A method for efficiently synthesizing oxygen reduction electrocatalyst, catalyst and application thereof

Abstract

The present invention belongs to the field of catalysts and relates to a method for efficiently synthesizing an oxygen reduction electrocatalyst, a catalyst thereof, and an application thereof. The method comprises the following steps: (1) selecting a metal source M and a base material N, and thoroughly mixing them to obtain an M-containing N powder; the metal source M is a metal element or a metal salt; and (2) placing the M-containing N powder in a metal container, and placing the metal container in a high-frequency induction heating device for induction heating to obtain the oxygen reduction electrocatalyst. The present invention uses instantaneous high-frequency electromagnetic induction heating to achieve instantaneous heating and calcination of the catalyst, achieving rapid reduction and anchoring of the metal substance on the surface of the base material in a very short time. The synthesis time is highly efficient, and the single sintering time is reduced by more than 10 times. The synthesis steps are simple, the power consumption is low, and the cost is low. The resulting catalyst has the characteristics of being difficult to agglomerate, having a higher loading capacity, and having high catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts, and specifically relates to a method for efficiently synthesizing an oxygen reduction electrocatalyst, an oxygen reduction electrocatalyst prepared by the method, and applications of the catalyst in fuel cells, electrochemical oxygen production, and electrochemical oxygen removal. Background Art

[0002] Energy and environmental issues are currently the most critical challenges facing human society, and there is an urgent need to develop a widely accessible green and clean energy source. In recent years, solar energy, fuel cells, and water electrolysis technologies have all achieved significant development. The oxygen reduction reaction, as the anode-side reaction in fuel cells, has a high activation energy due to the adsorption of oxygen molecules, the breaking of oxygen-oxygen bonds, and the formation of a large number of intermediates. This limits its widespread application. Therefore, developing superior oxygen reduction catalysts has become a crucial issue in this field.

[0003] The current focus of electrochemical oxygen reduction catalyst research is on ensuring high performance while reducing the use of precious metals, thereby achieving the synthesis of high-performance, low-cost catalysts. Consequently, from the early, expensive, high-loaded platinum-on-carbon catalysts to the recent design and research of alloy-based, single-atom, or non-precious metal nitrogen-on-carbon catalysts, extensive research and development efforts have been made in areas such as increasing active site density, regulating active sites to enhance intrinsic activity, promoting mass transfer, and optimizing testing processes.

[0004] However, all of the above studies have prioritized the use of precious metals in terms of cost, with little research on the feasibility of scaled-up synthesis, scale-up uniformity, and efficiency of synthesis steps. Therefore, whether it is platinum alloys or nitrogen-carbon materials based on non-precious metals such as iron, cobalt, and nickel, a high-temperature calcination process in a tubular furnace is basically used. This method has the problems of long synthesis time and high cost (a series of processes such as programmed temperature rise, calcination, and cooling, with a total time of more than 10 hours), low efficiency (only small batches can be synthesized for a long time, and a single synthesis level cannot be simply and directly scaled up to achieve mass production). At the same time, long-term high-temperature heating will also cause certain damage to the active material substrate (the loaded metal will cause damage to the conductive substrate material), exacerbating the further agglomeration of the loaded metal nanoparticles, thereby reducing the active sites and area. Summary of the Invention

[0005] In response to the problems of existing oxygen reduction electrocatalyst synthesis methods such as long synthesis time, low efficiency, high cost, and easy agglomeration of active metals, the present invention provides a method for efficiently synthesizing oxygen reduction electrocatalysts. Through instantaneous high-frequency electromagnetic induction heating, the catalyst is instantly heated and calcined, and the metal substance is quickly reduced and anchored on the surface of the substrate material in an extremely short time.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for efficiently synthesizing an oxygen reduction electrocatalyst, which comprises the following steps: (1) selecting a metal source M and a base material N, and thoroughly mixing them to obtain an M-containing N powder; the metal source M is a metal element or a metal salt; (2) placing the M-containing N powder in a metal container, and then placing the metal container in a high-frequency induction heating device for induction heating to obtain the oxygen reduction electrocatalyst.

[0007] In this invention, a high-frequency induction heating device capable of instantaneous heating is used to instantly heat and calcine the catalyst, thereby rapidly reducing and anchoring the metal material surrounding the support. This allows the specific metal to be quickly and efficiently anchored to the specific substrate material, resulting in a highly active oxygen reduction electrocatalyst. This synthesis method is simple, efficient, and low-cost, and can well meet the mass production requirements of practical industrial applications.

