CN115101766A

CN115101766A - Preparation method and application of low-platinum-content cathode oxygen reduction catalyst

Info

Publication number: CN115101766A
Application number: CN202210851502.XA
Authority: CN
Inventors: 张光晋; 张旭; 张敬贤; 曾识
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2022-07-19
Filing date: 2022-07-19
Publication date: 2022-09-23

Abstract

The invention discloses a preparation method of a cathode oxygen reduction catalyst with low platinum content, which comprises the following steps: dissolving a platinum metal precursor, a transition metal (M) precursor, a nitrogen-containing organic compound and a zinc precursor in anhydrous methanol, uniformly stirring to obtain a solution A, dissolving dimethyl imidazole in the anhydrous methanol, and uniformly stirring to obtain a solution B; and mixing the solution A and the solution B, uniformly stirring, centrifuging, washing with a solvent, drying, and then sending into a high-temperature carbonization device for high-temperature carbonization to obtain an atomic-scale dispersion product Pt, M/NC. Compared with the original commercial Pt/C catalyst, the Pt, M/NC catalyst prepared by the invention has the advantages of obviously improved performance, higher quality activity and stability, high-efficiency proton-charge transmission capability, reinforced electronic structure and the like; the Pt atom content is only 0.06 wt%, and the catalyst mass activity is 85 times of that of Pt/C in the oxygen reduction reaction process.

Description

Preparation method and application of low-platinum-content cathode oxygen reduction catalyst

Technical Field

The invention belongs to the technical field of new energy fuel cells, and particularly relates to a preparation method and application of a low-platinum-content cathode oxygen reduction catalyst.

Background

With the large consumption of fossil fuels, environmental pollution and climate change becoming more severe, the development of green and efficient renewable energy and novel energy storage and conversion devices is urgent, and people have an increasing demand for clean and green sustainable new energy. A low-temperature Proton Exchange Membrane Fuel Cell (PEMFC) is widely regarded as a portable energy device with a promising application prospect due to its advantages of high energy conversion efficiency, convenient storage and transportation, and environmental friendliness, as a clean and sustainable energy conversion device. And the low-temperature Proton Exchange Membrane Fuel Cell (PEMFC) has the advantages of high energy density, low-temperature quick start, simple structure, good safety, low noise and the like, is an optimal device for replacing an internal combustion engine as a power supply of an automobile, can be widely applied to large-scale equipment such as new energy automobiles, spaceflight, ships and the like, and can effectively relieve the problems of excessive use of traditional fossil energy, environmental pollution, climate change and the like caused by the excessive use of the traditional fossil energy.

The most critical of low temperature Proton Exchange Membrane Fuel Cells (PEMFC) is the use of a catalyst. At present, the noble metal Pt catalyst is the catalyst material which is most widely applied to the cathode of the PEMFC, but the development and the application of the catalyst are limited due to the defects of low storage capacity, high cost, easy poisoning by intermediate products and the like. There are also related art studies in the prior art for platinum composite catalysts, such as: 1. chinese patent application CN202110398417.8 discloses a low platinum alloy catalyst modulated by a crystal face, a preparation method and application thereof in a fuel cell, wherein the preparation method adopts a specific transition group metal carbonyl compound as a modulator and a stabilizer modulated by the crystal face of the alloy catalyst, and utilizes a gas-liquid two-phase coexisting synthesis system generated in a reaction kettle under the critical state of ethylene glycol reaction liquid to prepare the low platinum alloy catalyst with the preferred orientation of the high (111) crystal face, so that the obtained commercial carbon black loaded alloy nanoparticle composite catalyst is black powder; the size of alloy particles is 1-5 nm, the alloy particles are uniformly dispersed on the surface of the carbon carrier, and the texture coefficient of preferred orientation of the modulated alloy crystal plane reaches more than 1.24. The method improves the ORR catalytic performance and activity stability of the platinum alloy catalyst by modulating the crystal face of the platinum alloy catalyst, the catalyst has high electrocatalytic activity and stability for oxygen reduction reaction in an acid medium, the performance of the catalyst is superior to that of a commercial platinum-carbon (Pt/C) catalyst, and the catalyst can be applied to proton membrane fuel cells to replace the conventional commercial platinum-carbon catalyst.

