Preparation method of a nano-cemented carbide compound electrocatalyst with multiple defective active sites

Abstract

Preparation method of nano-cemented carbide compound electrocatalyst with multiple defect active sites. The present invention relates to a preparation method of nano-cemented carbide compound electrocatalyst, and solves the problem that it is difficult to improve the catalytic activity of cemented carbide type compounds through defect engineering. The preparation method includes: 1. Synthesis of precursor; 2. Preparation of active substance; 3. Applying inductively coupled plasma to the active substance. The present invention is used for the preparation of nano-cemented carbide compound electrocatalyst with multiple defect active sites.

Description

Technical Field

[0001] The present invention relates to a preparation method of a nano-carbide composite electrocatalyst. Background Art

[0002] High catalytic activity and high stability are the two most important indicators concerned by electrocatalysts. Designing and developing electrocatalysts with both high catalytic activity and high stability is the cornerstone of preparing high-purity hydrogen and developing a hydrogen energy economy.

[0003] Nano-structured carbide composite compounds represented by carbides and nitrides exhibit excellent chemical stability and mechanical properties, but their natural lack of catalytic activity limits their potential for industrial catalytic applications. How to improve their catalytic activity has become a problem of widespread concern. In recent years, methods for improving carbide composite compounds by designing nano-structures, doping, surface reconstruction, morphology control, etc. have been widely studied. However, due to the hard and brittle nature of carbide-type compounds, creating controllable defects on them has always been a problem that is difficult to overcome. Therefore, there is little research on improving the catalytic activity of carbide composite compounds through defect engineering. Summary of the Invention

[0004] The present invention aims to solve the problem that it is difficult to improve the catalytic activity of carbide-type compounds through defect engineering, and further provides a preparation method of a nano-carbide composite electrocatalyst with multiple defect active sites.

[0005] A preparation method of a nano-carbide composite electrocatalyst with multiple defect active sites is carried out according to the following steps:

[0006] I. Precursor synthesis:

[0007] Mix a molybdate solution with dilute hydrochloric acid to obtain a mixed solution. Immerse the activated conductive substrate in the mixed solution and place it in the inner container. Seal the inner container and put it into the stainless steel outer cover. Then, under the condition of a temperature of 150 °C to 300 °C, keep warm for 8 h to 20 h. After cooling to room temperature, take out the conductive substrate, wash and dry it to obtain a substrate with a precursor grown on it;

[0008] The concentration of molybdate in the mixed solution is 0.05 mol / L to 0.08 mol / L, and the concentration of hydrochloric acid in the mixed solution is 0.5 mol / L to 1 mol / L;

[0009] II. Preparation of active substances:

[0010] Place the activation source upstream of the gas in the tube furnace, place the substrate with the precursor grown on it downstream of the gas, introduce the reaction gas, and connect to the external air to maintain normal pressure inside the furnace. Under the conditions that the reaction gas flow rate is 50 sccm to 200 sccm and the heating rate is 10 °C / min to 15 °C / min, raise the temperature inside the furnace from room temperature to 750 °C to 900 °C, and keep it warm for 1.5 h to 4 h under the condition that the temperature is 750 °C to 900 °C. After cooling, take it out to obtain the substrate with the active substance grown on it;

[0011] III. Apply inductive plasma to the active substance:

[0012] ①. Place the substrate with the active substance grown on it inside the furnace chamber of the plasma chemical vapor deposition furnace;

[0013] ②. At room temperature, close the intake valve, open the exhaust valve, use the exhaust pump to pump the air pressure inside the furnace to 0.1 torr to 10 torr, then close the exhaust valve, open the intake valve, and introduce the gas at a flow rate of 10 sccm to 200 sccm until the air pressure is 100 torr to 700 torr;

[0014] ③. Repeat step III② 2 to 3 times, then open the exhaust valve and the intake valve, adjust the air pressure inside the furnace to 0.2 torr to 0.7 torr. Under the conditions that the low pressure inside the furnace is 0.2 torr to 0.7 torr and the heating rate is 10 °C / min to 15 °C / min, raise the temperature inside the furnace from room temperature to 200 °C to 500 °C;

[0015] ④. At the temperature of 200 °C to 500 °C, start the plasma radio frequency power supply. Under the conditions that the low pressure inside the furnace is 0.2 torr to 0.7 torr, the temperature is 200 °C to 500 °C, and the plasma radio frequency power is 200 W to 300 W, use the plasma to etch the active substance, and thus complete the preparation of the electrocatalyst of the nano-hard alloy compound with multiple defect active sites.

