Preparation of a nickel complex containing an S2N2-type ligand and its application in catalytic hydrogen production

Abstract

This invention belongs to the fields of chemical synthesis technology and hydrogen energy science and technology, specifically the preparation of a nickel complex containing an S2N2-type ligand and its application in catalytic hydrogen production. The nickel complex is di(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane nickel ([{edt(CH2Py')2}Ni(NCS)2]), and its chemical structure is as follows: The nickel complex of this invention has the advantages of simple preparation method, mild reaction conditions, short preparation cycle, and high yield. It is also applicable to the preparation of nickel complexes with other nitrogen heterocycles modified with ethylenedithiol S2N2-type ligands. The nickel complex of this invention exhibits highly efficient electrocatalytic and photocatalytic hydrogen production activities, and has potential application value in the field of hydrogen energy.

Description

Technical Field

[0001] This invention belongs to the fields of chemical synthesis technology and hydrogen energy science and technology, specifically the preparation of a nickel complex containing an S2N2 type ligand and its application in catalytic hydrogen production. Technical Background

[0002] With the ever-increasing energy demand of human society, traditional energy resources are becoming increasingly depleted, and environmental problems are becoming more and more serious. To address this challenge, researchers worldwide are actively exploring and developing various renewable energy sources. Hydrogen energy, as a highly efficient, clean, and renewable energy form, is considered an important direction for future energy development. The efficiency of hydrogen energy lies in its extremely high energy density, three times that of oil and 2.5 times that of natural gas. Furthermore, the heat generated by burning hydrogen is two to three times that of the same mass of fossil fuels. Unlike traditional fossil fuels, hydrogen combustion only produces water vapor and does not release any greenhouse gases or harmful substances, achieving zero emissions.

[0003] Based on highly efficient catalytic proton reduction hydrogen production using metal-based hydrogenases, a large number of nickel complexes containing bidentate or tetradentate ligands have been synthesized, continuously exploring the ability to produce hydrogen through proton reduction using non-noble metal complex catalysts. Hydrogen is a clean energy source and one of the most ideal alternatives to fossil fuels in the future, representing a crucial measure to reduce humanity's over-reliance on fossil fuels. Electrolysis or photocatalysis of water are ideal pathways for hydrogen production. In particular, photocatalyst-driven hydrogen production is one of the most attractive schemes for utilizing solar energy and sustainable energy production. To reduce energy consumption and improve hydrogen production efficiency, electrocatalysts and photocatalysts need to be introduced. Clearly, hydrogenases containing nickel or iron complexes can effectively catalyze hydrogen production. Inspired by this biomimicry, many researchers have focused on designing and synthesizing novel non-noble metal (such as nickel, cobalt, and iron) transition metal complexes as electrocatalysts and photocatalysts for hydrogen production. Compared with metal-based hydrogenases, these transition metal complexes have technical advantages such as milder synthesis conditions, lower preparation costs, and stronger stability under electrocatalytic and photocatalytic conditions. However, the catalytic hydrogen production activities of transition metal complexes vary considerably, which mainly depends on the properties of the metal center and ligands, as well as the molecular structure of the complex.

[0004] Therefore, developing transition metal complexes with catalytic hydrogen production properties, simple preparation methods, and mild reaction conditions is of great practical significance for alleviating the increasingly serious energy crisis and controlling environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a nickel complex containing an S2N2-type ligand, which is di(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane nickel ([{edt(CH2Py')2}Ni(NCS)2]). Using [{edt(CH2Py')2}Ni(NCS)2] as an electrocatalyst and photocatalyst for hydrogen production has significant application value in the field of hydrogen energy science and technology.

[0006] Another objective of this invention is to provide a method for preparing the nickel complexes described above, which features a simple synthetic route, mild reaction conditions, easy operation, short preparation cycle, and high yield; it can also be used to prepare derivatives of this type of complex.