2. Chinese patent application CN202110202172.7 discloses a preparation method of an ordered low platinum alloy catalyst, which comprises the steps of carrying out oil bath treatment on a carbon carrier by nitric acid, adding the carbon carrier into deionized water after filtering and drying, and carrying out ultrasonic dispersion to obtain a carbon carrier water ion solution; dissolving a platinum source and a transition metal salt in deionized water, performing ultrasonic dispersion to obtain a mixed solution I, then dropwise adding the mixed solution I into a carbon carrier water ion solution, controlling the dropwise adding speed, stirring to obtain a mixed solution II, heating by using infrared radiation to evaporate a solvent in the mixed solution II, drying, and grinding to obtain an intermediate solid material; and (3) placing the intermediate material in a microwave heating furnace, and calcining the intermediate material in a reduction/inert atmosphere in different temperature intervals in a segmented manner to obtain the ordered low-platinum alloy catalyst particles, wherein the core material contains low-platinum alloy with an ordered dual-phase structure, and the shell layer is a thin platinum layer with a stable surface structure. The method can separate out platinum metal and attach the platinum metal to the surface of the multiphase ordered platinum alloy to form core-shell structure nano particles, the prepared catalyst particles are uniform in dispersion, ideal in particle size and high in catalytic activity, the utilization rate of platinum in the catalyst can be improved, the consumption of platinum is reduced, the catalytic activity and stability of platinum elements on the surface layer of the nano particles can be obviously improved under the influences of the appearance, electronic effect and the like of nuclear metal, and the catalyst has high ORR oxygen catalytic performance and good stability.

3. Chinese patent application CN201810607646.4 discloses a preparation method of a supported high-dispersion platinum alloy catalyst for a proton exchange membrane fuel cell, which is obtained by taking a salt solution of Pt and transition metal as a catalyst precursor, taking polyalcohol as a solvent and a weak reducing agent, and adopting a microwave heating mode in the presence of imidazole type ionic liquid. The PtM alloy catalyst prepared by the method has smaller particle size and uniform particle size distribution, has good dispersibility on a carrier, can improve the utilization rate of platinum, reduce the using amount of the platinum, shows higher catalytic activity on oxygen reduction reaction, and can be used as a cathode oxygen reduction (ORR) catalyst of a Proton Exchange Membrane Fuel Cell (PEMFC).

The monatomic catalyst material is currently paid attention to a large number of researchers due to excellent catalytic performance and extremely high atom utilization rate, and the activity of the M-N-C material in an oxygen reduction reaction is comparable to that of a noble metal material, but the stability of the M-N-C material in an acidic condition still has certain challenges. Therefore, in order to develop a proton exchange membrane electrode, it is necessary to develop an oxygen reduction catalyst having a low platinum content, a long life and high stability.

Disclosure of Invention

The invention provides a preparation method and application of a cathode oxygen reduction catalyst with low platinum content to solve the technical problems. The low-platinum-content cathode oxygen reduction catalyst prepared by the method has the Pt content of only 0.08 wt%, the Pt mass activity of the catalyst is 85 times that of commercial Pt/C in the cathode oxygen reduction process of a fuel cell, and the catalyst shows remarkably improved activity and excellent stability for oxygen reduction and has considerable commercial prospect. The preparation method is simple, safe and easy to operate, and the prepared catalyst can be used as a cathode material of a proton exchange membrane fuel cell.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a preparation method of a low platinum content cathode oxygen reduction catalyst comprises the following steps:

(a) dissolving a platinum metal precursor, a transition metal (M) precursor, a nitrogen-containing organic compound and a zinc precursor in anhydrous methanol, uniformly stirring, and marking as a solution A, dissolving dimethyl imidazole in the anhydrous methanol, uniformly stirring, and marking as a solution B;

(b) mixing the solution A and the solution B, uniformly stirring, centrifuging, washing with a solvent, and drying to obtain a precursor product Pt, M-ZIF-8;

(c) and (3) sending the precursor product Pt, M-ZIF-8 into a high-temperature carbonization device for high-temperature carbonization, and then obtaining an atomic-scale dispersion product Pt, M/NC, thus obtaining the low-platinum-content cathode oxygen reduction catalyst for the fuel cell.

Further, in the step (a), the platinum metal precursor is selected from one of potassium chloroplatinate, chloroplatinic acid, platinum nitrate, potassium chloroplatinite, platinum acetylacetonate or sodium chloroplatinate.

Further, in the step (a), the transition metal (M) precursor is selected from one of ferric nitrate, ferric chloride, ferric sulfate, ferric acetylacetonate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate, copper chloride and copper sulfate.