[0016] The beneficial effects of the present invention are:

[0017] (1) In the present invention, the nano-hard alloy compound is grown on the surface of the conductive substrate. The nano-hard alloy compound is nano-ribbon-shaped, with a width of about 500 nm and a thickness of about 50 nm. Using uniform plasma as the medium for nano-hard alloy processing can ensure the overall surface treatment of the nano-hard alloy compound in the plasma atmosphere. On the premise of controlling that the basic geometric structure is not damaged, the uniformity of defects on the nano-hard alloy structure can be achieved, and the degree of defects can be flexibly regulated by the plasma temperature. This method has good effectiveness and flexibility for creating the defect structure of the nano-hard alloy.

[0018] (2) After plasma treatment, the defect active sites created on the surface of the nano-hard alloy-type compound effectively enhance the electrocatalytic performance for both hydrogen and oxygen evolution. In the hydrogen evolution and oxygen evolution reactions, at a current density of 10 mA / cm 2 , the overpotentials for hydrogen evolution and oxygen evolution of Ar-Mo2C are 151 mV and 446 mV, respectively. Description of the Drawings

[0019] Figure 1 is an X-ray diffraction spectrum. a is the substrate with active substances grown in Step 2 of Example 1, and b is the electrocatalyst of nano-hard alloy compound with multiple defect active sites prepared in Step 3 of Example 1;

[0020] Figure 2 is a scanning electron microscope image of Mo2C prepared in Step 2 of Example 1;

[0021] Figure 3 is a scanning electron microscope image of Ar-Mo2C prepared in Step 3 of Example 1;

[0022] Figure 4 is the stability test curve of the electrocatalytic hydrogen evolution reaction of Ar-Mo2C prepared in Step 3 of Example 1;

[0023] Figure 5 is the stability test curve of the electrocatalytic oxygen evolution reaction of Ar-Mo2C prepared in Step 3 of Example 1;

[0024] Figure 6 is the impedance spectrum of the electrocatalytic hydrogen evolution reaction. 1 is the carbon cloth, 2 is Mo2C prepared in Step 2 of Example 1, and 3 is Ar-Mo2C prepared in Step 3 of Example 1;

[0025] Figure 7 is the impedance spectrum of the electrocatalytic oxygen evolution reaction. 1 is the carbon cloth, 2 is Mo2C prepared in Step 2 of Example 1, and 3 is Ar-Mo2C prepared in Step 3 of Example 1. Detailed Embodiments

[0026] Detailed Embodiment 1: A preparation method of an electrocatalyst of nano-hard alloy compound with multiple defect active sites is carried out according to the following steps:

[0027] I. Synthesis of the precursor:

[0028] Mix the molybdenum salt solution with dilute hydrochloric acid to obtain a mixed solution. Immerse the activated conductive substrate in the mixed solution and place it in the inner container. Seal the inner container and put it into the stainless steel outer cover. Then, under the condition of a temperature of 150 °C to 300 °C, keep it warm for 8 h to 20 h. After cooling to room temperature, take out the conductive substrate, wash and dry it to obtain the substrate with the precursor grown on it;

[0029] The concentration of molybdate in the mixed solution is 0.05 mol / L to 0.08 mol / L, and the concentration of hydrochloric acid in the mixed solution is 0.5 mol / L to 1 mol / L;

[0030] II. Preparation of active substances:

[0031] Place the activation source upstream of the gas in the tubular furnace, place the substrate with the precursor grown thereon downstream of the gas, introduce the reaction gas, and connect to the outside air to maintain normal pressure in the furnace. Under the conditions that the reaction gas flow rate is 50 sccm to 200 sccm and the heating rate is 10 °C / min to 15 °C / min, raise the temperature in the furnace from room temperature to 750 °C to 900 °C, and keep it at a temperature of 750 °C to 900 °C for 1.5 h to 4 h, then take it out after cooling to obtain the substrate with the active substance grown thereon;

[0032] III. Apply inductively coupled plasma to the active substance:

[0033] ① Place the substrate with the active substance grown thereon in the chamber of the plasma chemical vapor deposition furnace;

[0034] ② At room temperature, close the intake valve, open the exhaust valve, use the exhaust pump to pump the air pressure in the furnace to 0.1 torr to 10 torr, then close the exhaust valve, open the intake valve, and introduce the gas at a flow rate of 10 sccm to 200 sccm until the air pressure is 100 torr to 700 torr;

[0035] ③ Repeat step III ② 2 to 3 times, then open the exhaust valve and the intake valve, adjust the air pressure in the furnace to 0.2 torr to 0.7 torr, and under the conditions that the low pressure in the furnace is 0.2 torr to 0.7 torr and the heating rate is 10 °C / min to 15 °C / min, raise the temperature in the furnace from room temperature to 200 °C to 500 °C;

[0036] ④ At a temperature of 200 °C to 500 °C, start the plasma radio frequency power supply, and under the conditions that the low pressure in the furnace is 0.2 torr to 0.7 torr, the temperature is 200 °C to 500 °C, and the plasma radio frequency power is 200 W to 300 W, use the plasma to etch the active substance, thus completing the preparation of the electrocatalyst of the nano-hard alloy compound with multiple defect active sites.

