Non-metal modified hydrogen evolution material and preparation method thereof

Abstract

The application discloses a non-metal modified hydrogen evolution material and a preparation method. The Sx-CoPTA is prepared by a ligand regulation strategy, a precursor solution is prepared from cobalt nitrate hexahydrate, 4,4-biphenyldicarboxylic acid, 1,4-benzenedithiol, N,N-dimethylformamide, ethanol and water, and during the preparation, ultrasonic treatment, stirring, washing, drying and low-temperature centrifugal reaction treatment are carried out, and finally, the S-CoPTA is generated, and the hydrogen evolution electrode material is synthesized by smearing the Nafion solution on the nickel foam. The catalytic electrode material S1-CoPTA prepared by the application has a large specific surface area of the MOF material, breaks the original symmetrical structure of the MOF material, effectively improves the conductivity of the MOF material, and further improves the hydrogen evolution efficiency of the electrode material, and has a center structure and a function simulation similar to the [Fe-Fe] hydrogenase.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrocatalytic hydrogen evolution materials, in particular to a non-metal modified hydrogen evolution material and a preparation method thereof. BACKGROUND

[0002] The scarcity of fossil fuels such as petroleum, coal and natural gas and the problems caused by environmental pollution during use have led to widespread attention to the development and utilization of green energy such as hydrogen. Currently, hydrogen can be obtained by chemical fuel and electrolysis of water hydrogen evolution. Compared with fuel hydrogen production, the electrolysis of water hydrogen evolution reaction (HER) has been widely concerned due to its simple equipment, low environmental pollution degree in production process and high yield. The material used for electrolysis of water hydrogen evolution is generally a noble metal platinum-based material, but its scarcity and high price limit its large-scale commercial application. Therefore, the development of efficient and low-cost electrocatalytic materials is a key factor to promote the electrolysis of water hydrogen evolution.

[0003] Organometallic framework (MOF) materials, also known as porous coordination polymers, are two-dimensional or three-dimensional porous crystalline materials, which are self-assembled framework structures of organic ligands obtained by coordination of metal cations or metal ion clusters and organic linkers. The structure of MOF material is flexible, which can be adjusted by controlling the types and proportions of metal ions and organic ligands, and is widely used in gas storage, energy conversion, chemical sensing, drug delivery, proton conductivity and catalysis.

[0004] [Fe-Fe] hydrogenase is a metal enzyme with the best hydrogen production effect known in nature, which widely exists in anaerobic organisms.

[0005] According to research, in the application of electrocatalysis, MOF materials can expose more active sites in the reaction process due to their high surface area and regular voids, so that the mass transfer reaction of electrocatalysis can occur rapidly. However, MOF materials have low conductivity and unstable reaction process in practical application, which greatly limits their direct use in the field of electrocatalysis. Therefore, in practical application, MOF materials are generally used as precursors. The existing modification method of MOF is to change its original structure by physical / chemical exfoliation, dissolution-thermal method, ultrasonic method, etc. so that the MOF material has a nanoscale size to increase the active sites in the catalytic process, or the conductivity of the MOF material can be improved, that is, the specific metal center and functional group ligand are grown on the surface of the MOF material in situ to improve its reaction activity. SUMMARY

[0006] The purpose of the present application is to provide a non-metal modified hydrogen evolution material and a preparation method, which is an efficient electrocatalytic material of non-metallic sulfur-doped cobalt-based metal organic framework prepared by regulating the strategy of ligand, and is mainly applied in the field of water electrolysis hydrogen evolution.

[0007] The purpose of the present application is realized by the following technical scheme: a preparation method of a non-metal modified hydrogen evolution material, comprising the following steps:

[0008] 1. The untreated foam nickel is cut into a rectangular sheet, and is sequentially washed with acetone, ethanol and deionized water by ultrasonic washing, and then is placed in a vacuum air drying oven for drying, to complete the pretreatment of the foam nickel material.

