Low-noble-metal-loading oxygen evolution and hydrogen evolution bifunctional catalyst and preparation method thereof

Abstract

The invention discloses a low-noble-metal-loading oxygen evolution and hydrogen evolution bifunctional catalyst and a preparation method thereof, and belongs to the field of electrocatalytic water decomposition catalysts.The catalyst takes Ni and La double-doped non-noble metal Co3O4 as a carrier to load Ir and Pt noble metals, and the bifunctional catalyst has the oxygen evolution and hydrogen evolution catalysis functions. The invention provides a design thought of concerted catalytic reaction of the carrier and the bifunctional catalyst, and the carrier has full dispersion and anchoring effects on the noble metal and can be concerted catalytic reaction with the noble metal, so that the prepared bifunctional catalyst improves the overall catalytic activity and stability of the catalyst while reducing the loading capacity of the noble metal.

Description

Technical Field

[0001] The invention relates to a low-noble metal-loaded bifunctional catalyst for oxygen and hydrogen evolution and a preparation method thereof, and belongs to the field of electrocatalytic water splitting hydrogen production catalysts. Background Art

[0002] Proton exchange membrane water electrolysis technology is the most rapidly developing water splitting hydrogen production technology in recent years. The anode oxygen evolution reaction catalyst and the cathode hydrogen evolution reaction catalyst are the key to restricting the application of PEMWE technology. The development of bifunctional oxygen evolution / hydrogen evolution catalysts is the key to promoting the industrial application of PEMWE. Existing research mainly focuses on the field of single-functional catalysts. Ir-based precious metal catalysts are typical catalysts for oxygen evolution reaction, and Pt-based catalysts are typical catalysts for hydrogen evolution reaction.

[0003] Although monofunctional catalysts have been widely developed, the research and development of bifunctional catalysts is not in-depth. Chinese patent 202210996048.7 discloses "Fe-doped Co catalyst for electrocatalytic water splitting". 3 O 4 Ru-loaded bifunctional catalyst and preparation method thereof", firstly synthesized Fe-doped Co by template method 3 O 4 Nano-mesoporous materials were used as carriers, and then ruthenium salts were loaded onto Fe-doped Co by impregnation. 3 O 4 On the carrier, Ru / Fe-Co was obtained after heat treatment 3 O 4 Catalyst, namely the Fe-doped Co 3 O 4 Loaded Ru bifunctional electrocatalyst.

[0004] However, whether it is a monofunctional catalyst or a bifunctional catalyst, the precious metal loading is high, which leads to extremely high catalyst costs and limits the widespread development of the field of water splitting hydrogen production. Furthermore, the working environment of water splitting hydrogen production catalysts is a strong oxidizing or acidic environment, and the stability of existing catalysts cannot meet the requirements of industrial applications.

[0005] Purpose of the Invention

[0006] Based on the above problems, the first aspect of the present invention is to provide a bifunctional catalyst for oxygen and hydrogen evolution with low noble metal dosage and good catalytic activity.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A low-precious metal loading oxygen and hydrogen evolution dual-function catalyst, the catalyst is a non-precious metal Co doped with Ni and La 3 O 4The catalyst is a bifunctional catalyst with Ir and Pt noble metals as carrier and has both oxygen evolution and hydrogen evolution catalysis.

[0009] The low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution of the present invention has a bifunctional catalyst carrier with a small-particle porous structure, and the noble metal is evenly distributed on the carrier surface and in the pore structure.

[0010] The low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution of the present invention has a noble metal content of less than 7% as measured by ICP testing. More specifically, the total content of Ir and Pt in the catalyst is 6.7%.

[0011] The low noble metal loading oxygen and hydrogen evolution bifunctional catalyst of the present invention reduces the amount of noble metals used and reduces the cost while improving the overall activity of the catalyst.

[0012] The second aspect of the present invention is to provide a method for preparing a low noble metal loading oxygen and hydrogen evolution bifunctional catalyst, comprising the following steps:

[0013] (1) Preparation of carrier:

[0014] Add cobalt nitrate, lanthanum nitrate and nickel nitrate into a solvent to dissolve to form liquid A; add 2-methylimidazole into a solvent to dissolve to form liquid B; pour liquid A into liquid B, let stand, centrifuge and wash to obtain a precipitate; ball mill and calcine the precipitate to obtain a carrier LN-MOF-C;

[0015] (2) Preparation of bifunctional catalysts:

[0016] Ir, Pt, terephthalaldehyde or glyoxal and citric acid are added to benzyl alcohol to form a mixed solution; LN-MOF-C prepared in step (1) is added to the mixed solution, ultrasonicated and stirred to obtain a uniform suspension, the suspension is heated while being stirred, and after cooling, the suspension is centrifuged to obtain a precipitate, which is washed, and the precipitate is dried and sintered to obtain a bifunctional catalyst.

