Porous catalytic electrode and method of making and using same

Abstract

The present application relates to the technical field of electrode preparation, and particularly relates to a porous catalytic electrode and a preparation method and application thereof. The preparation method comprises the following steps: S1: mixing a first powder and a second powder to obtain a spraying powder; S2: depositing the spraying powder on a substrate electrode to obtain a catalytic electrode; and S3: using alkali liquor to perform dealumination activation on the catalytic electrode; wherein the first powder comprises an aluminum-containing mixed powder and / or an alloy powder, and the second powder is aluminum powder; the particle size of the first powder is 200-400 mesh, and the particle size of the second powder is 450-1500 mesh. By optimizing the composition and particle size of the spraying powder, the present application can improve the adhesion between powders in the plasma spraying process, and finally improve the coating bonding force, and can also improve the catalytic activity of the electrode.

Description

Technical Field

[0001] This invention relates to the field of electrode preparation technology, and in particular to a porous catalytic electrode, its preparation method, and its application. Background Technology

[0002] Currently, plasma spraying technology is commonly used for alkaline water electrolysis hydrogen production electrodes. This typically involves mechanically mixing ① (mixed powder) nickel and aluminum (or introducing other metals) or directly using ② (alloy powder) aluminum-containing alloy powder as the spraying formulation. During the spraying process, the powder is heated to a semi-molten state to enhance the adhesion between the coating and the substrate. Finally, it undergoes alkaline treatment to partially remove the aluminum, resulting in a porous structure after activation to improve electrode activity (see details in [link]). Figure 1 ).

[0003] However, the above-mentioned powder coating has the following problems:

[0004] 1. For type ① formulations (mixed powders), the coating adhesion is limited. The semi-molten nickel and aluminum phase separation structure in the plasma spraying process makes it easy for aluminum to be removed during the activation process, which to some extent reduces the adhesion between the coating and the substrate.

[0005] 2. For type ② formulations (alloy powder), the coating adhesion is generally poor. Although its activity is often better, the aluminum in the alloy phase has already undergone one exothermic process during alloying. The heat release during the spraying process is limited, and only a limited part is heated to a semi-molten state, which leads to a decrease in the adhesion between the alloy and the substrate. Furthermore, after activation, the aluminum is further lost, which further reduces the adhesion.

[0006] 3. After alkaline treatment, the pore structure is relatively independent or closed, resulting in limited improvement in electrode activity. Because nickel and aluminum form a stacked structure after melting during plasma spraying, even after alkaline treatment, there are still many non-through-hole structures and few through-hole structures.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a porous catalytic electrode, its preparation method, and its application, in order to overcome the above-mentioned defects in the prior art.

[0009] This invention first provides a method for preparing a porous catalytic electrode, comprising:

[0010] S1: Mix the first powder and the second powder to obtain the coating powder;

[0011] S2: The sprayed powder is deposited onto the substrate electrode to obtain a catalytic electrode;

[0012] S3: The catalytic electrode is activated by aluminum removal using an alkaline solution;

[0013] Wherein, the first powder includes aluminum-containing mixed powder and / or alloy powder, and the second powder is aluminum powder;

[0014] The particle size of the first powder is 200-400 mesh, and the particle size of the second powder is 450-1500 mesh.

[0015] According to the method for preparing a porous catalytic electrode provided by the present invention, the amount of the first powder in the sprayed powder is 70-99 wt%.

[0016] According to the method for preparing a porous catalytic electrode provided by the present invention, the first powder is a mixture of aluminum powder and other metal powders; the other metal powders include one or more of nickel powder, iron powder, molybdenum powder, cobalt powder, nickel-iron alloy powder, nickel-molybdenum alloy powder, iron-molybdenum alloy powder, and cobalt-nickel alloy powder; wherein, the amount of aluminum powder in the first powder is 3 to 40 wt%.

[0017] According to the method for preparing a porous catalytic electrode provided by the present invention, the sprayed powder in S1 further contains carbon nanotubes and / or carbon nanofibers.

[0018] According to the method for preparing a porous catalytic electrode provided by the present invention, the amount of carbon nanotubes in the sprayed powder is 0.1-10 wt%.

[0019] According to the method for preparing a porous catalytic electrode provided by the present invention, the preparation method further includes S4, wherein S4 includes: subjecting the catalytic electrode to a first calcination treatment to obtain a porous catalytic electrode;

[0020] The first calcination treatment includes: first calcining the catalytic electrode in a calcination atmosphere of 90-100 vol% inert gas and 1-10 vol% oxygen, and then calcining it in an inert gas calcination atmosphere.

