CN110205636B - Preparation method of self-supporting three-dimensional porous structure bifunctional catalytic electrode - Google Patents

Abstract

The invention discloses a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode belonging to the technical field of electrolyzing water to produce hydrogen and oxygen. The bifunctional catalytic electrode is prepared by using a nickel mesh as the cathode and an inert conductor as the anode. In an aqueous solution of nickel chloride and ammonium chloride, electrodeposition is performed under normal temperature and pressure conditions to prepare three-dimensional hierarchical porous nickel; thereafter The obtained nickel mesh is used as the cathode for electrodeposition, and an inert conductor is used as the anode. It is immersed in an aqueous solution containing nickel nitrate, ferrous sulfate, and ethylene glycol, and then electrodeposited under normal temperature and normal pressure conditions to obtain a porous Hierarchical structure of nickel-iron/nickel/nickel catalytic electrode; the invention achieves a large effective active area, bubble precipitation channels and excellent conductivity through two-step electrodeposition, and exhibits excellent electrochemical hydrogen and oxygen evolution under alkaline conditions performance of the electrode. The preparation process is simple, fast, pollution-free and easy to scale up, making it convenient for industrial production and manufacturing.

Description

A kind of preparation method of self-supporting three-dimensional porous structure bifunctional catalytic electrode

technical field

The invention belongs to the technical field of producing hydrogen and oxygen by electrolysis of water. In particular, it relates to a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode,

Background technique

With the rapid growth of energy demand and the depletion of fossil fuels, it is urgent to develop a green and clean energy to replace fossil fuels. Hydrogen is considered as a future energy carrier due to its advantages of high combustion calorific value, wide sources and non-polluting reaction products. However, at present, most of the hydrogen comes from the reforming process of natural gas or coal and petroleum, which is accompanied by the emission of a large amount of carbon dioxide, sulfur dioxide and other environmental pollutants. Therefore, the development of a zero-carbon-emission water electrolysis hydrogen production technology is one of the most potential hydrogen production technologies in the future. The current process of electrolysis of water for hydrogen production has high energy consumption and high cost, which seriously hinders the development of large-scale water electrolysis industry. The development of hydrogen evolution catalysts and oxygen evolution catalysts with high catalytic activity is an effective method to reduce the energy consumption of water electrolysis process. Platinum group noble metals are considered to be the best performing hydrogen evolution catalysts, while iridium dioxide or ruthenium dioxide are the best oxygen evolution catalysts. Due to the small content of these metal elements in the earth's crust and the high market price, they cannot be popularized and applied in the field of commercial electrolyzed water. Therefore, it is very important to research and develop low-cost, simple preparation process, and highly active catalysts for electrolysis of water. In addition, when the hydrogen evolution and oxygen evolution catalytic electrodes are prepared, if the anode and the cathode are made of different materials, the number of manufacturing equipment will be increased, and the manufacturing cost will be increased. Therefore, the research and development of self-supporting bifunctional catalytic electrodes with simple preparation process, low price and high catalytic activity is of great value.

At present, most of the electrocatalysts used in industry are powder catalysts, which require the use of binders to fix the active materials on the current collector. This type of process has obvious defects. On the one hand, the catalytically active sites are easily covered by the binder, which reduces the catalytic activity; on the other hand, the use of the binder inevitably increases the preparation cost and the preparation process is cumbersome. In order to solve this problem, the present invention proposes a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode. Combining the electrocatalyst and the current collector can not only reduce the cost of electrode preparation, but also significantly improve the stability of the catalytic electrode. At the same time, the prepared electrode can not only be used as an anode hydrogen evolution electrode, but also can be used as a cathode oxygen evolution electrode, which greatly reduces the preparation cost of a special electrode for electrolyzed water.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode, characterized in that the method prepares a NiFe/Ni/Ni catalytic electrode with a porous hierarchical structure;

The preparation of the self-supporting three-dimensional porous structure bifunctional catalytic electrode comprises the following steps:

Step 1: take the nickel mesh as the cathode and the inert conductor as the anode, and carry out electrodeposition treatment in an aqueous solution of nickel chloride and ammonium chloride under the conditions of normal temperature, normal pressure and current density of 1-5A/cm ² ;

Step 2: Rinse the cathode metal nickel mesh obtained in step 1 with deionized water. The metal nickel mesh is used as the cathode of the second step of electrodeposition, and an inert conductor is used as the anode. In an aqueous solution of alcohol, electrodeposition is carried out under the conditions of normal temperature, normal pressure, and a current density of 2-50 mA/cm ² to obtain a nickel-iron/nickel/nickel catalytic electrode with a porous hierarchical structure, that is, a self-supporting three-dimensional porous structure double Functional catalytic electrode;

Step 3: After the two-step electrodeposition treatment in the above given sequence, the nickel mesh of the nickel-iron/nickel/nickel electrode of the porous hierarchical structure is taken out, the surface is cleaned with deionized water, and the finished self-supporting type is obtained after drying. Three-dimensional porous structure bifunctional catalytic electrode.

