Preparation method and application of nitrogen-doped nanocarbon non-noble metal catalyst

Abstract

The application relates to a preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst, which comprises the following steps: ball-milling a cobalt compound and a cerium compound into powders and uniformly mixing the powders, then adding a solvent to stir into a uniform paste, and adding a carrier and a reinforcing agent under stirring; placing the product obtained in step 1) in a constant-temperature water bath at 60-80 DEG C and ultrasonically stirring, and then standing at room temperature after the stirring is finished; vacuum-filtering the product obtained in step 2), and then baking in a vacuum oven at 100-150 DEG C for 1-3 hours; grinding the product obtained in step 3) into powders; and then placing the powders into a vacuum tube furnace to sinter at 900-1000 DEG C for 1-3 hours, so that the catalyst is obtained. When the catalyst is applied as a positive electrode catalytic layer material of a fuel cell, the discharge performance of the fuel cell can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalyst material preparation, and mainly relates to a preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst and application of the nitrogen-doped nanocarbon non-noble metal catalyst as a positive electrode catalytic layer material of a fuel cell. BACKGROUND

[0002] Energy and environment are two major themes in the development of the world in the 21st century, and efficient and clean use of energy will be the driving force and goal of power generation technology development in the 21st century. Fuel cells, as an efficient and environmentally friendly power generation method, will become the fourth largest power generation system after thermal, hydro and nuclear power generation systems; fuel cell power generation has the advantages of high efficiency, low pollution, low noise and high mobility, and represents a clean energy utilization method with high energy and low consumption, which is very valuable in terms of economy, environment and the like.

[0003] The positive electrode material of a fuel cell is a key in the battery, and the performance thereof is crucial to the overall performance of the battery. Generally, the positive electrode is composed of a catalytic layer, a current collector and a waterproof and air-permeable layer, wherein the catalytic layer mainly provides a place for the electrolyte to react with air, and the catalytic factor in the catalytic layer can improve the activity of the catalytic layer, thereby improving the discharge performance of the battery.

[0004] At present, the best positive electrode catalytic layer material is Pt-C, but Pt is a noble metal and is expensive, so the applicability is not strong. In the present application, Co and Ce are used as non-noble metal elements to form oxides with stable morphology, and after doping, a solid solution is formed, the lattice disorder degree is increased, a large number of oxygen vacancies are generated, the surface oxygen vacancies of the oxide of Ce can capture gaseous oxygen and convert it into active oxygen species, thereby improving the activity of the catalytic layer. SUMMARY

[0005] The present application aims to overcome the defects of the prior art, and provides a nitrogen-doped nanocarbon non-noble metal catalyst and a preparation method thereof, so as to overcome the technical problems of the prior Pt-C catalyst, such as high manufacturing cost, poor applicability, low catalytic activity and poor stability of other conventional catalysts.

[0006] The present application also provides application of the above-mentioned nitrogen-doped nanocarbon non-noble metal catalyst as a positive electrode catalytic layer material of a fuel cell.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst, comprising the following steps:

[0009] 1) Put the cobalt compound and cerium compound in a planetary ball mill jar in a certain proportion, ball mill into powder and mix uniformly, then add solvent to stir into a uniform paste, and then add carrier and reinforcing agent under stirring;

[0010] 2) Put the product obtained in step 1) into a constant temperature water bath at 60-80℃, and ultrasonically stir to make the paste solution enter the pores of the carrier, and then stand at room temperature after the end;

[0011] 3) The product obtained in step 2) is suction filtered, and then baked in a vacuum oven at 100-150℃ for 1-3 hours;

[0012] 4) Put the block product obtained in step 3) into a ball mill to grind into powder, and then put it into a vacuum tube furnace to sinter at 900-1000℃ for 1-3 hours, and then obtain.

[0013] Specifically, in step 1), the cobalt compound can be cobalt acetate and / or cobalt oxide, etc.; and the cerium compound can be cerium acetate and / or cerium oxide, etc.