[0008] According to the present invention, preferably, the metal source M is selected from at least one of the metal salts of iron, cobalt, nickel, manganese, zinc, copper, gold, silver, palladium, ruthenium and platinum, preferably selected from at least one of the metal salts of iron, cobalt, nickel and platinum; the base material N is selected from at least one of activated carbon black porous carbon material, acetylene black porous carbon material and porous nitrogen carbon material.

[0009] According to the present invention, preferably, the base material N is BP2000 carbon black and / or a porous nitrogen-carbon material based on MOF calcination.

[0010] In the present invention, preferably, the metal source is in powder form.

[0011] According to the present invention, preferably, the thorough mixing is carried out in one of the following two ways:

[0012] A) dissolving a metal source M in a solvent to form a metal source M solution, then adding a base material N to the metal source M solution, and repeatedly grinding until the solution is dry to obtain an M-containing N powder; the solvent is at least one of water, methanol, ethanol, and isopropanol, and the amount used is 1000-10000% by weight of the base material N;

[0013] B) directly mixing the metal source M with the base material N and subjecting them to ball milling to obtain N powder containing M; the ball milling time is 0.5-10 hours and the rotation speed is 200-800 rpm.

[0014] In the present invention, preferably, the ball milling time is 2-4 hours and the rotation speed is 300-400 rpm.

[0015] In the present invention, to ensure sufficient mixing, the metal source can be first dissolved in a small amount of solvent and then mixed and ground with the base material N. Since the base material N is relatively light and fluffy, a solvent several dozen times its weight is required to better disperse the metal source M therein to form a uniform mixture. Therefore, the amount of solvent used in the present invention is 1000-10000% by weight of the base material N, preferably 1000-5000%. At the same time, in order to reduce the time required to grind until the solution dries, the present invention can use a highly volatile solvent to dissolve the metal source M, or water can be used as a solvent to dissolve the metal source M and grind at 50-60°C.

[0016] According to the present invention, preferably, after the M-containing N powder is placed in a metal tool, the metal tool is placed in an atmosphere tube, and then a protective gas flow is introduced into the atmosphere tube to induction heat the metal tool under a protective atmosphere; wherein, the atmosphere tube passes through the middle of the electromagnetic induction heating coil, and the protective gas flow is at least one of nitrogen, argon and a hydrogen-argon mixture.

[0017] In the present invention, the metal tool is preferably a magnetic or semi-magnetic metal, such as iron, nickel, etc. Catalytic materials that are particularly sensitive to oxygen can be heated under nitrogen protection.

[0018] According to the present invention, preferably, the amount of the metal source M added is such that the mass ratio of the metal element to the base material N in the oxygen reduction electrocatalyst is 1:20-200, and the material of the metal tool is at least one of iron, iron-nickel alloy, steel, cast iron, nickel and cobalt, preferably at least one of materials with high magnetic permeability such as iron, iron-nickel alloy and steel, more preferably iron; the shape of the metal tool can tightly fit the M-containing N powder, preferably, the shape of the metal tool is a flat metal trough, more preferably, the flat trough is covered with a metal sheet.

[0019] According to the present invention, preferably, the amount of the metal source M added is such that the mass ratio of the metal element to the base material N in the oxygen reduction electrocatalyst is 1:50-100.

[0020] In the present invention, the metal tank is an instantaneous heating plate, N powder containing M is spread flat in the metal tank, and a metal sheet is covered on the metal tank, and current induction generates a thermal effect.

[0021] According to the present invention, preferably, the high-frequency induction is an ordinary high-frequency induction heater, the power of the induction heating is not less than 1000W, and the time of the induction heating is 10-200s.

[0022] In the present invention, preferably, the power is 1000-3000W.

[0023] The second aspect of the present invention provides an oxygen reduction electrocatalyst prepared by the method for efficiently synthesizing an oxygen reduction electrocatalyst.

[0024] The third aspect of the present invention provides an application of the oxygen reduction electrocatalyst in fuel cells, zinc-air batteries, electrochemical oxygen production or electrochemical oxygen removal.

[0025] The present invention has the following advantages:

[0026] (1) The synthesis time is highly efficient, and the single sintering time is reduced by more than 10 times.