[0021] According to the method for preparing a porous catalytic electrode provided by the present invention, the preparation method further includes S5, wherein S5 includes S51 or S52:

[0022] S51: The porous catalytic electrode is subjected to a second calcination treatment under a reducing atmosphere;

[0023] S52: The porous catalytic electrode is assembled as a cathode in an electrolytic cell to carry out an electrochemical reduction reaction, wherein the electrolyte is an alkaline solution.

[0024] According to the method for preparing a porous catalytic electrode provided by the present invention, the calcination temperature of the first calcination treatment is 400-900 degrees Celsius;

[0025] The calcination temperature for the second calcination treatment is 200–700 degrees Celsius.

[0026] The present invention also provides a porous catalytic electrode, which is prepared by the above-described preparation method.

[0027] The present invention also provides the application of the porous catalytic electrode in the hydrogen evolution reaction.

[0028] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0029] This invention optimizes the composition and particle size of the sprayed powder, thereby improving the adhesion between powders during the plasma spraying process, ultimately enhancing the coating adhesion, and also improving the catalytic activity of the electrode. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a flowchart of the traditional plasma spraying method for preparing alkaline water electrolysis hydrogen production electrodes in the background technology;

[0032] Figure 2 The flowchart of the preparation of the porous catalytic electrode in Example 1 provided by the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] In existing research on alkaline water electrolysis hydrogen production electrodes, most studies focus on optimizing the powder composition, with the powder particle size generally selected within the conventional range of 200-300 mesh. This invention breaks away from this conventional thinking and unexpectedly discovers that the simultaneous presence of aluminum powder with different particle sizes in the spraying powder can ensure the catalytic activity of the electrode while significantly improving the adhesion between powders during the plasma spraying process, ultimately enhancing the coating adhesion.

[0035] Based on this, the present invention first provides a method for preparing a porous catalytic electrode, comprising:

[0036] S1: Mix the first powder and the second powder to obtain the coating powder;

[0037] S2: The sprayed powder is deposited onto the substrate electrode to obtain a catalytic electrode;

[0038] S3: The catalytic electrode is activated by aluminum removal using an alkaline solution;

[0039] Wherein, the first powder includes aluminum-containing mixed powder and / or alloy powder, and the second powder is aluminum powder;

[0040] The particle size of the first powder is 200-400 mesh, and the particle size of the second powder is 450-1500 mesh.

[0041] In this invention, the substrate electrode can be a nickel alloy woven mesh, an iron / iron alloy woven mesh, a copper / copper alloy woven mesh, or their punched or sheet metal structures.

[0042] More preferably, the particle size of the first powder is 200-300 mesh, and the particle size of the second powder is 450-1500 mesh.

[0043] In specific implementation, those skilled in the art can use plasma spraying technology to perform the deposition, and no further limitations are made here. Preferably, the spraying parameters are: current 600-900 amperes, voltage 40-60 volts, argon flow rate 35-60 liters / minute, hydrogen flow rate 0.5-35 liters / minute, and gun distance 10-30 mm.

[0044] In the specific implementation process, those skilled in the art can use mechanical mixing or ball milling to mix the spray powder evenly.

[0045] In this invention, the alkaline solution comprises 3-30 wt% sodium hydroxide or potassium hydroxide solution.

[0046] According to a preferred embodiment of the present invention, the amount of the first powder in the spraying powder is 70-99 wt%.

[0047] According to a preferred embodiment of the present invention, when the mass ratio of the first powder to the second powder is 85-95:5-10, the finer aluminum powder can be fully melted into smaller droplets during the spraying process, resulting in more sufficient contact between the metal powders and ultimately improving the coating adhesion.

[0048] According to a preferred embodiment of the present invention, the first powder is a mixture of aluminum powder and other metal powders; the other metal powders include one or more of nickel powder, iron powder, molybdenum powder, cobalt powder, nickel-iron alloy powder, nickel-molybdenum alloy powder, iron-molybdenum alloy powder, and cobalt-nickel alloy powder; wherein the amount of aluminum powder in the first powder is 3 to 40 wt%, more preferably 15 to 20 wt%.

[0049] According to a preferred embodiment of the present invention, the spray powder in S1 further contains carbon nanotubes and / or carbon nanofibers.

[0050] The carbon nanotube is one of single-walled carbon nanotubes, multi-walled carbon nanotubes, twisted carbon nanotubes, Armstrong carbon nanotubes, Wilson carbon nanotubes, single-end open carbon nanotubes, double-end open carbon nanotubes, and non-metallic element-doped carbon nanotubes, with an outer diameter of 5-25 nanometers and a length of 1-100 micrometers; more preferably, the outer diameter is 15-25 nanometers and the length is 5-20 micrometers.

