阅读说明：本技术 一种碳负载铂钇催化剂及其制备方法和应用 (Carbon-supported platinum yttrium catalyst and preparation method and application thereof ) 是由 彭洪亮 高伟 马姣君 刘思焱 杨会田 黄鹏儒 林向成 徐芬 孙立贤 于 2020-12-16 设计创作，主要内容包括：本发明公开了一种碳负载铂钇催化剂,由乙酰丙酮铂与乙酰丙酮钇作为铂源和钇源,通过水热反应得到铂钇材料,再经过碳负载得到,所得材料具有低铂含量为6.0-6.5%。其制备方法包括以下步骤：1)铂钇材料的制备；2)碳负载铂钇催化剂的制备。作为燃料电池催化剂的应用,半波电位为0.863V,其质量活性为0.09Amg _(pt)~(-1)@0.9V,电化学活性表面积为43-45 m~2g_(pt)~(-1)。本发明整体工艺过程简单,清洁环保,无危险,解决了原料价格高的问题,降低了铂的载量,具有优异的催化性能。(The invention discloses a carbon-loaded platinum yttrium catalyst, which is prepared by taking platinum acetylacetonate and yttrium acetylacetonate as a platinum source and an yttrium source, performing hydrothermal reaction to obtain a platinum yttrium material, and loading carbon to obtain the material with low platinum content of 6.0-6.5%. The preparation method comprises the following steps: 1) preparing a platinum yttrium material; 2) and (3) preparing a carbon-supported platinum yttrium catalyst. The catalyst has a half-wave potential of 0.863V and a mass activity of 0.09Amg pt ‑1 @0.9V, electrochemical active surface area of 43-45 m 2 g pt ‑1 . The invention has simple integral process, cleanness, environmental protection and no danger, solves the problem of high price of raw materials, reduces the loading capacity of platinum and has excellent catalytic performance.)

1. A carbon-supported platinum yttrium catalyst characterized by: platinum acetylacetonate and yttrium acetylacetonate are used as a platinum source and an yttrium source, a platinum yttrium material is obtained through hydrothermal reaction, and the material is obtained through carbon loading, and has low platinum content of 6.0-6.5%.

2. A preparation method of a carbon-supported platinum yttrium catalyst is characterized by comprising the following steps:

step 1) preparing a platinum yttrium material, namely placing acetylacetone platinum and acetylacetone yttrium hydrate in a certain substance amount ratio in N, N-dimethylformamide for stirring and dispersing, and then performing hydrothermal reaction under certain conditions to obtain a platinum yttrium solution containing the platinum yttrium material;

and 2) preparing the carbon-supported platinum yttrium catalyst, namely putting carbon black into the platinum yttrium solution obtained in the step 1, uniformly mixing, and then centrifuging and drying in vacuum to obtain the carbon-supported platinum yttrium catalyst.

3. The method according to claim 3, wherein: step 1 is that the mass ratio of platinum acetylacetonate to yttrium acetylacetonate hydrate is 2: 1.

4. The method according to claim 3, wherein: the reaction temperature of the hydrothermal reaction in the step 1 is 150 ℃, and the reaction time is 12 h.

5. The method according to claim 3, wherein: and 2, uniformly mixing at room temperature for 1-2h, and vacuum drying at 50-60 ℃ for 10-12 h.

6. The application of a carbon-supported platinum yttrium catalyst as a fuel cell catalyst is characterized in that: half-wave potential of 0.863V and mass activity of 0.09Amg_pt ^-1@0.9V, electrochemical active surface area of 43-45 m²g_pt ^-1。

Technical Field

The invention belongs to the field of fuel cell catalysis, and particularly relates to a carbon-loaded platinum yttrium catalyst, and a preparation method and application thereof.

Background

With the global rapid development and the increasing demand for energy, the search for a new energy is imminent, and the fuel cell is widely concerned as a new energy technology with high efficiency, low pollution and low cost. At present, commercial battery catalysts are mainly Pt/C catalysts, are expensive, and hinder the development of large-scale commercialization of proton exchange membrane fuel cells.

The chloroplatinic acid impregnated inside and on the surface of Vulcan XC-72 carbon black is commercially reduced into platinum nanoparticles by a chemical reduction method, and the half-wave potential of the prepared 40% Pt/C catalyst reaches 0.868V. The disadvantage of the materials obtained by the current commercial processes is the low utilization of platinum. Therefore, current research and development focuses on achieving low platinum catalysts.