The volume ratio of water to ethylene glycol in the aqueous liquid used in the second step is 1:0 to 1:4.

The molar ratio of nickel nitrate and ferrous sulfate in the water liquid of the second step is 1:5～5:1

The inert conductor is platinum or titanium plated with ruthenium.

The metal nickel mesh in the first step can be replaced by foamed nickel, nickel wire, foamed copper, copper mesh, carbon cloth, and graphene film.

The prepared nickel-iron/nickel/nickel electrode with porous hierarchical structure is used for electrolysis of potassium hydroxide aqueous solution to produce hydrogen and oxygen, and the nickel-iron/nickel/nickel electrode is used as both a hydrogen evolution electrode and an oxygen evolution electrode.

The concentration of the electrolytic potassium hydroxide aqueous solution is 1-6 molar concentration.

Compared with the prior art, the beneficial effects of the present invention are that the preparation process of the present invention is simple, the technical method is easy to enlarge, the raw material price is low, the prepared electrode has high catalytic activity and excellent stability, and can be used as an anode oxygen evolution electrode. , and can also be used as a cathode hydrogen evolution electrode. The electrode is used for large-scale electrolysis of water for hydrogen production, and effectively reduces the energy consumption and hydrogen production cost of electrolyzed water for hydrogen production. Therefore, it has the following advantages:

1. The synthesis process is simple and fast, and the catalyst is only realized by two-step short-time electrodeposition;

2. The self-supporting three-dimensional porous structure bifunctional catalytic electrode is used as anode and cathode to electrolyze water. When the current density is 10mA/ ^cm2 , the overpotential is only 33 mV, which is better than the precious metal platinum and commercial iridium Performance of tantalum oxide as cathode and anode in electrolytic cells.

3. The bifunctional catalytic electrode can maintain low overpotential and long-term stability even under high current density, and its technical performance is better than that of noble metal catalysts.

Description of drawings

Fig. 1 Scanning electron microscope images of the catalytic electrode. Among them, a and b are the scanning electron microscope images of the porous layered nickel at different magnifications on the nickel mesh; c and d are the scanning electron microscope images of the nickel-iron/nickel/nickel catalytic electrodes at different magnifications.

Figure 2 shows the oxygen evolution characteristics of the self-supporting three-dimensional porous NiFe/Ni/Ni catalytic electrode;

Fig. 3 is the influence of current density on the catalytic activity of oxygen evolution of nickel-iron/nickel/nickel catalytic electrode in step 1;

Fig. 4 is the influence of the composition of the aqueous solution in step 2 on the catalytic activity of nickel-iron/nickel/nickel catalytic electrode for oxygen precipitation;

Figure 5 shows the hydrogen evolution performance of NiFe/Ni/Ni catalytic electrodes.

Figure 6-1. Linear voltammetric sweep curves of NiFe/Ni/Ni catalytic electrodes as anode and cathode for water electrolysis.

Figure 6-2. Technical performance of nickel-iron/nickel/nickel catalytic electrodes for water electrolysis

Detailed ways

The invention provides a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode, which prepares a nickel-iron/nickel/nickel catalytic electrode with a porous hierarchical structure.

The preparation of the self-supporting three-dimensional porous structure bifunctional catalytic electrode comprises the following steps:

Step 1: take the nickel mesh as the cathode, the inert conductor (platinum or titanium plated with ruthenium) as the anode, in the aqueous solution of nickel chloride and ammonium chloride, under the conditions of normal temperature, normal pressure, and current density of 1～5A/cm ² Electrodeposition treatment;

Step 2: rinse the cathode metal nickel mesh obtained in step 1 with deionized water. It is 1:5～5:1), in the aqueous solution of ethylene glycol, carry out electrodeposition treatment under the conditions of normal temperature, normal pressure, and current density of 2～50mA/cm ² Nickel electrode, that is, self-supporting three-dimensional porous structure bifunctional catalytic electrode;

Step 3: After the two-step electrodeposition treatment in the above given sequence, the nickel mesh of the nickel-iron/nickel/nickel electrode of the porous hierarchical structure is taken out, the surface is cleaned with deionized water, and the finished self-supporting type is obtained after drying. Three-dimensional porous structure bifunctional catalytic electrode. The present invention will be further described below in conjunction with specific implementation cases.