[0009] 2. 148.62mg of cobalt nitrate hexahydrate, 123.93mg of 4,4-biphenyldicarboxylic acid and 9.0mg of 1,4-benzenedithiol are dissolved in a mixed solvent prepared from 16mL of N,N-dimethylformamide, 1mL of ethanol and 1mL of deionized water, and are stirred by a magnetic stirrer to ensure complete dissolution, and the obtained magenta clear solution is used as a precursor solution, wherein the molar ratio of cobalt nitrate hexahydrate and 4,4-biphenyldicarboxylic acid is 1:1, and the mass concentration of 1,4-benzenedithiol is 0.05-0.50g / L.

[0010] 3. 0.8ml of triethylamine is quickly added to the precursor solution prepared in step 2, and is stirred by a magnetic stirrer for 12-48h to ensure complete dissolution, and then the precursor solution is centrifuged by a low-temperature centrifuge, and a magenta precipitate is obtained after the centrifugation, and the precipitate is placed at room temperature, wherein the temperature of the low-temperature centrifuge is 0-10℃, and the centrifugation time is 3h.

[0011] 4. The precipitate placed at room temperature after step 3 is repeatedly washed with N,N-dimethylformamide, ethanol and water solution, and then is placed in a vacuum air drying oven for drying, to obtain a sulfur-doped MOF derived material, which is named as S-CoPTA.

[0012] 5. 5mg of S-CoPTA and 2.5mg of carbon black obtained in step 4 are added to 25uL of 0.5% mass concentration of Nafion solution, and are ultrasonically washed to ensure complete mixing, and then are applied on the foam nickel pretreated in step 1 to form a sulfur-doped MOF derived electrode material loaded on the foam nickel, which is named as S1-CoPTA.

[0013] Further, the foam nickel in step 1 is cut into a rectangular sheet with a size of 1x4cm 2 , and the ultrasonic washing time is 20 minutes.

[0014] Further, the drying temperature in step 1 is 60 DEG C.

[0015] Further, the purity of all chemical reagents in step 1 and step 2 is AR.

[0016] Further, in step 2, the transition metal cobalt provided by the cobalt nitrate hexahydrate exists in the form of element, and the nonmetallic sulfur provided by 1,4-benzenedimethanethiol exists in the form of PTA group.

[0017] Further, in step 3, the temperature of the low-temperature centrifuge is T=4 DEG C.

[0018] Further, the drying temperature in step 4 is 60 DEG C.

[0019] A nonmetallic modified hydrogen evolution material, wherein the S1-CoPTA structure of the nonmetallic modified hydrogen evolution material comprises two adjacent nickel atoms and cobalt atoms, and is bridged by a carbonyl group and a dithiol ligand.

[0020] The nonmetallic modified hydrogen evolution material is used as a working electrode in a three-electrode system to catalyze the hydrogen evolution reaction of water electrolysis.

[0021] The beneficial effects of the present application are as follows:

[0022] The electrode material prepared by the present application breaks the original symmetrical metal structure of the MOF material, and synthesizes a [Fe-Fe] hydrogenase structure, thereby enhancing the conductivity and catalytic efficiency of the electrode material, reducing the energy consumption, and having reference significance for replacing traditional Pt / C and other noble metal catalytic materials.

[0023] The electrode material prepared by the present application is subjected to a 1000-cycle test by a cyclic voltammetry (CV) test method, and the overpotential of the electrode material before and after the test changes little, indicating that the stability of the electrode material is strong. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A transmission electron microscope (TEM) image of the MOF derived material S-CoPTA prepared in Example 2;

[0025] Figure 2 A cold field emission scanning electron microscope (FESEM) 1-micron image of the MOF derived material S-CoPTA prepared in Example 2;

[0026] Figure 3 A cold field emission scanning electron microscope (FESEM) 5-micron image of the MOF derived material S-CoPTA prepared in Example 2;

[0027] Figure 4A cold field emission scanning electron microscope 1-micron FESEM image of MOF-derived material CoPTA prepared for Comparative Example 1;

[0028] Figure 5 A cold field emission scanning electron microscope 5-micron FESEM image of MOF-derived material CoPTA prepared for Comparative Example 1;

