CN114147221A

CN114147221A - Preparation method of Ag @ CoMoO4 oxygen evolution electrocatalyst

Info

Publication number: CN114147221A
Application number: CN202111460990.3A
Authority: CN
Inventors: 张美琳; 杨绍华; 温婷婷; 高义灏; 刘伟东; 弓亚琼
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2022-03-08
Anticipated expiration: 2041-12-03
Also published as: CN114147221B

Abstract

The invention relates to the technical field of electrolytic water catalytic materials, in particular to a preparation method of an Ag @ CoMoO4 oxygen evolution electrocatalyst; the method comprises the following steps: (1) mixing polyvinylpyrrolidone and 1, 2-propylene glycol, stirring at a certain temperature, and then adding a sodium chloride solution and a silver nitrate solution with certain concentrations to prepare a silver nanowire solution; (2) purifying the silver nanowires by acetone and washing for several times for later use; (3) weighing 2-methylimidazole in mixed solution of silver nanowires and methanol with different amounts, adding methanol solution of cobalt nitrate hexahydrate, dissolving the mixed solution in ethanol, and stirring at normal temperature; (4) adding sodium molybdate nonahydrate into the product obtained in the step (3) to perform hydrothermal reaction; after naturally cooling to room temperature, centrifugally collecting, washing with ethanol for a plurality of times, and drying to obtain a catalyst; the method has low production cost, is easy to realize large-scale production, can keep the microstructure and good catalytic activity of the catalyst for a long time under the alkaline condition, and has potential industrial application value in the aspect of electrocatalytic hydrogen production.

Description

Preparation method of Ag @ CoMoO4 oxygen evolution electrocatalyst

Technical Field

The invention relates to the technical field of electrolytic water catalytic materials, in particular to a preparation method of an Ag @ CoMoO4 oxygen evolution electrocatalyst.

Background

The increasing severity of energy crisis and environmental pollution caused by fossil fuels become two obstacles to sustainable development of human society at present, and the development and storage problems of renewable energy sources cause wide attention of researchers at home and abroad. The electrochemical process can realize the interconversion between the electric energy and the chemical energy stored in the chemical bond, thereby being used for solving the following key problems involved in the energy storage and conversion processes: first, electrochemical energy is converted into a charged interfacial reaction, so electrochemical cell conversion is theoretically much higher than conventional thermal efficiency; secondly, the electrochemical system provides an efficient and stable platform for energy conversion and storage; thirdly, the whole process of the electrochemical system is an environment-friendly reaction, and the hydrogen energy which does not cause environmental pollution or other environmental problems has the advantages of high energy conversion efficiency, high energy density, zero emission of carbon dioxide, good environmental compatibility and the like, and is considered as an ideal energy source for replacing the traditional fossil fuel. Based on the principle of electrochemical water decomposition, renewable solar energy or electric energy is utilized to drive water to be decomposed into hydrogen and oxygen, which is considered to be an efficient and sustainable hydrogen production way. The water electrolysis process comprises two half reactions, namely an Oxygen Evolution Reaction (OER) and a hydrogen evolution reaction, wherein the oxygen evolution reaction is a four-electron transfer process, the catalysis mechanism is complex, the reaction kinetics is slow, the required overpotential is high, and the overpotential is a key ring for limiting the water electrolysis efficiency. So far, noble metal catalysts ruthenium dioxide (RuO2) and iridium dioxide (IrO2) are considered as high-efficiency OER electrocatalysts, but due to their rare reserves and high price, their commercial application is directly restricted. Therefore, there is an urgent need to develop an inexpensive, efficient, durable OER electrocatalyst to replace the noble metal catalyst. In recent years, transition metal-based nanomaterials based on iron, cobalt, nickel, copper, molybdenum and manganese exhibit excellent electrochemical activity, but their durability in catalyzing oxygen evolution reaction is relatively poor, especially under severe environments such as strongly alkaline electrolytes and high potentials, and therefore, development of highly efficient alkaline oxygen-generating electrocatalysts is important for research.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a preparation method of an Ag @ CoMoO4 oxygen evolution electrocatalyst.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of an Ag @ CoMoO4 oxygen evolution electrocatalyst comprises the following steps:

(1) mixing polyvinylpyrrolidone and 1, 2-propylene glycol, stirring at a certain temperature, and then adding a sodium chloride solution and a silver nitrate solution with certain concentrations to prepare a silver nanowire solution;

(2) purifying the silver nanowires by acetone and washing for several times for later use;

(3) weighing 2-methylimidazole in mixed solution of silver nanowires and methanol with different amounts, adding methanol solution of cobalt nitrate hexahydrate, dissolving the mixed solution in ethanol, and stirring at normal temperature;

(4) adding sodium molybdate nonahydrate into the product obtained in the step (3) to perform hydrothermal reaction; after naturally cooling to room temperature, centrifugally collecting, washing for a plurality of times by ethanol, and drying to obtain Ag @ CoMoO₄、CoMoO₄、Ag₅@CoMoO₄And Ag₂₀@CoMoO₄Four catalysts.

The invention uses the framework structure of ZIF-67 (zeolite imidazole ester framework material) to separate and stackSilver nanowires. ZIF-67 has a porous structure, so that the specific surface area of the catalyst is increased; the silver nanowire has excellent conductivity, and can effectively promote the transfer of interface electrons, so that the current density of the catalytic material is improved. Ag @ CoMoO designed in the invention₄The preparation process of the catalytic material fully utilizes the advantages of ordered structure, large specific surface area, excellent conductivity of the silver nanowire and the like of the ZIF-67, and prepares the prepared Ag @ CoMoO₄The catalytic material has uniform structure and excellent electro-catalytic oxygen evolution performance, adopts conventional equipment, is cheap and easy to obtain, has simple and easy preparation process, and is suitable for industrial large-scale production.

The method has the advantages of simple operation, low production cost and easy realization of large scale, can keep the microstructure and good catalytic activity of the catalyst for a long time under the alkaline condition, and has potential industrial application value in the aspect of electrocatalytic hydrogen production.

Further, the concentration of the sodium chloride solution in the step (1) is 10 mM, and the concentration of the silver nitrate solution is 0.15M.

Further, in the step (1), the mass-to-volume ratio of the polyvinylpyrrolidone, the 1, 2-propylene glycol, the sodium chloride solution and the silver nitrate solution is as follows: 75 mg: 5 mL of: 50 μ L of: 2 mL.

Further, in the step (3), the mass-to-volume ratio of the mixed solution of 2-methylimidazole, silver nanowires and methanol to cobalt nitrate hexahydrate is 0.3284 g: 20mL: 0.291 g; the mass volume ratio of the cobalt nitrate hexahydrate to the methanol in the methanol solution of the cobalt nitrate hexahydrate is 0.291 g: 20 mL.

Further, in the mixed solution of the silver nanowires and the methanol, when the volume ratio of the silver nanowires to the methanol is 1:1, Ag @ CoMoO is obtained₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 0:2, the CoMoO is obtained₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 1:3, Ag is obtained₅@CoMoO₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 2:0, Ag is obtained₂₀@CoMoO₄A catalyst.

Further, the mass ratio of the sodium molybdate nonahydrate in the step (4) to the 2-methylimidazole in the step (3) is 1: 5.

in addition, the invention also provides application of the Ag @ CoMoO4 catalyst prepared by the preparation method in water electrolysis oxygen evolution electrocatalysis.

The invention also provides a method for testing the catalytic performance of the Ag @ CoMoO4 catalyst prepared by the preparation method in electrolytic water oxygen evolution electrocatalysis, the Ag @ CoMoO4 catalyst is dissolved in a mixed solution of ethanol and naphthol, the mixture is dispersed to be uniform by ultrasonic dispersion, the obtained dispersion liquid is dropped on carbon paper, and the carbon paper is used as a working electrode and is tested by an electrochemical workstation.

Further, the mass fraction of naphthol in the mixed solution of ethanol and naphthol was 5 Wt%.

Furthermore, the testing method adopts a three-electrode working system, Hg/HgO is used as a reference electrode, a carbon rod is used as a counter electrode, and a potassium hydroxide solution is used as an electrolyte.

