Preparation method of oxygen evolution and hydrogen evolution bifunctional catalyst carrier

Abstract

The invention discloses a preparation method of an oxygen and hydrogen evolution bifunctional catalyst carrier, and belongs to the technical field of electrocatalytic water splitting hydrogen production catalyst carriers, and the preparation method comprises the following steps: adding cobalt nitrate, lanthanum nitrate and nitric acid M into methanol to completely dissolve to form a solution A; 2-methylimidazole is added into methyl alcohol to be completely dissolved, and a solution B is formed; pouring the solution A into the solution B to obtain a precipitate; carrying out ball milling and sintering on the precipitate to obtain an oxygen evolution and hydrogen evolution bifunctional catalyst carrier; the carrier is subsequently loaded with noble metal / non-noble metal, so that the noble metal / non-noble metal can be effectively anchored and dispersed, the overall activity and stability of the catalyst are enhanced, and meanwhile, the bifunctional catalyst carrier can be synergistically catalyzed with the subsequently loaded noble metal, so that the overall activity of the catalyst is further improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution, and belongs to the field of electrocatalytic water splitting hydrogen production catalysts. Background Art

[0002] At present, the main oxygen evolution catalyst used in industry is IrO2, and the hydrogen evolution catalyst is Pt / C. The academic and industrial circles have conducted extensive research on the development of single-function catalysts and have achieved many results. The research and development of a small number of bifunctional catalysts for oxygen and hydrogen evolution is mainly concentrated in the field of Ir and Pt precious metal catalysts.

[0003] However, the reserves of Ir and Pt on Earth are relatively small, and the use of pure precious metals of Ir and Pt will make the cost of hydrogen production by water splitting extremely high, thus limiting its large-scale application. In addition, the activity and stability of existing bifunctional catalysts cannot meet the requirements of industrial application fields. Therefore, the technical problem to be solved by the present invention is to explore a method that is conducive to reducing the precious metal loading of bifunctional catalysts while improving the activity and stability of the catalyst.

[0004] Purpose of the Invention

[0005] Based on the above problems, the first object of the present invention is to propose a method for preparing a bifunctional catalyst carrier that can effectively reduce the loading amount of precious metals.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution comprises the following steps:

[0008] (1) Preparation of Co-MOF precursor:

[0009] Cobalt nitrate, lanthanum nitrate and nitric acid M are added to methanol and completely dissolved to form liquid A; 2-methylimidazole is added to methanol and completely dissolved to form liquid B; liquid A is poured into liquid B, mixed thoroughly and allowed to stand for 1-48 hours; the mixed liquid after standing is centrifuged and washed to obtain a precipitate;

[0010] (2) Ball milling of Co-MOF precursor:

[0011] The precipitate obtained in step (1) is ball-milled at a speed of 200-600 rpm for a time of 10-240 min;

[0012] (3) Sintering:

[0013] The powder obtained by ball milling in step (1) is calcined in an air atmosphere or an argon atmosphere to obtain a bifunctional catalyst carrier for oxygen and hydrogen evolution.

[0014] Further settings are:

[0015] In step (1):

[0016] The nitric acid M is selected from nickel nitrate, or any one of lithium nitrate, iron nitrate, manganese nitrate, cerium nitrate, zinc nitrate, copper nitrate, and phosphomolybdic acid.

[0017] The molar ratio of cobalt nitrate to lanthanum nitrate is maintained at 7:1-4:1; the molar ratio of cobalt nitrate to nitric acid M is maintained at 15:1-4:1; and the molar ratio of cobalt nitrate to 2-methylimidazole is maintained at 20:1-4:1.

[0018] The mixed liquid after standing is centrifuged and then washed with methanol or ethanol to obtain a precipitate.

[0019] In step (2):

[0020] The ball milling speed is 600 rpm and the ball milling time is 60 min.

[0021] In step (3):

[0022] The sintering is carried out in an argon atmosphere at 400-650° C. for 0.5-6 hours.

[0023] Alternatively, the calcination may be carried out at 300-450°C in an air atmosphere for 2-8 hours.