[0014] Specifically, the reinforcing agent can be melamine, etc.

[0015] Further, the solvent can be anhydrous ethanol, etc.

[0016] Further, the carrier can be one or more of high-porosity activated carbon, multi-walled carbon nanotube, etc.

[0017] Further preferably, in step 1), 250-350g of cobalt compound and 100-180g of cerium compound are ball milled into powder and mixed uniformly by a planetary ball mill, then an appropriate amount of solvent is added to stir into a uniform paste, and then 20-66g of carrier and 320-410g of reinforcing agent are added under stirring.

[0018] Specifically, in step 2), ultrasonic stirring can be performed for 1-2h, and then stand at room temperature for 1-3h after the end.

[0019] Specifically, in step 4), the product obtained in step 3) is ground into a powder with a particle size not less than 300 mesh. Further, the block product of step 3) can be put into a ball mill to grind into powder, and then screened by an ultrasonic powder screener, and the fine powder screened out is directly subjected to the next step, and the coarse particles are subjected to re-ball milling and screening to ensure that the powder particle size is not less than 300 mesh.

[0020] The application provides a nitrogen-doped nanocarbon non-noble metal catalyst prepared by the above method.

[0021] The application also provides an application of the above nitrogen-doped nanocarbon non-noble metal catalyst as a positive electrode catalytic layer material of a fuel cell.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The present application uses non-noble metal cobalt (Co) and cerium (Ce) as the matrix, which not only saves the cost, but also the oxides of the two are stable in shape and the crystal lattice shape is not easy to deform; the enhancer melamine contains N element, which can form C3N4 structure under high temperature conditions, the structure has excellent chemical inertness, high specific surface area and rich nano multi-level structure, which further speeds up the carrier into the solution and significantly improves the stability of the catalyst; the active carbon and multi-walled carbon nanotube with high porosity are used as the carrier, not only because of the good multi-layer nano structure, but also because of the good electrical conductivity, and at the same time, the metal oxide can be combined with the metal oxide, and the metal oxide can also be attached to the surface, which can further improve the electrical conductivity of the catalyst. When the catalyst of the present application is used as the positive electrode catalytic layer material of the fuel cell, the discharge performance of the fuel cell can be significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The electrochemical curve of the catalyst of Example 1 is shown in the following figure;

[0025] Figure 2 The electrochemical curve of the catalyst of Comparative Example 1 is shown in the following figure;

[0026] Figure 3 The electrochemical curve of the catalyst of Example 1 after accelerated aging is shown in the following figure;

[0027] Figure 4 The electrochemical curve of the catalyst of Comparative Example 1 after accelerated aging is shown in the following figure;

[0028] Figure 5 The first day discharge curve of the battery assembled with different catalysts is shown in the following figure;

[0029] Figure 6 The second day discharge curve of the battery assembled with different catalysts is shown in the following figure;

[0030] Figure 7 The discharge data of the battery assembled with different catalysts is shown in the following table. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are further described in detail below in combination with examples, but the protection scope of the present application is not limited thereto.

[0032] In the following examples, the raw materials used are ordinary commercially available products that can be directly purchased, or can be prepared by conventional methods in the art. For example, the multi-walled carbon nanotube is purchased from GH-25001 product of Qihang Technology.

[0033] Room temperature refers to 25±5℃.

[0034] Example 1

[0035] A preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst (the mass ratio of each raw material of the catalyst is shown in Table 1 below) includes the following steps:

[0036] Table 1. Ratio of each raw material of the catalyst (mass ratio)

[0037]

[0038] Step 1, according to the above ratio, each raw material is weighed;

[0039] Step 2, the above weighed cobalt acetate and cerium acetate are put into a ball mill jar, and a planetary ball mill is used for ball milling for 1 h, and then anhydrous ethanol is added to form a uniform paste;

