An oxygen evolution reaction electrocatalyst and its preparation method and application

Abstract

The present invention discloses an oxygen evolution reaction electrocatalyst and a preparation method and application thereof. The preparation method of the oxygen evolution reaction electrocatalyst comprises: ball milling a mixture of carbon nanotubes, a ruthenium source and a cobalt source to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst. The oxygen evolution reaction electrocatalyst prepared by the method of the present invention has high electrocatalytic activity and stability for the oxygen evolution reaction, and its performance is significantly better than that of a commercial iridium oxide catalyst, and the preparation method of the present invention is simple to operate, environmentally friendly, and conducive to large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of oxygen evolution reaction electrocatalysts, and in particular relates to an oxygen evolution reaction electrocatalyst and a preparation method and application thereof. Background Art

[0002] OER electrocatalysts are important components of water electrolysis hydrogen production electrolyzers and metal-air batteries. However, currently commercially available OER electrocatalysts are mainly composed of precious metals ruthenium and iridium and their compounds. Since ruthenium and iridium are expensive and scarce on Earth, the development of OER electrocatalysts that do not contain precious metals or contain only a small amount of precious metals has become an important research field. Since carbon nanotubes have excellent characteristics such as high conductivity and low density, and can produce synergistic effects with metals and metal compounds to improve the electrocatalytic activity of OER, carbon nanotubes have been widely studied as a substrate for the preparation of OER electrocatalysts. However, past preparation methods such as hydrothermal method and chemical vapor deposition method often have problems such as low yield, complex operation, environmental unfriendliness, and low catalyst activity, which limit the large-scale application of carbon nanotube-based OER electrocatalysts. Summary of the invention

[0003] The main purpose of the present invention is to provide an oxygen evolution reaction electrocatalyst and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising: ball milling a mixture of carbon nanotubes, a ruthenium source and a cobalt source to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is the oxygen evolution reaction electrocatalyst.

[0006] In a second aspect, the present invention further provides an oxygen evolution reaction electrocatalyst prepared by the above preparation method, wherein the oxygen evolution reaction electrocatalyst comprises carbon nanotubes, and the outer wall of the carbon nanotubes is loaded with ruthenium nanoparticles and cobalt oxide nanoparticles.

[0007] In a third aspect, the present invention also provides the use of the above-mentioned oxygen evolution reaction electrocatalyst in a water electrolysis hydrogen production electrolyzer and a metal-air battery.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The oxygen evolution reaction electrocatalyst prepared by the method of the present invention has high electrocatalytic activity and stability for the oxygen evolution reaction, and its performance is significantly better than that of a commercial iridium oxide catalyst. In addition, the preparation method of the present invention is simple to operate, environmentally friendly, and conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 It is a schematic diagram of the preparation process of the oxygen evolution reaction electrocatalyst of the present invention.

[0012] FIG. 2( a ) is a low-magnification scanning electron microscope photograph of an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0013] FIG. 2( b ) is a high-magnification scanning electron microscope photograph of an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0014] FIG3( a ) is a transmission electron microscope photograph of an electrocatalyst for oxygen evolution reaction provided in a typical embodiment of the present invention.

[0015] FIG3( b ) is a high-resolution transmission electron micrograph of ruthenium nanoparticles in an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0016] FIG3( c ) is a high-resolution transmission electron micrograph of cobalt oxide nanoparticles in an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0017] FIG. 4( a ) is an XPS spectrum of an electrocatalyst for oxygen evolution reaction provided in a typical embodiment of the present invention.

[0018] FIG4( b ) is a high-resolution XPS spectrum of Co 2p 3 / 2 in an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0019] FIG4( c ) is a high-resolution XPS spectrum of Ru3p in an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0020] Figure 5 This is an XRD spectrum of an oxygen evolution reaction electrocatalyst provided in a typical implementation case of the present invention.

[0021] FIG. 6 ( a ) is a linear sweep voltammetric curve of the electrocatalytic performance of an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0022] 6( b ) is a Tafel polarization curve of a carbon nanotube / ruthenium / cobalt oxide composite material, carbon nanotube / ruthenium, iridium oxide and carbon nanotube in the electrocatalytic performance of an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0023] FIG6( c ) is an electrochemical impedance spectrum of the electrocatalytic performance of an oxygen evolution reaction electrocatalyst provided in a typical embodiment of the present invention.