[0007] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows:

[0008] A nickel complex containing an S2N2-type ligand, named di(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane nickel, has the molecular formula [{edt(CH2Py')2}Ni(NCS)2], and its molecular structure is shown below:

[0009]

[0010] Furthermore, the preparation route of the aforementioned nickel complex is as follows:

[0011]

[0012] Furthermore, the preparation method of the nickel complex described above includes the following steps:

[0013] 1) Add CH3ONa to a methanol solution of ethylene dithiol, stir and react at room temperature for a period of time to obtain a transparent, colorless solution:

[0014] 2) Add a methanol solution of 2-chloromethyl-3,4-dimethoxypyridine hydrochloride to the transparent and colorless solution obtained in step 1), and continue to stir the reaction at room temperature for a period of time.

[0015] 3) Remove the solvent from the reaction product after step 2) using a rotary evaporator under reduced pressure. Dissolve the residue in methanol, filter, collect the filtrate, remove the solvent again, dissolve and filter in dichloromethane, and collect the filtrate.

[0016] 4) Concentrate the filtrate, use a mixed solvent as the developing solvent, perform thin-layer chromatography separation, collect the product band, and elute to obtain a white solid edt(CH2Py')2;

[0017] 5) Mix {edt(CH2Py')2}, NiCl2·6H2O and NaSCN with an organic solvent, stir and react at room temperature for a period of time, filter and wash to obtain a light blue nickel complex solid.

[0018] In a preferred embodiment of the method for preparing the nickel complex of the present invention, in step 1), the ratio of CH3ONa to ethylenedithiol is 4-4.2:2; and the stirring reaction time at room temperature is 20-30 min.

[0019] In a preferred embodiment of the method for preparing the nickel complex of the present invention, in step 2), the molar ratio of ethylenedithiol to 2-chloromethyl-3,4-dimethoxypyridine hydrochloride is 1:2-2.4; and the reaction time is 3-6 h at room temperature.

[0020] In a preferred embodiment of the method for preparing the nickel complex of the present invention, the developing solvent in step 4) is a mixture of petroleum ether and ethyl acetate, with a volume ratio of 1:2-3; the silica gel plate required for thin-layer chromatography separation has dimensions of 26×20×0.25cm. 3 .

[0021] In a preferred embodiment of the method for preparing the nickel complex of the present invention, the ratio of edt(CH2Py')2, NiCl2·6H2O, NaSCN and organic solvent in step 5) is 1 mmol:1 mmol:2 mmol:40-60 mL.

[0022] In a preferred embodiment of the method for preparing the nickel complex of the present invention, the organic solvent in step 5) is acetonitrile, methanol or ethanol; the reaction time at room temperature is 2-4 hours.

[0023] In a preferred embodiment of the preparation method of the nickel complex described in this invention, the 1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane ligand in the nickel complex obtained by any of the above methods or combinations of methods is coordinated with the nickel atom in an S2N2 chelate manner, and the nickel complex has a six-coordinated distorted octahedral configuration.

[0024] The third objective of this invention is to protect the application of the nickel complexes described above in electrocatalytic hydrogen production.

[0025] Furthermore, nickel complexes can be used as electrocatalysts for hydrogen production. The acidic media for electrocatalytic hydrogen production are acetic acid, trifluoroacetic acid, or p-toluenesulfonic acid.

[0026] The fourth objective of this invention is to protect the application of the nickel complexes described above in photocatalytic hydrogen production.

[0027] Furthermore, nickel complexes can be used as photocatalysts for hydrogen production. The photocatalytic system consists of an aqueous solution of [{edt(CH2Py')2}Ni(NCS)2], CdS NRs, and a sacrificial agent, which can be ascorbic acid, triethanolamine, or lactic acid.

[0028] The advantages of the nickel complex described in this invention compared to the prior art are as follows:

[0029] (i) The nickel complex of the present invention is a new complex. The edt(CH2Py')2 ligand contained in its molecular structure is an S2N2 type ligand that is easy to prepare, compared with existing tetradentate ligands. Its structure is significantly different from the related nickel complexes that have been disclosed in terms of composition and structure.

