CN110624573A - A kind of nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst and preparation method thereof - Google Patents

Abstract

A nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst and a preparation method thereof relate to an electrocatalytic hydrogen evolution catalyst and a preparation method thereof. It aims to solve the technical problems of complex preparation steps, high cost and poor safety of the existing doped cobalt selenide electrocatalytic hydrogen evolution catalyst. The general chemical formula of the catalyst is Co _x Ni _y Se ₂ , x=0.6-0.8, y=0.1-0.35. Preparation method: Dissolve selenium powder in potassium hydroxide solution, then add Co(NO ₃ ) ₂ 6H ₂ O, Ni(NO ₃ ) ₂ 6H ₂ O, EDTA‑2Na and ultrapure water, stir evenly, The mixed solution was obtained; then transferred to the reactor for hydrothermal reaction, and then washed and dried to obtain the catalyst; the overpotential of the catalyst reached 170-195mV VS RHE, after 1000 cycles of continuous cyclic voltammetry test, the polarization curve and the initial curve Almost overlapping, high stability, can be used in electrocatalytic hydrogen evolution reaction.

Description

A kind of nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst and preparation method thereof

technical field

The invention relates to an electrocatalytic hydrogen evolution catalyst and a preparation method thereof.

Background technique

With the development of the global economy, fossil fuels are gradually depleted. At the same time, environmental problems such as air pollution caused by the burning of fossil fuels force people to look for clean and renewable solar energy, wind energy, biomass energy, hydrogen energy and other new energy sources. Among these new energy sources, hydrogen has attracted widespread attention due to its wide sources, non-polluting water as its combustion product, and the higher energy output per unit mass of hydrogen than other energy sources and its high energy utilization rate. However, the electrolysis of water to generate hydrogen has a slow kinetic process and often requires a high overpotential. Therefore, a hydrogen evolution reaction catalyst is needed to reduce the high energy consumption required in the electrolysis process and achieve an efficient water electrolysis reaction. At present, platinum group metals are the best electrochemical hydrogen evolution catalysts, but their rarity and high cost also make it difficult to promote their use on a large scale. Among other non-precious metal catalysts, cobalt-based compounds, including cobalt disulfide, cobalt selenide, and cobalt carbide, etc., have attracted extensive attention in the past few years, but the catalytic performance of cobalt-based compounds is poor. In order to further enhance the electrocatalytic performance of cobalt-based compounds, they were modified by doping.

The Chinese patent application number 201810123010.2 discloses a preparation method and application of an iron-doped cobalt diselenide composite nitrogen-doped carbon material. In this method, metal-organic framework ZIF-67 is used as a precursor, and iron-modified Fe-ZIF-67 is obtained by etching with ferric ions, and Fe-ZIF-67 is carbonized and selenized with selenium vapor at high temperature to obtain nitrogen Doped porous carbon-supported iron-doped cobalt diselenide (Fe-CoSe ₂ @NC) powder electrode material. Fe-CoSe ₂ @NC powder was made into slurry and brushed on conductive carbon fiber paper to make Fe-CoSe ₂ @NC/CFP electrode. The electrochemical catalytic hydrogen production performance index of Fe-CoSe ₂ @NC/CFP electrode is: the Tafel slope is 40.9mV/decade; the overpotential to reach the current density of 10mA/cm ² is -0.143V (vsRHE). The steps involved in this patent are more complicated and require chemical etching and high-temperature carbonization. The Chinese patent application number 201910171517.X, a preparation method of nitrogen and nickel co-doped cobalt selenide ultra-thin nanosheets, discloses a preparation method of doped cobalt selenide material, which is a cobalt source, a selenium source, Nickel source, nitrogen source, water and diethylenetriamine are mixed for solvothermal reaction to obtain nitrogen and nickel co-doped cobalt selenide precursor; then the precursor is washed and dried to obtain nitrogen and nickel co-doped selenium cobalt ultrathin nanosheets. This patent also applies metal doping and non-metal doping to modify cobalt selenide, which has higher preparation costs and poor safety.

Contents of the invention

The invention aims to solve the technical problems of complex preparation steps, high cost and poor safety of the existing electrocatalytic hydrogen evolution catalyst doped with cobalt selenide, and provides a nickel doped cobalt selenide electrocatalytic hydrogen evolution catalyst and a preparation method thereof.

The nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present invention has a general chemical formula of Co _x Ni _y Se ₂ , x=0.6-0.8, y=0.1-0.35.