[0037] The beneficial effects of this specific embodiment are:

[0038] (1) In this specific embodiment, a nano-cemented carbide compound is grown on the surface of a conductive substrate. The nano-cemented carbide compound is nano-ribbon-shaped, with a width of about 500 nm and a thickness of about 50 nm. By using uniform plasma as the medium for processing nano-cemented carbide, it can ensure the overall surface treatment of the nano-cemented carbide compound in a plasma atmosphere. On the premise of controlling the basic geometric structure from being damaged, the uniformity of defects on the nano-cemented carbide structure can be achieved, and the degree of defects can be flexibly regulated by the plasma temperature. This method has good effectiveness and flexibility in creating a defective structure of nano-cemented carbide.

[0039] (2) After plasma treatment, the defective active sites created on the surface of the nano-cemented carbide compound effectively improve the electrocatalytic hydrogen production and oxygen production performance on both sides. In the hydrogen evolution and oxygen evolution reactions, at a current density of 10 mA / cm 2 the overpotentials of Ar-Mo2C for hydrogen evolution and oxygen evolution reactions are 151 mV and 446 mV respectively.

[0040] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: in Step 1, the cleaning and drying is specifically carried out by rinsing with deionized water, and then drying for 5 h to 12 h under vacuum conditions at a temperature of 60 °C to 80 °C. Others are the same as Specific Embodiment 1.

[0041] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that: the molybdate in Step 1 is one or a mixture of several of (NH4)2MoO4, (NH4)6Mo7O 24 , Na2MoO4 and K2MoO4. Others are the same as Specific Embodiment 1 or 2.

[0042] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that: the activated conductive substrate in Step 1 is specifically prepared according to the following steps: placing the conductive substrate in concentrated nitric acid with a mass percentage of 60% to 70%, and then carrying out a water bath at a temperature of 80 °C to 100 °C for 1 h to 5 h. Others are the same as Specific Embodiments 1 to 3.

[0043] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that: the conductive substrate is carbon cloth, carbon paper or carbon felt. Others are the same as Specific Embodiments 1 to 4.

[0044] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that: the activation source in Step 2 is cyanamide, dicyandiamide, melamine, sulfur powder, NaH2PO2 or KH2PO2; the reaction gas in Step 2 is one or a mixture of several of NH3, CH4, PH3, S vapor and O2. Others are the same as Specific Embodiments 1 to 5.

[0045] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is that: the mass ratio of the activation source to the substrate growing the precursor in Step 2 is 1:(2 - 5). Others are the same as those in Embodiments 1 to 6.

[0046] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that: the active substance in the substrate growing the active substance in Step 2 is one or a mixture of several of MoN, Mo2C, MoC, MoP, and MoS. Others are the same as those in Embodiments 1 to 7.

[0047] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is that: the gas in Step 3 ② is one or a mixture of several of Ar, N2, and CO2. Others are the same as those in Embodiments 1 to 8.

[0048] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is that: in Step 3 ④, the active substance is etched by plasma for 5 min to 30 min. Others are the same as those in Embodiments 1 to 9.

[0049] The following examples are used to verify the beneficial effects of the present invention:

[0050] Example 1:

[0051] A preparation method of a nano - hard alloy compound electrocatalyst with multiple defective active sites is carried out according to the following steps:

[0052] I. Precursor synthesis:

[0053] Mix the molybdate solution with dilute hydrochloric acid to obtain a mixed solution. Immerse the activated conductive substrate in the mixed solution and place it in the inner tank. Seal the inner tank and put it into the stainless - steel outer cover. Then, under the condition of a temperature of 160 °C, keep it warm for 15 h. After cooling to room temperature, take out the conductive substrate, wash it, and dry it to obtain the substrate growing the precursor;

[0054] The concentration of molybdate in the mixed solution is 0.06 mol / L, and the concentration of hydrochloric acid in the mixed solution is 0.5 mol / L;