[0030] (II) The preparation method of the nickel complex of the present invention is simple, the reaction conditions are mild, and the yield is high. In particular, the preparation process of the nickel complex adopts a three-component raw material "one-pot cooking" process, which effectively simplifies the preparation process and reaction flow, thereby reducing the preparation cost. This preparation method is also suitable for the preparation of nickel complexes of other nitrogen heterocycles modified with dithiol-type S2N2 ligands.

[0031] (III) The nickel complex of the present invention has highly efficient electrocatalytic hydrogen production activity and can produce hydrogen by electrocatalytic reduction of protons in the presence of acetic acid, trifluoroacetic acid or p-toluenesulfonic acid.

[0032] (iv) The nickel complex of the present invention has highly efficient photocatalytic hydrogen production activity and exhibits photocatalytic hydrogen production performance in an aqueous system of nickel complex, CdS NRs and sacrificial agent (ascorbic acid, triethanolamine or lactic acid).

[0033] (v) The nickel complex of the present invention has high stability under electrocatalytic and photocatalytic conditions. Attached Figure Description

[0034] Figure 1 The 1H NMR spectrum of edt(CH2Py')2 prepared in Example 1;

[0035] Figure 2 The carbon NMR spectrum of edt(CH2Py')2 prepared in Example 1;

[0036] Figure 3 The infrared spectrum of edt(CH2Py')2 prepared in Example 1;

[0037] Figure 4 The crystal structure diagram of [{edt(CH2Py')2}Ni(NCS)2] prepared in Example 1 is shown.

[0038] Figure 5 The infrared spectrum of [{edt(CH2Py')2}Ni(NCS)2] prepared in Example 1;

[0039] Figure 6 The electrochemical cyclic voltammogram of [{edt(CH2Py')2}Ni(NCS)2] prepared in Example 2 in acetic acid;

[0040] Figure 7 i is the [{edt(CH2Py')2}Ni(NCS)2] in Example 2 cat / i pc Graph showing the relationship between acetic acid concentration and the square root of acetic acid concentration;

[0041] Figure 8 The electrochemical cyclic voltammetry diagram of [{edt(CH2Py')2}Ni(NCS)2] prepared in Example 3 in trifluoroacetic acid;

[0042] Figure 9 i is the [{edt(CH2Py')2}Ni(NCS)2] in Example 3. cat / i pc Graph showing the relationship between trifluoroacetic acid concentration and the square root of trifluoroacetic acid concentration;

[0043] Figure 10 The electrochemical cyclic voltammetry of [{edt(CH2Py')2}Ni(NCS)2] prepared in Example 4 in p-toluenesulfonic acid;

[0044] Figure 11 i is the [{edt(CH2Py')2}Ni(NCS)2] in Example 4. cat / i pc Graph showing the relationship between the concentration of p-toluenesulfonic acid and the square root of the concentration.

[0045] Figure 12 The coulomb accumulation plot is shown for the electrolysis of [{edt(CH2Py')2}Ni(NCS)2] in Example 5 in a tetrabutylammonium hexafluorophosphate acetonitrile solution containing trifluoroacetic acid for 4 hours under constant potential conditions.

[0046] Figure 13 The image shows the gas chromatogram of [{edt(CH2Py')2}Ni(NCS)2] in the electrolytic cell in Example 5.

[0047] Figure 14 This is a graph showing the cumulative hydrogen production of [{edt(CH2Py')2}Ni(NCS)2] in an aqueous solution of CdS NRs and ascorbic acid in Example 6.

[0048] Figure 15This is a graph showing the cumulative hydrogen production of [{edt(CH2Py')2}Ni(NCS)2] in an aqueous solution of CdS NRs and triethanolamine in Example 7.

