Preparation method and application of rare earth yttrium-based low-Pt alloy catalyst

Abstract

The invention belongs to the field of fuel cell catalysis, and particularly relates to a preparation method and application of a rare earth yttrium-based low-Pt alloy catalyst. The preparation method comprises the following steps: 1) preparing a porous carbon carrier material by adopting a pyrolysis method; 2) loading an active metal component on the carrier material by an impregnation method; and 3) carrying out pyrolysis treatment on the metal-loaded carrier to finally prepare the catalyst. The preparation process is simple, the cost is low, no pollution is caused, the safety coefficient is high, the problem of high raw material price is further solved by reducing the Pt loading capacity, and the catalyst has excellent catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cell catalysis, and specifically relates to a preparation method and application of a rare earth yttrium-based low-Pt alloy catalyst. Background Art

[0002] With the continuous progress and development of society, humanity's demand for energy is increasing dramatically. Coupled with environmental pollution and the dwindling reserves of traditional fossil energy, humanity urgently needs sustainable, green, and clean renewable energy. Proton exchange membrane fuel cells (PEMFCs) have been extensively studied for their high energy density, zero emissions, and safety, and are widely used in transportation, aerospace, and stationary power plants. However, the commercial development of PEMFCs is significantly limited by the activation / cracking of the O-O bond and the removal of the products during the oxygen reduction reaction (ORR) at the cathode.

[0003] Currently, commercial catalysts are mainly based on the presence of precious metal Pt, but due to problems such as high cost and poor stability, they are difficult to meet the requirements of fuel cell use.

[0004] Rare earth metals have also attracted widespread attention due to their unique 4f-layer electronic configuration. Patent CN112510217A discloses a carbon-supported platinum-yttrium catalyst. Platinum acetylacetonate and yttrium acetylacetonate are used as platinum and yttrium sources, respectively. The platinum-yttrium material is obtained through a hydrothermal reaction and then carbon-supported. The resulting material has a low platinum content of 6.0-6.5%. The half-wave potential can reach 0.863V, and the mass activity is 0.09Amg. pt -1 @0.9V, electrochemically active surface area is 43-45m 2 g pt -1 However, the patent has the following shortcomings: the raw materials are organic reagents, which are highly toxic and less safe; the quality and activity of the catalyst are still far from that of commercial Pt / C; and the stability of the catalyst needs to be improved.

[0005] Therefore, alloying Pt with rare earth metals can effectively promote electronic synergy between Pt and rare earth metals, thereby improving electrocatalytic activity and durability. The electron orbital structure of rare earth metals has excellent electron transfer capabilities, which can further accelerate charge transfer during the reaction, reduce electron transfer energy, and promote catalytic reactions. Therefore, rare earth-based materials as catalysts for electrochemical reactions deserve further research. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method and application of a rare earth yttrium-based low-Pt alloy catalyst.

[0007] Based on the unique electronic structure of rare earth metals, the applicant can effectively promote the electronic synergy between Pt and rare earth metals by alloying them, thereby improving the electrocatalytic activity and durability.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0009] A method for preparing a rare earth yttrium-based low-Pt alloy catalyst comprises the following steps: 1) preparing a porous carbon support material by a pyrolysis method; 2) loading an active metal component onto the support material by an impregnation method; and 3) pyrolyzing the metal-loaded support to finally obtain the catalyst.

[0010] Furthermore, the step 1) is specifically as follows: polytetrafluoroethylene, melamine and silicone grease are mixed and ground, pyrolyzed in a tube furnace under a nitrogen atmosphere, and naturally cooled to room temperature to obtain a porous carbon support material.

[0011] Furthermore, the step 2) is specifically as follows:

[0012] (a) dissolving chloroplatinic acid, cupric chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate, and yttrium chloride hexahydrate in deionized water in a molar ratio to prepare a mixed metal salt solution;

[0013] (b) adding the support material to the mixed metal salt solution, ultrasonically treating the solution, and dropwise adding a NaOH solution during the ultrasonic treatment to obtain a post-ultrasonic slurry; vacuum drying the post-ultrasonic slurry, collecting the bottom product, and obtaining a metal-loaded support.

[0014] Furthermore, the polytetrafluoroethylene, melamine and silicone grease are mixed in a weight ratio of 1:1:1, and the pyrolysis conditions are 900° C. for 60 minutes.

[0015] Furthermore, the molar ratio of the chloroplatinic acid, copper chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and yttrium chloride hexahydrate is 0.8:1:1:1:(0.25-1).

[0016] Furthermore, the step 3) is specifically as follows: placing the metal-loaded carrier in a tube furnace, and pyrolyzing it in a hydrogen-argon mixed gas atmosphere at 700° C. for 60 minutes to finally obtain the catalyst.

[0017] Furthermore, the hydrogen-argon mixed gas consists of 5% hydrogen and 95% argon by volume.

[0018] The present invention also provides the use of the rare earth yttrium-based low-Pt alloy catalyst obtained by the above preparation method in fuel cell catalysts.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1) The preparation process of the present invention is simple, environmentally friendly and pollution-free, reduces the amount of Pt used, and greatly saves costs.