[0029] Figure 6 An X-ray diffraction (XRD) image of MOF-derived material S-CoPTA prepared for Example 2;

[0030] Figure 7 A cold field emission scanning electron microscope 5-micron FESEM image of MOF-derived material S-CoPTA prepared for Comparative Examples 2-7 at different centrifugation temperatures, times and different sulfur addition amounts, wherein (a) is an FESEM image of S-CoPTA with 18 mg of 1,4-benzenedimercaptan added, (b) is an FESEM image of S-CoPTA at a low-temperature centrifugation temperature of 10°C, (c) is an FESEM image of S-CoPTA at a low-temperature centrifugation temperature of 0°C, (d) is an FESEM image of S-CoPTA at a low-temperature centrifugation time of 12 h, (e) is an FESEM image of S-CoPTA at a low-temperature centrifugation time of 48 h, and (f) is an FESEM image of S2-CoPTA at a centrifugation temperature of 25°C;

[0031] Figure 8 A Faraday efficiency (FE) plot of electrode material S1-CoPTA prepared for Example 2 in the application field of water electrolysis for hydrogen evolution;

[0032] Figure 9 An LSV plot of electrode material S1-CoPTA prepared for Example 2 in the application field of water electrolysis for hydrogen evolution after 1000 cycles of CV;

[0033] Figure 10 A schematic diagram of the microstructure “CoNi-S1” of electrode material S1-CoPTA prepared for Example 2. DETAILED DESCRIPTION

[0034] In order to better understand the present application, the following examples are further illustrations of the present application, but the present application is not limited only to the following examples.

[0035] Example 1

[0036] 1. Cobalt salt, 4,4-biphenyldicarboxylic acid, 1,4-benzenedimercaptan were dissolved in a mixed solution of N,N-dimethylformamide (DMF), ethanol and water, and stirred to obtain a precursor solution;

[0037] 2. Add triethylamine to the precursor solution of step 1, stir thoroughly, and then centrifuge using a low-temperature centrifuge to obtain a magenta precipitate;

[0038] 3. The obtained magenta precipitate is repeatedly washed with DMF, ethanol, and water solution, and then dried in a 60°C drying oven to obtain a sulfur-doped MOF-derived electrode material.

[0039] The cobalt salt in step 1 can be selected from cobalt chloride, cobalt sulfate, cobalt nitrate, and hydrates thereof.

[0040] The stirring time in step 1 is 10-30 min, and the stirring mode can be selected from ultrasonic stirring or magnetic stirring to completely dissolve the cobalt salt, 4,4-biphenyldicarboxylic acid, and 1,4-benzenedithiol in the mixed solution of N,N-dimethylformamide (DMF), ethanol, and water to obtain a uniform solution.

[0041] The stirring time in step 2 is 24 h, and the stirring mode is magnetic stirring to fully dissolve triethylamine in the precursor solution obtained in step 1.

[0042] Example 2

[0043] 1. Unprocessed 10×10 cm 2 foam nickel (NF) is cut into 1×4 cm 2 rectangular pieces, and then ultrasonically washed with acetone, ethanol, and deionized water (DI) for 20 min, respectively, and dried at 60°C to complete the pretreatment of the foam nickel material.

[0044] 2. 148.62 mg of cobalt nitrate hexahydrate, 123.93 mg of 4,4-biphenyldicarboxylic acid (molar ratio of cobalt nitrate hexahydrate to 4,4-biphenyldicarboxylic acid 1:1), and 9.0 mg of 1,4-benzenedithiol (mass concentration 0.05-0.50 g / L) are dissolved in 16 mL of a mixed solvent of N,N-dimethylformamide (DMF), 1 mL of ethanol, and 1 mL of deionized water, and stirred for 30 min using magnetic stirring to ensure complete dissolution. The obtained magenta clear solution is used as a precursor solution.