[0024] Figure 7 This is a chronoamperometric curve of an oxygen evolution reaction electrocatalyst provided in a typical implementation case of the present invention.

[0025] Explanation of the reference numerals: 1. carbon nanotube, 2. triphenylphosphine ruthenium chloride, 3. cobalt nitrate hexahydrate, 4. anhydrous ethanol, 5. stainless steel ball, 6. ruthenium nanoparticles, 7. cobalt oxide nanoparticles. DETAILED DESCRIPTION

[0026] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0028] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0029] The present invention provides a method which is simple to operate, environmentally friendly and conducive to large-scale production for preparing a highly active oxygen evolution reaction electrocatalyst.

[0030] One aspect of an embodiment of the present invention provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising: ball milling a mixture of carbon nanotubes, a ruthenium source and a cobalt source to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is the oxygen evolution reaction electrocatalyst.

[0031] In some preferred embodiments, the method for preparing the oxygen evolution reaction electrocatalyst comprises: placing a mixture of carbon nanotubes, a ruthenium source, a cobalt source and anhydrous ethanol into a stainless steel ball mill containing stainless steel balls, and sealing and fixing the ball mill in a planetary ball mill for ball milling.

[0032] In some more preferred embodiments, the rotation speed of the ball mill is 400-600 rpm, and the ball milling time is 40-56 h.

[0033] In some more preferred embodiments, the rotation speed of the ball mill is 500 rpm and the ball milling time is 48 h.

[0034] In some more preferred embodiments, the mass ratio of the carbon nanotubes, the ruthenium source and the cobalt source is 10:2:2-10, and the volume ratio of the mass of the carbon nanotubes to the anhydrous ethanol is 1 g:2-8 mL.

[0035] In some more preferred embodiments, the ratio of the volume of the stainless steel ball mill to the mass of the stainless steel balls is 5 mL: 10-20 g.

[0036] In some more preferred embodiments, the ruthenium source may include triphenylphosphine ruthenium chloride, ruthenium acetate or ruthenium trichloride, but is not limited thereto.

[0037] In some more preferred embodiments, the cobalt source may include cobalt nitrate hexahydrate or cobalt chloride, but is not limited thereto.

[0038] In some preferred embodiments, the process comprises: taking out the ball-milled mixture, soaking it in hydrochloric acid, and then performing vacuum freeze-drying to obtain a carbon nanotube / ruthenium / cobalt oxide composite material.

[0039] In some more preferred embodiments, the concentration of the hydrochloric acid is 0.5-1.5 mol / L.

[0040] In some more preferred embodiments, the soaking time is 2-10 hours.

[0041] In some more preferred embodiments, the vacuum degree of the vacuum freeze drying is 0.02-0.08 mmHg, the temperature is -60 to -120°C, and the drying time is 10-20 hours.

[0042] As a more specific implementation, the present invention provides a method for preparing an oxygen evolution reaction electrocatalyst, such as Figure 1 As shown, the specific steps include:

[0043] (1) placing a mixture of carbon nanotubes 1, triphenylphosphine ruthenium chloride 2, cobalt nitrate hexahydrate 3, and anhydrous ethanol 4 into a stainless steel ball mill containing stainless steel balls 5, then sealing the ball mill and fixing it in a planetary ball mill, and running it at a speed of 400-600 rpm for 40-56 hours;

[0044] (2) The ball-milled mixture is taken out and soaked in hydrochloric acid with a concentration of 0.5-1.5 mol / L for 2-10 hours. After soaking, the mixture is vacuum freeze-dried for 10-20 hours at a vacuum degree of 0.02-0.08 mmHg and a temperature of -60°C to -120°C to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst. The oxygen evolution reaction electrocatalyst includes carbon nanotubes 1, and the outer wall of the carbon nanotubes 1 is loaded with ruthenium nanoparticles 6 and cobalt oxide nanoparticles 7.