[0027] (2) The synthesis steps are simple, the power consumption is low, and the cost is low.

[0028] (3) Not easy to agglomerate and has a higher loading capacity.

[0029] (4) High catalytic performance.

[0030] (5) The synthesis method has good universality.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

[0033] Figure 1 The TEM image of the electrocatalyst synthesized in Comparative Example 1 is shown.

[0034] Figure 2 TEM image of the Fe / NC type electrocatalyst synthesized in Example 2 is shown.

[0035] Figure 3 The linear voltammetric scanning curves of the electrocatalysts synthesized in Examples 2-4 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0037] In this invention, the oxygen reduction (ORR) test method is: the ORR half-reaction test is carried out using a Chenhua 760e electrochemical workstation and a disk electrode. The catalyst loading (including the substrate) is 1 mg / cm 2The test environment was a 0.1M KOH solution saturated with oxygen at 25°C. The counter electrode was a platinum sheet, and the reference electrode was an Ag / AgCl sheet. The LSV test was conducted at a rotational speed of 1600 rpm. The reference platinum-carbon was 20% Pt / C from JM Company.

[0038] Example 1

[0039] 1. Weigh 50 mg of FeCl3 salt and dissolve it in 50 ml of ethanol to form a solution.

[0040] 2. Take 1g of BP2000 carbon black in a mortar, slowly add the above solution, and grind until dry.

[0041] 3. Spread the carbon black adsorbed with iron salt between two iron sheets (size 2.5cm*4cm*0.3cm) and place it in the middle of the electromagnetic induction heating coil.

[0042] 4. Turn on the electromagnetic induction heating device and turn off the power after running for 20 seconds.

[0043] 5. Wait for 4 minutes to cool down, then take it out and uncover the upper iron sheet to get the synthesized FeO X / NC-type oxygen reduction electrocatalysts.

[0044] Example 2

[0045] 1. Weigh 60 mg of Fe(NO3)3 salt and dissolve it in 50 ml of ethanol to form a solution;

[0046] 2. Take 1g of BP2000 carbon black in a mortar, slowly add the above solution, and grind until dry;

[0047] 3. Spread the carbon black adsorbed with iron salt between two iron sheets (size 2.5cm*4cm*0.3cm), and then place it in the atmosphere tube, which passes through the middle of the electromagnetic induction heating coil.

[0048] 4. Turn on the nitrogen protective gas flow, then turn on the electromagnetic induction heating device, run for 20 seconds and then turn off the power.

[0049] 5. Wait for 4 minutes to cool down, then take it out and uncover the upper iron sheet to obtain the synthesized Fe / NC type oxygen reduction electrocatalyst.

[0050] Example 3

[0051] 1. Weigh 40 mg of Co(NO3)2 salt and add it to 1 g of XC-72 carbon black;

[0052] 2. Ball mill the above mixture for 1 hour at a speed of 300 rpm to mix thoroughly;

[0053] 3. Spread the fully mixed carbon black flat in an iron trough (size 2.5cm*4cm*0.3cm), and then place it in the atmosphere tube, which passes through the middle of the electromagnetic induction heating coil.

[0054] 4. Turn on the nitrogen protective gas flow, then turn on the electromagnetic induction heating device, and turn off the power after running for 15 seconds.

[0055] 5. Wait for 3 minutes to cool down, then take it out and uncover the upper iron sheet to obtain the synthesized Co / NC type oxygen reduction electrocatalyst.

[0056] Example 4

[0057] 1. Weigh 10 mg of Fe(NO3)3 salt and dissolve it in 50 ml of ethanol to form a solution;

[0058] 2. Take 1g of BP2000 carbon black in a mortar, slowly add the above solution, and grind until dry;

[0059] 3. Spread the carbon black adsorbed with iron salt between two iron sheets (size 2.5cm*4cm*0.3cm), and then place it in the atmosphere tube, which passes through the middle of the electromagnetic induction heating coil.

[0060] 4. Turn on the nitrogen protective gas flow, then turn on the electromagnetic induction heating device, run for 20 seconds and then turn off the power.

[0061] 5. Wait for 4 minutes to cool down, then take it out and uncover the upper iron sheet to obtain the synthesized Fe / NC type oxygen reduction electrocatalyst.

