Nano-catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nano-catalyst as well as a preparation method and application thereof, and belongs to the technical field of a catalyst for a proton exchange membrane fuel cell (PEMFC) and preparation of the catalyst. The invention solves the problems of limited resources, high price and the like of the existing Pt / C catalyst for the proton exchange membrane fuel cell. The metal organic framework material provided by the invention is doped with Ni in the preparation process, and the doped Ni makes the obtained alloy particles have a polyhedral structure with wrinkles on the surface, can be in good contact with an electrolyte, also has a relatively high specific surface area, has relatively high catalytic activity when being used as a catalyst, and can be used for preparing a catalyst. Therefore, the catalyst also has good catalytic activity and stability when loading low-content Pt. Furthermore, thiourea containing S is also added in the preparation process of the metal organic framework material, and the microstructure of the catalyst is further improved by utilizing S, so that the catalytic activity and the stability of the catalyst are improved.

Description

Technical Field

[0001] The invention relates to a nano catalyst and a preparation method and application thereof, belonging to the technical field of catalysts for proton exchange membrane fuel cells (PEMFC) and preparation thereof. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is a promising energy conversion technology that uses hydrogen and oxygen to generate electricity through electrochemical reactions and is one of the most promising new energy technologies. However, the development of existing PEMFCs is limited by the demand for platinum group metal (PGM) electrocatalysts, especially electrocatalysts in hydrogen oxidation reaction (HOR). In the research of hydrogen oxidation reaction (HOR) catalysts, platinum-based carbon supports (Pt / C) have become the mainstream choice due to their excellent catalytic activity, but they face challenges such as limited resources, high prices, and sensitivity to carbon monoxide. Therefore, it is very necessary to provide a HOR catalyst for proton exchange membrane fuel cells (PEMFCs) that can reduce the use of Pt. Summary of the invention

[0003] In order to solve the problems of limited resources and high price faced by the existing Pt / C catalyst used in proton exchange membrane fuel cells (PEMFC), the present invention provides an electrocatalyst with good electrical conductivity, low cost and good chemical stability.

[0004] The technical solution of the present invention:

[0005] One of the purposes of the present invention is to provide a method for preparing a nanocatalyst, characterized in that it comprises:

[0006] (1) dissolving zinc salt, nickel salt and thiourea in methanol to obtain a metal solution, adding a ligand solution to the metal solution, stirring for reaction, aging, centrifuging to obtain a metal organic framework, drying, grinding and setting aside;

[0007] (2) subjecting the metal organic framework to high temperature calcination to obtain nickel nano alloy particles;

[0008] (3) Adding nickel nano alloy particles to deionized water and chloroplatinic acid solution, stirring, washing, drying and high temperature treatment in sequence, to obtain Pt-loaded nickel nano alloy particles, i.e., nano catalysts.

[0009] It is further defined that the molar ratio of zinc salt, nickel salt, thiourea and ligand in (1) is 20-40:1-3:0-0.05:110-130.

[0010] It is further defined that the molar ratio of the zinc salt to the nickel salt is 25 to 35:1.

[0011] In a further embodiment, the zinc salt is zinc nitrate and the nickel salt is nickel nitrate.

[0012] It is further defined that the ligand in the ligand solution is a 2-methylimidazole solution and the solvent is methanol.

[0013] It is further defined that the molar ratio of zinc nitrate, nickel nitrate and 2-methylimidazole is 20-30:1-2.5:110-120.

[0014] It is further defined that the molar ratio of zinc nitrate, nickel nitrate and 2-methylimidazole is 20-25:1-2:110-115.

[0015] It is further defined that the stirring reaction time in (1) is 5 to 8 hours, and the aging time is 1 to 4 hours.

[0016] It is further defined that the stirring reaction time in (1) is 5 to 7 hours.

[0017] It is further defined that the stirring reaction time in (1) is 6 to 7 hours.

[0018] It is further defined that the aging time in (1) is 1 to 3 hours.

[0019] It is further defined that the aging time in (1) is 1 to 2.5 hours.

[0020] It is further defined that in (1), the zinc salt and the nickel salt are dissolved in methanol by ultrasonic dissolution, and the specific ultrasonic power is 300-2000W and the time is 1-20min.

