A cobalt-nickel alloy / porous carbon oxygen evolution catalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of electrocatalysts, and relates to a cobalt-nickel alloy / porous carbon oxygen evolution catalyst, a preparation method and an application thereof. It comprises porous carbon and a cobalt-nickel alloy supported on the porous carbon, wherein the porous carbon has a porous three-dimensional network structure, and the diameter of the cobalt-nickel alloy is at the nanometer level. The preparation method comprises mixing sucrose, cobalt metal salt and nickel metal salt, and then pre-calcining the mixture in a tubular furnace under an inert atmosphere to form a porous network structure; after pre-calcining, high-temperature carbonization treatment is performed in a tubular furnace under an inert atmosphere to obtain a cobalt-nickel alloy / porous carbon oxygen evolution catalyst. The obtained electrocatalyst has the advantages of good conductivity and a large number of catalytic active sites.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysts, and in particular relates to a cobalt-nickel alloy / porous carbon oxygen evolution catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen energy is known as an ideal form of energy storage due to its high energy density (140kJ / kg) and zero carbon emissions during the oxidation process, and has received attention from countries around the world. At present, hydrogen is mainly produced by fossil energy reforming or water electrolysis. The process of hydrogen production by water electrolysis involves two half-reaction processes: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The OER process involves four electron transfers and the adsorption and desorption of multiple reaction intermediates. Its slow kinetics restrict the improvement of the overall water electrolysis efficiency. Therefore, the OER process needs the help of an electrocatalyst to enable it to proceed smoothly at a smaller overpotential, thereby improving energy storage efficiency and conversion rate.

[0003] Currently, commercial OER electrocatalysts are mainly noble metals such as ruthenium (Ru), iridium (Ir) and their corresponding oxides. However, these noble metals have low abundance in the earth's crust, are difficult to develop and smelt, and are expensive, which severely limits the widespread application of noble metal OER electrocatalysts. Currently, non-noble metal catalysts generally have problems such as few active sites, poor electrical conductivity, and slow mass transfer between reactants and products. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a cobalt-nickel alloy / porous carbon oxygen evolution catalyst and a preparation method and application thereof. The present invention provides a non-precious metal electrocatalyst, which increases the number of catalytic active sites and accelerates mass transfer and electron transfer processes.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] In a first aspect, a cobalt-nickel alloy / porous carbon oxygen evolution catalyst comprises porous carbon and a cobalt-nickel alloy supported on the porous carbon, wherein the porous carbon has a porous three-dimensional network structure, and the diameter of the cobalt-nickel alloy is at the nanometer level.

[0007] Nano-scale alloy grows on the surface of porous carbon. The nickel-cobalt alloy in the present invention is in the form of a single metal, i.e., NixCoy. The alloy particles are mainly on the surface, but the particles and porous carbon are directly bonded very tightly.

[0008] The present invention relates to an electrocatalyst of porous carbon loaded with cobalt-nickel alloy. The porous carbon is used as a carrier and has a porous three-dimensional network structure. The cobalt-nickel alloy is used as an active material. The porous carbon has good electrical conductivity. Its structural characteristics enable it to have a large number of catalytic active sites, thereby improving the catalytic oxygen evolution reaction performance, improving the energy storage efficiency and conversion efficiency, and facilitating the electrocatalytic hydrogen evolution process to proceed smoothly at a smaller potential.

[0009] In some embodiments of the present invention, the diameter of the cobalt-nickel alloy is 10 nm to 20 nm. The cobalt-nickel alloy has a nano-particle size and has a high catalytic activity.

[0010] In some embodiments of the present invention, the porous carbon has a multi-level pore structure from mesopores to macropores. The porous carbon has a multi-level pore size structure of mesopores and macropores, which is beneficial to improve electrical conductivity and catalytic performance.

[0011] In the second aspect, the preparation method of the above-mentioned cobalt-nickel alloy / porous carbon oxygen evolution catalyst is as follows:

[0012] Sucrose is mixed with cobalt metal salt and nickel metal salt, and the mixture is then pre-calcined in a tube furnace under an inert atmosphere to form a porous network structure;

[0013] After pre-sintering, a high-temperature carbonization treatment is carried out in a tubular furnace under an inert atmosphere to obtain a cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0014] Sucrose is selected as the precursor of porous carbon in the present invention because after sucrose and metal salt are mixed, H and O elements in sucrose are quickly removed during low-temperature rapid burning, and the volume of sucrose expands rapidly under the catalytic action of metal ions to form a porous carbon structure.