[0040] Step 3, the multi-walled carbon nanotubes weighed in step 1 are added to the paste obtained in step 2, and the multi-walled carbon nanotubes should be added gradually and not all at once, and stirring should be accompanied during the addition;

[0041] Step 4, the mixture obtained in step 3 is stirred, and then melamine powder is added, and stirring is performed at any time during the addition, and attention should be paid to the morphology of the mixture at all times during the stirring, and if agglomeration occurs, it should be treated in time (the agglomerates are selected and placed in a beaker, and a small amount of anhydrous ethanol is added for stirring, and complete dissolution can be achieved);

[0042] Step 5, the mixture obtained in step 4 is placed in a constant-temperature water bath, the temperature of the water bath is maintained at about 70°C, and ultrasonic stirring is performed for 1 h to make the solution fully enter the pores of the multi-walled carbon nanotubes, and after the end, it is left to stand at room temperature for 2 h;

[0043] Step 6, the solution in the product of step 5 is filtered and drained, and then placed in a vacuum oven at about 125°C for 2 hours;

[0044] Step 7, the blocky product after drying in step 6 is placed in a ball mill to grind into a powder, and an ultrasonic powder sieve machine is used for sieving, and the fine particles sieved out are directly subjected to the next step, and the coarse particles are subjected to ball milling and sieving again to ensure that the particle size of the powder is not less than 300 mesh;

[0045] Step 8, the fine powder sieved out in step 7 is placed in a vacuum tube furnace and sintered at 950°C for 2 hours;

[0046] Step 9, after sintering is completed, it can be taken out.

[0047] The method of the present application only aims at the problems of expensive Pt-C catalyst, poor applicability, low catalytic activity and poor stability of conventional catalysts, and the catalyst prepared by the method can better improve the catalytic activity of conventional catalysts.

[0048] Example 2

[0049] A preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst, the mass ratio of each raw material of the catalyst is shown in Table 2 below, and the specific preparation steps can refer to Example 1.

[0050] Table 2 Mass ratio of each raw material of the catalyst

[0051]

[0052] Example 3

[0053] A preparation method of a nitrogen-doped nanocarbon non-noble metal catalyst, the mass ratio of each raw material of the catalyst is shown in Table 3 below, and the specific preparation steps can refer to Example 1.

[0054] Table 3 Mass ratio of each raw material of the catalyst

[0055]

[0056] Comparative Example 1

[0057] A preparation method of a catalyst (the mass ratio of each raw material of the catalyst is shown in Table 4 below), which comprises the following steps: the difference between the present comparative example and Example 1 is that no reinforcing agent melamine is added;

[0058] Table 4 Mass ratio of each raw material of the catalyst

[0059]

[0060] Step 1, the required each raw material is weighed according to the above ratio respectively;

[0061] Step 2, the above weighed cobalt acetate and cerium acetate are put into a ball mill jar, and are ball milled for 1h by using a planetary ball mill, and then anhydrous ethanol is added, and the mixture is stirred into a uniform paste;

[0062] Step 3, the weighed multi-walled carbon nanotubes in Step 1 are added to the paste obtained in Step 2, and the multi-walled carbon nanotubes should be added gradually and not at one time, and stirring should be accompanied during the adding process;

[0063] Step 4, the mixture obtained in Step 3 is placed in a constant-temperature water bath, the temperature of the water bath is kept at about 70℃, and ultrasonic stirring is carried out for 1h to make the solution enter the pores of the multi-walled carbon nanotubes, and after the end, the solution is left to stand at room temperature for 2h;

[0064] Step 5, the solution in the product of step 4 is filtered and drained, and placed in a vacuum oven at 125°C for 2 hours;

[0065] Step 6, the block product after drying in step 5 is ground into powder in a ball mill, and sieved with an ultrasonic powder sieve machine. The fine particles sieved out are directly subjected to the next step, and the coarse particles are subjected to ball milling and sieving again to ensure that the powder particle size is not less than 300 mesh;

[0066] Step 7, the fine powder sieved out in step 6 is placed in a vacuum tube furnace and sintered at 950°C for 2 hours;

[0067] Step 8, after sintering, it can be taken out.

