阅读说明：本技术 一种氢氧化镍电催化剂、制备方法、电化学活化方法及其应用 (Nickel hydroxide electrocatalyst, preparation method, electrochemical activation method and application thereof ) 是由 杜海威 胡杰 朱储红 袁玉鹏 于 2021-04-01 设计创作，主要内容包括：本发明涉及电催化剂技术领域,具体涉及一种氢氧化镍电催化剂、制备方法、电化学活化方法及其应用,先将金属镍盐和碱性化合物通过水热法合成氢氧化镍粉末,然后将获得的氢氧化镍粉末涂覆在导电基底上作为阳极,以石墨棒作为阴极,银/氯化银电极为参比电极,置于氢氧化钾溶液中施加一定电压进行电化学活化,之后,将活化后的氢氧化镍材料直接用于电催化分解水制氢；这种电化学活化方法具有操作简单、成本低、适用于各类电催化剂的改性以及活化后电催化性能好等特点,在电解水制氢和电化学储能等方面具有潜在的应用前景。(The invention relates to the technical field of electrocatalysts, in particular to a nickel hydroxide electrocatalyst, a preparation method, an electrochemical activation method and application thereof, wherein metal nickel salt and an alkaline compound are synthesized into nickel hydroxide powder by a hydrothermal method, then the obtained nickel hydroxide powder is coated on a conductive substrate to be used as an anode, a graphite rod is used as a cathode, a silver/silver chloride electrode is used as a reference electrode, the conductive substrate is placed in a potassium hydroxide solution to be applied with certain voltage for electrochemical activation, and then the activated nickel hydroxide material is directly used for hydrogen production through electrocatalytic decomposition of water; the electrochemical activation method has the characteristics of simple operation, low cost, suitability for modification of various electrocatalysts, good electrocatalysis performance after activation and the like, and has potential application prospects in the aspects of hydrogen production by water electrolysis, electrochemical energy storage and the like.)

1. A preparation method of a nickel hydroxide electrocatalyst is characterized by comprising the following steps:

s1: weighing metal nickel salt and an alkaline compound, and respectively dissolving the metal nickel salt and the alkaline compound in a solvent to obtain a metal nickel salt solution and an alkaline compound solution;

s2: adding a metal nickel salt solution into an alkaline compound solution, stirring for 30min, pouring into a polytetrafluoroethylene lining, then putting into a reaction kettle, heating to 110-150 ℃, preserving heat for 10-14 h, and cooling to room temperature after the reaction is finished;

s3: and taking out the product obtained by the reaction in the step S2, centrifuging and respectively cleaning the product for 3 times by using deionized water and absolute ethyl alcohol, drying the product at the temperature of 80 ℃, and grinding the dried product to obtain the nickel hydroxide powder.

2. The method of claim 1, wherein the metallic nickel salt in step S1 is any one of nickel nitrate, nickel sulfate, and nickel chloride.

3. The method of claim 1, wherein the basic compound is sodium hydroxide, the molar ratio of the metal nickel salt to the sodium hydroxide is 1:30, and the solvent is water in step S1.

4. The method of claim 1, wherein the basic compound is sodium carbonate, the molar ratio of the metal nickel salt to the sodium carbonate is 1:1, and the solvent is water in step S1.

5. The method of claim 1, wherein in step S1, the basic compound is urea, the molar ratio of the metal nickel salt to the urea is 1:4, the solvent is a mixed solution of propylene glycol and water, and the volume ratio of the propylene glycol to the water is 4: 1.

6. A nickel hydroxide electrocatalyst prepared by the preparation method according to any one of claims 1 to 5.

7. A method of electrochemically activating a nickel hydroxide electrocatalyst according to claim 6, comprising the steps of:

a. dispersing nickel hydroxide powder in a mixed solution of water, alcohol and perfluorosulfonic acid, and performing ultrasonic dispersion to obtain a suspension;

b. coating the suspension obtained in the step a on the surface of a surface conductive substrate;

c. and c, taking the conductive substrate coated with the nickel hydroxide in the step b as an anode, a graphite rod as a cathode, a silver/silver chloride electrode as a reference electrode, and a potassium hydroxide or sodium hydroxide solution as an electrolyte, and then applying voltage by using a cyclic voltammetry method.

8. The method for electrochemically activating a nickel hydroxide electrocatalyst according to claim 7, wherein the voltage applied in step c is in the range of 0 to-0.5V.