[0021] It is further limited that the ultrasonic power is 300 to 1800W.

[0022] It is further limited that the ultrasonic power is 500 to 1800W.

[0023] It is further limited that the ultrasonic time is 1 to 15 minutes.

[0024] It is further limited that the ultrasonic time is 5 to 15 minutes.

[0025] It is further defined that (2) the medium-high temperature calcination temperature is 500-1500° C. and the time is 1-5 hours.

[0026] It is further defined that (2) the medium-high temperature calcination temperature is 500-1000°C.

[0027] It is further defined that (2) the medium-high temperature calcination temperature is 700-900°C.

[0028] It is further defined that (2) the medium-high temperature calcination time is 1 to 4 hours.

[0029] It is further defined that (2) the medium-high temperature calcination time is 2 to 3 hours.

[0030] It is further defined that the mass volume ratio of the nickel nano-alloy particles, deionized water and chloroplatinic acid solution in (3) is 1-10 mg: 30-100 ml: 0.05-0.5 ml, wherein the concentration of the chloroplatinic acid solution is 0.01-0.1 mol / L.

[0031] It is further defined that the stirring time in (3) is 1 to 5 hours; the high temperature treatment temperature is 200 to 1000° C., and the time is 1 to 5 hours.

[0032] It is further defined that the stirring time in (3) is 1 to 4 hours.

[0033] It is further defined that the stirring time in (3) is 2 to 3 hours.

[0034] It is further defined that (3) the medium to high temperature treatment temperature is 200 to 800°C.

[0035] It is further defined that the medium-high temperature treatment temperature (3) is 300-700°C.

[0036] It is further defined that (3) the medium to high temperature treatment time is 1 to 4 hours.

[0037] It is further defined that (3) the medium to high temperature treatment time is 1 to 3 hours.

[0038] The second purpose of the present invention is to provide a nanocatalyst prepared by the above method.

[0039] The third object of the present invention is to provide an application of the above-mentioned nanocatalyst, specifically a HOR catalyst for proton exchange membrane fuel cells.

[0040] Beneficial effects of the present invention:

[0041] The metal organic framework material provided by the present invention is doped with Ni during the preparation process, and Ni is used to form a single atom for subsequent catalysis, so that the alloy particles obtained have a polyhedral structure with wrinkles on the surface, which can be well contacted with the electrolyte, and also have a high specific surface area. It has high catalytic activity when used as a catalyst, so it also has good catalytic activity and stability when loaded with a low content of Pt. Further, the present invention also adds thiourea containing S during the preparation process of the metal organic framework material to change the conductivity of the catalyst and the metal electron cloud density.

[0042] The nano catalyst provided by the present invention has high catalytic activity and high stability when applied to a fuel cell. Experimental results show that the nano catalyst exhibits high catalytic activity and stability in a 0.1M HClO4 electrolyte.

[0043] The preparation method of the nanocatalyst provided by the present invention is simple, the raw materials used are all commercial products, and the amount of Pt used is small, which can greatly reduce the cost of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a scanning electron microscope photo of the zif-8 nano alloy particles prepared in Comparative Example 1 (200 nm);

[0045] Figure 2 This is a scanning electron microscope photo of the Ni nano alloy particles prepared in Example 1 (200 nm);

[0046] Figure 3 This is a scanning electron microscope photograph (200 nm) of the Ni-S nano alloy particles prepared in Example 2;

[0047] Figure 4 The XRD spectrum of the zif-8 nano alloy particles prepared in Comparative Example 1;

[0048] Figure 5 The XRD spectrum of the Ni nano alloy particles prepared in Example 1;

[0049] Figure 6 The XRD spectrum of the Ni-S nano alloy particles prepared in Example 2;

[0050] Figure 7 This is the LSV performance diagram of the Pt-loaded zif-8 nano alloy catalyst prepared in comparative example 1 in an acidic electrolyte;

[0051] Figure 8 This is a LSV performance diagram of the Pt-loaded Ni nano-alloy catalyst prepared in Example 1 in an acidic electrolyte;

[0052] Fig. 9 This is the LSV performance diagram of the Pt-loaded Ni-S nano alloy catalyst prepared in Example 2 in an acidic electrolyte. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0055] Comparative Example 1