[0017] As a preferred embodiment:

[0018] In step (1):

[0019] The solvent is methanol.

[0020] The ball milling has a ball milling speed of 200-600 rpm and a ball milling time of 10-240 min.

[0021] The calcination is carried out at 400-650° C. in an argon atmosphere for 0.5-6 h.

[0022] In step (2):

[0023] The suspension is heated while being stirred at a temperature of 150-220° C. for 1-12 hours.

[0024] The drying is vacuum drying or freeze drying, and the drying time is 12-72 hours.

[0025] The sintering is carried out at 300-480 degrees Celsius in an air atmosphere for 1-8 hours.

[0026] Particularly preferably, the present invention provides a method for preparing a low noble metal loading oxygen and hydrogen evolution bifunctional catalyst, comprising the following steps:

[0027] (1) Preparation of carrier:

[0028] 2-10g of cobalt nitrate, 0.5-6g of lanthanum nitrate, and 0.5-3g of nickel nitrate are added to methanol to completely dissolve to form liquid A; 2-20g of 2-methylimidazole is added to methanol to completely dissolve to form liquid B; liquid A is poured into liquid B while stirring liquid B, and the mixture is allowed to stand for 1-48h after the AB liquids are fully mixed; the mixed liquid is centrifuged after being fully allowed to stand, and then washed with methanol or ethanol to obtain a precipitate; the precipitate is ball-milled at a ball-milling speed of 200-600rpm and a ball-milling time of 10-240min; the ball-milled powder is calcined at 400-650°C in an argon atmosphere for 0.5-6h to obtain a carrier LN-MOF-C;

[0029] (2) Preparation of bifunctional catalysts:

[0030] 20-60 mg Ir, 20-60 mg Pt, 1-6 g terephthalaldehyde or glyoxal and 0.5-6 g citric acid are added to 40-90 ml benzyl alcohol, and the mixture is thoroughly sonicated and stirred to form a uniform mixed solution. 100 mg LN-MOF-C prepared in step (1) is added to the mixed solution, and then sonicated and stirred to obtain a uniform suspension. The suspension is heated to 150-220° C. while stirring and kept warm for 1-12 h. After cooling, the suspension is centrifuged to obtain a precipitate, which is washed with ethanol or acetone. The precipitate is vacuum dried or freeze-dried for 12-72 h. After drying, it is sintered in an air atmosphere at 300-480° C. for 1-8 h to obtain a bifunctional catalyst.

[0031] The third aspect of the present invention is to provide an application of the low noble metal loading oxygen and hydrogen evolution bifunctional catalyst in the electrolytic water catalytic reaction, including the electrolytic water catalytic oxygen evolution reaction and the hydrogen evolution reaction.

[0032] Specifically, the low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution of the present invention is used to electrocatalyze water splitting to produce hydrogen under an acidic environment. The bifunctional catalyst material is used as the cathode and anode of a proton membrane electrode, respectively, and then used in a proton membrane electrolyzer to electrocatalyze water splitting to produce hydrogen.

[0033] The beneficial effects of the present invention are as follows:

[0034] (1) The present invention provides a design idea for the synergistic catalytic reaction between a carrier and a bifunctional catalyst, using non-precious metal Co 3 O 4 The substrate is used to reduce Ir and Pt simultaneously on its surface. The carrier has a sufficient dispersion and anchoring effect on the precious metals and can synergistically catalyze the reaction with the precious metals. Therefore, the prepared bifunctional catalyst reduces the precious metal loading while improving the overall catalytic activity and stability of the catalyst.

[0035] (2) The present invention provides a method for preparing a bifunctional catalyst for oxygen evolution and hydrogen evolution with a low noble metal loading. The prepared bifunctional catalyst for oxygen evolution and hydrogen evolution with a low noble metal loading has a small-particle porous structure, and the noble metal is evenly distributed on the carrier surface and in the pore structure. The content of the noble metal is less than 7% as tested by ICP. The test shows that the bifunctional catalyst for oxygen evolution and hydrogen evolution with a low noble metal loading has an anode oxygen evolution reaction stability of more than 20 h at 10 mA / cm2, an overpotential of 370 mV at 10 mA / cm2 corresponding to a potential of 1.6 V at 10 mA / cm2, a hydrogen evolution reaction stability of more than 16 h at -10 mA / cm2, and an overpotential of 81 mV at -10 mA / cm2 corresponding to a potential of -0.081 V at -10 mA / cm2, which proves that the catalyst has excellent oxygen and hydrogen evolution activities.

[0036] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the XRD pattern of the bifunctional catalyst prepared in the embodiment of the present invention.