[0045] In the embodiment of the present invention, a mixture of carbon nanotubes, ruthenium source and cobalt source is ball-milled to prepare a carbon nanotube / ruthenium / cobalt oxide composite material. The obtained composite material has high electrocatalytic activity and stability for oxygen evolution reaction, and its performance is significantly better than that of commercial iridium oxide catalyst.

[0046] Another aspect of an embodiment of the present invention provides an oxygen evolution reaction electrocatalyst prepared by the aforementioned method, wherein the oxygen evolution reaction electrocatalyst comprises carbon nanotubes, and the outer wall of the carbon nanotubes is loaded with ruthenium nanoparticles and cobalt oxide nanoparticles.

[0047] Another aspect of the embodiments of the present invention further provides the use of the aforementioned oxygen evolution reaction electrocatalyst in a water electrolysis hydrogen production electrolyzer and a metal-air battery.

[0048] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising the following steps:

[0051] (1) A mixture of 5 g of carbon nanotubes, 1 g of triphenylphosphine ruthenium chloride, 2.5 g of cobalt nitrate hexahydrate, and 20 mL of anhydrous ethanol was placed in a 250 mL stainless steel ball mill containing 650.0 g of stainless steel balls. The ball mill was then sealed and fixed in a planetary ball mill and operated at 500 rpm for 48 h.

[0052] (2) The ball-milled mixture was taken out and soaked in 1 mol / L hydrochloric acid for 6 h. After soaking, it was vacuum freeze-dried for 12 h at a vacuum degree of 0.05 mmHg and a temperature of -100 °C to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

[0053] The oxygen evolution reaction electrocatalyst obtained in this example was subjected to electron microscope scanning, and its low-magnification scanning electron microscope photograph is shown in Figure 2 (a), and its high-magnification scanning electron microscope photograph is shown in Figure 2 (b). It can be clearly seen from Figures 2 (a) and 2 (b) that the surface of the carbon nanotubes is loaded with nanoparticles, proving that the carbon nanotubes have been doped.

[0054] The oxygen evolution reaction electrocatalyst obtained in this embodiment was subjected to transmission electron microscopy, and its transmission electron microscopy photograph is shown in Figure 3 (a), wherein the high-resolution transmission electron microscopy photograph of ruthenium nanoparticles is shown in Figure 3 (b), and the high-resolution transmission electron microscopy photograph of cobalt oxide nanoparticles is shown in Figure 3 (c). It can be seen from Figures 3 (a), 3 (b) and 3 (c) that the spacing between the lattice fringe surfaces of the material is consistent with CoO (002), proving that the main component of this cobalt oxide nanoparticle is CoO.

[0055] The oxygen evolution reaction electrocatalyst obtained in this embodiment was subjected to XPS spectrum analysis, as shown in FIG4 (a), and it can be seen that the composite material contains carbon, ruthenium, cobalt and oxygen elements; the Co 2p3 / 2 in the oxygen evolution reaction electrocatalyst obtained in this embodiment was subjected to high-resolution XPS spectrum analysis, as shown in FIG4 (b), and it can be seen that the cobalt element has +2 valence and +3 valence; among them, the cobalt elements corresponding to 780.3 eV and 781.8 eV are Co(OH)2 and CoO, and the cobalt element corresponding to 786.1 eV is Co3O; the Ru3p in the oxygen evolution reaction electrocatalyst obtained in this embodiment was subjected to high-resolution XPS spectrum analysis, as shown in FIG4 (c), which proves that ruthenium mainly exists in the form of metallic ruthenium.

[0056] The oxygen evolution reaction electrocatalyst obtained in this example was subjected to XRD spectrum analysis. Figure 5 As shown, obvious CoO

[002] , Co3O4

[222] and Ru

[101] peaks can be seen, indicating that the carbon nanotube surface is mainly loaded with cobalt oxide, cobalt tetraoxide and ruthenium.

[0057] The oxygen evolution reaction electrocatalyst obtained in this example was subjected to electrochemical testing, specifically as follows: The electrochemical test adopted a three-electrode system, using a Chenhua electrochemical workstation (CHI 760 E), wherein the platinum sheet was the counter electrode, the mercury / mercury oxide electrode was the reference electrode, the carbon nanotube / ruthenium / cobalt oxide composite material was the working electrode, and the electrolyte was 1 M KOH.