Further, in the step (a), the zinc metal precursor is one of zinc acetate, zinc nitrate and zinc oxide.

Further, in the step (a), the nitrogen-containing organic compound is one of melamine, guanidine salt, dicyandiamide, 1.10 phenanthroline and urea.

Further, in the step (a), the molar ratio of the platinum metal precursor, the transition metal (M) precursor, the zinc precursor and the nitrogen-containing organic compound is (0.5-10): (1-20): 1-20); in the step (a), the molar ratio of the addition amounts of the zinc metal precursor and the dimethyl imidazole is (0.5-2): (4-8); in the step (a), the volume of the methanol is 40-100 mL.

In step (a), the molar ratio of the zinc metal precursor to the dimethylimidazole is (1-2) to (4-6).

Further, in the step (a), the stirring is carried out uniformly for 0.5-1 h.

Further, in the step (b), the stirring time is 1-24 hours, preferably 2 hours; the washing solvent is absolute methanol and is washed for at least three times; the drying condition is vacuum drying: the temperature is 50-60 ℃, the time is 6-12 h, and the vacuum degree is-0.08 to-0.06 MPa.

Further, in the step (c), the temperature of the high-temperature carbonization is controlled to be 500-1200 ℃, the heating rate is 1-10 ℃/min, and the high-temperature carbonization time is 2-5 h.

Further, in the step (c), the high-temperature carbonization is performed under the protection of a protective gas, and the protective gas is one of nitrogen and argon.

Further, the application of the cathode oxygen reduction catalyst with low platinum content prepared by the preparation method in the preparation of proton exchange membrane fuel cells.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

(1) compared with the original commercial Pt/C catalyst, the Pt, M/NC catalyst prepared by the invention has the advantages of obviously improved performance, higher quality activity and stability, high-efficiency proton-charge transmission capability, reinforced electronic structure and the like; the Pt atomic mass content ICP test result is only 0.06 wt%, and the mass activity of the catalyst Pt is 85 times of that of Pt/C in the oxygen reduction reaction process.

(2) The invention adopts a one-step synthesis method, and the synthesis process is simple, safe and easy to operate.

(3) The Pt, M/NC catalyst prepared by the invention is applied to the preparation of the proton exchange membrane fuel cell, and the prepared proton exchange membrane fuel cell has wider application prospect.

Drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some examples of the present invention, and for a person skilled in the art, without inventive step, other drawings can be obtained according to these drawings:

FIG. 1 is a Transmission Electron Microscope (TEM) image of Pt, M/NC prepared in examples 1, 2 and 3 of the present application;

FIG. 2 is an energy spectrum (EDS) chart of Pt, M/NC prepared in example 1 of the present application;

FIG. 3 is an X-ray diffraction (XRD) pattern of a commercial Pt/C catalyst of example 1 of the present application and a commercial Pt/C catalyst of comparative example 1;

FIG. 4 shows the results of the Pt, M/NC catalysts prepared in examples 1, 2 and 3 of the present application and the commercial Pt/C catalyst of comparative example 1 in 0.1M HClO ₄ Comparative LSV test patterns in the mixed solution of (a);

FIG. 5 shows Pt, M/NC catalyst prepared in example 1 of the present application and commercial Pt/C catalyst of comparative example 1 at 0.1MHClO ₄ A comparative graph of chronoamperometry in the mixed solution of (a);

FIG. 6 shows Pt, M/NC catalyst prepared in example 1 of the present application and commercial Pt/C catalyst of comparative example 1 at 0.1MHClO ₄ ADT test in solution comparative figures.

Detailed Description

The following is a detailed description of the embodiments of the present invention, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are included in the scope of the present invention as claimed in the claims.

Example 1

As shown in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5 and fig. 6, a method for preparing a low platinum content cathode oxygen reduction catalyst comprises the following steps:

(a) dissolving platinum acetylacetonate, ferric sulfate, zinc nitrate and melamine in a molar ratio of 1:1:4:3 in 50mL of anhydrous methanol, stirring for 0.5h to uniformly disperse a solid reagent to form a solution A, and mixing the solution A and the zinc nitrate in a molar ratio of 2: dissolving 5 dimethyl imidazole in 50mL of anhydrous methanol, and stirring for 0.5h to uniformly disperse the solid reagent to form a solution B;

(b) mixing the solution A and the solution B, stirring for 6h at room temperature, centrifuging, washing for 4 times by using a methanol solvent, and drying in a vacuum drying oven at 50 ℃ for 12h with the vacuum degree of-0.06 MPa to obtain a precursor product Pt, M-ZIF-8;

(c) and (3) sending the dried precursor product Pt, M-ZIF-8 into a high-temperature carbonization device for high-temperature carbonization, heating to 850 ℃ at the speed of 10 ℃/min under the protection of argon, preserving the temperature for 3 hours, and then obtaining a black atomic-level dispersion product Pt, Fe/NC to obtain the low-platinum-content cathode oxygen reduction catalyst for the fuel cell.