The basic principle of using carbon-supported platinum as the catalyst is that the utilization rate of platinum is improved by using the carbon-supported platinum-based catalyst, and the catalytic activity equivalent to that of commercial 40% Pt/C is realized. Such a method has the following advantages: 1. has the advantage of environmental protection; 2. low platinum catalysts, which are inexpensive compared to commercial Pt/C catalysts; 3. the carbon-supported platinum-based catalyst has good catalytic activity. Therefore, the preparation of carbon-supported platinum-based catalysts is one of the effective methods for improving proton exchange membrane fuel cells.

The technical scheme adopted for solving the problem of low utilization rate of Pt is that an electrochemical corrosion method is adopted to prepare the PtNi material by using the prior art Tian et al, "Engineering bundled Pt-Ni alloy nanocages for effective oxygen reduction in practical functional cells. Science 2019", the PtNi material is loaded on a commercial industrial carbon carrier, the PtNi loading is 20%, and the quality activity of the obtained catalyst reaches 3.52Amg _pt ^-1@0.9V, is currently commercial P15 times of t/C catalyst. The principle of the technical scheme is that a one-dimensional and hollow string-shaped platinum-nickel nano cage structure is obtained by regulating and controlling the near-surface structure and components of the platinum-based material, and then the platinum-based material is loaded by carbon, so that the platinum-nickel nano cage structure has good catalytic activity. At the same time, the technical scheme has a remarkable technical problem that the adopted electrochemical corrosion method is complex in process flow, and more importantly, the electrochemical corrosion must be realized by etching in 0.5M nitric acid. Wherein, because the high-risk control medicine nitric acid is adopted, the following two problems are directly caused: 1. large-scale preparation is difficult to realize; 2. the requirement for equipment is high and certain danger is caused.

Aiming at the problems brought by the preparation process using nitric acid, the technical scheme provided by International Journal of Electrochemical Science 2016 of Han et al, "Electrodeposited nano PtY Alloy Electrodes with Enhanced Oxygen Reduction reaction", by carrying out electrodeposition in an anhydrous metal salt solution, such as an ionic liquid and an alcohol solution, can successfully prepare the PtY material without using nitric acid, overcomes the technical problems brought by using nitric acid, but the technical scheme still has the following technical problems: the preparation process is that the rotating glassy carbon electrode is used as a base material to carry out electrodeposition in an absolute ethyl alcohol solution. The preparation process causes the problem that the whole technical scheme has overhigh cost and is not suitable for large-scale production. Although the prepared PtY catalysts have the Pt and Y contents of 98.35 percent and 1.65 percent respectively and the half-wave potential of 0.884V, the method also has the problem that the Pt dosage in the obtained PtY catalyst is too high.

According to the research of the applicant, the problem of excessive Pt dosage can be solved by improving the catalytic efficiency of Pt. As can be seen from the d-band center theory described in Norskov et al, Electronic factors determining the reactivity of metal surfaces, Surface Science 1995, the d-band range is generally around the Fermi level, and the 2p orbital and sp bands of oxygen atoms are coupled to form a reforming band; and then coupled with the d energy band to form a final bonding energy band. The anti-bonding energy band is filled with electrons less and is stable in bonding; when the anti-bonding energy band is filled up with electrons, the bonding is unstable. Thus, the d band determines the stability and strength of the adsorption bonds.

Therefore, according to the above theory, this conclusion can be reached: through increasing the electrons filled in the anti-bonding energy band, the d energy band is moved downwards relative to the Fermi energy level, so that the bonding is relatively unstable, and the ORR is effectively improved.

Disclosure of Invention

The invention aims to provide a carbon-supported platinum yttrium catalyst, and a preparation method and application thereof.

According to the d-band center theory, the applicant finds that the addition of Y element can realize the reduction of the Pt metal relative to the Fermi level d-band center energy; the obtained carbon-supported platinum yttrium catalyst has good catalytic activity by combining carbon-supported platinum, wherein the platinum content is as low as 6.4%. Meanwhile, the catalytic performance is almost the same as that of commercial 40% Pt/C, and the catalyst has extremely high economic value.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that:

a carbon-loaded platinum yttrium catalyst is prepared by taking platinum acetylacetonate and yttrium acetylacetonate as a platinum source and an yttrium source, carrying out hydrothermal reaction to obtain a platinum yttrium material, and carrying out carbon loading on the platinum yttrium material to obtain the material with low platinum content of 6.0-6.5%.