[0055] II. Preparation of active substance:

[0056] Place the activation source upstream of the gas in the tubular furnace, place the substrate with the precursor grown on it downstream of the gas, introduce the reaction gas, and connect to the outside air to maintain normal pressure inside the furnace. Under the conditions of a reaction gas flow rate of 100 sccm and a heating rate of 10 °C / min, raise the temperature inside the furnace from room temperature to 850 °C, and keep it at 850 °C for 2 h. After cooling, take it out to obtain the substrate with the active substance grown on it;

[0057] III. Apply inductively coupled plasma to the active substance:

[0058] ①. Place the substrate with the active substance grown on it inside the chamber of the plasma chemical vapor deposition furnace;

[0059] ②. At room temperature, close the intake valve, open the exhaust valve, use the exhaust pump to pump the pressure inside the furnace to 0.1 torr, then close the exhaust valve, open the intake valve, and introduce the gas at a flow rate of 100 sccm until the pressure reaches 200 torr;

[0060] ③. Repeat step III② 3 times, then open the exhaust valve and the intake valve, adjust the pressure inside the furnace to 0.5 torr, and under the conditions of a low pressure inside the furnace of 0.5 torr and a heating rate of 10 °C / min, raise the temperature inside the furnace from room temperature to 300 °C;

[0061] ④. At a temperature of 300 °C, start the plasma radio frequency power supply. Under the conditions of a low pressure inside the furnace of 0.5 torr, a temperature of 300 °C, and a plasma radio frequency power of 200 W, use the plasma to etch the active substance for 15 min to obtain a nano-hard alloy compound electrocatalyst with multiple defective active sites.

[0062] The cleaning and drying described in step I are specifically to rinse with deionized water and then dry for 8 h under vacuum conditions at a temperature of 60 °C.

[0063] The molybdate salt described in step I is (NH4)6Mo7O 24 .

[0064] The activated conductive substrate described in step I is specifically prepared according to the following steps: Place the conductive substrate in concentrated nitric acid with a mass percentage of 68%, and then carry out a water bath at 100 °C for 3 h.

[0065] The conductive substrate is a carbon cloth of 2 cm × 5 cm.

[0066] The activation source described in step II is melamine.

[0067] The reaction gas described in step II is CH4.

[0068] The mass ratio of the activation source described in step II to the substrate with the precursor grown on it is 1:2;

[0069] The gas described in Step 3② is Ar.

[0070] Figure 1 is an X-ray diffraction pattern. a is the substrate with the active substance grown in Step 2 of Example 1, and b is the electrocatalyst of the nano-hard alloy compound with multiple defect active sites prepared in Step 3 of Example 1. As can be seen from the figure, the phases of the synthesized active substance and the nanostructure after plasma treatment are both Mo2C, where #CC is carbon cloth.

[0071] Therefore, the substrate with the active substance grown in Step 2 of Example 1 is abbreviated as Mo2C; the electrocatalyst of the nano-hard alloy compound with multiple defect active sites prepared in Step 3 of Example 1 is abbreviated as Ar-Mo2C.

[0072] Figure 2 is the scanning electron microscope image of Mo2C prepared in Step 2 of Example 1. As can be seen from the figure, the synthesized molybdenum carbide nanoribbons cover the surface of the conductive carbon cloth, with a width of about 500 nm and a thickness of about 50 nm.

[0073] Figure 3 is the scanning electron microscope image of Ar-Mo2C prepared in Step 3 of Example 1. After plasma treatment, the structure of the molybdenum carbide nanoribbons themselves is not damaged, and the morphology remains stable.

[0074] In a 1 mol / L KOH alkaline electrolyte solution, using a three-electrode electrolytic cell, the electrocatalytic hydrogen production reaction and the electrocatalytic oxygen production reaction are carried out on the activated carbon cloth, Mo2C prepared in Step 2 of Example 1, and Ar-Mo2C prepared in Step 3 of Example 1.

[0075] Figure 4 is the stability test curve of the electrocatalytic hydrogen evolution reaction of Ar-Mo2C prepared in Step 3 of Example 1; Figure 5 is the stability test curve of the electrocatalytic oxygen evolution reaction of Ar-Mo2C prepared in Step 3 of Example 1. As can be seen from the figure, at a current density of 10 mA / cm 2 the chronopotentiometry curve of the molybdenum carbide nanostructure electrocatalysis after plasma treatment is flat, showing good stability.