Fig. 1 is a TEM image of Pt, Fe/NC materials prepared in example 1, example 2 and example 3, and it can be seen that there is no obvious metal nanoparticle, which proves the atomic scale dispersion of the prepared material, and at the same time, the carbon substrate can maintain the basic morphology of MOF, which is beneficial to the improvement of the catalytic activity of the material.

FIG. 2 is an EDS diagram of the Pt, Fe/NC material prepared in example 1. The mass fraction of Pt and Fe elements in the material is 0.08:0.2, which can be obtained from an EDS spectrum of the material, and the ultralow loading of Pt is proved.

FIG. 3 is an XRD pattern of the Pt, Fe/NC material prepared in example 1 and the commercial Pt/C catalyst of comparative example 1. Compared with the XRD pattern of Pt/C, no obvious metal peak exists, and the Pt is proved to be on the surface of the carbon carrier with the dispersed atomic-scale grain diameter.

Example 2

As shown in fig. 1, a method for preparing a low platinum content cathode oxygen reduction catalyst comprises the following steps:

dissolving chloroplatinic acid, ferric chloride, zinc nitrate and melamine in a molar ratio of 2:1:6:3 in 50mL of anhydrous methanol to form a solution A, wherein the molar ratio of the chloroplatinic acid to the zinc nitrate is 1: dissolving 3 dimethyl imidazole in 50mL of anhydrous methanol to form a solution B, respectively stirring for 1h to uniformly disperse a solid reagent, mixing the solution A and the solution B, stirring for 6h at room temperature, centrifugally filtering, washing with a solvent, drying for 6h in a vacuum drying oven at 50 ℃, wherein the vacuum degree is-0.07 MPa, heating the dried product to 900 ℃ at the speed of 3 ℃/min under the protection of argon, and preserving heat for 3h to obtain a black product, namely Pt, Fe/NC, thus obtaining the low-platinum-content cathode oxygen reduction catalyst for the fuel cell.

Example 3

dissolving platinum nitrate, ferric sulfate, zinc nitrate and dicyandiamide in a molar ratio of 1:2:10:3 in 50mL of anhydrous methanol to form a solution A, and mixing the solution A and the zinc nitrate in a molar ratio of 1:4, dissolving the dimethyl imidazole in 50mL of anhydrous methanol to form a solution B, stirring for 1h to uniformly disperse a solid reagent, mixing the solution A and the solution B, stirring for 12h at room temperature, centrifugally filtering, washing with a solvent, drying for 12h in a vacuum drying oven at 60 ℃ with the vacuum degree of-0.08 MPa, heating the dried product to 1000 ℃ at the speed of 4 ℃/min under the protection of nitrogen, and preserving heat for 3h to obtain a black product, namely Pt, Fe/NC, thus obtaining the low-platinum-content cathode oxygen reduction catalyst for the fuel cell.

Comparative example 1

As shown in fig. 1, 3, 4, 5, and 6, a commercial catalyst Pt/C with a Pt loading of 20% was purchased from Johnson-matthermy.

To further illustrate that the present invention can achieve the technical effects, the following experiments were performed:

performance testing

The performance of the cathode oxygen reduction catalyst prepared in the examples 1 to 3 and the comparative example 1 of the present application was tested: a three-electrode system was used, in which a glassy carbon electrode having a diameter of 5mm coated with Pt prepared in examples of the present application, M/NC or commercial Pt/C prepared in comparative example 1 was used as a working electrode, an Ag/AgCl electrode was used as a reference electrode, and a platinum sheet (1 cm. times.1 cm) was used as a counter electrode, respectively. The LSV test was performed on the material in 0.1M perchloric acid solution saturated with oxygen, with a potential range of 0.05-1.1V vs. RHE, and the results are shown in FIG. 4. The material was subjected to a chronoamperometric test of 0.7V vs. rhe, 12h, with the results shown in figure 5. The material was subjected to ADT test in 0.1M perchloric acid solution, and the results are shown in fig. 6.