The preparation method of the above-mentioned nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst is carried out in the following steps:

1. Weigh selenium powder, Co(NO ₃ ) ₂ 6H ₂ O and Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio of Co _x Ni _y Se ₂ , x=0.6 in Co _x Ni _y Se ₂ ~0.8, y=0.1~0.35; then weigh potassium hydroxide solution, EDTA-2Na and ultrapure water;

2. Dissolve selenium powder in potassium hydroxide solution, stir for 25-35 minutes, then add Co(NO ₃ ) ₂ 6H ₂ O, Ni(NO ₃ ) ₂ 6H ₂ O, EDTA-2Na and ultrapure water, Continue to stir for about 1 to 1.5 hours to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react at a temperature of 160-200°C for 10-16 hours, and cool naturally to room temperature;

4. Wash the black precipitate obtained by the reaction with water and ethanol in sequence, and then place it in a vacuum oven at 60-65° C. for 12-15 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst.

The overpotential (potential when the current density is 10mA cm ^-2 ) of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present invention reaches 170-195mV VS RHE, and the Tafel slope reaches 32-62V VS RHE, which is comparable to that of platinum. It is comparable to the currently recognized best platinum catalyst, and also has ultra-high stability. After 1000 cycles of continuous cyclic voltammetry test, the polarization curve almost coincides with the initial curve. Under overpotential conditions for 10000s, the current There is no obvious change in density and good stability in acidic electrolyte.

The preparation steps of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present invention are simple and complex, and the cost is low and safe. It can be used in electrocatalytic hydrogen evolution reaction.

Description of drawings

Fig. 1 is the polarization curve figure of the material CNSe-1, CNSe- ₂ , CNSe-3, CNSe-4, CoSe2 and NiSe2 prepared by Examples 1～4 and Comparative Examples 1～ ₂ ;

Fig. ₂ is the Tafel slope figure of the material CNSe-1, CNSe- ₂ , CNSe-3, CNSe-4, CoSe2 and NiSe2 prepared by Examples 1～4 and Comparative Examples 1～2;

Fig. ₃ is the overpotential histogram of the material CNSe-1, CNSe- ₂ , CNSe-3, CNSe-4, CoSe2 and NiSe2 prepared by Examples 1-4 and Comparative Examples 1-2;

Fig. ₄ is the Tafel slope histogram of the materials CNSe-1, CNSe- ₂ , CNSe-3, CNSe-4, CoSe2 and NiSe2 prepared by Examples 1-4 and Comparative Examples 1-2;

Figure 5 is a comparison diagram of the polarization curve of the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ prepared in Example 3 and the polarization curve after 1,000 cycles of continuous cyclic voltammetry;

Fig. 6 is a graph showing the change in current density of the catalyst _CNSe - ₃ with the chemical formula _{Co0.77Ni0.25Se2} prepared in Example 3 at a potential of -179mV for 10,000s;

Fig. 7 is the scanning electron micrograph of the catalyst CNSe-3 that the chemical formula prepared in embodiment 3 is Co _0.77 Ni _0.25 Se ₂ ;

Fig. 8 is a transmission electron micrograph of the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ prepared in Example 3.

Detailed ways

Embodiment 1: The nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of this embodiment has a general chemical formula of Co _x Ni _y Se ₂ , x=0.6-0.8, y=0.1-0.35.

Specific embodiment two: the preparation method of nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst described in specific embodiment one, carry out according to the following steps:

1. Weigh selenium powder, Co(NO ₃ ) ₂ 6H ₂ O and Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio of Co _x Ni _y Se ₂ , x=0.6 in Co _x Ni _y Se ₂ ~0.8, y=0.1~0.35; then weigh potassium hydroxide solution, EDTA-2Na and ultrapure water;

2. Dissolve selenium powder in potassium hydroxide solution, stir for 25-35 minutes, then add Co(NO ₃ ) ₂ 6H ₂ O, Ni(NO ₃ ) ₂ 6H ₂ O, EDTA-2Na and ultrapure water, Continue to stir for about 1 to 1.5 hours to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react at a temperature of 160-200°C for 10-16 hours, and cool naturally to room temperature;

4. Wash the black precipitate obtained by the reaction with water and ethanol in sequence, and then place it in a vacuum oven at 60-65° C. for 12-15 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst.