[0015] The mixture is first pre-burned and then subjected to a high-temperature carbonization process. The pre-burning process is a rapid temperature increase, the purpose of which is to rapidly expand the volume of the sucrose to form a porous structure; the purpose of high-temperature slow burning is to fully crystallize the remaining porous carbon structure, improve the crystallinity and thus improve the conductivity of the material, and ultimately improve the oxygen evolution reaction performance.

[0016] In some embodiments of the present invention, the molar ratio of the cobalt metal salt to the nickel metal salt is any ratio, and the molar ratio of sucrose to the mixed metal salt of the cobalt metal salt and the nickel metal salt is (20-35):1.

[0017] In some embodiments of the present invention, the temperature of the pre-sintering treatment is 300-500°C, the time is 1-3 hours, further, the heating rate is 5-20°C / min, further, the temperature of the pre-sintering treatment is 300-350°C.

[0018] In some embodiments of the present invention, the temperature of the high temperature carbonization treatment is 800-1100°C, the time is 1-3 hours, further, the heating rate is 2-10°C / min, and further, the temperature of the high temperature carbonization treatment is 900-1100°C.

[0019] The heating rate of high-temperature carbonization treatment is lower than that of pre-burning treatment. High-temperature carbonization treatment is a high-temperature slow-burning process.

[0020] In some embodiments of the present invention, the cobalt metal salt is cobalt acetate tetrahydrate, and the nickel metal salt is nickel acetate tetrahydrate.

[0021] Thirdly, the above-mentioned cobalt-nickel alloy / porous carbon is used as an oxygen evolution catalyst in the field of hydrogen production by water electrolysis.

[0022] One or more technical solutions of the present invention have the following beneficial effects:

[0023] The cobalt-nickel alloy / porous carbon oxygen evolution catalyst proposed in the present invention includes porous carbon and cobalt-nickel alloy supported on porous carbon, and is a non-precious metal catalyst, which solves the problems of low reserves and high prices of precious metals; and solves the problems of few active sites, poor electrical conductivity, and slow mass transfer process of reactants and products of non-precious metal catalysts.

[0024] The method for preparing a cobalt-nickel alloy / porous carbon oxygen evolution catalyst proposed in the present invention uses sucrose as a precursor for preparing porous carbon, and forms a porous three-dimensional network structure during the pre-burning process and a high-temperature carbonization process to achieve graphitization of the porous carbon and the final formation of a cobalt-nickel alloy, thereby finally forming a cobalt-nickel alloy / porous carbon oxygen evolution catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a scan image of the cobalt-nickel alloy / porous carbon oxygen evolution catalyst of Example 1. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof. The present invention is further described below in conjunction with the embodiments

[0029] Example 1

[0030] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes in a molar ratio of 20:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 1 to 3 hours. Subsequently, the mixed materials are placed in a tubular furnace for low-temperature rapid pre-sintering treatment (10°C / min, 300°C, 1h) under Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 900°C, 3h) in a tubular furnace under Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0031] Figure 1 The dotted circle in the middle represents the loaded nano-cobalt-nickel alloy. Figure 1 It can be seen that the cobalt-nickel alloy / porous carbon oxygen evolution catalyst has a porous three-dimensional network structure.

[0032] Example 2

[0033] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes at a molar ratio of 30:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 1 hour. Subsequently, the mixed materials are placed in a tubular furnace and subjected to low-temperature rapid pre-sintering treatment (10°C / min, 300°C, 1h) under an Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 900°C, 3h) in a tubular furnace under an Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0034] Example 3

[0035] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes at a molar ratio of 35:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 1 hour. Subsequently, the mixed materials are placed in a tubular furnace for low-temperature rapid pre-sintering treatment (10°C / min, 350°C, 1h) under Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 900°C, 3h) in a tubular furnace under Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0036] Example 4

[0037] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes at a molar ratio of 20:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 1 hour. Subsequently, the mixed materials are placed in a tubular furnace and subjected to low-temperature rapid pre-sintering treatment (20°C / min, 300°C, 1h) under an Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 900°C, 3h) in a tubular furnace under an Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0038] Example 5