[0024] The bifunctional catalyst carrier for oxygen and hydrogen evolution prepared by the present invention can be used to load precious metals or non-precious metals. The carrier is subsequently loaded with precious metals / non-precious metals, which can effectively anchor and disperse the precious metals / non-precious metals, thereby enhancing the activity and stability of the catalyst as a whole. At the same time, the bifunctional catalyst carrier can cooperate with the subsequently loaded precious metals to further enhance the activity of the catalyst as a whole.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention first prepares a Co-MOF precursor, and utilizes the characteristic of Co-MOF being easy to dope, and successfully dopes metal atoms such as lanthanum, nickel, lithium, iron, manganese, cerium, zinc, copper, and molybdenum into MOF. Then, the organic skeleton in the MOF precursor is burned off, and a doped cobalt tetroxide carrier with a high specific surface area can be prepared. The carrier has a large specific surface area, and the precious metal / non-precious metal can be effectively dispersed later. The carrier contains doping elements, which can regulate the electronic state of the precious metal. And the carrier itself has the dual-functional catalytic activity of oxygen and hydrogen evolution, and can play a synergistic catalytic role with the precious metal / non-precious metal. The above characteristics can enable the carrier to reduce the precious metal loading and optimize the effect of catalyst activity and stability. Therefore, the carrier is a dual-functional catalyst carrier with great application potential.

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a TEM image of the bifunctional catalyst support for oxygen and hydrogen evolution prepared in Example.

[0029] Figure 2 TEM image of the Co-MOF precursor doped with Ce and La prepared in Example.

[0030] Figure 3 This is the anode OER activity test curve of Application Example 1.

[0031] Figure 4 This is the cathode OER activity test curve of Application Example 1. DETAILED DESCRIPTION

[0032] Example 1: Preparation of a bifunctional catalyst support for oxygen and hydrogen evolution

[0033] (1) Preparation of Co-MOF precursor: Add 6g of cobalt nitrate, lanthanum nitrate, and cerium nitrate into 150ml of methanol and dissolve them completely to form liquid A. Add 2-methylimidazole into 400ml of methanol and dissolve them completely to form liquid B. Pour liquid A into liquid B while stirring liquid B, and let liquid AB stand for 12 hours after they are fully mixed. The molar ratio of cobalt nitrate to lanthanum nitrate is maintained at 5:1, and the molar ratio of cobalt nitrate to cerium nitrate is maintained at 4:1. The molar ratio of cobalt nitrate to 2-methylimidazole is maintained at 10:1. After the mixed liquid has been fully allowed to stand, centrifuge it and wash it with methanol to obtain a precipitate.

[0034] (2) Ball milling of Co-MOF precursor: The precipitate obtained in step (1) was ball milled at a speed of 600 rpm for 60 min.

[0035] (3) Sintering: The ball-milled powder was directly sintered at 330 °C for 6 h in air to prepare a bifunctional oxygen and hydrogen evolution catalyst carrier labeled LN-Co3O4.

[0036] Structure confirmation:

[0037] Figure 1 This is a TEM image of a bifunctional catalyst carrier prepared in an embodiment of the present invention. It can be seen that there are many pore structures in the bifunctional catalyst carrier, which are beneficial to increase the specific surface area and facilitate the loading of precious metals / non-precious metals.

[0038] Figure 2 TEM images of Co-MOF precursors doped with Ce and La, demonstrating that the mentioned doping elements can be successfully doped.

[0039] Application Example 1

[0040] 40 mg of iridium trichloride (IrCl3), 40 mg of acetylacetonate platinum Pt(acac)2, 3 g of terephthalaldehyde or glyoxal and 1.5 g of citric acid were added to 70 ml of benzyl alcohol, and a uniform mixed solution was formed after sufficient ultrasonication and stirring. 100 mg of the carrier LN-Co3O4 prepared in the above embodiment was added to the mixed solution and ultrasonicated and stirred to obtain a uniform suspension. The suspension was heated to 200°C while stirring and kept warm for 6 h. After cooling, the suspension was centrifuged to obtain a precipitate and washed with ethanol or acetone. The precipitate was vacuum dried or freeze-dried for 48 h. After drying, it was sintered in an air atmosphere at 380 degrees Celsius for 4 h to obtain a bifunctional catalyst.

[0041] The bifunctional catalyst for oxygen and hydrogen evolution loaded with precious metals Ir and Pt on the carrier of the present invention was tested to examine the loading performance of the carrier prepared by the present invention. The test method is as follows: using a rotating disk electrode as a working electrode, a gold electrode as a counter electrode, a mercury / mercurous sulfate electrode as a reference electrode, and 0.1M HClO4 as an electrolyte, the intrinsic electrochemical activity of the material is tested under a typical three-electrode system; under the same system, the intrinsic electrochemical stability of the system is tested at a current density of ±10mA / cm2.