[0045] 3. 0.8 ml of triethylamine is quickly added to the precursor solution prepared in step 2, and magnetic stirring is continued for 12-48 h to ensure complete dissolution. The precursor solution is centrifuged using a low-temperature centrifuge, the temperature of the low-temperature centrifuge is set to 4°C, the centrifugation time is 3 h, and after the centrifugation is completed, a magenta precipitate is obtained. The precipitate is placed at room temperature;

[0046] 4. The precipitate placed at room temperature after step 3 is repeatedly washed with N,N-dimethylformamide, ethanol, and water solution, and then placed in a vacuum air drying oven and dried at 60°C to obtain a sulfur-doped MOF-derived material, which is named S-CoPTA;

[0047] 5. Dissolve 5 mg of sulfur-doped MOF-derived material S-CoPTA and 2.5 mg of carbon black into 25 uL of Nafion solution, after ultrasonic dispersion for 30 min, apply on the foam nickel (1 x 4 cm 2 ) obtained by pretreatment in step 1 to obtain a sulfur-doped MOF-derived electrode material, named S1-CoPTA.

[0048] The purity of all chemical reagents in steps 1 and 2 is AR analytical purity.

[0049] In step 2, the transition metal cobalt provided by cobalt nitrate hexahydrate exists in the form of elements, and the non-metallic sulfur provided by 1,4-benzenedithiol exists in the form of PTA group.

[0050] The TEM (Transmission Electron Microscope) image of S1-CoPTA prepared in Example 2 is shown in Figure 1 , the FESEM (Field Emission Scanning Electron Microscope) image of S1-CoPTA is shown in Figure 2 and Figure 3 The TEM image and the FESEM image show that the micro-morphology of S-CoPTA is a nanosheet and small ball array with an average thickness of 25-30 nm, and Co, S, Ni, C, O are uniformly distributed on the entire nanosheet, Ni and S elements are distributed on the small balls and nanosheets, Co element is mainly distributed on the small balls, which increases the specific surface area of the exposed active sites of the material, and the synergistic effect of the two metal elements makes the hydrogen evolution material have the structure of "CoNi-S1" hydrogenase, which accelerates the hybridization of H atoms in application, thereby improving the hydrogen evolution efficiency of the material. Compared with Figure 4 , Figure 5 the CoPTA sample without doping sulfur, the nanosheet array is more dense, the small ball structure is more abundant, the active area is more, the doping of non-metallic elements accelerates the hybridization of hydrogen atoms, and the energy consumption of hydrogen evolution is reduced. Figure 6 The XRD (X-ray diffraction) pattern of the catalyst S1-CoPTA is shown in the figure, and the synthesized S1-CoPTA has characteristic diffraction peaks of PTA-based (benzenedithiol) metal organic framework material and Co element, which shows that the S-CoPTA sample is successfully prepared.

[0051] Comparative Example 1

[0052] In step 2 of Example 2, the amount of 1,4-benzenedithiol doping is changed to 0 mg, and the prepared material is named CoPTA.

[0053] FESEM (Field Emission Scanning Electron Microscope) images of S1-CoPTA are shown in FIG. 1, which indicate that CoPTA is nanosheet before doping with non-metallic S, i.e. the doping of non-metallic sulfur does not change its own micro-morphology. Figure 4 and Figure 5 As shown in FIG. 1, it is indicated that CoPTA is nanosheet before doping with non-metallic S, i.e. the doping of non-metallic sulfur does not change its own micro-morphology.

[0054] Comparative Example 2

[0055] In Comparative Example 2, the amount of 1,4-benzenedimercaptan doped in step 2 of Example 2 is changed to 18 mg, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S-CoPTA (18 mg).

[0056] Comparative Example 3

[0057] In Comparative Example 3, the centrifugal temperature T of the low-temperature centrifuge in step 4 of Example 2 is set to 10°C, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S-CoPTA (10°C).

[0058] Comparative Example 4

[0059] In Comparative Example 4, the centrifugal temperature T of the low-temperature centrifuge in step 4 of Example 2 is set to 0°C, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S-CoPTA (0°C).

[0060] Comparative Example 5

[0061] In Comparative Example 5, the magnetic stirring time in step 3 of Example 2 is set to 12 h, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S-CoPTA (1 h).

[0062] Comparative Example 6

[0063] In Comparative Example 6, the magnetic stirring time in step 3 of Example 2 is set to 48 h, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S-CoPTA (6 h).