[0058] FIG6 (a) is a linear sweep voltammetric curve of the oxygen evolution reaction electrocatalyst obtained in this embodiment in the oxygen evolution reaction electrocatalytic performance test. It can be seen that the electrocatalytic activity of the carbon nanotube / ruthenium / cobalt oxide composite material in the oxygen evolution reaction is higher than that of iridium oxide, carbon nanotube / ruthenium and carbon nanotubes; the overpotentials corresponding to the current density of 10 mA / cm2 for the carbon nanotube / ruthenium / cobalt oxide composite material, carbon nanotube / ruthenium and carbon nanotubes are 300 mV, 323 mV and 386 mV, respectively; this proves that after carbon nanotubes are loaded with ruthenium and cobalt oxide, the electrocatalytic activity of the oxygen evolution reaction can be significantly enhanced; FIG6 (b) is the Tafel polarization curve of the carbon nanotube / ruthenium / cobalt oxide composite material, carbon nanotube / ruthenium, iridium oxide and carbon nanotubes. The carbon nanotube / ruthenium / cobalt oxide composite material has a lower Tafel slope (38 mV dec -1 ), which is significantly lower than commercial iridium oxide (48mV dec -1 ), carbon nanotube / ruthenium (51 mV dec -1 ) and carbon nanotubes (72 mV dec -1 ); This shows that the carbon nanotube / ruthenium / cobalt oxide composite material has a more favorable catalytic kinetics of oxygen evolution reaction; Figure 6 (c) is the electrochemical impedance spectrum. The interfacial charge transfer resistance (3.3 Ω) of the carbon nanotube / ruthenium / cobalt oxide composite material is smaller than that of carbon nanotube / ruthenium (8.9 Ω) and much smaller than that of carbon nanotube (12.7 Ω), which shows that the composite material has faster electron transfer characteristics than carbon nanotube / ruthenium and carbon nanotube.

[0059] Figure 7 This is the chronoamperometry curve of the oxygen evolution reaction electrocatalyst obtained in this example. It can be seen that after 24 hours, the current density of the carbon nanotube / ruthenium / cobalt oxide composite material is basically stable at the initial 10 mA / cm2, with almost no decrease, and the stability is significantly better than that of commercial iridium oxide.

[0060] In summary, from Figure 6 and Figure 7 It can be seen that the carbon nanotube / ruthenium / cobalt oxide composite material has excellent electrocatalytic activity and stability in oxygen evolution reaction.

[0061] Example 2

[0062] This embodiment provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising the following steps:

[0063] (1) A mixture of 5 g of carbon nanotubes, 1 g of triphenylphosphine ruthenium chloride, 1 g of cobalt nitrate hexahydrate, and 10 ml of anhydrous ethanol was placed in a 250 mL stainless steel ball mill containing 500 g of stainless steel balls. The ball mill was then sealed and fixed in a planetary ball mill and operated at 400 rpm for 40 h.

[0064] (2) The ball-milled mixture is taken out and soaked in 0.5 mol / L hydrochloric acid for 2 h. After soaking, it is vacuum freeze-dried for 10 h at a vacuum degree of 0.02 mmHg and a temperature of -60°C to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

[0065] The electrochemical test of the oxygen evolution reaction electrocatalyst obtained in this example showed that the overpotential of the oxygen evolution reaction corresponding to a current density of 10 mA / cm2 was 321 mV, and the Tafel slope was 45 mV dec. -1 .

[0066] Example 3

[0067] This embodiment provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising the following steps:

[0068] (1) A mixture of 10 g carbon nanotubes, 2 g triphenylphosphine ruthenium chloride, 10 g cobalt nitrate hexahydrate, and 80 mL anhydrous ethanol was placed in a 250 mL stainless steel ball mill containing 1000 g stainless steel balls, and then the ball mill was sealed and fixed in a planetary ball mill and operated at 600 rpm for 56 h;

[0069] (2) The ball-milled mixture was taken out and soaked in 1.5 mol / L hydrochloric acid for 10 h. After soaking, the mixture was freeze-dried at a vacuum degree of 0.08 mmHg and a temperature of -120°C for 20 h to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

[0070] The electrochemical test of the oxygen evolution reaction electrocatalyst obtained in this example showed that the overpotential of the oxygen evolution reaction corresponding to a current density of 10 mA / cm2 was 325 mV, and the Tafel slope was 45 mV dec. -1 .