[0049] Figure 16 The graph shows the cumulative hydrogen production of [{edt(CH2Py')2}Ni(NCS)2] in an aqueous solution of CdS NRs and lactic acid in Example 8. Detailed Implementation

[0050] To make the technical solution, objectives, and advantages of the present invention clearer, a detailed description will be provided below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and do not limit the scope of the invention. Furthermore, after understanding the content of the present invention, those skilled in the art can make various modifications or alterations, and these equivalent forms also fall within the scope defined by the appended claims.

[0051] The electrocatalytic hydrogen production performance tests of the nickel complexes in this application were all conducted on a CHI660E electrochemical workstation. A three-electrode system was used, comprising a platinum wire electrode as the counter electrode, a non-mercury ion electrode as the reference electrode, and a 3mm glassy carbon electrode as the working electrode. Before each test, each electrode underwent pretreatment: the glassy carbon electrode was polished on a polishing cloth with 0.3μm aluminum oxide powder, then cleaned with deionized water, ultrasonically cleaned, and rinsed with acetone, finally dried with cold air; the platinum wire electrode and the non-mercury ion electrode were similarly ultrasonically cleaned in acetone solution and dried. The solvent used in the test was spectrally pure acetonitrile, the supporting electrolyte was recrystallized and purified tetrabutylammonium hexafluorophosphate, and the electrolyte solution was a 0.1 mol / L tetrabutylammonium hexafluorophosphate acetonitrile solution containing 0.25 mmol / L nickel complex. The internal reference solution used for the reference electrode was a 0.1 mol / L tetrabutylammonium hexafluorophosphate acetonitrile solution containing 0.01 mol / L silver nitrate. The protic acid concentrations were 0, 10, 20, 30, 40, and 50 mmol / L, and the scan rate was 100 mV / s. Electrochemical tests were performed in a column electrolytic cell under a nitrogen atmosphere. Ferrocene was added as an internal standard before the end of the test, and all obtained potentials were corrected for ferrocene. Among them, i pc i represents the catalyst reduction current without the addition of a protic acid. cat This represents the catalytic current at a specific acid concentration.

[0052] The nickel complex exhibited the following performance in electrocatalytic hydrogen production tests: when electrochemical tests were performed on a system containing 0.25 mmol / L of the nickel complex, the current value of the catalytic reduction peak continuously increased with increasing protonic acid concentration. Simultaneously, the i... cat / i pc The value is linearly related to the increase of the square root of the protonic acid concentration.

[0053] Example 1:

[0054] A method for preparing a nickel-bis(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane complex with the chemical formula [{edt(CH2Py')2}Ni(NCS)2] is disclosed below, and the preparation reaction is as follows:

[0055]

[0056] The specific preparation steps are as follows:

[0057] 0.1884 g of ethylenedithiol (2 mmol), 30 mL of methanol, and 5 mL of methanol solution containing 0.216 g of CH3ONa (4 mmol) were added to a three-necked flask equipped with a magnetic stirrer. The mixture was stirred at room temperature for 28 min, and the reaction solution became colorless and transparent. Then, 20 mL of methanol solution containing 0.896 g of 2-chloromethyl-3,4-dimethoxypyridine hydrochloride (4 mmol) was added to the aforementioned reaction system, and the mixture was stirred at room temperature for 5.5 h, yielding a pale yellow solution. The solvent was removed by rotary evaporation under reduced pressure. The residue was dissolved in 60 mL of methanol and filtered. The filtrate was then subjected to rotary evaporation again to remove the solvent. The residue was dissolved in a suitable amount of dichloromethane and filtered. The filtrate was collected and appropriately concentrated. Preparative thin-layer chromatography was then performed using a mixture of petroleum ether and ethyl acetate (volume ratio 1:2.5) as the developing solvent. The product band was collected, and after elution, 0.634 g of the white product edt(CH2Py')2 was obtained, with a yield of 80%.