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

1. the catalyst prepared by the invention has the advantages of low cost of raw materials, short operation period, high repeatability and easy large-scale production.

2. The preparation method only needs conventional reaction equipment such as an oven, an oil bath pan, a centrifuge, a magnetic stirrer and the like, and has the advantages of low cost, easy acquisition and simple operation.

3. The material prepared by the invention has excellent oxygen evolution capacity, and the current density can reach 10 mA cm only by overpotential of 236 mV^-2The performance is even better than that of the noble metal catalyst; the catalytic activity did not decay in the stability test for up to 16 hours.

4. The invention fully utilizes the characteristics that the silver nanowires have excellent conductivity, can effectively promote interface electron transfer and improve the current density of the catalytic material, and utilizes the characteristics of good stability and many active sites of cobalt molybdate to show good electrocatalysis performance.

Drawings

FIG. 1 is the Ag @ CoMoO obtained in example 1₄XRD spectrum of the catalyst;

FIG. 2 shows silver nanowires prepared in example 1And the CoMoO prepared in example 2₄SEM photograph of the catalyst;

FIG. 3 is the Ag @ CoMoO obtained in example 1₄SEM photograph of the catalyst;

FIG. 4 is the Ag @ CoMoO obtained in example 1₄EDX mapping plot of catalyst;

FIG. 5 is the Ag @ CoMoO obtained in example 1₄EDX energy spectrum of the catalyst;

FIG. 6 is Ag @ CoMoO obtained in example 1₄XPS spectra of the catalyst;

FIG. 7 is the Ag @ CoMoO obtained in example 1₄And IrO₂And the CoMoO obtained in example 2₄Linear scanning voltammograms of the catalyst;

FIG. 8 is the Ag @ CoMoO obtained in example 1₄Ag obtained in example 3₅@CoMoO₄And Ag obtained in example 4₂₀@CoMoO₄Linear scanning voltammograms of the material;

FIG. 9 is the Ag @ CoMoO obtained in example 1₄And IrO₂EIS test curve of catalyst in alkaline (1M KOH) electrolyte;

FIG. 10 is the Ag @ CoMoO obtained in example 1₄Voltage-time stability test curve of the catalyst in alkaline (1M KOH) electrolyte.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example 1

375 mg of polyvinylpyrrolidone (55000) and 25 mL of 1, 2-propanediol were each added to a 100 mL round-bottom flask and magnetically stirred in an oil bath at 160 ℃ for 1 h. 250. mu.L of sodium chloride solution and 10 mL of silver nitrate solution were added, and the reaction was continued for 40 min. After naturally cooling to room temperature, the obtained mixed solution is placed in a centrifuge tube, acetone is added to 45 mL, and centrifugation is carried out (the rotation speed is 8000 rmp, and the time is 5 min). The supernatant was decanted, ethanol was added to 10 mL, dispersed by sonication until homogeneous, acetone was added to 45 mL, and centrifuged. The above operation is repeated. The product obtained above was dispersed in 120 mL of methanol and stored until use, and the amount was about 1 mg/mL.

0.3284 g of 2-methylimidazole were weighed into a 50 mL round-bottom flask, 10 mL of methanol and 10 mL of silver nanowires were added, and magnetic stirring was performed. 0.291 g of cobalt nitrate hexahydrate was weighed out and dissolved in 20mL of methanol, poured into a round bottom flask and stirred for 2 h. Centrifuging (rotating speed 5000 rmp, time 5 min), washing with ethanol for several times, and dispersing in 10 mL deionized water.

0.309 g of sodium molybdate nonahydrate is weighed and dissolved in 10 mL of deionized water, and the solution is added into the mixed solution to carry out hydrothermal reaction in a 50 mL reaction kettle, wherein the reaction temperature is 100 ℃, and the reaction time is 3 hours. Centrifuging (the rotating speed is 5000 rmp, the time is 5 min), washing with ethanol for several times, adding ethanol to 15 mL for later use, and finally obtaining Ag @ CoMoO₄A catalyst.

Example 2

As in example 1, except that the mixed solution of 10 mL of methanol and 10 mL of silver nanowires was changed to 20mL of methanol solution, the other synthesis conditions were not changed, and CoMoO was obtained₄A catalyst.