[0068] Catalytic activity test

[0069] The catalysts prepared in Example 1 and Comparative Example 1 were subjected to catalytic activity test by using a rotating disc electrode tester, and the specific test method was as follows:

[0070] 1) The electrolyte was prepared by weighing 1 g of NaOH solid and adding 250 mL of deionized water, stirring until the NaOH solid was completely dissolved, and then passing oxygen into the electrolyte;

[0071] Table 5 Test reagent ratio table

[0072]

[0073] 2) The reagents were prepared according to the above table to complete the measured sample, and then ultrasonic treatment was performed for 30 min;

[0074] 3) The potassium ferricyanide solution was used as the electrolyte, and the electrode was calibrated by cyclic voltammetry (CV) to make the potential difference of the double peaks in the CV curve within 80 mV as much as possible;

[0075] 4) The sample reagent prepared in step 2) was dropped on the surface of the electrode and dried;

[0076] 5) The test was performed by connecting the circuit. First, the CV mode was used for activation, the interval was 0.2- -0.8V, the scan rate was 0.1V / s, and the scanning was 100 times. Then, the LSV mode test was performed at different rotation speeds, the test interval was 0.2- -0.8V, and the scanning rate was 0.005V / s;

[0077] 6) The electrochemical test data at 1600 rad / min rotation speed were selected for comparison, and the comparison results were as follows.

[0078] Table 6 ORR test results of different catalysts

[0079]

[0080] Through the above Table 6 and Figure 1 , 2 Data comparison shows that, compared to Comparative Example 1 without the added reinforcing agent melamine, the catalyst in this embodiment of the invention has a higher limiting current density of 4.757 mA / cm². 2 With an initial potential of 0.977V and a half-wave potential of 0.801V, it exhibits better catalytic activity.

[0081] Taking into account the catalyst's operating temperature, accelerated aging tests were conducted according to the methods specified in GB / T 24135 2009 and GJB 899A-2009, with the specific implementation details as follows:

[0082] 1) Place the catalyst in an aging test chamber, and set the temperature of the chamber to 150-200℃;

[0083] 2) Continuous aging for 15 days;

[0084] 3) Remove the catalyst, cool it down at room temperature, and observe the surface condition of the catalyst;

[0085] 4) Conduct catalyst activity tests again.

[0086] Table 7 ORR test results after accelerated aging with different catalysts.

[0087]

[0088] Based on the table above and Figure 3 , 4 The test results show that after accelerated aging tests, the catalytic activity of the catalysts in the examples and comparative example 1 is still far superior to that in comparative example 1, and comparable to that of the catalysts without aging tests; indicating that the addition of C3N4 increases the stability of the catalysts.

[0089] Comparative Example 2

[0090] A method for preparing a catalyst (the mass ratio of each raw material for the catalyst is shown in Table 8 below) includes the following steps: The difference between this comparative example and Example 1 is that no multi-walled carbon nanotube support was added;

[0091] Table 8. Proportions of raw materials for the catalyst (mass ratio)

[0092]

[0093] Step 1: Weigh out the required raw materials according to the above proportions;

[0094] Step 2, the weighed cobalt acetate and cerium acetate are put into a ball mill tank, and are ball milled for 1 h by a planetary ball mill to form a powder and mix uniformly, then anhydrous ethanol is added to form a uniform paste;

[0095] Step 3, the weighed melamine in Step 1 is added to the paste obtained in Step 2, and is added gradually, and stirring should be accompanied during the adding process;

[0096] Step 4, the mixture obtained in Step 3 is placed in a constant temperature water bath, the temperature of the water bath is kept at about 70℃, and is ultrasonically stirred for 1 h, and after the end, is left to stand at room temperature for 2 h;

[0097] Step 5, the solution in the product of Step 4 is filtered and drained, and is placed in a vacuum oven and baked at about 125℃ for 2 h;

[0098] Step 6, the block product after baking in Step 5 is ground into a powder by a ball mill, and is screened by an ultrasonic powder screening machine, the fine particles screened out are directly subjected to the next step, and the coarse particles are subjected to ball milling and screening again, so as to ensure that the particle size of the powder is not less than 300 mesh;

[0099] Step 7, the fine powder screened out in Step 6 is placed in a vacuum tube furnace and sintered at 950℃ for 2 h;

[0100] Step 8, after sintering, it can be taken out.