[0021] 2) The catalytic performance of the present invention is superior to that of the commercial 40% Pt / C catalyst, with a half-wave potential of 0.897 V and a mass activity of 1.59 A mg pt -1 @0.9V, after 60,000 CV cycles, the half-wave potential loss is only 12mV.

[0022] 3) This invention realizes the alloying of rare earth metals and Pt, further promoting the research of rare earth-based materials as catalysts for electrochemical reactions BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the XRD pattern obtained in Example 1 of the present invention;

[0024] Figure 2 Graphs showing oxygen reduction polarization curves of the catalysts obtained in Examples 1 to 3 of the present invention and commercial 40% Pt / C on a rotating disk electrode;

[0025] Figure 3 The oxygen reduction polarization curve test diagrams of the catalysts obtained in Examples 1, 4 and 5 of the present invention and commercial 40% Pt / C on a rotating disk electrode are shown;

[0026] Figure 4 This is a stability test chart of the catalyst prepared in Example 1 of the present invention;

[0027] Figure 5 This is a mass activity diagram of the catalyst of Example 1 of the present invention and commercial 40% Pt / C at a potential of 0.9V. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and in detail below with reference to the accompanying drawings in the embodiments of the present invention, but this should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1:

[0030] A method for preparing a rare earth yttrium-based low-Pt alloy catalyst comprises the following steps:

[0031] Step 1): polytetrafluoroethylene powder, melamine and silicone grease are fully ground in a mass ratio of 1:1:1, pyrolyzed at 900° C. for 60 minutes in a tube furnace under a nitrogen atmosphere, and naturally cooled to room temperature to obtain a carrier material.

[0032] Step 2): Five metal chlorides, namely chloroplatinic acid, copper chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and yttrium chloride hexahydrate, are added sequentially to 10 ml of deionized water in a molar ratio of 0.8:1:1:1:0.5. 40 mg of the carrier material is weighed and added to the solution. Ultrasonication is performed using an ultrasonic machine for 30 minutes. During the ultrasonication process, 1 to 3 ml of 0.1 mol / L NaOH solution is slowly added dropwise. After the ultrasonication is completed, the mixture is placed in a vacuum drying oven and dried at 60°C for 10-12 hours to obtain the bottom product.

[0033] Step 3): The dried product was pyrolyzed in a tube furnace at 700 ° C in a hydrogen-argon mixed gas atmosphere (hydrogen volume 5%, argon volume 95%) for 60 min to obtain the final product catalyst, named PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -700.

[0034] In order to study the material composition of this embodiment 1, XRD test was carried out. The test results are as follows Figure 1 As shown, the peak at a diffraction angle of 41.7 corresponds to the (111) crystal plane of Pt, while the peak at a diffraction angle of 27.3 corresponds to the successful doping of Y element into the catalyst.

[0035] In order to demonstrate the performance of the present invention, an electrochemical test was performed, and the specific test method is as follows:

[0036] Take 5 mg of prepared PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -700 catalyst was dispersed in 1 mL of 0.25% Nafion / ethanol solution and ultrasonicated for 20 min. 10 μL of the ink solution was dropped onto a glassy carbon electrode. A three-electrode system was used, with an Ag / Agcl electrode as the reference electrode, a platinum wire as the counter electrode, a glassy carbon electrode as the working electrode, and 0.1 mol / L HClO4 as the electrolyte. The initial measured potential relative to Ag / Agcl (saturated KCl) was converted into the potential relative to the reversible hydrogen electrode (E RHE =E Ag / Agcl +0.266V). Before conducting the electrochemical test, O2 or N2 must be continuously introduced into the electrolyte for 40 minutes to saturate the electrolyte with O2 or N2.

[0037] In order to compare with commercial 40% Pt / C, electrochemical testing was also performed on the commercial 40% Pt / C. The test method adopted the Pt / C test method. The steps not specifically explained were the same as the aforementioned test method. The difference was that the electrochemical test of the commercial 40% Pt / C was performed by taking 5uL of the ink solution and applying it to the glassy carbon electrode.

[0038] To further demonstrate the electrochemical performance, linear sweep voltammetry was used to evaluate the oxygen reduction catalytic activity of the catalyst. The test was conducted in an O2-saturated 0.1 mol / L HClO4 solution using a rotating disk electrode, with the speed set at 1600 rpm and the sweep rate set at 10 mV s -1 , the step size is set to 5mV. The test results are as follows Figure 2 As shown, PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 The half-wave potential of the PMS-Pt-700 catalyst is 0.897 V, and the half-wave potential of commercial 40% Pt / C is 0.887 V, so the PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -700 catalyst has good oxygen reduction catalytic activity.

[0039] In order to study the effect of the rare earth metal content on the catalyst performance of the present invention, the proportion of yttrium chloride hexahydrate was adjusted, as shown in Examples 2 and 3:

[0040] Example 2:

[0041] The difference between this example and Example 1 is that in step 2) of Example 1, the molar ratio of yttrium chloride hexahydrate to other metals is changed from 0.5 to 0.25. The other parts are the same as Example 1. The sample is named PMS-Pt 0.8 Fe1Cu1Mn1Y 0.25 -700, the test results are as follows Figure 2 As shown, the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.25 The half-wave potential of -700 is 0.857V.