Example 3

The same as example 1, except that the mixture of 10 mL of methanol and 10 mL of silver nanowires was changed to a mixture of 5 mL of silver nanowires and 15 mL of methanol, and other synthesis conditions were not changed, and Ag was obtained₅@CoMoO₄A catalyst.

Example 4

The same as example 1, except that the mixed solution of 10 mL of methanol and 10 mL of silver nanowires was changed to 20mL of silver nanowire solution, the other synthesis conditions were not changed, and Ag was obtained₂₀@CoMoO₄A catalyst.

The catalyst prepared by the method is subjected to necessary structural characterization and electrochemical performance test. FIG. 1 shows the catalyst Ag @ CoMoO₄The X-ray diffraction (XRD) pattern of (1) is compared with standard cards (04-0783 and 26-0477), diffraction peaks at 2 theta values of about 38.1 degrees, 44.3 degrees, 64.4 degrees and 77.5 degrees respectively correspond to the (111), (200), (220) and (311) crystal planes of Ag (JCPDF No.04-0783), and diffraction peaks at 2 theta values of about 23.5 degrees, 26.6 degrees, 32.3 degrees and 53.9 degrees respectively correspond to CoMoO₄(JCPDF No.26-0477) (021), (012), (022) and (133) crystal planes, which indicates that Ag @ CoMoO was successfully synthesized₄. FIG. 2 shows prepared silver nanowires and CoMoO₄SEM photograph of (a), it can be seen that the diameter of the silver nanowire is about several tens of nanometers, CoMoO₄Is in a sheet structure. FIG. 3 shows the catalyst Ag @ CoMoO₄SEM photograph of (silicon nitride) shows that the silver nanowires are flaky CoMoO₄Are well stringed together, the specific surface area of the catalyst is greatly enhanced, and then the Ag @ CoMoO is improved₄OER catalytic activity of (a). FIG. 4 is the resulting Ag @ CoMoO₄The EDX mapping chart shows that the material contains four elements of Ag, Co, Mo and O, and the four elements are uniformly distributed in the material. FIG. 5 is the resulting Ag @ CoMoO₄The EDX spectrum of the material shows that the content of Co element in the material is 39.9 Wt% at most. FIG. 6 shows the resulting catalyst Ag @ CoMoO₄X-ray photoelectron spectroscopy (XPS) spectrum of Ag @ CoMoO as shown in FIG. 6 a, full spectrum₄In which Ag, Co, Mo and O elements are present. As shown in FIG. 6 b, Ag @ CoMoO₄The XPS spectrum of Ag 3d of (a) shows that the two main peaks 368.0 and 374.0 eV have a splitting width of 6.0 eV, confirming the presence of zero-valent silver. As shown in FIG. 6 c, Ag @ CoMoO₄The Co 2p spectrum of (A) is divided into two spin-orbit coupled Co²⁺(796.9 and 781.5 eV) and Co³⁺(795.9 and 780.1 eV). Furthermore, the two peaks of 786.1 and 802.3 eV can be attributed to two vibro-satellite peaks. As shown in FIG. 6 d, at Ag @ CoMoO₄The XPS spectrum of Mo 3d of (1) shows that the two main peaks 232.3 and 235.4 eV have a cleavage width of 3.1 eV, and it is confirmed that Mo⁶⁺Are present. As shown in FIG. 6 e, Ag @ CoMoO₄The spectrum of the O1 s consists of three kinds of oxygen, and the corresponding peaks are respectively 530.5, 531.0 and 532.3 eV, which shows that Ag @ CoMoO₄In the catalyst, O, Co and Mo have stronger bond.

Carrying out electrocatalytic water cracking oxygen production (OER) performance test on the catalyst material prepared by the method in a standard three-electrode electrolytic cell; wherein the cyclic scanning range is 0-1.0V, and the scanning rate is 2 mV/s. Note that all potentials obtained with the Hg/HgO electrode as a reference electrode in the electrocatalytic test were converted to reversible hydrogen electrode potentials in the property diagrams.