9. Use of a nickel hydroxide electrocatalyst activated by the electrochemical activation process according to claim 7 or 8 for electrocatalytic decomposition of water to produce hydrogen.

Technical Field

The invention relates to the technical field of electrocatalysts, in particular to a nickel hydroxide electrocatalyst, a preparation method, an electrochemical activation method and application thereof.

Background

The excessive consumption of fossil fuels raises energy and environmental issues, and the search for new clean and efficient energy substitutes is urgent. The hydrogen energy is a clean and carbon-free energy source with high combustion heat and wide application, and is the best choice for gradually replacing the traditional fossil energy source, reducing the emission of greenhouse gases and developing renewable energy industry. In 2019, the hydrogen yield in China is about 2000 ten thousand tons, wherein more than 90% of hydrogen comes from various fossil fuel hydrogen production technologies, the energy consumption is high, and the prepared hydrogen contains a certain amount of impurities. Only 4% of hydrogen is obtained by the water electrolysis technology, and due to high cost, the technology has not realized industrial production and does not embody the scale economic benefit. The core of the water electrolysis is an electrocatalyst, and the development of the electrocatalyst with low cost, high activity and good stability is the key of the industrialization of the water electrolysis technology.

At present, the commercial electrocatalyst is mainly made of noble metal, and industrial production is difficult to realize due to high price. Transition metal-based electrocatalysts represented by nickel hydroxide materials have the characteristics of high element abundance, low cost and the like, and are expected to be substitutes for noble metal catalysts. However, the intrinsic electrocatalytic properties of nickel hydroxide materials are poor, resulting in high overpotentials, which limit the efficiency of electrocatalytic reactions. The research aiming at the performance modification of the nickel hydroxide material mainly comprises the regulation and control of components and a microstructure, and has the disadvantages of more complicated process, time consumption and higher modification cost.

In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.

Disclosure of Invention

The invention aims to solve the problems that the intrinsic electrocatalysis performance of a nickel hydroxide material is poor, so that the overpotential is high, and the electrocatalysis reaction efficiency is limited, the existing research on the performance modification of the nickel hydroxide material mainly aims at regulating and controlling components and a microstructure, the process is complex, time is consumed, and the modification cost is high, and provides a nickel hydroxide electrocatalyst, a preparation method, an electrochemical activation method and application thereof.

In order to achieve the above object, the present invention discloses a method for preparing a nickel hydroxide electrocatalyst, comprising the steps of:

s1: weighing metal nickel salt and an alkaline compound, and respectively dissolving the metal nickel salt and the alkaline compound in a solvent to obtain a metal nickel salt solution and an alkaline compound solution;

s2: adding a metal nickel salt solution into an alkaline compound solution, stirring for 30min, pouring into a polytetrafluoroethylene lining, then putting into a reaction kettle, heating to 110-150 ℃, preserving heat for 10-14 h, and cooling to room temperature after the reaction is finished;

s3: and taking out the product obtained by the reaction in the step S2, centrifuging and respectively cleaning the product for 3 times by using deionized water and absolute ethyl alcohol, drying the product at the temperature of 80 ℃, and grinding the dried product to obtain the nickel hydroxide powder.

The metal nickel salt in step S1 is any one of nickel nitrate, nickel sulfate, and nickel chloride.

In the step S1, the alkaline compound is sodium hydroxide, the molar ratio of the metal nickel salt to the sodium hydroxide is 1:30, and the solvent is water.

In the step S1, the alkaline compound is sodium carbonate, the molar ratio of the metal nickel salt to the sodium carbonate is 1:1, and the solvent is water.

In the step S1, the alkaline compound is urea, the molar ratio of the metal nickel salt to the urea is 1:4, the solvent is a mixed solution of propylene glycol and water, and the volume ratio of the propylene glycol to the water is 4: 1.

The invention also discloses the nickel hydroxide electrocatalyst prepared by the preparation method.

The invention also discloses an electrochemical activation method of the nickel hydroxide electrocatalyst, which comprises the following steps:

a. dispersing nickel hydroxide powder in a mixed solution of water, alcohol and perfluorosulfonic acid, and performing ultrasonic dispersion to obtain a suspension;

b. coating the suspension obtained in the step a on the surface of a surface conductive substrate;

c. and c, taking the conductive substrate coated with the nickel hydroxide in the step b as an anode, a graphite rod as a cathode, a silver/silver chloride electrode as a reference electrode, and a potassium hydroxide or sodium hydroxide solution as an electrolyte, and then applying voltage by using a cyclic voltammetry method.