[0058] FTIR (KBr tablets, cm) -1 ):2946(s,v C＝C and v C＝N ),2069(vs,v C＝S ),1066(vs,v C＝S ),995(s,sh,v C-S ),836(m,v C-S ). 1 H NMR (600MHz, DMSO-d6, ppm): δ8.10 (m, 2H), 7.02 (d, J = 5.6Hz, 2H), 3.88 (m, 6H), 3.76 (d, J = 16.10Hz, 2H), 2.74 (d, J = 25.7Hz, 4H). 13C NMR(151MHz,DMSO-d6,ppm): δ158.12(3-Py'),152.40(1-Py'),145.20(2-Py'),142 .58(5-Py'),107.70(4-Py'),60.51(CH3),55.85(CH3),31.52,(CH2),31.22(CH2).

[0059] The proton NMR spectrum, carbon NMR spectrum, and infrared spectrum of edt(CH2Py')2 are shown in the appendix. Figure 1 Appendix Figure 2 and Figure 3 .

[0060] Preparation of nickel complex (1#): 30 mL of acetonitrile solution containing 0.396 g edt(CH2Py')2 (1 mmol) was added to a round-bottom flask equipped with a magnetic stirrer. While stirring, 15 mL of acetonitrile solution containing 0.237 g NiCl2·6H2O (1 mmol) was added, followed by 10 mL of acetonitrile solution containing 0.162 g NaSCN (2 mmol). The reaction was carried out at room temperature for 2 h, and a pale blue precipitate was formed. After filtration and washing, 0.427 g of pale blue solid [{edt(CH2Py')2}Ni(NCS)2] was obtained, with a yield of 78%.

[0061] Preparation of nickel complex (2#): 50 mL of ethanol solution containing 0.594 g edt(CH2Py')2 (1.5 mmol) was added to a round-bottom flask equipped with a magnetic stirrer. While stirring, 30 mL of ethanol solution containing 0.356 g NiCl2·6H2O (1.5 mmol) was added, followed by 15 mL of ethanol solution containing 0.243 g NaSCN (3 mmol). The reaction was carried out at room temperature for 3 h, and a green precipitate was formed. After filtration and washing, 0.556 g of pale blue solid [{edt(CH2Py')2}Ni(NCS)2] was obtained, with a yield of 69%.

[0062] Preparation of nickel complex (3#): 55 mL of methanol solution containing 0.792 g edt(CH2Py')2 (2 mmol) was added to a round-bottom flask equipped with a magnetic stirrer. While stirring, 30 mL of methanol solution containing 0.474 g NiCl2·6H2O (2 mmol) was added, followed by 20 mL of methanol solution containing 0.324 g NaSCN (4 mmol). The mixture was stirred at room temperature for 3.5 h, resulting in the precipitation of a green precipitate. After filtration and washing, 0.912 g of green solid [{edt(CH2Py')2}Ni(NCS)2] was obtained, with a yield of 87%.

[0063] Anal.Calcd.(%) for C20 H 24 N4NiO4S4: C, 42.04; H, 4.23; N, 9.81; S, 22.44. Found (%): C, 42.02; H, 4.25; N, 9.88; S, 22.41. FTIR (KBr tablets, cm -1 ):2078(s,v C＝S ),1596(s,v C-C ),1419(vs,v C＝C ),1067(vs,v C＝S ),993(s,sh,v C-S ),821(m,v C-S ).

[0064] The crystal structure diagram and infrared spectrum of [{edt(CH2Py')2}Ni(NCS)2] are attached. Figure 4 and Figure 5 Furthermore, the above operating methods and data demonstrate that the operating methods of this invention can synthesize nickel complexes in high yield.

[0065] Example 2:

[0066] This embodiment provides the application of the nickel complex prepared in Example 1 in the electrocatalytic reduction of protons to produce hydrogen in acetic acid medium.