FIG. 7 is Ag @ CoMoO₄CoMoO4 and IrO₂Linear scanning voltammogram of the material. With CoMoO4And IrO₂By way of comparison, it can be seen that Ag @ CoMoO₄The electrochemical performance of (2) is the best. When the current density is 10 mA cm^-2In time, Ag @ CoMoO₄Is only 236 mV.

FIG. 8 is Ag @ CoMoO₄、Ag₅@CoMoO₄And Ag₂₀@CoMoO₄Linear scanning voltammogram of the material. As shown, Ag @ CoMoO₄Has better electrochemical performance than Ag₅@CoMoO₄And Ag₂₀@CoMoO₄。

FIG. 9 is a graph of the impedance of the catalyst versus the noble metal IrO₂Catalyst comparison, Ag @ CoMoO₄The impedance of (a) is the smallest, indicating that it possesses the fastest electron transfer capability.

FIG. 10 shows the catalyst at a current density of 10 mA cm^-2The stability test below, which is maintained in a stable state for more than 16 hours and has no performance reduction, shows the excellent stability of the catalyst.

Claims

1. A preparation method of an Ag @ CoMoO4 oxygen evolution electrocatalyst is characterized by comprising the following steps of:

(2) purifying the silver nanowires obtained in the step (1) by using acetone and washing for several times for later use;

2. The method for preparing the Ag @ CoMoO4 oxygen evolution electrocatalyst according to claim 1, wherein the concentration of the sodium chloride solution in step (1) is 10 mM, and the concentration of the silver nitrate solution is 0.15M.

3. The preparation method of the Ag @ CoMoO4 oxygen evolution electrocatalyst according to claim 2, wherein the mass-to-volume ratio of the polyvinylpyrrolidone, the 1, 2-propylene glycol, the sodium chloride solution and the silver nitrate solution in the step (1) is as follows: 75 mg: 5 mL of: 50 μ L of: 2 mL.

4. The preparation method of the Ag @ CoMoO4 oxygen evolution electrocatalyst according to claim 1, wherein the mass-to-volume ratio of the mixed solution of 2-methylimidazole, silver nanowires and methanol and cobalt nitrate hexahydrate in the step (3) is 0.3284 g: 20mL: 0.291 g; the mass volume ratio of the cobalt nitrate hexahydrate to the methanol in the methanol solution of the cobalt nitrate hexahydrate is 0.291 g: 20 mL.

5. The preparation method of the Ag @ CoMoO4 oxygen evolution electrocatalyst according to claim 4, wherein in the mixed solution of the silver nanowires and the methanol, when the volume ratio of the silver nanowires to the methanol is 1:1, the Ag @ CoMoO is obtained₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 0:2, the CoMoO is obtained₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 1:3, Ag is obtained₅@CoMoO₄A catalyst; when the volume ratio of the silver nanowires to the methanol is 2:0, Ag is obtained₂₀@CoMoO₄A catalyst.

6. The method for preparing the Ag @ CoMoO4 oxygen evolution electrocatalyst according to claim 4, wherein the molar ratio of sodium molybdate nonahydrate in step (4) to 2-methylimidazole in step (3) is 1: 5.

7. the application of the Ag @ CoMoO4 catalyst prepared by the preparation method of any one of claims 1 to 6 in water electrolysis oxygen evolution electrocatalysis.

8. A method for testing the catalytic performance of the Ag @ CoMoO4 catalyst prepared by the preparation method of any one of claims 1 to 6 in the electro-catalysis of oxygen evolution by electrolyzing water, which is characterized by comprising the following steps: dissolving the Ag @ CoMoO4 catalyst in a mixed solution of ethanol and naphthol, ultrasonically dispersing until the solution is uniform, dropping the obtained dispersion liquid on carbon paper, taking the carbon paper as a working electrode, and testing by using an electrochemical workstation.

9. The catalytic performance test method according to claim 7, characterized in that: the mass fraction of naphthol in the mixed solution of ethanol and naphthol was 5 Wt%.

10. The catalytic performance test method according to claim 7, characterized in that: the testing method adopts a three-electrode working system, takes Hg/HgO as a reference electrode, takes a carbon rod as a counter electrode, and takes a potassium hydroxide solution as electrolyte.