Embodiment 3: This embodiment differs from Embodiment 2 in that the concentration of the potassium hydroxide solution described in step 1 is 20-25 mol/L; other aspects are the same as Embodiment 2.

Specific embodiment four: what this embodiment is different from specific embodiment two or three is that in step one, the mol ratio of selenium powder and potassium hydroxide in potassium hydroxide solution is 1: (50～60); Other and specific embodiment Two or three of the same.

Specific embodiment five: this embodiment is different from one of specific embodiments two to four in that in step one, the molar ratio of selenium powder and EDTA-2Na is 1: (0.8～0.9); other and specific embodiments two to four one of the same.

Specific embodiment six: what this embodiment is different from one of specific embodiment 2 to 5 is that in step 1, the ratio of the amount of substance of selenium powder and the volume of ultrapure water is 1mmol: (10～12) mL; One of the specific embodiments 2 to 5 is the same.

Use the following examples to verify the beneficial effects of the present invention.

Embodiment 1: The preparation method of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present embodiment is carried out according to the following steps:

1. Weigh 2mmol of selenium powder, 1.0mmol of Co(NO ₃ ) ₂ 6H ₂ O, 0.25mmol of Ni(NO ₃ ) ₂ 6H ₂ O, then weigh 5mL of potassium hydroxide solution with a concentration of 20mol/L, 1.60mmol EDTA-2Na and 20mL ultrapure water;

2. Dissolve 2mmol of selenium powder in 5mL of potassium hydroxide solution with a concentration of 20mol/L. After stirring for 30min, add 1.0mmol of Co(NO ₃ ) ₂ 6H ₂ O and 0.25mmol of Ni(NO ₃ ) ₂ . 6H ₂ O, 1.60mmol EDTA-2Na and 20mL ultrapure water, continue stirring for about 1h to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react for 12 hours at a temperature of 180°C, and cool to room temperature naturally;

4. Wash the black precipitate obtained by the reaction three times with water and ethanol in turn, and then place it in a vacuum oven at 60°C for 12 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst. The chemical formula of the catalyst is Co _0.78 Ni _0.13 Se ₂ is denoted as CNSe-1.

Embodiment 2: The preparation method of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present embodiment is carried out according to the following steps:

1. Weigh 2.00 mmol of selenium powder, 1.00 mmol of Co(NO ₃ ) ₂ 6H ₂ O, 0.50 mmol of Ni(NO ₃ ) ₂ 6H ₂ O; then weigh 5 mL of potassium hydroxide with a concentration of 20 mol/L Solution, 1.60mmol EDTA-2Na and 20mL ultrapure water;

2. Dissolve 2.00mmol of selenium powder in 5mL of 20mol/L potassium hydroxide solution, stir for 30min, then add 1.00mmol of Co(NO ₃ ) ₂ 6H ₂ O, 0.50mmol of Ni(NO ₃ ) ₂ 6H ₂ O, 1.60mmol EDTA-2Na and 20mL ultrapure water, continue stirring for about 1-1.5h to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react for 12 hours at a temperature of 180°C, and cool to room temperature naturally;

4. Wash the black precipitate obtained by the reaction three times with water and ethanol in turn, and then place it in a vacuum oven at 65°C for 12 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst. The chemical formula of the catalyst is Co _0.73 Ni _0.20 Se ₂ is denoted as CNSe-2.

Embodiment 3: The preparation method of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present embodiment is carried out according to the following steps:

1. Weigh 2.00 mmol of selenium powder, 1.00 mmol of Co(NO ₃ ) ₂ 6H ₂ O, 0.75 mmol of Ni(NO ₃ ) ₂ 6H ₂ O, 5 mL of potassium hydroxide solution with a concentration of 20 mol/L, 1.60 mmol EDTA-2Na and 20mL ultrapure water;

2. Dissolve 2.00mmol of selenium powder in 5mL of 20mol/L potassium hydroxide solution, stir for 30min, then add 1.00mmol of Co(NO ₃ ) ₂ ·6H ₂ O, 0.75mmol of Ni(NO ₃ ) ₂ 6H ₂ O, 1.60mmol EDTA-2Na and 20mL ultrapure water, continue stirring for about 1-1.5h to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react for 12 hours at a temperature of 180°C, and cool to room temperature naturally;

4. Wash the black precipitate obtained from the reaction three times with water and ethanol in turn, and then place it in a vacuum oven at 60°C for 12 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst. The chemical formula of the catalyst is Co _0.77 Ni _0.25 Se ₂ is denoted as CNSe-3.