[0038] Figure 2 The stability test data of the anode oxygen evolution reaction of the bifunctional catalyst prepared in the embodiment of the present invention at 10 mA / cm2.

[0039] Figure 3 The stability test data of the cathode hydrogen evolution reaction of the bifunctional catalyst prepared in the embodiment of the present invention at -10mA / cm2. DETAILED DESCRIPTION

[0040] In the following examples, unless otherwise specified, existing or commercially available products are used.

[0041] Example 1

[0042] (1) Preparation and sintering of carrier:

[0043] Add 6g of cobalt nitrate, 2g of lanthanum nitrate, and 1g of nickel nitrate to 150ml of methanol to completely dissolve to form liquid A. Add 14g of 2-methylimidazole to 400ml of methanol to completely dissolve to form liquid B. Pour liquid A into liquid B while stirring liquid B, wait until liquid AB is fully mixed and let stand for 12 hours. After centrifuging the mixed liquid after sufficient standing, wash with methanol or ethanol to obtain a precipitate. Ball mill the precipitate at a ball milling speed of 600rpm and a ball milling time of 60min. Calcine the ball-milled powder at 550℃ in an argon atmosphere for 4h to obtain the carrier LN-MOF-C.

[0044] (2) Precious metals are loaded on the carrier to make bifunctional catalysts:

[0045] Add 40 mg Ir, 40 mg Pt, 3 g terephthalaldehyde or glyoxal and 1.5 g citric acid to 70 ml benzyl alcohol, and form a uniform mixed solution after sufficient ultrasonication and stirring. Add 100 mg of carrier LN-MOF-C to the mixed solution, and then ultrasonicate and stir to obtain a uniform suspension. Heat the suspension to 200 ° C while stirring for 6 hours. 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] Catalyst structure confirmation:

[0047] Reference Figure 1 TEM image of the bifunctional catalyst. The bifunctional catalyst carrier prepared by the present invention has a small-particle porous structure, and the noble metal is evenly distributed on the carrier surface and in the pore structure. The ICP test results show that the Ir and Pt content in the bifunctional catalyst is 6.7%.

[0048] Performance Testing:

[0049] The intrinsic electrochemical activity of the material was tested in a typical three-electrode system using a rotating disk electrode as the working electrode, a gold electrode as the counter electrode, a mercury / mercurous sulfate electrode as the reference electrode, and 0.1M HClO4 as the electrolyte. In the same system, the intrinsic electrochemical stability of the system was tested at a current density of 10mA / cm2.

[0050] analyze:

[0051] like Figure 2 The figure shows the test data of the stability of the anode oxygen evolution reaction of the bifunctional catalyst at 10 mA / cm2. The stability of the anode oxygen evolution reaction at 10 mA / cm2 exceeds 20 hours, which proves that the bifunctional catalyst prepared by the present invention has good stability of oxygen evolution reaction. Figure 2It can be read that the potential of the bifunctional catalyst at 10 mA / cm2 is 1.6 V (RHE, uncompensated), and the corresponding overpotential at 10 mA / cm2 is 370 mV (uncompensated), which proves that the catalyst has excellent oxygen evolution activity.

[0052] Figure 3 The test data of the cathode hydrogen evolution reaction stability of the bifunctional catalyst at -10 mA / cm2 is shown. The stability of the hydrogen evolution reaction at -10 mA / cm2 exceeds 16 hours, proving that the bifunctional catalyst prepared by the present invention has good hydrogen evolution reaction activity and stability. Figure 3 It can be read that the potential of the bifunctional catalyst at -10 mA / cm2 is -0.081 V (RHE, uncompensated), and the corresponding -10 mA / cm2 overpotential is 81 mV (uncompensated), proving that the catalyst has excellent hydrogen evolution activity.

[0053] In summary, the bifunctional catalyst prepared by the present invention can be fully dispersed in the anchored precious metal due to its large specific surface area of ​​the carrier, the small particle size of the precious metal, the large specific surface area, and the synergistic catalytic effect between the carrier and the precious metal. Therefore, it can be used for water splitting to produce hydrogen in an acidic environment, and has excellent performance in oxygen evolution reaction and hydrogen evolution reaction.

[0054] Example 2

[0055] The preparation method is the same as that of Example 1, except that in step (2), after the precipitant is dried, it is sintered in an air atmosphere at 360 degrees Celsius for 2 hours to obtain a bifunctional catalyst.

[0056] Example 3

[0057] The preparation method is the same as that of Example 1, except that in step (2), after the precipitant is dried, it is sintered in an air atmosphere at 360 degrees Celsius for 4 hours to obtain a bifunctional catalyst.

[0058] Example 4

[0059] The preparation method is the same as that of Example 1, except that in step (2), after the precipitant is dried, it is sintered in an air atmosphere at 400 degrees Celsius for 2 hours to obtain a bifunctional catalyst.