[0042] Test results:

[0043] like Figure 3 As shown, after the carrier of the present invention is loaded with precious metals Ir and Pt, the catalyst is tested for anodic oxygen evolution reaction activity at 10 mA / cm2. The overpotential at 10 mA / cm2 is 285 mV, which proves that the bifunctional catalyst prepared by the present invention has good oxygen evolution reaction performance. Figure 4 The cathode hydrogen evolution reaction test data of the catalyst at -10 mA / cm2 is shown. The overpotential of the hydrogen evolution reaction at -10 mA / cm2 is 65 mV, which proves that the bifunctional catalyst loaded with Ir and Pt prepared by the present invention has good hydrogen evolution performance.

[0044] Application Example 2

[0045] Add 40 mg of cobalt acetate, 40 mg of acetylacetonate platinum Pt(acac)2, and 1.5 g of citric acid to 20 ml of oleylamine, and form a uniform mixed solution after sufficient ultrasonication and stirring. Add 100 mg of carrier LN-Co3O4 to the mixed solution, and then ultrasonicate and stir to obtain a uniform suspension. Heat the suspension to 250°C while stirring for 6 hours, and after cooling, centrifuge the suspension to obtain a precipitate and wash it with ethanol or acetone. Vacuum dry or freeze-dry the precipitate for 48 hours. After drying, sinter at 400 degrees Celsius in an air atmosphere for 4 hours to obtain a bifunctional catalyst.

[0046] The bifunctional catalyst for oxygen and hydrogen evolution loaded with Co and Pt on the carrier of the present invention was tested to examine the loading performance of the carrier prepared by the present invention. The test method is as follows: using a rotating disk electrode as a working electrode, a gold electrode as a counter electrode, a mercury / mercurous sulfate electrode as a reference electrode, and 0.1M HClO4 as an electrolyte, the intrinsic electrochemical activity of the material is tested under a typical three-electrode system; under the same system, the intrinsic electrochemical stability of the system is tested at a current density of ±10mA / cm2.

[0047] After testing, the oxygen evolution overpotential of the bifunctional catalyst for oxygen and hydrogen evolution loaded with Co and Pt is 350 mV at 10 mA / cm2, and the hydrogen evolution reaction overpotential is 90 mV at -10 mA / cm2, which proves that the carrier prepared by the present invention still has good catalytic performance for the bifunctional catalyst loaded with precious metal / non-precious metal.

Claims

1. A method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution, characterized in that: The following steps are involved: (1) Preparation of Co-MOF precursor: Cobalt nitrate, lanthanum nitrate and nitric acid M are added to methanol and completely dissolved to form liquid A; 2-methylimidazole is added to methanol and completely dissolved to form liquid B; liquid A is poured into liquid B, mixed thoroughly and allowed to stand for 1-48 hours; the mixed liquid after standing is centrifuged and washed to obtain a precipitate; (2) Ball milling of Co-MOF precursor: The precipitate obtained in step (1) is ball-milled at a speed of 200-600 rpm for a time of 10-240 min; (3) Sintering: The powder obtained by ball milling in step (1) is calcined in an air atmosphere or an argon atmosphere to obtain a bifunctional catalyst carrier for oxygen and hydrogen evolution.

2. The method for preparing a bifunctional catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (1), the nitric acid M is selected from any one of nickel nitrate, lithium nitrate, iron nitrate, manganese nitrate, cerium nitrate, zinc nitrate, copper nitrate and phosphomolybdic acid.

3. The method for preparing a bifunctional catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (1): the molar ratio of cobalt nitrate to lanthanum nitrate is maintained at 7:1-4:

1.

4. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (1): the molar ratio of cobalt nitrate to nitric acid M is maintained at 15:1-4:

1.

5. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (1), the molar ratio of cobalt nitrate to 2-methylimidazole is maintained at 20:1-4:

1.

6. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (1): the mixed liquid after standing is centrifuged and then washed with methanol or ethanol to obtain a precipitate.

7. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (2), the ball milling speed is 600 rpm and the ball milling time is 60 min.

8. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (3): the sintering is carried out in an argon atmosphere at 400-650°C for 0.5-6h.

9. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: In step (3): the sintering is carried out in an air atmosphere at 300-450°C for 2-8 hours.

10. The method for preparing a dual-function catalyst carrier for oxygen and hydrogen evolution according to claim 1, characterized in that: The oxygen and hydrogen evolution dual-function catalyst carrier is used to load precious metals and / or non-precious metals to obtain the oxygen and hydrogen evolution dual-function catalyst.

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