Embodiment 4: The preparation method of the nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst of the present embodiment is carried out according to the following steps:

1. Weigh 2.00mmol of selenium powder, 1.0mmol of Co(NO ₃ ) ₂ 6H ₂ O, 1.00mmol of Ni(NO ₃ ) ₂ 6H ₂ O. 2. Dissolve 2.00mmol of selenium powder in 5mL with a concentration of 20mol /L potassium hydroxide solution, after stirring for 30min, add 1.0mmol Co(NO ₃ ) ₂ ·6H ₂ O, 1.00mmol Ni(NO ₃ ) ₂ ·6H ₂ O, 1.60mmol EDTA-2Na and 20mL super Pure water, continue stirring for about 1-1.5 hours to obtain a mixed solution;

3. Transfer the mixture to a Teflon reactor, react for 12 hours at a temperature of 180°C, and cool to room temperature naturally;

4. Wash the black precipitate obtained from the reaction three times with water and ethanol in turn, and then place it in a vacuum oven at 65°C for 12 hours to obtain a nickel-doped cobalt selenide electrocatalytic hydrogen evolution catalyst. The chemical formula of the catalyst is Co _0.61 Ni _0.31 Se ₂ is denoted as CNSe-4.

Comparative Example 1: Ni element is not doped in the catalyzer of the present embodiment, and concrete preparation method is carried out according to the following steps:

1. Dissolve 2.00mmol of selenium powder in 5mL of potassium hydroxide solution with a concentration of 20mol/L. After stirring for 30min, add 1.0mmol of Co(NO ₃ ) ₂ 6H ₂ O, 1.60mmol of EDTA-2Na and 20mL of ultrapure water, continue to stir for about 1 to 1.5 hours to obtain a mixed solution;

2. Transfer the mixture to a Teflon reactor, react at a temperature of 180°C for 12 hours, and cool to room temperature naturally;

3. The black precipitate obtained from the reaction was washed with water and ethanol three times respectively, and then placed in a vacuum oven at 65° C. for 12 hours to obtain the catalyst as CoSe ₂ .

Comparative example 2: the catalyzer of the present embodiment does not add Co element, and concrete preparation method is carried out according to the following steps:

1. Dissolve 2.00mmol of selenium powder in 5mL of potassium hydroxide solution with a concentration of 20mol/L. After stirring for 30min, add 2.00mmol of Ni(NO ₃ ) ₂ 6H ₂ O, 1.60mmol of EDTA-2Na and 20mL of ultrapure water, continue to stir for about 1 to 1.5 hours to obtain a mixed solution;

2. Transfer the mixture to a Teflon reactor, react at a temperature of 180°C for 12 hours, and cool to room temperature naturally;

3. The black precipitate obtained from the reaction was washed three times with water and ethanol in turn, and then placed in a vacuum oven at 65° C. for 12 hours to obtain NiSe ₂ as the catalyst.

The materials CNSe-1, CNSe-2, CNSe-3, CNSe-4, CoSe ₂ and NiSe ₂ prepared in Examples 1-4 and Comparative Examples 1-2 are electrochemically tested, and the obtained polarization curves are shown in Figure 1 As shown, the Tafel slope is shown in Figure 2, the overpotential histogram is shown in Figure 3, and the Tafel slope histogram is shown in Figure 4,

As can be seen from Figure 1, the overpotentials of CNSe-1, CNSe-2, CNSe-3, and CNSe-4 (potential when the current density is 10mA cm ^-2 ) are higher than those of pure phase cobalt selenide and nickel selenide. In particular, the overpotential of CNSe-3 is as low as –172mV, which is better than most transition metal chalcogenides.

It can be seen from Figure 2 that the Tafel slope of CNSe-3 is the lowest, about 32.4mV dec ^–1 , which is slightly larger than 30.7mV dec ^–1 of commercial platinum carbon, indicating that its catalytic activity is higher.

It can be seen from Figure 3 that the overpotential of all doped samples decreases after the introduction of nickel into cobalt selenide, and the overall change is in the shape of a "V". The doping amount of nickel in CNSe-3 is the best value, After the cobalt selenide is doped with nickel, defects are formed on the cobalt selenide basal surface, which increases the active sites of the composite material and enhances the catalytic activity.