Example 1

Step 1: The nickel mesh is cleaned with dilute hydrochloric acid, ethanol and ultrapure water as the cathode, the platinum sheet is used as the anode, and the 0.1M Ni(Cl) ₂ and 2M NH ₄ Cl solutions are placed in the beaker as the electrolyte, and the DC power supply is placed in the beaker. The positive and negative electrodes were connected to platinum sheets and nickel meshes, respectively, and were installed in the beaker, so that the solution was immersed in the electrodes; at room temperature, the current density was set to 3A/cm ² , and the electrodeposition treatment was performed for 90 seconds.

Step 2: Use the porous nickel electrodeposited in step 1 as a cathode, and immerse it in an electrolyte solution containing 1.5M Fe(NO ₃ ) ₂ and 1.5M Ni(NO ₃ ) ₂ (volume ratio 1:1), The positive electrode of the DC power supply was connected to a platinum sheet, and the negative electrode was connected to a nickel mesh. At room temperature, the current density was set to 5 mA/cm ² , and the electrodeposition was performed for 450 seconds to obtain a self-supporting three-dimensional porous NiFe/Ni/Ni electrode.

In Fig. 1, a and b are scanning electron microscope (SEM) images of porous nickel obtained by electrodeposition in step 1 in Example 1. It can be seen that a hierarchical porous structure is formed on the nickel mesh fibers. In Fig. 1, c and d are SEM images of NiFe/Ni/Ni after step 2 electrodeposition in Example 1. It can be seen that NiFe layered hydroxide grows uniformly on the hierarchical porous nickel.

The prepared oxygen evolution electrode was used as the working electrode, the platinum sheet was used as the counter electrode, and the mercury mercuric oxide was used as the reference electrode for testing. Electrochemical linear voltammetry was performed in a 1M KOH solution. /Ni/Ni exhibited excellent oxygen evolution activity, and the required overpotential was only 190mV at a current density of 10mA/ ^cm2 .

Example 2

The nickel mesh was cleaned with dilute hydrochloric acid, ethanol and ultrapure water as the cathode, the platinum sheet was used as the anode, 0.1M Ni(Cl) ₂ and 2M NH ₄ Cl solutions were used as the electrolyte, and the current density was set to 1A at room temperature. /cm ² , 3A/cm ² , 5A/cm ² , electrodeposition for 90 seconds. The electrodeposited porous nickel was used as the cathode, 1.5MFe(NO ₃ ) ₂ and 1.5M Ni(NO ₃ ) ₂ (volume ratio 1:1) were used as the electrolyte, and the current density was 5 mA/cm ² at room temperature. Electrodeposition was performed for 450 seconds to obtain a self-supporting three-dimensional porous hierarchical NiFe/Ni/Ni electrode. This method can also be implemented in the range of 2-50mA/ ^cm2 in the second-step electrodeposition current density

Figure 3 shows the influence of the current density in step 1 of Example 2. It can be seen that when the electrodeposition in step 2 is guaranteed to be the same, the current density of electrodeposition in step 1 increases, and its catalytic activity as an oxygen evolution catalytic electrode also increases significantly. But when the current density in step one is greater than 3 mA/cm ² , the catalytic activity is similar.

Example 3

The nickel mesh was cleaned with dilute hydrochloric acid, ethanol, and ultrapure water as the cathode, platinum sheet as the anode, 0.1M Ni(Cl) ₂ and 2M NH ₄ Cl solution as the electrolyte, and the current density was 3A/cm at room temperature. ^2. Electrodeposition for 90 seconds. The electrodeposited porous nickel was used as the cathode, 1.5M Fe(NO ₃ ) ₂ and 1.5M Ni(NO ₃ ) ₂ (volume ratio 1:1) were used as the electrolyte, and the proportions soluble in water and ethylene glycol were In 1:0, 1:1, and 1:4 electrolyte aqueous solutions, at room temperature, the current density was kept at 5 mA/cm ² , and the electrodeposition was performed for 450 seconds to obtain a self-supporting three-dimensional porous NiFe/Ni/Ni electrode. This method can also be implemented in the range of 2-50mA/ ^cm2 in the second-step electrodeposition current density

Figure 4 shows the effect of different electrolyte ratios on the activity of the catalytic electrode in Example 3. It can be seen that with the increase in the proportion of ethylene glycol, the catalytic activity increases in a small range.