[0056] The method for preparing the Pt-loaded zif-8 nano alloy catalyst in this comparative example is carried out according to the following steps:

[0057] Step 1: Add 0.3 g of zinc nitrate to 12 ml of methanol solution, place it in a 1000 W ultrasonic machine for 5 min, so that the zinc nitrate is completely dissolved and dispersed in the methanol solution to obtain a metal solution; add 0.08 g of 2-methylimidazole to 12 ml of methanol, place it in a 1000 W ultrasonic machine for 5 min, so that the 2-methylimidazole is completely dissolved and dispersed in the methanol solution to obtain a ligand solution; mix the metal solution and the ligand solution at room temperature (25°C), stir for 6 hours, then settle for 2 hours, centrifuge, and place in a 70°C oven for drying for 12 hours to obtain a metal precursor;

[0058] Step 2: Place the metal precursor into a tube furnace, calcine at 900°C for 3 hours, grind it thoroughly, and pass it through a 300-400 mesh sieve to obtain ZIF-8 nano alloy particles;

[0059] Step 3: Weigh 50 mg of zif-8 nano-alloy particles and dissolve them in 50 ml of water, add 5% chloroplatinic acid solution, stir for 2 hours, filter, dry at 70°C, put them in a tubular furnace and calcine them at 500°C for 2 hours, grind them thoroughly, and pass them through a 300-400 mesh sieve to obtain a Pt-loaded zif-8 nano-alloy catalyst, named Pt-Zn-NC.

[0060] Example 1

[0061] The method for preparing the Pt-loaded Ni nano alloy catalyst in this embodiment is carried out according to the following steps:

[0062] Step 1: add 0.3 g of zinc nitrate and 0.01 g of nickel nitrate to 12 ml of methanol, place it in a 1000 W ultrasonic machine for 5 min, so that the zinc nitrate and nickel nitrate are completely dissolved and dispersed in the methanol solution to obtain a metal solution; add 0.08 g of 2-methylimidazole to 12 ml of methanol, place it in a 1000 W ultrasonic machine for 5 min, so that the 2-methylimidazole is completely dissolved and dispersed in the methanol to obtain a ligand solution; mix the metal solution and the ligand solution at room temperature (25°C), stir for 6 hours, then settle for 2 hours, centrifuge, and place in a 70°C oven for drying for 12 hours to obtain a metal precursor;

[0063] Step 2: placing the metal precursor into a tube furnace, calcining it at 900° C. for 3 h, grinding it thoroughly, and passing it through a 300-400 mesh sieve to obtain Ni nano alloy particles;

[0064] Step 3: Weigh 50 mg of Ni nano-alloy particles and dissolve them in 50 ml of water, add 5% chloroplatinic acid solution, stir for 2 h, filter, dry at 70 ° C, put into a tubular furnace and calcine at 500 ° C for 2 h, grind thoroughly, and pass through a 300-400 mesh sieve to obtain a Pt-loaded Ni nanocatalyst, named Pt-Ni-NC.

[0065] Example 2

[0066] The method for preparing the Pt-loaded Ni nano alloy catalyst in this embodiment is carried out according to the following steps:

[0067] Step 1: add 0.3 g of zinc nitrate, 0.015 g of nickel nitrate and 0.003 g of thiourea to 12 ml of methanol, place it in a 1000 W ultrasonic machine for 8 min, so that the zinc nitrate, nickel nitrate and thiourea are completely dissolved and dispersed in the methanol to obtain a metal solution; add 0.08 g of 2-methylimidazole to 12 ml of methanol, place it in a 1000 W ultrasonic machine for 5 min, so that the 2-methylimidazole is completely dissolved and dispersed in the methanol to obtain a ligand solution; mix the metal solution and the ligand solution at room temperature (25°C), stir for 6 hours, settle for 2 hours, centrifuge, and place in a 70°C oven for drying for 12 hours to obtain a metal precursor;

[0068] Step 2: placing the metal precursor into a tube furnace, calcining it at 900° C. for 3 h, grinding it thoroughly, and passing it through a 300-400 mesh sieve to obtain Ni-S nano alloy particles;

[0069] Step 3: Weigh 50 mg of Ni-S nano alloy particles and dissolve them in 50 ml of water, stir for 2 h, filter, dry at 70 °C, put them in a tubular furnace and calcine them at 500 °C for 2 h, grind them thoroughly to obtain a Pt-loaded Ni-S nano catalyst, named Pt-Ni-SNC.