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising the following steps:

[0073] (1) A mixture of 5 g of carbon nanotubes, 1 g of triphenylphosphine ruthenium chloride, 0.2 g of cobalt nitrate hexahydrate, and 20 mL of anhydrous ethanol was placed in a 250 mL stainless steel ball mill containing 650.0 g of stainless steel balls, and then the ball mill was sealed and fixed in a planetary ball mill and operated at a speed of 500 rpm for 48 h;

[0074] (2) The ball-milled mixture was taken out and soaked in 1.5 mol / L hydrochloric acid for 12 h. After soaking, the mixture was freeze-dried under vacuum conditions of 0.05 mmHg and -100 °C for 12 h to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

[0075] The oxygen evolution reaction electrocatalyst obtained in this comparative example was subjected to electrochemical testing. The overpotential of the oxygen evolution reaction corresponding to a current density of 10 mA / cm2 was 360 mV, and the Tafel slope was 90 mV dec. -1 This indicates that the composite structures of Examples 1 to 3 have a more favorable oxygen evolution reaction.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing an oxygen evolution reaction electrocatalyst, comprising the following steps:

[0078] (1) A mixture of 5 g of carbon nanotubes, 1 g of triphenylphosphine ruthenium chloride, 10 g of cobalt nitrate hexahydrate, and 20 mL of anhydrous ethanol was placed in a 250 mL stainless steel ball mill containing 650.0 g of stainless steel balls, and then the ball mill was sealed and fixed in a planetary ball mill and operated at a speed of 500 rpm for 48 h;

[0079] (2) The ball-milled mixture was taken out and soaked in 1.5 mol / L hydrochloric acid for 12 h. After soaking, the mixture was freeze-dried under vacuum conditions of 0.05 mmHg and -100 °C for 12 h to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

[0080] The oxygen evolution reaction electrocatalyst obtained in this comparative example was subjected to electrochemical testing. The overpotential of the oxygen evolution reaction corresponding to a current density of 10 mA / cm2 was 330 mV, and the Tafel slope was 75 mV dec. -1 This indicates that the composite structures of Examples 1 to 3 have a more favorable oxygen evolution reaction.

[0081] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an oxygen evolution reaction electrocatalyst, characterized in that: include: Putting a mixture of carbon nanotubes, triphenylphosphine ruthenium chloride, cobalt nitrate hexahydrate and anhydrous ethanol into a stainless steel ball mill containing stainless steel balls, and sealing and fixing the ball mill in a planetary ball mill, and ball milling for 40-56 hours at a rotation rate of 400-600 rpm; wherein the mass ratio of the carbon nanotubes, triphenylphosphine ruthenium chloride and cobalt nitrate hexahydrate is 10:2:2-10, and the mass ratio of the carbon nanotubes to the volume ratio of anhydrous ethanol is 1g:2-8mL; The ball-milled mixture is taken out and soaked in 0.5-1.5 mol / L hydrochloric acid for 2-10 hours. After soaking, vacuum freeze-drying is performed for 10-20 hours at a vacuum degree of 0.02-0.08 mmHg and a temperature of -60°C to -120°C to obtain a carbon nanotube / ruthenium / cobalt oxide composite material, which is an oxygen evolution reaction electrocatalyst.

2. The method for preparing an oxygen evolution reaction electrocatalyst according to claim 1, characterized in that: The mass ratio of the volume of the carbon nanotubes and the stainless steel ball mill to the stainless steel balls is 5 mL: 10-20 g.

3. The oxygen evolution reaction electrocatalyst prepared by the method of claim 1 or 2, characterized in that: The oxygen evolution reaction electrocatalyst comprises carbon nanotubes, and the outer wall of the carbon nanotubes is loaded with ruthenium nanoparticles and cobalt oxide nanoparticles.

4. Use of the oxygen evolution reaction electrocatalyst according to claim 3 in a water electrolysis hydrogen production electrolyzer and a metal-air battery.

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