It can be seen from Figure 4 that the Tafel slope distribution trend of all samples is similar to the overpotential, which again confirms that the nickel doping amount in CNSe-3 is the optimal value.

The continuous cyclic voltammetry curve of the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ prepared in Example 3 is shown in Figure 5. After 1,000 cycles of continuous cyclic voltammetry test, the polarization curve almost coincides with the initial curve. Under overpotential conditions for 10,000s, the current density did not change significantly, indicating that the material also has ultra-high stability.

The chemical formula prepared in Example 3 is that the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ is shown in Figure 6 under the potential of -179mV for 10,000s. It can be seen from Figure 6 that the CNSe The current density of -3 showed periodic changes, but the overall maintained at about 13mA cm ^-2 , which again confirmed the good stability of the sample.

The scanning electron microscope photo of the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ prepared in Example 3 is shown in Figure 7. It can be seen from Figure 7 that CNSe-3 is composed of nanosheets with a size of 200-300nm. This structure is conducive to the contact between the electrolyte and the catalyst, and the bubbles generated by hydrolysis are easy to remove from the surface of the catalyst. During the continuous electrocatalysis process, the catalyst will not fall off from the surface of the working electrode due to too large bubbles, improving the stability.

The transmission electron microscope photo of the catalyst CNSe-3 with the chemical formula Co _0.77 Ni _0.25 Se ₂ prepared in Example 3 is shown in Figure 8, as can be seen from Figure 8, the results are consistent with the scanning electron microscope test, the sample consists of 200-300nm two-dimensional nanosheets.

The components of CNSe-1, CNSe-2, CNSe-3, and CNSe-4 obtained by energy spectrum testing are shown in Table 1.

Table 1.Atomic percentages obtained from EDX spectra

It can be seen from Table 1 that the atomic number ratios of nickel, cobalt and selenium in all nickel-doped cobalt selenide samples are consistent with their molecular formulas.

Claims (6)

1. A nickel-doped cobalt selenide electro-catalysis hydrogen evolution catalyst is characterized in that the chemical general formula of the catalyst is Co_xNi_ySe₂Wherein x is 0.6-0.8, and y is 0.1-0.35.

2. The method for preparing the nickel-doped cobalt selenide electro-catalytic hydrogen evolution catalyst as claimed in claim 1, which is characterized by comprising the following steps:

one, press Co_xNi_ySe₂Weighing selenium powder and Co (NO) according to the stoichiometric ratio₃)₂·6H₂O and Ni (NO)₃)₂·6H₂O，Co_xNi_ySe₂Wherein x is 0.6-0.8, and y is 0.1-0.35; then weighing potassium hydroxide solution, EDTA-2Na and ultrapure water;

secondly, dissolving the selenium powder in a potassium hydroxide solution, stirring for 25-35 min, and adding Co (NO)₃)₂·6H₂O、Ni(NO₃)₂·6H₂O, EDTA-2Na and ultrapure water, and continuously stirring for about 1-1.5 h to obtain a mixed solution;

thirdly, transferring the mixture into a Teflon reaction kettle, reacting for 10-16 h at the temperature of 160-200 ℃, and naturally cooling to room temperature;

and fourthly, washing the black precipitate obtained by the reaction with water and ethanol in sequence, and then placing the black precipitate in a vacuum oven at the temperature of 60-65 ℃ for 12-15 hours to obtain the nickel-doped cobalt selenide electro-catalysis hydrogen evolution catalyst.

3. The preparation method of the nickel-doped cobalt selenide electro-catalytic hydrogen evolution catalyst as claimed in claim 2, wherein the concentration of the potassium hydroxide solution in the step one is 20-25 mol/L.

4. The method for preparing a nickel-doped cobalt selenide electro-catalytic hydrogen evolution catalyst according to claim 2 or 3, wherein the molar ratio of the selenium powder to the potassium hydroxide in the potassium hydroxide solution in the step one is 1: (50-60).

5. The method for preparing the nickel-doped cobalt selenide electro-catalytic hydrogen evolution catalyst according to claim 2 or 3, wherein the molar ratio of the selenium powder to the EDTA-2Na in the step one is 1: (0.8-0.9).

6. The method for preparing a nickel-doped cobalt selenide electro-catalytic hydrogen evolution catalyst as claimed in claim 2 or 3, wherein in the first step, the ratio of the amount of the selenium powder to the volume of the ultrapure water is 1 mmol: (10-12) mL.