FIG. 4 is a graph comparing LSV tests of Pt, Fe/NC catalyst prepared in example 1 and commercial Pt/C catalyst of comparative example 1 in 0.1M perchloric acid solution. It can be seen that the Pt, Fe/NC catalyst has the same half-wave potential as the commercial Pt/C catalyst compared to the commercial Pt/C catalyst.

FIG. 5 is a comparison of chronoamperometric tests of the Pt, Fe/NC catalyst prepared in example 1 and the commercial Pt/C catalyst of comparative example 1 in a 0.1M perchloric acid solution. It can be seen that after 12h, Pt, Fe/NC still maintained a current density of 54%. Whereas after 12h, only 6% of commercial Pt/C remained, indicating that the Pt, Fe/NC catalyst had excellent stability.

FIG. 6 is a graph comparing ADT testing of Pt, Fe/NC catalyst prepared in example 1 and commercial Pt/C catalyst of comparative example 1 in 0.1M perchloric acid solution. It can be seen that the half-wave potential decreases by only 16mV for Pt, Fe/NC after 8000 ADT tests. And after 8000 ADT tests of commercial Pt/C, the half-wave potential is obviously reduced, which shows that the Pt and Fe/NC catalyst has excellent stability under acidic conditions.

The excellent activity and stability of the Pt, Fe/NC catalyst obtained in example 1 benefits from the synergistic effect of the material composition and structure. The advantages of the structure of the first material include high electrical conductivity, high specific surface area, more points of contact with the carbon support and enhanced atomic interaction not only to promote oxygenProton/charge transfer to the catalyst surface and inhibition of intermediate H ₂ O ₂ And (4) generating. Secondly, the introduction of M atoms greatly improves the electronic structure of Pt atoms, reduces the solubility in acid electrolytes and thus improves the service life of the catalyst.

In summary, the present invention provides a low platinum content cathodic oxygen reduction catalyst: pt, M/NC, the catalyst realizes the atomic-scale dispersion of Pt metal on a carbon carrier, the preparation method is simple, safe and easy to operate, and the catalyst can be used for the cathode oxygen reduction process of a fuel cell and shows remarkably enhanced electrochemical activity and stability. Compared with commercial Pt/C, the Pt, M/NC prepared by the invention has obviously improved electrochemical activity and stability and extremely high Pt metal quality activity to the oxygen reduction reaction under the acidic condition, and can be used as a cathode oxygen reduction catalyst of a proton exchange membrane fuel cell.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A preparation method of a cathode oxygen reduction catalyst with low platinum content is characterized by comprising the following steps:

2. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (a), the platinum metal precursor is selected from one of potassium chloroplatinate, chloroplatinic acid, platinum nitrate, potassium chloroplatinite, platinum acetylacetonate or sodium chloroplatinate.

3. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (a), the transition metal (M) precursor is selected from one of ferric nitrate, ferric chloride, ferric sulfate, ferric acetylacetonate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate, copper nitrate, copper chloride, and copper sulfate.

4. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (a), the zinc metal precursor is selected from one of zinc acetate, zinc nitrate, zinc oxide or zinc chloride.

5. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (a), the nitrogen-containing organic compound is one of melamine, guanidine salt, dicyandiamide, 1.10 phenanthroline and urea.

6. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (a), the molar ratio of the platinum metal precursor to the transition metal (M) precursor to the zinc precursor to the nitrogen-containing organic compound is (0.5-10): 1-20); in the step (a), the molar ratio of the addition amounts of the zinc metal precursor and the dimethyl imidazole is (0.5-2): (4-8).

7. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (b), the stirring time is 1-24 h, preferably 2 h; the washing solvent is absolute methanol and is washed for at least three times; the drying condition is vacuum drying: the temperature is 50-60 ℃, the time is 6-12 h, and the vacuum degree is-0.08 to-0.05 MPa.

8. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (c), the high-temperature carbonization temperature is controlled to be 500-1200 ℃, the heating rate is 1-10 ℃/min, and the high-temperature carbonization time is 2-5 h.

9. The method of claim 1 for preparing a low platinum cathodic oxygen reduction catalyst, wherein: in the step (c), the high-temperature carbonization is carried out under the protection of protective gas, and the protective gas is one of nitrogen, argon and helium.

10. The application of the cathode oxygen reduction catalyst with low platinum content prepared by the preparation method in the preparation of proton exchange membrane fuel cells.