[0101] Battery test experiment

[0102] The catalysts of Example 1 and Comparative Examples 1 and 2 are prepared into films, and are respectively combined with a waterproof and air-permeable layer and a current collector by rolling to form air electrodes, the air electrodes are bonded on a substrate frame, an aluminum electrode is placed in the substrate frame, an electrolyte is added, and a battery monomer is assembled, then a battery unit is assembled from each monomer, a battery discharge experiment is carried out, and the discharge voltage is used to measure the advantages and disadvantages, and the specific experiment is as follows:

[0103] 1) Each of the two battery units is composed of 5 battery monomers;

[0104] 2) The two battery units are under the condition of constant temperature T=25±5℃;

[0105] 3) The same type and size of direct current electronic load is used, and constant current I=20A is discharged; and the results are shown in Tables Figure 5 、 6 and 7:

[0106] It can be seen from the results of Figures 5 to 7 that, compared with the comparative examples, the discharge voltage of the catalyst of the example in the battery working process is the highest, and the stability and durability are also the best.

[0107] In conclusion, the catalyst prepared by the application has high catalytic activity, good stability and low cost, and is suitable for fuel cell anode materials.

Claims

1. Use of a nitrogen-doped nanocarbon non-noble metal catalyst as a positive electrode catalyst layer material for a fuel cell, characterized in that, The nitrogen-doped nanocarbon non-noble metal catalyst is prepared by the following steps: 1) a cobalt compound and a cerium compound are ball milled into a powder and uniformly mixed, then a solvent is added to stir into a uniform paste, and a carrier and a reinforcing agent are added under stirring; 2) the product obtained in step 1) is placed in a constant temperature water bath at 60-80°C and ultrasonically stirred, and after the end, it is left to stand at room temperature; 3) the product obtained in step 2) is suction filtered, and then baked in a vacuum oven at 100-150°C for 1-3 hours; 4) the product obtained in step 3) is ground into a powder; then it is put into a vacuum tube furnace and sintered at 900-1000°C for 1-3 hours, and thus the nitrogen-doped nanocarbon non-noble metal catalyst is obtained; in step 1), the cobalt compound is cobalt acetate and / or cobalt oxide; the cerium compound is cerium acetate and / or cerium oxide; the reinforcing agent is melamine; the carrier is one or more of activated carbon and multi-walled carbon nanotubes.

2. The use of the nitrogen-doped nanocarbon non-noble metal catalyst according to claim 1, wherein the solvent is anhydrous ethanol.

3. The application of the nitrogen-doped nano-carbon non-noble metal catalyst as described in claim 1, characterized in that, in step 1), 250-350g of the cobalt compound and 100-180g of the cerium compound are ball milled into a powder and uniformly mixed by using a planetary ball mill, then an appropriate amount of the solvent is added to stir into a uniform paste, and 20-66g of the carrier and 320-410g of the reinforcing agent are added under stirring.

4. The use of the nitrogen-doped nanocarbon non-noble metal catalyst according to claim 1, wherein in step 2), the ultrasonic stirring is performed for 1-2h, and after the end, it is left to stand at room temperature for 1-3h.

5. The use of the nitrogen-doped nanocarbon non-noble metal catalyst according to claim 1, wherein the non-noble metal catalyst is selected from the group consisting of transition metals, lanthanides, and actinides. in step 4), the product obtained in step 3) is ground into a powder with a particle size not less than 300 mesh.

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