[0067] This experiment was conducted on a CHI660E electrochemical workstation using a three-electrode system: a platinum wire electrode as the counter electrode, a non-mercury ion electrode as the reference electrode, and a 3mm glassy carbon electrode as the working electrode, in a cylindrical electrolytic cell under a nitrogen atmosphere. Before electrochemical testing, each electrode underwent pretreatment. The glassy carbon electrode was polished with 0.3μm alumina powder, washed with deionized water, then ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode underwent the same treatment as the non-mercury ion electrode, being ultrasonically cleaned in acetone solution and dried with cold air. The solvent in the test system was spectrally pure acetonitrile, and the supporting electrolyte was tetrabutylammonium hexafluorophosphate. The electrochemical test solution was an acetonitrile solution containing 0.25 mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1 mol / L tetrabutylammonium hexafluorophosphate. Acetic acid concentrations were 0, 10, 20, 30, 40, and 50 mmol / L, and the scan rate was 100 mV / s. The potentials of the obtained nickel complexes were all ferrocene-corrected potentials. Among them, i pc i represents the magnitude of the catalyst reduction current without the addition of acetic acid. cat This represents the magnitude of the catalytic current at a given acetic acid concentration.

[0068] Appendix Figure 6The electrochemical cyclic voltammograms of [{edt(CH2Py')2}Ni(NCS)2] at different acetic acid concentrations show that [{edt(CH2Py')2}Ni(NCS)2] exhibits electrocatalytic proton reduction hydrogen production performance in the presence of acetic acid.

[0069] Appendix Figure 7 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The graph showing the relationship between i and the square root of acetic acid concentration indicates that when acetic acid is the protic acid, i cat / i pc The activity of [{edt(CH2Py')2}Ni(NCS)2] in electrocatalytic proton reduction to hydrogen production is linearly related to the square root of the acetic acid concentration. The higher the acetic acid concentration, the greater the activity of [{edt(CH2Py')2}Ni(NCS)2].

[0070] Example 3:

[0071] This embodiment provides the application of the nickel complex prepared in Example 1 in the electrocatalytic reduction of protons to produce hydrogen in trifluoroacetic acid medium.

[0072] This experiment was conducted on a CHI660E electrochemical workstation using a three-electrode system: a platinum wire electrode as the counter electrode, a non-mercury ion electrode as the reference electrode, and a 3mm glassy carbon electrode as the working electrode, in a cylindrical electrolytic cell under a nitrogen atmosphere. Before electrochemical testing, each electrode underwent pretreatment. The glassy carbon electrode was polished with 0.3μm alumina powder, washed with deionized water, then ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode underwent the same treatment as the non-mercury ion electrode, being ultrasonically cleaned in acetone solution and dried with cold air. The solvent in the test system was spectrally pure acetonitrile, and the supporting electrolyte was tetrabutylammonium hexafluorophosphate. The electrochemical test solution was an acetonitrile solution containing 0.25 mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1 mol / L tetrabutylammonium hexafluorophosphate. Trifluoroacetic acid concentrations were 0, 10, 20, 30, 40, and 50 mmol / L, and the scan rate was 100 mV / s. The potentials of the obtained nickel complexes were all ferrocene-corrected potentials. Among them, i pc i represents the magnitude of the catalyst reduction current without the addition of trifluoroacetic acid. cat This represents the magnitude of the catalytic current at a given trifluoroacetic acid concentration.

[0073] Appendix Figure 8The electrochemical cyclic voltammograms of [{edt(CH2Py')2}Ni(NCS)2] at different trifluoroacetic acid concentrations show that [{edt(CH2Py')2}Ni(NCS)2] exhibits electrocatalytic proton reduction hydrogen production performance in the presence of trifluoroacetic acid.

[0074] Appendix Figure 9 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The graph showing the relationship between i and the square root of trifluoroacetic acid concentration indicates that when the protic acid is trifluoroacetic acid, i cat / i pc The activity of [{edt(CH2Py')2}Ni(NCS)2] in electrocatalytic proton reduction to hydrogen production is linearly related to the square root of the acid concentration. The higher the concentration of trifluoroacetic acid, the greater the activity of [{edt(CH2Py')2}Ni(NCS)2].

[0075] Example 4:

[0076] This embodiment provides the application of the complex prepared in Example 1 in the electrocatalytic reduction of protons to produce hydrogen in a p-toluenesulfonic acid medium.