The voltage applied in the step c is 0 to-0.5V.

The nickel hydroxide material is placed in the air, and the divalent nickel ions (Ni) on the surface²⁺) Oxidation inevitably occurs to form trivalent nickel ions (Ni)³⁺). The invention utilizes an electrochemical activation method to apply negative voltage to the nickel hydroxide material to remove Ni on the surface of the nickel hydroxide material³⁺Reduction to Ni²⁺、Ni⁺Even the simple substance of nickel. At the same time as the reduction of the cations takes place, oxygen vacancies will form on the surface, thus maintaining charge balance. After electrochemical reduction, a large number of low-valence nickel ions and oxygen vacancies exist on the surface of the nickel hydroxide material and are used as active sites of electrocatalytic reaction, and the existence of the oxygen vacancies can cause lattice oxygen to participate in the electrocatalytic reaction, so that the electrocatalytic performance of the product is improved.

The invention also discloses application of the nickel hydroxide electrocatalyst after electrochemical activation in hydrogen production by electrocatalysis decomposition of water.

Compared with the prior art, the invention has the beneficial effects that:

(1) the electrocatalyst designed by the invention and the synthesis process thereof do not contain any noble metal component, the cost of the raw material is low, and the economic benefit is outstanding compared with the existing commercial noble metal electrocatalyst;

(2) the electrochemical activation method adopted by the invention does not need to introduce any other impurity elements, the operation steps are simple and quick, and the current density of the nickel hydroxide after electrochemical activation is 10mA cm^-2The overpotential of time is only 327mV, and the Tafel slope is 48mV dec^-1The electrocatalytic performance is obviously improved.

Drawings

FIG. 1 is a multi-cycle voltammogram used in the electrochemical activation of nickel hydroxide in the present invention;

FIG. 2 is an X-ray diffraction pattern of the material prepared by the present invention before and after electrochemical activation;

FIG. 3 shows the results of the contact angle test of nickel hydroxide before and after electrochemical activation;

FIG. 4 is an X-ray photoelectron spectrum of nickel element and oxygen element in nickel hydroxide before and after electrochemical activation;

FIG. 5 is a comparison of current density and electric double layer capacitance of nickel hydroxide in the non-faradaic potential interval before and after electrochemical activation;

FIG. 6 is a plot of the voltammetry of nickel hydroxide in the Faraday potential region before and after electrochemical activation;

FIG. 7 is a comparison of the electrochemical impedance of nickel hydroxide before and after electrochemical activation;

FIG. 8 is a graph of the results of characterization of the electrochemical oxygen evolution performance of nickel hydroxide before and after electrochemical activation;

FIG. 9 is a comparison of the Tafel slopes of nickel hydroxide before and after electrochemical activation;

fig. 10 is a plot of polarization curves and current densities of nickel hydroxide at different pH conditions before and after electrochemical activation.

Detailed Description

The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

Example 1

1. Weighing 1.6mmol of Ni (NO)₃)₂·6H₂O, adding the mixture into 100mL of deionized water to prepare a solution A; weighing 0.05mol of Na₂CO₃And 0.05mol of NaOH into 25mL of deionized water to prepare a solution B.

2. Adding the solution A into the solution B, stirring for 30min, uniformly pouring the solution A into two 100mL polytetrafluoroethylene linings, then putting the mixture into a reaction kettle, heating the mixture to 120 ℃ in an oven and preserving the heat for 6 h.

3. After the reaction is finished, cooling to room temperature, taking out the mixture in the reaction kettle, centrifuging and respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol, then drying in an oven at 80 ℃, taking out after drying, and grinding.

4. The nickel hydroxide powder was dispersed in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), and subjected to ultrasonic dispersion to obtain a suspension. The coating area is 1 × 1cm²The carbon paper surface of (2).

5. Putting an electrode coated with nickel hydroxide, a graphite rod and a silver/silver chloride electrode into 1mol L^-1In the potassium hydroxide solution, a voltage of 0 to-0.5V is applied by cyclic voltammetry, and the scanning speed is 20mV s^-1The electrochemical activation was performed 50 times in total. The electrochemical voltammogram is shown in FIG. 1. X-ray diffraction patterns of electrocatalyst before and after electrochemical activationAs shown in fig. 2, it was confirmed that the electrocatalyst prepared according to the present invention was nickel hydroxide, and the crystal structure of the electrochemically activated material was not significantly changed, when compared with the standard card. The contact angle of the electrocatalyst before and after activation is smaller than that of the electrocatalyst after electrochemical activation, as shown in fig. 3, so that the contact between the catalyst and the electrolyte is more favorable, and the number of oxygen vacancies on the surface of the product is increased. The X-ray photoelectron spectrum of the electrocatalyst before and after electrochemical activation is shown in FIG. 4, the nickel element signal moves to high binding energy after chemical activation, the number of oxygen vacancies increases, and the reduction of the valence of nickel ions is shown.