[0064] Comparative Example 7

[0065] In Comparative Example 7, the low-temperature centrifuge in step 4 of Example 2 is changed to a general centrifuge, and the centrifugal temperature T is set to 25°C, and other steps and parameters are the same as those of Example 2, and the prepared material is named as S2-CoPTA.

[0066] Comparative Example 8

[0067] The pretreated nickel foam and precursor solution obtained in steps 1 and 2 were placed in a hydrothermal reactor lined with polytetrafluoroethylene. The temperature of the vacuum blower drying oven was set to T = 160°C. The hydrothermal reaction time was 3 hours, and then the obtained electrode material was rinsed and dried, and named S3-CoPTA.

[0068] The FESEM (Field Emission Scanning Electron Microscope) images of the S-CoPTA prepared in Comparative Examples 2-6 and the S2-CoPTA prepared in Comparative Example 7 are as follows: Figure 7 As shown in Figure 1, (a) shows that adding too much 1,4-benzenedimethanethiol to the surface will lead to stacking of the material morphology. Figures (b) and (c) show that if the low-temperature centrifugation temperature is too high and the time is too long during preparation, the surface of the S1-CoPTA nanosheets and the nanosheets will agglomerate and overlap with the surface spherical structure, making it impossible to fully expose the active sites of the material. Conversely, as shown in Figures (d) and (e), if the low-temperature centrifugation temperature is too low and the time is too short, the metal ions and ligands on the surface of the S1CoPTA nanosheets cannot fully contact each other. Figure (f) shows that the low-temperature centrifugation method can ensure that the nanosheets grow more uniformly and densely, increasing the specific surface area of ​​the active sites of the material.

[0069] The rose-red precipitate of the S3-CoPTA material prepared in Comparative Example 8 is unevenly distributed. This is because the closed nature of polytetrafluoroethylene during preparation in the hydrothermal reactor makes it impossible for humans to intervene in the growth of the material, resulting in its inability to grow evenly on the surface of the nickel foam. However, the method of mixing the material with carbon black and then applying it with Nafion solution can ensure the uniform distribution of the microstructure.

[0070] Application Examples

[0071] An efficient application of a non-metallic modified material in the field of hydrogen evolution comprises the following steps:

[0072] 1. A three-electrode system (electrolyte volume of 100 mL) was used, with the electrode material S1-CoPTA prepared in Example 2 as the working electrode, Ag / AgCl as the reference electrode, and a graphite rod as the counter electrode. The test was performed at room temperature. The electrolyte was 1.0 M KOH solution, and the addition amount was 50 mL.

[0073] 2. CV activation: Using a Shanghai Chenhua CHI 760e electrochemical workstation, nitrogen was introduced into the electrolyte for 30 minutes before testing the performance of the electrode material S1-CoPTA. The CV program was used with a test range of 0 to -1.2 V vs. reversible hydrogen electrode (RHE) at a scan rate of 50 mVs. -1, and the electrode material S1-CoPTA reached a steady state after 50 cycles. Linear sweep voltammetry (LSV) tests were performed on the catalysts prepared in Example 2 and Comparative Examples 1-6. After CV activation, the program was switched to LSV, and the test range was 0- -0.8 V vs. RHE at a scan rate of 5 mV / s.

[0074] Figure 8 The Faraday efficiency (FE) plot of S1-CoPTA prepared in Example 2 for application in the field of electrocatalytic hydrogen evolution (HER) shows that almost all of the electrons generated by the external circuit in the actual application of the material to catalyze hydrogen evolution are used to produce the target product, hydrogen (H2), Figure 9 The LSV plot of S1-CoPTA after 1000 cycles of CV in the field of electrocatalytic hydrogen evolution (HER) shows that the material has good catalytic activity and stability, Figure 10 The schematic diagram of the microstructure of S1-CoPTA prepared in Example 2 is "CoNi-S1".