Example 4

The nickel mesh was cleaned with dilute hydrochloric acid, ethanol, and ultrapure water as the cathode, platinum sheet as the anode, 0.1M Ni(Cl) ₂ and 2M NH ₄ Cl solution as the electrolyte, and the current density was 3A/cm at room temperature. ^2. Electrodeposition for 90 seconds. Electrodeposited porous nickel was used as cathode, 1.5M Fe(NO ₃ ) ₂ and 1.5M Ni(NO ₃ ) ₂ (volume ratio 1:1) were used as electrolytes at room temperature at a current density of 5 mA/ cm ² , and electrodeposited for 200 seconds to obtain a self-supporting three-dimensional porous hierarchical NiFe/Ni/Ni electrode.

Figure 5 shows the NiFe/Ni/Ni electrode in Example 3 as the hydrogen evolution electrode. The NiFe bimetal is grown on the porous layer of nickel in situ, which can significantly improve the hydrogen evolution activity of NiFe. For NiFe/Ni/Ni The electrode, which requires an overpotential of only 132mV at a current density of 10mA/ ^cm2 .

Example 5

Using the electrode prepared in Example 2 as the anode and the electrode prepared in Example 4 as the cathode, electrochemical linear voltammetry was performed in a 1M KOH solution (Fig. 6-1), showing excellent electrochemical performance, which is in the When the current density is 10mA/cm ² , the required electrolysis voltage is only 1.56V. At the same time, the bifunctional catalyst shows excellent stability, under the current density of 500mA/cm ² , the constant current electrolyzed water runs for 200 hours ( Figure 6-2), the electrolysis voltage did not change significantly.

Claims (2)

1. a preparation method of a self-supporting three-dimensional porous structure bifunctional catalytic electrode, is characterized in that, the method prepares a kind of nickel-iron/nickel/nickel catalytic electrode with porous hierarchical structure; The preparation of the self-supporting three-dimensional porous structure bifunctional catalytic electrode comprises the following steps: Step 1: take the nickel mesh as the cathode and the inert conductor as the anode, and carry out electrodeposition treatment in an aqueous solution of nickel chloride and ammonium chloride under the conditions of normal temperature, normal pressure and current density of 1-5A/cm ² ; Step 2: Rinse the cathode metal nickel mesh obtained in step 1 with deionized water. The metal nickel mesh is used as the cathode of the second step of electrodeposition, and the inert conductor platinum or titanium plated with ruthenium is used as the anode. Electrodeposition is carried out in an aqueous solution of ferrous and ethylene glycol under the conditions of normal temperature, normal pressure, and a current density of 2 to 50 mA/cm ² to obtain a nickel-iron/nickel/nickel catalytic electrode with a porous hierarchical structure, that is, self-supporting Three-dimensional porous structure bifunctional catalytic electrode; Step 3: After the two-step electrodeposition treatment in the above given sequence, the nickel mesh of the nickel-iron/nickel/nickel electrode of the porous hierarchical structure is taken out, the surface is cleaned with deionized water, and the finished self-supporting type is obtained after drying. Three-dimensional porous structure bifunctional catalytic electrode; the volume ratio of water to ethylene glycol in the water liquid used in the second step is 1:0 to 1:4; the immersion in the second step contains nickel nitrate, ferrous sulfate, ethylene glycol The molar ratio of nickel nitrate and ferrous sulfate in the aqueous solution of diol is 1:5 to 5:1. 2. the preparation method of a kind of self-supporting three-dimensional porous structure bifunctional catalytic electrode according to claim 1, is characterized in that, the nickel-iron/nickel/nickel electrode of the porous hierarchical structure of described preparation is used for electrolysis of potassium hydroxide aqueous solution Production of hydrogen and oxygen, the nickel-iron/nickel/nickel electrodes are used as both hydrogen and oxygen evolution electrodes; The concentration of the electrolytic potassium hydroxide aqueous solution is 1-6 molar concentration.

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