[0070] Effect example

[0071] (1) The microscopic morphology of the nano alloy particles prepared in Example 1, Example 2 and Comparative Example 1 was characterized. The results are as follows: Figures 1 to 3 As shown. Figure 1 It can be seen that an obvious polyhedral structure appears. Figure 2 It can be seen that the morphology shrinks significantly after adding Ni. Figure 3 It can be seen that the morphology still shrinks and does not change after the introduction of S. Figure 1 and Figure 2 It can be seen that the addition of Ni shrinks the morphology and provides more active sites. Figure 2 and Figure 3 It can be seen that further introduction of S increases the number of active sites.

[0072] (2) Figures 4 to 6 The XRD spectra of the nano alloy particles prepared in Example 1, Example 2 and Comparative Example 1 are shown in FIG. Figure 4 It can be seen that zif-8 is mainly composed of mixed carbon peaks. Figure 5 , Figure 6 It can be seen that there are carbon peaks and Ni peaks of different intensities.

[0073] (3) The performance of the nanocatalysts prepared in Example 1, Example 2 and Comparative Example 1 was characterized. Specifically, in a three-electrode test system, the electrolyte was 0.1M HClO4, the reversible hydrogen electrode was the reference electrode, the platinum sheet was the counter electrode, the potential window was -0.1V to 0.8V, the sweep rate was 5mV / s, and the test was performed at 1600rpm. The LSV performance in an acidic electrolyte is shown in FIG. Figures 7 to 9 As shown. Figure 7 It can be seen that the LSV performance of zif-8 can reach 2.2mA / cm 2 .Depend on Figure 8 It can be seen that the LSV performance of Ni-doped catalyst can reach 2.6 mA / cm 2 , which has faster reaction kinetics than the comparative example. Fig. 9 It can be seen that the LSV performance of the catalyst after the introduction of S can reach 2.8mA / cm 2 . Compared with Pt / C catalyst, the performance is significantly improved.

[0074] The above description is only a preferred embodiment of the present invention. In view of the fact that technicians in the field of the present invention can make appropriate changes and modifications to the above implementation, the present invention is not limited to the specific implementation described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a nanocatalyst, characterized in that: include: (1) dissolving zinc salt, nickel salt and thiourea in methanol to obtain a metal solution, adding a ligand solution to the metal solution, stirring for reaction, aging, centrifuging to obtain a metal organic framework, drying, grinding and setting aside; (2) subjecting the metal organic framework to high temperature calcination to obtain nickel nano alloy particles; (3) Adding nickel nano alloy particles to deionized water and chloroplatinic acid solution, stirring, washing, drying and high temperature treatment in sequence, to obtain Pt-loaded nickel nano alloy particles, i.e., nano catalysts.

2. The method according to claim 1, characterized in that (1) The molar ratio of zinc salt, nickel salt, thiourea and ligand is 20-40:1-3:0-0.05:110-130.

3. The method according to claim 2, characterized in that The molar ratio of zinc salt to nickel salt is 25-35:

1.

4. The method according to claim 1 or 2, characterized in that: The ligand in the ligand solution is 2-methylimidazole solution, and the solvent is methanol.

5. The method according to claim 1, characterized in that: (1) The stirring reaction time is 5 to 8 hours, and the aging time is 1 to 4 hours.

6. The method according to claim 1, characterized in that (2) The medium-high temperature calcination temperature is 500-1500°C and the time is 1-5 hours.

7. The method according to claim 1, characterized in that (3) The mass volume ratio of the nickel nano-alloy particles, deionized water and chloroplatinic acid solution is 1-10 mg: 30-100 ml: 0.05-0.5 ml, wherein the concentration of the chloroplatinic acid solution is 0.01-0.1 mol / L.

8. The method according to claim 1, characterized in that (3) The stirring time is 1 to 5 hours; the high temperature treatment temperature is 200 to 1000°C, and the time is 1 to 5 hours.

9. A nanocatalyst prepared by the method according to any one of claims 1 to 7.

10. Use of the nanocatalyst according to claim 9, characterized in that: HOR catalysts for proton exchange membrane fuel cells.

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