And carrying out electrochemical test on the activated electrode in the same electrolytic cell. As shown in fig. 5, the current density and electric double layer capacitance ratio in the non-faradaic potential range before and after electrochemical activation of nickel hydroxide increase the electric double layer capacitance of the catalyst after electrochemical activation, and the surface adsorption property is improved. The voltammograms before and after electrochemical activation of nickel hydroxide were plotted in the faraday potential region as shown in figure 6. The electrochemical impedance of nickel hydroxide before and after electrochemical activation showed a significant decrease in resistance after electrochemical activation, as shown in fig. 7.

When the electrochemical oxygen evolution polarization curve is tested, the test voltage is 0-0.8V, and the scanning speed is 5mV s^-1. The oxygen evolution performance and tafel slope of the electrocatalyst before and after activation are shown in fig. 8 and 9, the overpotential of the nickel hydroxide after electrochemical activation is reduced, the electrochemical performance is improved, and the tafel slope of the nickel hydroxide after electrochemical activation is reduced, and the electrochemical performance is improved. In addition, as shown in fig. 10, the pH of the solution did not significantly affect the current density during the test of the sample before activation, and the current density increased significantly with the increase of pH after activation, indicating that the lattice oxygen participates in the electrocatalytic reaction, i.e., the electrochemical activation proposed by the present invention can form oxygen vacancies in the nickel hydroxide.

Example 2

1. 0.5mmol of Ni (NO) was weighed₃)₂·6H₂O, dissolved in 2.5mL of deionized water, and then 2mmol of CH is added₄N₂O, and then 10mL of 1, 2-propanediol solution was added.

2. The mixed solution is poured into a 100mL polytetrafluoroethylene lining, then is placed into a reaction kettle, and is heated to 120 ℃ in an oven and is kept warm for 6 hours.

3. After the reaction is finished, cooling to room temperature, taking out the mixture in the reaction kettle, centrifuging and respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol, then drying in an oven at 80 ℃, taking out after drying, and grinding.

4. Dispersing nickel hydroxide powder in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), ultrasonically dispersing to obtain a suspension, and coating the suspension on an area of 1X 1cm²The carbon paper surface of (2).

5. Putting an electrode coated with nickel hydroxide, a graphite rod and a silver/silver chloride electrode into 1mol L^-1In the potassium hydroxide solution, a voltage of 0 to-0.4V is applied by cyclic voltammetry, and the scanning speed is 20mV s^-1The electrochemical activation was performed 50 times in total.

Testing the electrochemical oxygen evolution polarization curve of the activated electrode in the same electrolytic cell, wherein the testing voltage is 0-0.8V, and the scanning speed is 5mV s^-1。

Example 3

1. Weighing 1.6mmol of NiSO₄·6H₂O, adding the mixture into 100mL of deionized water to prepare a solution A; weighing 0.05mol of Na₂CO₃And 0.05mol of NaOH, and adding the mixture into 25mL of deionized water to prepare a solution B.

2. Adding the solution A into the solution B, stirring for 30min, uniformly pouring the solution A into two 100mL polytetrafluoroethylene linings, then putting the mixture into a reaction kettle, heating the mixture to 120 ℃ in an oven and preserving the heat for 6 h.

3. After the reaction is finished, the mixture is cooled to room temperature, the mixture in the reaction kettle is taken out and is respectively washed by deionized water and absolute ethyl alcohol for 5 times in a centrifugal mode, then the mixture is dried in an oven at the temperature of 80 ℃, and the mixture is taken out and ground after being dried.

4. The nickel hydroxide powder was dispersed in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), and subjected to ultrasonic dispersion to obtain a suspension. The coating area is 1 × 1cm²The carbon paper surface of (2).

5. Putting the electrode coated with nickel hydroxide, graphite rod and silver/silver chloride electrode into1mol L^-1In the potassium hydroxide solution, a voltage of 0 to-0.5V is applied by cyclic voltammetry, and the scanning speed is 30mV s^-1The electrochemical activation was performed 50 times in total.