[0077] This experiment was conducted on a CHI660E electrochemical workstation using a three-electrode system: a platinum wire electrode as the counter electrode, a non-mercury ion electrode as the reference electrode, and a 3mm glassy carbon electrode as the working electrode, in a cylindrical electrolytic cell under a nitrogen atmosphere. Before electrochemical testing, each electrode underwent pretreatment. The glassy carbon electrode was polished with 0.3μm alumina powder, washed with deionized water, then ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode underwent the same treatment as the non-mercury ion electrode, being ultrasonically cleaned in acetone solution and dried with cold air. The solvent in the test system was spectrally pure acetonitrile, and the supporting electrolyte was tetrabutylammonium hexafluorophosphate. The electrochemical test solution was an acetonitrile solution containing 0.25 mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1 mol / L tetrabutylammonium hexafluorophosphate. The concentrations of p-toluenesulfonic acid were 0, 10, 20, 30, 40, and 50 mmol / L, and the scan rate was 100 mV / s. The potentials of the nickel complexes obtained were all ferrocene-corrected potentials. Among them, i pc i represents the magnitude of the catalyst reduction current without the addition of p-toluenesulfonic acid. cat The value represents the magnitude of the catalytic current at a given concentration of p-toluenesulfonic acid.

[0078] Appendix Figure 10The electrochemical cyclic voltammograms of [{edt(CH2Py')2}Ni(NCS)2] at different p-toluenesulfonic acid concentrations show that [{edt(CH2Py')2}Ni(NCS)2] exhibits electrocatalytic proton reduction hydrogen production properties in the presence of p-toluenesulfonic acid.

[0079] Appendix Figure 11 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The graph showing the relationship between i and the square root of p-toluenesulfonic acid concentration indicates that when the protic acid is p-toluenesulfonic acid, i cat / i pc The activity of [{edt(CH2Py')2}Ni(NCS)2] in electrocatalytic proton reduction to hydrogen production is linearly related to the square root of the p-toluenesulfonic acid concentration. The higher the p-toluenesulfonic acid concentration, the greater the activity of [{edt(CH2Py')2}Ni(NCS)2].

[0080] Example 5:

[0081] This embodiment provides the application of the complex prepared in Example 1 in controlled-potential electrolysis for hydrogen production in a trifluoroacetic acid medium.

[0082] This experiment was conducted on a CHI660E electrochemical workstation using a three-electrode system: a platinum wire electrode as the counter electrode, a non-mercury ion electrode as the reference electrode, and a 3mm glassy carbon electrode as the working electrode, in a 100mL column electrolytic cell under a nitrogen atmosphere. Before electrochemical testing, each electrode underwent pretreatment. The glassy carbon electrode was polished with 0.3μm alumina powder, washed with deionized water, then ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode underwent the same treatment as the non-mercury ion electrode, being ultrasonically cleaned in acetone solution and dried with cold air. The solvent for the test system was spectrally pure acetonitrile, and the supporting electrolyte was tetrabutylammonium hexafluorophosphate. The solution system used for electrochemical testing was an acetonitrile solution containing 0.25 mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1 mol / L tetrabutylammonium hexafluorophosphate. 53.8 mmol / L trifluoroacetic acid and 50 mL of 0.1 mol / L tetrabutylammonium hexafluorophosphate acetonitrile electrolyte were added to a 100 mL electrolytic cell, and electrolysis was carried out at a constant potential of -1.51 V for 4 h.

[0083] Figure 12The image shows the coulombic accumulation of [{edt(CH2Py')2}Ni(NCS)2] from Example 5 after electrolysis in an acetonitrile solution containing tetrabutylammonium hexafluorophosphate with trifluoroacetic acid for 4 hours under constant potential. The red line represents the coulombic accumulation without the complex, and the black line represents the coulombic accumulation after the complex is added. The results indicate that [{edt(CH2Py')2}Ni(NCS)2] possesses electrocatalytic hydrogen production performance.