[0042] Example 3:

[0043] The difference between this example and Example 1 is that in step 2) of Example 1, the molar ratio of yttrium chloride hexahydrate to other metals is changed from 0.5 to 1. The other parts are the same as Example 1. The sample is named PMS-Pt 0.8 Fe1Cu1Mn1Y1-700, test results are as follows Figure 2 As shown, the catalyst PMS-Pt 0.8 The half-wave potential of Fe1Cu1Mn1Y1-700 is 0.882V.

[0044] Examples 2 and 3 show that increasing the content of yttrium chloride hexahydrate appropriately can improve the oxygen reduction half-wave potential of the catalyst. When the molar ratio of yttrium chloride hexahydrate is 0.5, the half-wave potential can reach 0.897 V, indicating good application prospects.

[0045] In order to study the effect of different high-temperature reduction temperatures on catalyst performance, the present invention provides Examples 4 and 5, which are as follows:

[0046] Example 4:

[0047] The difference between this embodiment and embodiment 1 is that the temperature of the tube furnace in step 3) of embodiment 1 is changed from 700°C to 650°C. The other parts are the same as those in embodiment 1, and the sample is named PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -650, the test results are as follows Figure 3 As shown, the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 The half-wave potential of -650 is 0.857V.

[0048] Example 5:

[0049] The difference between this embodiment and embodiment 1 is that the temperature of the tube furnace in step 3) of embodiment 1 is changed from 700°C to 750°C. The other parts are the same as those in embodiment 1, and the sample is named PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -750, the test results are as follows Figure 3 As shown, the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 The half-wave potential of -750 is 0.822V.

[0050] Examples 4 and 5 show that the high-temperature reduction temperature has a significant effect on the oxygen reduction activity of the catalyst. This may be because different temperatures will lead to the formation of different catalytic sites, among which 700°C is a better high-temperature reduction temperature.

[0051] In order to prove that the PMS-Pt prepared in Example 1 0.8 Fe1Cu1Mn1Y 0.5 -700 has good durability, and the accelerated aging test (ADT) was used. The test results are as follows Figure 4 As shown in the figure, after 60,000 CV cycles, its half-wave potential only lost 12 mV. This result shows that the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -700 has very good durability.

[0052] In order to evaluate the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 -700 ORR catalytic activity, for the catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5The mass activities of Pt-700 and commercial 40% Pt / C at 0.9 V were calculated. Figure 5 As shown, PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 The mass activity of -700 is 1.59A / mg Pt The mass activity of commercial 40% Pt / C is 0.12 A / mg Pt , catalyst PMS-Pt 0.8 Fe1Cu1Mn1Y 0.5 The mass activity of -700 is 13.25 times that of commercial 40% Pt / C, thus demonstrating excellent catalytic activity.

[0053] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing a rare earth yttrium-based low-Pt alloy catalyst, characterized in that: The method comprises the following steps: 1) preparing a porous carbon support material by a pyrolysis method; 2) loading an active metal component onto the support material by an impregnation method; and 3) pyrolyzing the metal-loaded support to finally obtain the catalyst.

2. The preparation method according to claim 1, characterized in that The step 1) specifically comprises: mixing and grinding polytetrafluoroethylene, melamine and silicone grease, pyrolyzing them in a tube furnace under a nitrogen atmosphere, and naturally cooling them to room temperature to obtain a porous carbon support material.

3. The preparation method according to claim 1, characterized in that The step 2) is specifically as follows: (a) dissolving chloroplatinic acid, cupric chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate, and yttrium chloride hexahydrate in deionized water in a molar ratio to prepare a mixed metal salt solution; (b) adding the support material to the mixed metal salt solution, ultrasonically treating the solution, and dropwise adding a NaOH solution during the ultrasonic treatment to obtain a post-ultrasonic slurry; vacuum drying the post-ultrasonic slurry, collecting the bottom product, and obtaining a metal-loaded support.

4. The preparation method according to claim 2, wherein: The polytetrafluoroethylene, melamine and silicone grease are mixed in a weight ratio of 1:1:1, and the pyrolysis condition is 900° C. for 60 minutes.

5. The preparation method according to claim 3, wherein: The molar ratio of the chloroplatinic acid, cupric chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and yttrium chloride hexahydrate is 0.8:1:1:1:(0.25-1).

6. The preparation method according to claim 1, wherein: The step 3) specifically comprises placing the metal-loaded carrier in a tube furnace and pyrolyzing it in a hydrogen-argon mixed gas atmosphere at 700° C. for 60 minutes to finally obtain the catalyst.

7. The preparation method according to claim 6, characterized in that: The hydrogen-argon mixed gas consists of 5% hydrogen and 95% argon by volume.

8. Use of the rare earth yttrium-based low-Pt alloy catalyst obtained by the preparation method according to any one of claims 1 to 7 in fuel cell catalysts.

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