[0060] Performance Test:

[0061] The bifunctional catalysts prepared in Examples 2-4 were tested for their catalytic performance using the aforementioned method to evaluate the effects of different preparation processes on the catalyst performance, as shown in Table 1:

[0062]

Claims

1. A low noble metal loading oxygen and hydrogen evolution bifunctional catalyst, characterized in that: The catalyst uses Ni and La doped non-precious metal Co3O4 as a carrier, loaded with Ir and Pt precious metals, and is a bifunctional catalyst with both oxygen evolution and hydrogen evolution catalytic effects.

2. A low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 1, characterized in that: The bifunctional catalyst carrier is a small-particle porous structure, and the precious metal is evenly distributed on the carrier surface and in the pore structure.

3. A low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 1, characterized in that: The ICP test result of the catalyst shows that the content of precious metal is less than 7%.

4. A method for preparing a low noble metal loading oxygen and hydrogen evolution bifunctional catalyst, characterized in that: The following steps are involved: (1) Preparation of carrier: Add cobalt nitrate, lanthanum nitrate and nickel nitrate into a solvent to dissolve to form liquid A; add 2-methylimidazole into a solvent to dissolve to form liquid B; pour liquid A into liquid B, let stand, centrifuge and wash to obtain a precipitate; ball mill and calcine the precipitate to obtain a carrier LN-MOF-C; (2) Preparation of bifunctional catalysts: Ir, Pt, terephthalaldehyde or glyoxal and citric acid are added to benzyl alcohol to form a mixed solution; LN-MOF-C prepared in step (1) is added to the mixed solution, ultrasonicated and stirred to obtain a uniform suspension, the suspension is heated while being stirred, and after cooling, the suspension is centrifuged to obtain a precipitate, which is washed, and the precipitate is dried and sintered to obtain a bifunctional catalyst.

5. The method for preparing a low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 4, characterized in that: In step (1), the solvent is methanol, the ball milling speed is 200-600 rpm, the ball milling time is 10-240 min, and the calcination is performed at 400-650° C. in an argon atmosphere for 0.5-6 h.

6. The method for preparing a low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 4, characterized in that: In step (2), the suspension is heated while being stirred at a temperature of 150-220° C. for 1-12 hours. The drying is vacuum drying or freeze drying for 12-72 hours. The sintering is performed at 300-480° C. in an air atmosphere for 1-8 hours.

7. The method for preparing a low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 4, characterized in that: The following steps are involved: (1) Preparation of carrier: 2-10g of cobalt nitrate, 0.5-6g of lanthanum nitrate, and 0.5-3g of nickel nitrate are added to methanol to completely dissolve to form liquid A; 2-20g of 2-methylimidazole is added to methanol to completely dissolve to form liquid B; liquid A is poured into liquid B while stirring liquid B, and the mixture is allowed to stand for 1-48h after the AB liquids are fully mixed; the mixed liquid is centrifuged after being fully allowed to stand, and then washed with methanol or ethanol to obtain a precipitate; the precipitate is ball-milled at a ball-milling speed of 200-600rpm and a ball-milling time of 10-240min; the ball-milled powder is calcined at 400-650°C in an argon atmosphere for 0.5-6h to obtain a carrier LN-MOF-C; (2) Preparation of bifunctional catalysts: 20-60 mg Ir, 20-60 mg Pt, 1-6 g terephthalaldehyde or glyoxal and 0.5-6 g citric acid are added to 40-90 ml benzyl alcohol, and the mixture is thoroughly sonicated and stirred to form a uniform mixed solution. 100 mg LN-MOF-C prepared in step (1) is added to the mixed solution, and then sonicated and stirred to obtain a uniform suspension. The suspension is heated to 150-220° C. while stirring and kept warm for 1-12 h. After cooling, the suspension is centrifuged to obtain a precipitate, which is washed with ethanol or acetone. The precipitate is vacuum dried or freeze-dried for 12-72 h. After drying, it is sintered in an air atmosphere at 300-480° C. for 1-8 h to obtain a bifunctional catalyst.

8. Use of the low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution according to claim 1 in a catalytic reaction of water electrolysis, comprising a catalytic oxygen evolution reaction and a hydrogen evolution reaction in water electrolysis.

9. An application of the low noble metal loading oxygen and hydrogen evolution bifunctional catalyst according to claim 1 in the catalytic reaction of water electrolysis, characterized in that: The low noble metal loading bifunctional catalyst for oxygen and hydrogen evolution electrocatalyzes water splitting to produce hydrogen in an acidic environment. The bifunctional catalyst material is used as the cathode and anode of a proton membrane electrode, respectively, and then used in a proton membrane electrolyzer to electrocatalyze water splitting to produce hydrogen.

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