer to Fig. 10, which is the stability curve of electrocatalytic performance of carbon-supported platinum nanomaterial catalysts with different platinum ratios in 0.5MH ₂ SO ₄ +0.5MCH ₃ OH solution, that is, for carbon-supported platinum nanomaterial catalysts with different platinum ratios in 0.5mol Cyclic voltammetry in /LH ₂ SO ₄ +0.5mol/L CH ₃ OH solution, the scanning potential range is -0.2V-1.1V, the scanning speed is 0.05V/s, and the current is based on the methanol oxidation peak of 0.65V potential. The intensity is plotted against the number of cycles. As can be seen from the figure, except for the platinum nanomaterial catalyst with a platinum ratio of 1:1/2, the other catalysts with a platinum ratio have a large signal attenuation after 400 cycles of the cycle test, and the performance is significantly lower than that in Figure 9 The platinum nanomaterial catalyst with zero iron content in the middle; while the platinum nanomaterial catalyst with a platinum ratio of 1:1/2 still maintains a high catalytic activity after 1000 cycle tests.

The carbon-supported platinum-based nanomaterial provided by the present invention has the following advantages: the carbon-supported platinum nanomaterial with a platinum-to-iron ratio of 1:1/40 and a carbon-supported platinum nanomaterial with a platinum-to-metal ratio of 1:1/2 all have higher resistance to methanol good electrocatalytic performance and high stability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. A carbon-supported platinum-based nanomaterial for a catalyst of a methanol fuel cell, wherein the carbon-supported platinum-based nanomaterial comprises a carbon-supported material and a platinum-based material, the platinum-based material comprises platinum and a single metal, and the single metal is iron or gold; when the single metal is iron, the mass ratio of platinum to iron is 1: 1/40; when the single metal is gold, the mass ratio of platinum to gold is 1: 1/2.

2. The carbon-supported platinum-based nanomaterial of claim 1, wherein the carbon-supported material is round or oval carbon particles.

3. The carbon-supported platinum-based nanomaterial of claim 2, wherein the size of the carbon particles is in the range of 20nm to 50 nm.

4. The carbon-supported platinum-based nanomaterial of claim 1, wherein the single metal is iron and the platinum particles have a diameter of less than 10 nm.

5. The carbon-supported platinum-based nanomaterial of claim 1, wherein the single metal is gold and the platinum particles have a diameter of less than 10 nm.

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