Testing the electrochemical oxygen evolution polarization curve of the activated electrode in the same electrolytic cell, wherein the testing voltage is 0-0.8V, and the scanning speed is 5mV s^-1。

Example 4

1. Weighing 0.5mmol of NiSO₄·6H₂O, dissolved in 2.5mL of deionized water, and then 2mmol of CH is added₄N₂O, and then 10mL of 1, 2-propanediol solution was added.

2. The mixed solution is poured into a 100mL polytetrafluoroethylene lining, then is placed into a reaction kettle, and is heated to 120 ℃ in an oven and is kept warm for 6 hours.

3. After the reaction is finished, cooling to room temperature, taking out the mixture in the reaction kettle, centrifuging and respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol, then drying in an oven at 80 ℃, taking out after drying, and grinding. The X-ray diffraction pattern of the prepared electrocatalyst is shown in fig. 1.

4. The nickel hydroxide powder was dispersed in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), and subjected to ultrasonic dispersion to obtain a suspension. The coating area is 1 × 1cm²The carbon paper surface of (2).

5. Putting an electrode coated with nickel hydroxide, a graphite rod and a silver/silver chloride electrode into 1mol L^-1In the potassium hydroxide solution, a voltage of 0 to-0.4V is applied by cyclic voltammetry, and the scanning speed is 50mV s^-1The electrochemical activation was performed 50 times in total.

Testing the electrochemical oxygen evolution polarization curve of the activated electrode in the same electrolytic cell, wherein the testing voltage is 0-0.8V, and the scanning speed is 5mV s^-1。

Example 5

1. Weighing 1.6mmol NiCl₂·6H₂O, adding the mixture into 100mL of deionized water to prepare a solution A; weighing 0.05mol of Na₂CO₃And 0.05mol of NaOH into 25mL of deionized water to prepare a solution B.

2. Adding the solution A into the solution B, stirring for 30min, uniformly pouring the solution A into two 100mL polytetrafluoroethylene linings, then putting the mixture into a reaction kettle, heating the mixture to 120 ℃ in an oven and preserving the heat for 6 h.

3. After the reaction is finished, cooling to room temperature, taking out the mixture in the reaction kettle, centrifuging and respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol, then drying in an oven at 80 ℃, taking out after drying, and grinding.

4. The nickel hydroxide powder was dispersed in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), and subjected to ultrasonic dispersion to obtain a suspension. The coating area is 1 × 1cm²The carbon paper surface of (2).

5. Putting an electrode coated with nickel hydroxide, a graphite rod and a silver/silver chloride electrode into 1mol L^-1In the potassium hydroxide solution, a voltage of 0 to-0.5V is applied by cyclic voltammetry, and the scanning speed is 30mV s^-1The electrochemical activation was performed 50 times in total.

Testing the electrochemical oxygen evolution polarization curve of the activated electrode in the same electrolytic cell, wherein the testing voltage is 0-0.8V, and the scanning speed is 5mV s^-1。

Example 6

1. 0.5mmol of NiCl was weighed₂·6H₂O, dissolved in 2.5mL of deionized water, and then 2mmol of CH is added₄N₂O, and then 10mL of 1, 2-propanediol solution was added.

2. The mixed solution is poured into a 100mL polytetrafluoroethylene lining, then is placed into a reaction kettle, and is heated to 120 ℃ in an oven and is kept warm for 6 hours.

3. After the reaction is finished, cooling to room temperature, taking out the mixture in the reaction kettle, centrifuging and respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol, then drying in an oven at 80 ℃, taking out after drying, and grinding. The X-ray diffraction pattern of the prepared electrocatalyst is shown in fig. 1.

4. The nickel hydroxide powder was dispersed in a mixed solution of deionized water (490. mu.L), ethanol (490. mu.L) and perfluorosulfonic acid (40. mu.L), and subjected to ultrasonic dispersion to obtain a suspension. The coating area is 1 × 1cm²The carbon paper surface of (2).

5. Will be coated with hydrogen hydroxidePutting 1mol L of electrode of nickel, graphite rod and silver/silver chloride electrode^-1In the potassium hydroxide solution, a voltage of 0 to-0.5V is applied by cyclic voltammetry, and the scanning speed is 20mV s^-1The electrochemical activation was performed 50 times in total.

Testing the electrochemical oxygen evolution polarization curve of the activated electrode in the same electrolytic cell, wherein the testing voltage is 0-1V, and the scanning speed is 5mV s^-1。

The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.