[0075] The catalyst prepared in Example 2 exhibited high hydrogen evolution performance in an electrolyte of 1.0 M KOH solution. The synthesized material has a ternary hydrogen evolution microstructure "CoNi-S1", which has the central structure and functional simulation of [Fe-Fe] hydrogenase, i.e., the degree of hydrogen atom hybridization is improved by non-metallic doping, and the nickel and cobalt coordinated with sulfur in the material capture and activate water molecules, and the water molecules are dissociated into H atoms and OH - , and the generated hydrogen atoms are adsorbed on the S site through S-H ＊ bonds and further generate H2, thereby significantly improving the catalytic activity and stability of the material.

[0076] Obviously, the above examples and comparative examples are merely examples for the sake of clarity, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the scope of the present application.

Claims

1. A method for preparing a non-metal modified hydrogen evolution material, characterized in that: Specifically include the following steps: (1) Cutting the untreated nickel foam into rectangular sheets, ultrasonically washing them with acetone, ethanol, and deionized water in sequence, and then drying them in a vacuum blower drying oven to complete the pretreatment of the nickel foam material; (2) 148.62 mg of cobalt nitrate hexahydrate, 123.93 mg of 4,4-diphenyldicarboxylic acid, and 9.0 mg of 1,4-benzenedimethylenethiol were dissolved in a mixed solvent of 16 mL of N,N-dimethylformamide, 1 mL of ethanol, and 1 mL of deionized water. The mixture was stirred with a magnetic stirrer to ensure full dissolution. The resulting rose-red clear solution was used as a precursor solution, wherein the molar ratio of cobalt nitrate hexahydrate to 4,4-diphenyldicarboxylic acid was 1:1; the mass concentration of 1,4-benzenedimethylenethiol was 0.05-0.50 g / L; (3) Quickly add 0.8 ml of triethylamine to the precursor solution prepared in step (2), stir with a magnetic stirrer for 12-48 hours to ensure full dissolution, and then centrifuge the precursor solution in a low-temperature centrifuge to obtain a rose-red precipitate. The precipitate is allowed to cool to room temperature. The temperature of the low-temperature centrifuge is 0-10°C, and the centrifugation time is 3 hours. (4) After the precipitate was cooled to room temperature in step (3), it was repeatedly rinsed with N,N-dimethylformamide, ethanol, and aqueous solution, and then dried in a vacuum blower drying oven to obtain a sulfur-doped MOF derivative material, named S-CoPTA; (5) 5 mg of S-CoPTA and 2.5 mg of carbon black synthesized in step (4) were added to 25 μL of 0.5% mass concentration Nafion solution and ultrasonically washed to ensure sufficient mixing. The solution was then applied to the nickel foam pretreated in step (1) to form a sulfur-doped MOF-derived electrode material loaded on nickel foam, which was named S1-CoPTA.

2. The method for preparing the non-metal modified hydrogen evolution material according to claim 1, wherein: In step (1), the nickel foam is cut into 1×4 cm 2 The ultrasonic washing time is 20 minutes.

3. The method for preparing the non-metal modified hydrogen evolution material according to claim 1, wherein: The drying temperature in step (1) is 60°C.

4. The method for preparing the non-metal modified hydrogen evolution material according to claim 1, wherein: The purity of all chemical reagents in step (1) and step (2) is AR analytical grade.

5. The method for preparing the non-metal modified hydrogen evolution material according to claim 1, wherein: In the step (2), the transition metal cobalt provided by the cobalt nitrate hexahydrate exists in the form of an element, and the non-metallic sulfur provided by 1,4-benzenedimethanethiol exists in the form of a PTA group.

6. The method for preparing the non-metal modified hydrogen evolution material according to claim 1, wherein: In step (3), the temperature of the low-temperature centrifuge is T=4°C.

7. The method for preparing a non-metal modified hydrogen evolution material according to claim 1, wherein: The drying temperature in step (4) is 60°C.

8. An application of a non-metal modified hydrogen evolution material prepared by the method according to any one of claims 1 to 7 in the field of hydrogen evolution, characterized in that: A non-metal modified hydrogen evolution material is used as a working electrode in a three-electrode system to catalyze the hydrogen evolution reaction by electrolysis of water.

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