A preparation method of a carbon-supported platinum yttrium catalyst comprises the following steps:

step 1) preparing a platinum yttrium material, namely placing acetylacetone platinum and acetylacetone yttrium hydrate in a certain substance amount ratio in N, N-dimethylformamide for stirring and dispersing, and then performing hydrothermal reaction under certain conditions to obtain a platinum yttrium solution containing the platinum yttrium material;

the mass ratio of platinum acetylacetonate to yttrium acetylacetonate hydrate in the step 1 is 2: 1;

the reaction temperature of the hydrothermal reaction in the step 1 is 150 ℃, and the reaction time is 12 hours;

step 2) preparing a carbon-supported platinum yttrium catalyst, namely putting carbon black into the platinum yttrium solution obtained in the step 1, uniformly mixing, and then centrifuging and drying in vacuum to obtain the carbon-supported platinum yttrium catalyst;

and 2, uniformly mixing at room temperature for 1-2h, and vacuum drying at 50-60 ℃ for 10-12 h.

The application of carbon supported platinum yttrium catalyst as fuel cell catalyst has half-wave potential of 0.863V and mass activity of 0.09Amg_pt ^-1@0.9V, electrochemical active surface area of 43-45 m²g_pt ^-1。

The carbon-supported platinum yttrium catalyst obtained by the invention is detected by experiments, and the result is as follows:

XRD tests show that the platinum is single-phase and yttrium element is not detected;

the yttrium element is detected by a transmission electron microscope-EDS experiment;

the elements are uniformly distributed through the detection of a transmission electron microscope experiment;

ICP experiment detection shows that the content of platinum in the prepared carbon-supported platinum yttrium catalyst is 6.4%;

the electrochemical test experiment detects that the prepared carbon-loaded platinum yttrium has excellent catalytic performance, the half-wave potential reaches 0.863V, and the mass activity reaches 0.09A/mg Pt @ 0.9V.

Therefore, compared with the prior art, the invention has the following advantages:

1) the invention is designed to use N, N-dimethylformamide as both a reducing agent and a solvent, and has the advantages of simple integral process, cleanness, environmental protection, low cost and no danger;

2) according to the invention, platinum acetylacetonate and yttrium acetylacetonate are used as raw materials, and the preparation method has mild conditions;

3) has a low platinum content almost the same catalytic performance as commercial 40% Pt/C.

Drawings

FIG. 1 is an XRD pattern of PtY and PtY/C-1 prepared in example 1;

FIG. 2 is a TEM topography and TEM-EDS map of a PtY/C-1 fuel cell catalyst prepared in example 1;

FIG. 3 is a CV diagram comparison of PtY/C-1 fuel cell catalyst prepared in example 1 with commercial 40% Pt/C;

FIG. 4 is a comparative plot of LSV plots for a PtY/C-1 fuel cell catalyst prepared in example 1, commercial 40% Pt/C and PtY;

FIG. 5 is a graph of mass activity of the PtY/C-1 fuel cell catalyst prepared in example 1 and commercial 40% Pt/C at a potential of 0.9V;

FIG. 6 is a comparison of the LSV maps of 3000 turns and PtY/C-1 of the PtY/C-1 fuel cell prepared in example 1;

FIG. 7 is a CV diagram comparing the PtY/C-2 fuel cell catalyst prepared in comparative example 1 with a commercial 40% Pt/C.

FIG. 8 is a comparison graph of LSV plots of PtY/C-2 fuel cell catalysts prepared in comparative example 1 versus commercial 40% Pt/C;

FIG. 9 is a CV diagram comparison of PtY/C-3 fuel cell catalyst prepared in comparative example 2 with commercial 40% Pt/C;

FIG. 10 is a comparison graph of LSV plots of PtY/C-3 fuel cell catalysts prepared in comparative example 2 versus commercial 40% Pt/C;

FIG. 11 is a CV diagram comparing the PtY/C-4 fuel cell catalyst prepared in comparative example 3 with commercial 40% Pt/C.

FIG. 12 is a comparison of LSV plots for the PtY/C-4 fuel cell catalyst prepared in comparative example 3 with commercial 40% Pt/C.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings, which are given by way of examples, but are not intended to limit the present invention.