[0062] Comparative Example 1

[0063] 1. Weigh 60 mg of Fe(NO3)3 salt and dissolve it in 50 ml of ethanol to form a solution;

[0064] 2. Take 1g of BP2000 carbon black in a mortar, slowly add the above solution, and grind until dry;

[0065] 3. Take 100 mg of the above-ground sample and place it in a magnetic boat in a tube furnace. In a nitrogen atmosphere, heat it to 900°C at a rate of 5°C / min, maintain it at 900°C for 2 hours, and then cool it naturally.

[0066] 4. When the temperature reaches about 25 degrees, open the tube furnace and take out the sample.

[0067] Test Case

[0068] The synthesized electrocatalyst was observed using a TEM electron microscope. The TEM electron microscope of the electrocatalyst synthesized in Comparative Example 1 showed the following Figure 1As shown, the TEM electron microscope of the Fe / NC type electrocatalyst synthesized in Example 2 shows that Figure 1 As shown, from Figure 1 and Figure 2 It can be seen that no obvious metal nanoparticles were found in the oxygen reduction electrocatalysts synthesized by the two methods, but Figure 2 The sintering agglomeration of medium calcination is lower and the loading capacity can be higher.

[0069] The electrocatalysts synthesized in Examples 2-4 and Comparative Example 1 and the Pt / C electrocatalyst were subjected to oxygen reduction catalytic performance evaluation. Figure 3 As shown. Figure 3 It can be seen that the half-wave potential is about 0.87 V for Example 2, 0.86 V for Pt / C, and 0.85 V for Comparative Example 1; the Fe / NC oxygen reduction electrocatalyst obtained in Example 2 has the best catalytic performance.

[0070] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for synthesizing an oxygen reduction electrocatalyst, wherein the catalyst is instantaneously heated and calcined by instantaneous high-frequency electromagnetic induction heating, thereby achieving rapid reduction and anchoring of a metal substance on the surface of a substrate material, characterized in that: The method comprises the following steps: (1) selecting a metal source M and a base material N, and thoroughly mixing them to obtain an M-containing N powder; the metal source M is a metal salt of iron or cobalt; the amount of the metal source M added is such that the mass ratio of the metal element in the oxygen reduction electrocatalyst to the base material N is 1:50-100; (2) placing the M-containing N powder in a metal container, and placing the metal container in a high-frequency induction heating device for induction heating to obtain the oxygen reduction electrocatalyst; the induction heating power is 1000-3000 W, and the induction heating time is 10-200 s; The base material N is selected from at least one of activated carbon black porous carbon material, acetylene black porous carbon material and porous nitrogen carbon material; After placing the M-containing N powder in a metal tool, the metal tool is placed in an atmosphere tube, and then a protective gas flow is introduced into the atmosphere tube to induction heat the metal tool under the protective atmosphere; wherein the atmosphere tube passes through the middle of the electromagnetic induction heating coil, and the protective gas flow is at least one of nitrogen, argon and a hydrogen-argon mixture.

2. The method for synthesizing an oxygen reduction electrocatalyst according to claim 1, wherein: The substrate material N is BP2000 carbon black and / or a porous nitrogen-carbon material based on MOF calcination.

3. The method for synthesizing an oxygen reduction electrocatalyst according to claim 1 or 2, wherein: The thorough mixing is carried out in one of the following two ways: A) dissolving a metal source M in a solvent to form a metal source M solution, then adding a base material N to the metal source M solution, and repeatedly grinding until the solution is dry to obtain an M-containing N powder; the solvent is at least one of water, methanol, ethanol, and isopropanol; B) directly mixing the metal source M with the base material N and subjecting them to ball milling to obtain N powder containing M; the ball milling time is 0.5-10 hours and the rotation speed is 200-800 rpm.

4. The method for synthesizing an oxygen reduction electrocatalyst according to claim 1 or 2, wherein: The material of the metal tool is at least one of iron, iron-nickel alloy, steel, nickel and cobalt; the shape of the metal tool is a flat groove, and the flat groove is covered with a metal sheet.

5. An oxygen reduction electrocatalyst prepared by the method for synthesizing an oxygen reduction electrocatalyst according to any one of claims 1 to 4.

6. Use of the oxygen reduction electrocatalyst according to claim 5 in the fields of fuel cells, zinc-air batteries, electrochemical oxygen production or electrochemical oxygen removal.

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