[0039] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes at a molar ratio of 20:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 3 hours. Subsequently, the mixed materials are placed in a tubular furnace for low-temperature rapid pre-sintering treatment (10°C / min, 300°C, 1h) under Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 900°C, 3h) in a tubular furnace under Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0040] Example 6

[0041] First, sucrose and metal salts (cobalt acetate tetrahydrate and nickel acetate tetrahydrate) are ground and premixed for 5 minutes at a molar ratio of 20:1, wherein the molar ratio of cobalt acetate tetrahydrate and nickel acetate tetrahydrate can be any ratio; then the premixed materials are finally mixed with a ball mill, and the mixing time is 3 hours. Subsequently, the mixed materials are placed in a tubular furnace for low-temperature rapid pre-sintering treatment (10°C / min, 300°C, 1h) under Ar gas atmosphere. Finally, the pre-sintered sample is ground and then subjected to high-temperature carbonization treatment (2°C / min, 1100°C, 3h) in a tubular furnace under Ar atmosphere to obtain the final cobalt-nickel alloy / porous carbon oxygen evolution catalyst.

[0042] Experimental example

[0043] The catalysts of Examples 1 to 6 were used as oxygen evolution electrocatalysts to carry out oxygen evolution reaction at the anode. The experimental process was as follows:

[0044] First, 1 mg of oxygen evolution electrocatalyst and 30 μL of Nafion solution were ultrasonically dispersed in 500 μL of anhydrous ethanol to form a uniform suspension. Then, 10 μL of the suspension was measured with a pipette and evenly dispersed on a rotating disk electrode (RDE) substrate with a diameter of 5 mm, and then dried naturally for use.

[0045] All electrochemical tests were performed using a three-electrode system in a 1.0 M KOH electrolyte. The reference electrode was an Ag / AgCl (3 M KCl) electrode, the counter electrode was a graphite electrode, and the working electrode was a catalyst-coated RDE. The test instrument was a CHI760E electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. The linear sweep voltammetry (LSV) curve (or polarization curve) was obtained by linear sweep voltammetry at a scan rate of 10 mV / s, with a scan range of 0 to 0.8 V (vs. Ag / AgCl). According to the LSV curve, 10 mA / cm 2 The overpotential value under current density; the LSV curve can be converted into the Tafel curve through the Tafel formula, and the slope of the linear region of the Tafel curve is the Tafel slope value.

[0046] Under the condition of maintaining the voltage value at 0.5V, the test results are shown in Table 1.

[0047]

[0048]

[0049] It can be seen from Table 1 that the catalyst of the present invention has good conductivity and stability. The stability test is to measure 10mA / cm 2The change of current density with time at the corresponding overpotential. The performance of the catalysts of Examples 1 to 6 remained almost unchanged for 55 hours or more.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An application of cobalt-nickel alloy / porous carbon as an oxygen evolution catalyst in the field of hydrogen production by water electrolysis, characterized in that: The cobalt-nickel alloy / porous carbon oxygen evolution catalyst comprises porous carbon and cobalt-nickel alloy supported on the porous carbon, the porous carbon has a porous three-dimensional network structure, and the diameter of the cobalt-nickel alloy is nanometer level; The preparation method of the cobalt-nickel alloy / porous carbon oxygen evolution catalyst is as follows: Sucrose is mixed with cobalt metal salt and nickel metal salt, and the mixture is then pre-calcined in a tube furnace under an inert atmosphere to form a porous network structure; After pre-sintering, a high-temperature carbonization treatment is performed in a tube furnace under an inert atmosphere to obtain a cobalt-nickel alloy / porous carbon oxygen evolution catalyst; The molar ratio of the cobalt metal salt to the nickel metal salt is any ratio, and the molar ratio of sucrose to the mixed metal salt of the cobalt metal salt and the nickel metal salt is (20-35):1; The temperature of the pre-sintering treatment is 300~500℃ and the time is 1-3h; The temperature of high temperature carbonization treatment is 800~1100℃ and the time is 1-3h.

2. The use according to claim 1, characterized in that: The diameter of cobalt-nickel alloy is 10nm-20nm.

3. The use according to claim 1, characterized in that: Porous carbon has a hierarchical pore structure ranging from mesopores to macropores.

4. The use according to claim 1, characterized in that: The heating rate is 5~20℃ / min.

5. The use according to claim 4, characterized in that: The heating rate is 2~10℃ / min.

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