Example 1

A preparation method of a carbon-supported platinum yttrium catalyst with a hydrothermal reaction temperature of 150 ℃ comprises the following steps:

step 1) preparation of a platinum yttrium material, namely mixing platinum acetylacetonate and yttrium acetylacetonate hydrate according to the mass ratio of 2:1, stirring and dispersing in N, N-dimethylformamide, and then carrying out hydrothermal reaction at 150 ℃ to obtain a platinum yttrium solution containing a platinum yttrium material, namely a PtY material;

in order to confirm the composition of the PtY material obtained, XRD testing was performed. The test results are shown in fig. 1, and show that peaks with diffraction angles of 39.89, 46.40, and 67.71 correspond to face-centered cubic structures (111), (200), and (220) of Pt, and thus, the test results show that the PtY material has single-phase platinum, but no yttrium element is detected.

And 2) preparing the carbon-supported platinum yttrium catalyst, namely adding carbon black into the platinum yttrium solution obtained in the step 1 at room temperature, uniformly stirring, centrifuging, and drying in vacuum to obtain the carbon-supported platinum yttrium catalyst. Is named PtY/C-1.

To confirm the composition of the resulting PtY/C material, XRD testing was performed. As shown in fig. 1, the peaks with diffraction angles of 39.89, 46.40 and 67.71 are the same as those of PtY material, i.e. they correspond to face-centered cubic structures (111), (200) and (220) of Pt, so that the test results show that the PtY material has single-phase platinum, but no yttrium element is detected. In addition, the peak with the diffraction angle of 25 corresponds to a carbon carrier, and XRD results of the PtY material and the PtY/C material show that the PtY material is successfully loaded on the carbon black in the step 2; and Pt is present in the material in the elemental state.

Since the XRD test did not detect Y element, the EDS test was performed to confirm the presence of yttrium element, and the test result is shown in fig. 2, confirming that the PtY/C material contains Y element; the existence form of the Y element in the PtY/C material is amorphous through combined analysis of XRD and EDS test results.

In order to confirm the uniform dispersion of the elements, a TEM test was performed, and the results are shown in fig. 2, and the distribution of the elements in the PtY/C material was uniform by combining the TEM and EDS test results.

In order to prove the performance of the invention, electrochemical tests are carried out, and the specific test method is as follows:

dispersing 5mg of prepared PtY/C-1 in 1mL of 0.25% Nafion/ethanol solution, performing ultrasonic treatment for 20min, dropping 10uL of mixed solution on a glassy carbon electrode, drying under an infrared lamp, performing calibration in a 0.1M HClO4 solution by using a three-electrode electrolytic cell test mode, and performing cyclic voltammetry on the solution at 0.1M-N by using E (RHE) = E (Ag/AgCl) +0.268V₂Saturated HClO₄Tested in solution, the test range is 0.018-1.068V, and the scanning speed is 5mVs^-1The test was carried out under the conditions, the test results are shown in FIG. 3, and it was calculated that the electrochemical active surface area of PtY/C-1 of the present invention was 43.75m²g_pt ^-1。

For comparison with commercial 40% Pt/C, electrochemical testing was performed on commercial 40% Pt/C using the Pt/C test method, with the same steps as the previous test method, except that: a commercial 40% Pt/C electrochemical test was performed by dropping 5uL of the mixed solution onto a glassy carbon electrode. The results of the test are shown in FIG. 3, and the electrochemical active surface area calculated for a commercial 40% Pt/C is 62.19m²g_pt ^-1。

In order to further prove the electrochemical performance, the half-wave potential data is tested by adopting a linear sweep voltammetry method, and the oxygen reduction catalytic activity is evaluated. Specific tests passed PtY/C-1 with commercial 40% Pt/C catalyst at O₂Saturated 0.1M HClO₄Polarization curves in solution using a 1600rpm rotating disk electrode gave test results as shown in figure 4, PtY showed no catalytic activity in the absence of support; the half-wave potential of the PtY/C-1 catalyst was 0.863V, with a similar half-wave potential as commercial 40% Pt/C. Therefore, PtY/C-1 has excellent oxygen reduction catalytic performance.

To evaluate the ORR catalytic activity of PtY/C-1, the mass activities of PtY/C-1 and commercial 40% Pt/C at a voltage of 0.9V were calculated, and the result was shown in FIG. 5 to be 0.09Amg for PtY/C-1_pt ^-140% Pt/C mass activity of 0.037 Amg_pt ^-1PtY/C-1 mass activity was 2.43 times that of commercial 40% Pt/C.