[0051] The carbon nanofibers have an outer diameter of 5–200 nanometers and a length of 1–200 micrometers; more preferably, the outer diameter is 50–100 nanometers and the length is 5–20 micrometers.

[0052] This invention discovers that carbon nanotubes and carbon nanofibers, compared to other carbon-based materials, have a unique slender structure that allows for uniform doping in the coating after spraying. After dealumination activation, further heat treatment removes the uniformly doped carbon nanotubes, forming a through-hole / through-pore structure. Therefore, introducing carbon nanotubes can construct a through-hole structure, which not only increases the specific surface area of ​​the electrode, but also improves the mass transfer efficiency and significantly enhances the electrode activity.

[0053] According to a preferred embodiment of the present invention, the amount of carbon nanotubes in the spray powder is 0.1-10 wt%, more preferably 5-8 wt%.

[0054] According to a preferred embodiment of the present invention, the preparation method further includes S4, which includes: subjecting the catalytic electrode to a first calcination treatment to obtain a porous catalytic electrode;

[0055] The first calcination process is carried out at high temperature in air or an oxygen-containing mixed atmosphere. The oxygen-containing mixed atmosphere is a mixture of oxygen and an inert gas. The oxygen concentration in the mixed gas is not higher than 5%, and the remaining components are inert gases, which are either nitrogen or argon.

[0056] More preferably, the first calcination treatment includes: first calcining the catalytic electrode in a calcination atmosphere of 95-99 wt% inert gas and 1-5 wt% oxygen, and then calcining it in an inert gas calcination atmosphere.

[0057] This invention has found that the above-mentioned post-calcination treatment process is beneficial for removing carbon nanotubes to form a porous structure, thereby improving both coating adhesion and electrode activity.

[0058] In this invention, the switching of the calcination atmosphere can reduce the metal oxides formed under the previous oxygen-containing atmosphere calcination, thereby improving the electrode conductivity.

[0059] According to a preferred embodiment of the present invention, the calcination time of the first calcination treatment is 0.1 to 2 hours.

[0060] In this invention, before performing S4, the electrode is first activated by the alkaline solution and then dried. The preferred drying conditions are drying at 50-70 degrees Celsius for 10-15 hours.

[0061] According to a preferred embodiment of the present invention, the preparation method further includes S5, wherein S5 includes S51 or S52:

[0062] S51: The porous catalytic electrode is thermally reduced, preferably the porous catalytic electrode is subjected to a second calcination treatment in a mixed atmosphere containing a reducing gas, wherein the reducing gas is one of H2 or ammonia, and the remaining gas in the mixed atmosphere is nitrogen or argon.

[0063] S52: The porous catalytic electrode is electro-reduced, preferably the porous catalytic electrode is assembled as a cathode in an electrolytic cell for electrochemical reduction reaction, wherein the electrolyte is an alkaline solution; preferably, the electrochemical reduction reaction includes cyclic voltammetry (CV), constant current electrolysis, and constant voltage electrolysis.

[0064] According to a preferred embodiment of the present invention, the calcination temperature of the first calcination treatment is 400-900 degrees Celsius;

[0065] The calcination temperature for the second calcination treatment is 400–800 degrees Celsius.

[0066] According to a preferred embodiment of the present invention, the calcination time of the second calcination treatment is 0.5 to 6 hours.

[0067] According to a preferred embodiment of the present invention, the method for preparing the porous catalytic electrode includes:

[0068] S1: The first powder, the second powder, and carbon nanotubes are mixed to obtain a coating powder; wherein the first powder includes an aluminum-containing mixed powder and / or alloy powder, and the second powder is aluminum powder; the particle size of the first powder is 200-300 mesh, and the particle size of the second powder is 450-1500 mesh.

[0069] S2: The sprayed powder is deposited onto the substrate electrode to obtain a catalytic electrode;

[0070] S3: The catalytic electrode is activated by aluminum removal using an alkaline solution;

[0071] S4: The catalytic electrode is subjected to a first calcination treatment to obtain a porous catalytic electrode; wherein, the first calcination treatment includes: first calcining the catalytic electrode in a calcination atmosphere of 90-100 wt% inert gas and 1-10 wt% oxygen, and then calcining it in an inert gas calcination atmosphere, with a calcination temperature of 400-900 degrees Celsius.