[0076] Figure 6 is the impedance spectrum of the electrocatalytic hydrogen production reaction. 1 is the carbon cloth, 2 is Mo2C prepared in Step 2 of Example 1, and 3 is Ar-Mo2C prepared in Step 3 of Example 1; Figure 7 is the impedance spectrum of the electrocatalytic oxygen production reaction. 1 is the carbon cloth, 2 is Mo2C prepared in Step 2 of Example 1, and 3 is Ar-Mo2C prepared in Step 3 of Example 1; In the hydrogen evolution and oxygen evolution reactions, at a current density of 10 mA / cm 2At the current density, the overpotentials of Ar-Mo2C (the overpotentials of hydrogen evolution and oxygen evolution reactions are 151 mV and 446 mV respectively) are reduced by 62 mV and 15 mV respectively compared with Mo2C (the overpotentials of hydrogen evolution and oxygen evolution reactions are 213 mV and 461 mV respectively), and the charge transfer resistance is significantly reduced.

Claims

1. A preparation method of a nano-cemented carbide compound electrocatalyst with multiple defective active sites, characterized in that It is carried out according to the following steps: I. Precursor synthesis: Mix the molybdenum salt solution with dilute hydrochloric acid to obtain a mixed solution. Immerse the activated conductive substrate in the mixed solution and place it in the inner container. Seal the inner container and put it into the stainless steel outer cover. Then, under the condition of a temperature of 150°C to 300°C, keep it warm for 8h to 20h. After cooling to room temperature, take out the conductive substrate, wash and dry it to obtain the substrate with the precursor grown on it; The concentration of molybdate in the mixed solution is 0.05 mol / L to 0.08 mol / L, and the concentration of hydrochloric acid in the mixed solution is 0.5 mol / L to 1 mol / L; the molybdate is (NH4)6Mo7O 24 ; The specifically prepared activated conductive substrate is prepared according to the following steps: Place the conductive substrate in concentrated nitric acid with a mass percentage of 60% to 70%, and then under the condition of a temperature of 80°C to 100°C, carry out water bath for 1h to 5h; II. Preparation of active substances: Place the activation source at the upstream of the gas in the tubular furnace, place the substrate with the precursor grown on it at the downstream of the gas, introduce the reaction gas, and connect to the external air to maintain normal pressure in the furnace. Under the condition of a reaction gas flow rate of 50sccm to 200sccm and a heating rate of 10°C / min to 15°C / min, raise the temperature in the furnace from room temperature to 750°C to 900°C, and under the condition of a temperature of 750°C to 900°C, keep it warm for 1.5h to 4h. After cooling, take it out to obtain the substrate with the active substances grown on it; The activation source is melamine; the reaction gas is CH4; the active substance in the substrate with the active substances grown on it is Mo2C; The mass ratio of the activation source to the substrate with the precursor grown on it is 1:(2 to 5); III. Apply inductive plasma to the active substances: ①. Place the substrate with the active substances grown on it in the furnace chamber of the plasma chemical vapor deposition furnace; ②. At room temperature, close the intake valve, open the exhaust valve, use the exhaust pump to pump the air pressure in the furnace to 0.1torr to 10torr, then close the exhaust valve, open the intake valve, and introduce the gas at a flow rate of 100sccm until the air pressure is 100torr to 700torr; ③. Repeat step III ② 2 to 3 times, then open the exhaust valve and the intake valve, adjust the air pressure in the furnace to 0.2torr to 0.7torr, and under the condition of a low air pressure in the furnace of 0.2torr to 0.7torr and a heating rate of 10°C / min to 15°C / min, raise the temperature in the furnace from room temperature to 200°C to 500°C; ④. Under the condition of a temperature of 200°C to 500°C, start the plasma radio frequency power supply. Under the conditions of a low air pressure in the furnace of 0.2torr to 0.7torr, a temperature of 200°C to 500°C, and a plasma radio frequency power of 200W to 300W, use the plasma to etch the active substances for 5min to 30min, and the preparation of the electrocatalyst of the nano-hard alloy compound with multiple defect active sites is completed.

2. The preparation method of a nano-carbide compound electrocatalyst with multiple defective active sites according to claim 1, characterized in that The washing and drying in step I are specifically carried out by rinsing with deionized water, and then drying for 5h to 12h under vacuum conditions at a temperature of 60°C to 80°C.

3. The preparation method of a nano-hard alloy compound electrocatalyst with multiple defective active sites according to claim 1, characterized in that The conductive substrate is carbon cloth, carbon paper or carbon felt.

4. The preparation method of a nano-hard alloy compound electrocatalyst with multiple defective active sites according to claim 1, characterized in that The gas in step III ② is Ar.

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