In order to prove that the PtY/C-1 prepared in example 1 has good durability, a cycle test was carried out, the test result is shown in FIG. 6, and the durability test of 3000 cycles proves that the current density is-5.79 mAcm^-2The half-wave potential was 0.793V. The result shows that PtY/C-1 still has good catalytic activity.

To explore the influence of the preparation process, which adopts different carbon addition methods, on the performance, comparative example 1 is provided, specifically, a one-step method is adopted, and carbon loading is performed while synthesizing the PtY material.

Comparative example 1

A preparation method of a carbon-supported platinum yttrium material prepared by a one-step method is the same as the preparation method described in example 1, except that: in the step 1, the carbon black, platinum acetylacetonate and yttrium acetylacetonate hydrate are placed in N, N-dimethylformamide together to be stirred and dispersed, and then hydrothermal reaction is carried out, and the carbon-supported platinum yttrium material can be obtained through centrifugation and vacuum drying, wherein the material obtained without the step 2 is named as PtY/C-2.

In order to demonstrate the performance of the present invention, an electrochemical test was conducted in the same manner as in example 1, and the test results are shown in FIG. 7, in which PtY/C-2 of the present invention had an electrochemically active surface area of 0m²g_pt ^-1。

To further demonstrate the electrochemical performance, the oxygen reduction catalytic activity was evaluated using linear sweep voltammetry to test half-wave potential data, the test method being as in example 1. The test result is shown in FIG. 8, the half-wave potential of the catalyst is 0.818V, the half-wave potential is negatively shifted by 45mV compared with PtY/C-1, and the limiting current density is also obviously reduced.

As can be seen from comparative example 1, the effect of the carbon addition method on the performance was significant.

In order to investigate the effect of the temperature of the hydrothermal reaction on a carbon-supported platinum yttrium catalyst, comparative example 2 and comparative example 3 were provided, and the hydrothermal temperatures were 140 ℃ and 160 ℃ for the carbon-supported platinum yttrium materials, respectively.

Comparative example 2

A preparation method of a carbon-supported platinum yttrium material with a hydrothermal temperature of 140 ℃ is the same as the preparation method described in example 1, except that: the hydrothermal temperature in the step 1) is 140 ℃. The material prepared is denoted PtY/C-3.

In order to demonstrate the performance of the present invention, an electrochemical test was conducted in the same manner as in example 1, and the test results are shown in FIG. 9, in which PtY/C-3 of the present invention had an electrochemically active surface area of 0m²g_pt ^-1。

To further demonstrate the electrochemical performance, the oxygen reduction catalytic activity was evaluated using linear sweep voltammetry to test half-wave potential data, the test method being as in example 1. The test result is shown in FIG. 10, the half-wave potential of the catalyst is 0.688V, the half-wave potential is negatively shifted by 175mV compared with PtY/C-1, and the limiting current density is also obviously reduced.

As can be seen from comparative example 1, the effect of temperature drop on the performance was significant.

Comparative example 3

A preparation method of a carbon-supported platinum yttrium material with a hydrothermal temperature of 160 ℃, wherein the steps which are not particularly described in the specific steps are the same as the preparation method described in the embodiment 1, except that: the hydrothermal temperature of step 1) was changed to 160 ℃. The material prepared is designated PtY/C-4.

In order to demonstrate the performance of the present invention, an electrochemical test was conducted in the same manner as in example 1, and the test results are shown in FIG. 10, in which PtY/C-4 of the present invention had an electrochemically active surface area of 0m²g_pt ^-1。

To further demonstrate the electrochemical performance, the oxygen reduction catalytic activity was evaluated using linear sweep voltammetry to test half-wave potential data, the test method being as in example 1. The test result is shown in FIG. 10, the half-wave potential of the catalyst is 0.803V, the half-wave potential is negatively shifted by 60mV compared with PtY/C-1, and the limiting current density is also obviously reduced.

As can be seen from comparative example 1, the effect on the properties at temperature is significant.

As can be seen from comparative examples 1, 2 and 3, the catalytic performances of the material PtY/C-3 and the material PtY/C-4 are lower than that of the material PtY/C-1, and the remarkable influence on the material under different hydrothermal conditions is proved.

Therefore, the obtained carbon-supported platinum yttrium catalyst can fully exert the electrochemical performance only through the process technology provided by the invention.