[0072] S5 includes S51 or S52:

[0073] S51: The porous catalytic electrode is subjected to a second calcination treatment under a reducing atmosphere; wherein the calcination temperature of the first calcination treatment is 400-900 degrees Celsius;

[0074] S52: The porous catalytic electrode is assembled as a cathode in an electrolytic cell to carry out an electrochemical reduction reaction, wherein the electrolyte is an alkaline solution.

[0075] According to a preferred embodiment of the present invention, the method for preparing the porous catalytic electrode includes:

[0076] S1: The first powder, the second powder, and carbon nanotubes are mixed to obtain a coating powder; wherein the first powder includes an aluminum-containing mixed powder and / or alloy powder, and the second powder is aluminum powder; the particle size of the first powder is 200-300 mesh, and the particle size of the second powder is 400-500 mesh.

[0077] S2: The spray powder is deposited onto the substrate electrode using plasma spraying to obtain a catalytic electrode;

[0078] S3: The catalytic electrode is activated by aluminum removal using an alkaline solution, and then dried;

[0079] S4: The catalytic electrode is subjected to a first calcination treatment to obtain a porous catalytic electrode; wherein, the first calcination treatment includes: first calcining the catalytic electrode in a calcination atmosphere of 95-99 vol% inert gas and 1-5 vol% oxygen, then calcining it in a calcination atmosphere of inert gas, and then cooling it to room temperature; the calcination temperature is 400-900 degrees Celsius; after calcination, the electrode is cleaned and dried.

[0080] S5 includes S51 or S52:

[0081] S51: The porous catalytic electrode is subjected to a second calcination treatment in a calcination atmosphere of 90-100 vol% inert gas and 1-10 vol% hydrogen, and then cooled to room temperature; wherein the calcination temperature of the first calcination treatment is 400-900 degrees Celsius.

[0082] S52: The porous catalytic electrode is assembled as a cathode in an electrolytic cell and an electrochemical reduction reaction is carried out at a current density of 3 kA / m² for 8–12 hours; wherein the electrolyte is an alkaline solution.

[0083] Preferably, the alkaline solution is a 30 wt% aqueous solution of potassium hydroxide.

[0084] Secondly, the present invention provides a porous catalytic electrode, which is prepared by the above-described preparation method.

[0085] Thirdly, the present invention provides the application of the porous catalytic electrode in the hydrogen evolution reaction.

[0086] Unless otherwise specified, all raw materials used in the embodiments are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0087] Example 1

[0088] This embodiment provides a porous catalytic electrode (see the fabrication flowchart). Figure 2 The preparation method includes the following steps:

[0089] (1) 250 mesh nickel powder, 250 mesh aluminum powder, 450 mesh aluminum powder and carbon nanotubes in a mass ratio of 70:20:8:2 are mixed evenly by ball milling; wherein the carbon nanotubes are single-walled carbon nanotubes with an outer diameter of 20 nanometers and a length of 10 micrometers.

[0090] (2) The above powder was sprayed onto a conductive base material nickel braided mesh using a plasma spraying process. The spraying parameters were: current 680 amps, voltage 51 volts, argon flow rate 48 liters / minute, hydrogen flow rate 1.5 liters / minute, and gun distance 200 mm.

[0091] (3) Place the woven mesh from step (2) in a 30wt% potassium hydroxide solution for activation and dealuminization, and then dry it.

[0092] (4) The activated electrode obtained in (3) was placed in an atmosphere of 85 vol% inert gas and 0.15 vol% oxygen and calcined at 800 degrees Celsius for 1 hour. Then the atmosphere was changed to pure inert gas and cooled to room temperature.

[0093] (5) Clean and dry the electrode in (4).

[0094] (6) The electrode in (5) was placed in an atmosphere of 95 vol% inert gas and 5 vol% hydrogen, and reduced at 700 degrees Celsius for 4 hours. After cooling to room temperature, the atmosphere was removed.

[0095] Example 2

[0096] This embodiment provides a porous catalytic electrode, the preparation method of which differs from that of Example 1 only in that step (6) is changed to: the electrode in (5) is cut to any size as required and assembled into an electrolytic cell as a cathode, the electrolyte is 30wt% potassium hydroxide, and it is reduced for 10 hours at a current density of 3 kA / m².

[0097] Example 3

[0098] This embodiment provides a porous catalytic electrode, the only difference between which is the preparation method and that of Example 1: the mixture of 250 mesh nickel powder and 250 mesh aluminum powder is replaced with an equal amount of 200 mesh nickel-aluminum alloy powder.

[0099] Example 4

[0100] This embodiment provides a porous catalytic electrode, the only difference between its preparation method and that of Embodiment 1 is that the carbon nanotubes are replaced with an equal amount of carbon nanofibers; the carbon nanofibers have an outer diameter of 50 meters and a length of 10 micrometers.

[0101] Example 5

[0102] This embodiment provides a porous catalytic electrode, the only difference between its preparation method and that of Example 1 is that step (6) is not included.

[0103] Example 6

[0104] This embodiment provides a porous catalytic electrode, the only difference between its preparation method and that of Example 1 is that the calcination temperature in step (4) is 700 degrees Celsius and the calcination temperature in step (6) is 800 degrees Celsius.

[0105] Comparative Example 1

[0106] This embodiment provides a porous catalytic electrode, the only difference between its preparation method and that of Example 1 is that the particle size of the metal powder in step (1) is 250 mesh.

[0107] Comparative Example 2

[0108] This embodiment provides a porous catalytic electrode, the only difference between its preparation method and that of Example 1 is that the carbon nanotubes are replaced with an equal amount of carbon black.

[0109] Experimental Example

[0110] The present invention further tested the effects (including the bonding strength between the substrate electrode and the coating, electrode performance, etc.) of the porous catalytic electrodes prepared in the examples and comparative examples. The test results are shown in Table 1:

[0111] Table 1

[0112]

[0113] The electrode weight loss test method includes the following steps: 1. Weigh the electrode to be tested before the test; 2. Immerse the electrode to be tested in a beaker filled with water, place the beaker in an ultrasonic machine, and sonicate continuously for 3 hours. After cleaning and drying, weigh the electrode after the test; 3. Calculate the difference in electrode weight before and after the test, and further calculate to obtain the percentage of electrode weight loss.

[0114] Potential testing method: A three-electrode electrochemical testing system was used, with a saturated calomel electrode as the reference electrode, at 3kA / m 2 The potential of the working electrode was tested under electrical pressure. The working electrode was used as the cathode and anode respectively to test the hydrogen evolution overpotential and oxygen evolution overpotential of the electrode.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous catalytic electrode, characterized in that, include: S1: Mix the first powder and the second powder to obtain the coating powder; S2: The sprayed powder is deposited onto the substrate electrode to obtain a catalytic electrode; S3: The catalytic electrode is activated by aluminum removal using an alkaline solution; Wherein, the first powder is a mixture of aluminum powder and other metal powders, and the second powder is aluminum powder; The particle size of the first powder is 200-400 mesh, and the particle size of the second powder is 450-1500 mesh; The amount of aluminum powder in the first powder is 3~40 wt%; The spray powder also contains carbon nanotubes and / or carbon nanofibers.

2. The method for preparing a porous catalytic electrode according to claim 1, characterized in that, In the spraying powder, the amount of the first powder is 70~99wt%.

3. The method for preparing a porous catalytic electrode according to claim 1, characterized in that, The other metal powders include one or more of the following: nickel powder, iron powder, molybdenum powder, cobalt powder, nickel-iron alloy powder, nickel-molybdenum alloy powder, iron-molybdenum alloy powder, and cobalt-nickel alloy powder.

4. The method for preparing a porous catalytic electrode according to claim 1, characterized in that, The amount of carbon nanotubes used in the spray powder is 0.1~10wt%.

5. The method for preparing a porous catalytic electrode according to any one of claims 1 to 4, characterized in that, The preparation method further includes S4, which includes: subjecting the dealuded and activated catalytic electrode to a first calcination treatment to obtain a porous catalytic electrode; The first calcination treatment includes: first calcining the dealuminized and activated catalytic electrode in a calcination atmosphere of 90-100 vol% inert gas and 1-10 vol% oxygen, and then calcining it in an inert gas calcination atmosphere.

6. The method for preparing a porous catalytic electrode according to claim 5, characterized in that, The preparation method further includes step S5, wherein step S5 includes step S51 or step S52: S51: The porous catalytic electrode is subjected to a second calcination treatment under a reducing atmosphere; S52: The porous catalytic electrode is assembled as a cathode in an electrolytic cell to carry out an electrochemical reduction reaction, wherein the electrolyte in the electrolytic cell is an alkaline aqueous solution.

7. The method for preparing a porous catalytic electrode according to claim 6, characterized in that, The calcination temperature of the first calcination treatment is 400~900 degrees Celsius; the calcination temperature of the second calcination treatment is 200~700 degrees Celsius.

8. A porous catalytic electrode, characterized in that, It is prepared by any one of claims 1 to 7.

9. The application of the porous catalytic electrode according to claim 8 in the hydrogen evolution reaction.

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