[0084] Figure 13 The image shows the gas chromatogram of [{edt(CH2Py')2}Ni(NCS)2] in the electrolytic cell in Example 5, which indicates that hydrogen gas is generated during the 4-hour electrolysis process.

[0085] Example 6:

[0086] This embodiment provides the application of the complex prepared in Example 1 in the photocatalytic hydrogen production of CdS NRs and ascorbic acid in an aqueous solution.

[0087] The photocatalytic hydrogen production test employed the CEL-PAEM-D8Pro water splitting system. Prior to the test, the photocatalytic reactor and the entire pipeline were evacuated using a vacuum pump to ensure a clean reactor environment. During the test, condensate was used to maintain a constant reaction temperature. In the experiment, 120 mg / L CdS NRs, 0.12 mol / L ascorbic acid, and 0.1 mmol / L [{edt(CH2Py')2}Ni(NCS)2] were uniformly dispersed in 100 mL of water. A 300W Xe lamp with a 420 nm wavelength filter was used as the visible light source for catalytic hydrogen production. High-purity Ar2 was used as the carrier gas. The generated hydrogen was automatically extracted every 60 minutes for analysis, and detected using a GC-7980 gas chromatograph.

[0088] Figure 14 The graph shows the cumulative hydrogen production from the photocatalytic water production of [{edt(CH2Py')2}Ni(NCS)2] in Example 6, indicating that hydrogen is produced during the 5-hour photocatalytic process.

[0089] Example 7:

[0090] This embodiment provides the application of the complex prepared in Example 1 in the photocatalytic hydrogen production of CdS NRs and triethanolamine in an aqueous solution.

[0091] The photocatalytic hydrogen production test employed the CEL-PAEM-D8Pro water splitting system. Prior to the test, the photocatalytic reactor and the entire pipeline were evacuated using a vacuum pump to ensure a clean reactor environment. During the test, condensate was used to maintain a constant reaction temperature. A 300W Xe lamp with a 420nm wavelength filter was used as the visible light source. High-purity Ar2 was used as the carrier gas during the experiment. The generated hydrogen was automatically extracted every 60 minutes for analysis, and detected using a GC-7980 gas chromatograph.

[0092] Appendix Figure 15 The graph shows the cumulative amount of hydrogen produced by photocatalytic hydrogen production in Example 7, where 120 mg / L CdS NRs, 0.12 mol / L triethanolamine, and 0.1 mmol / L [{edt(CH2Py')2}Ni(NCS)2] were uniformly dispersed in 100 mL of water. The results indicate that hydrogen was produced during the 5-hour photocatalytic process.

[0093] Example 8:

[0094] This embodiment provides the application of the complex prepared in Example 1 in the photocatalytic hydrogen production of CdS NRs and lactic acid in an aqueous solution.

[0095] The photocatalytic hydrogen production test employed the CEL-PAEM-D8Pro water splitting system. Prior to the test, the photocatalytic reactor and the entire pipeline were evacuated using a vacuum pump to ensure a clean reactor environment. During the test, condensate was used to maintain a constant reaction temperature. A 300W Xe lamp with a 420nm wavelength filter was used as the visible light source. High-purity Ar2 was used as the carrier gas during the experiment. The generated hydrogen was automatically extracted every 60 minutes for analysis, and detected using a GC-7980 gas chromatograph.

[0096] Appendix Figure 16 The graph shows the cumulative amount of hydrogen produced by photocatalytic hydrogen production in Example 6, where 120 mg / L CdS NRs, 0.12 mol / L lactic acid, and 0.1 mmol / L [{edt(CH2Py')2}Ni(NCS)2] were uniformly dispersed in 100 mL of water. The results indicate that hydrogen was produced during the 5-hour photocatalytic process.

[0097] The examples described above are merely preferred embodiments of this patent, but the scope of protection of this patent is not limited thereto. For those skilled in the art, without departing from the principles of this patent, various improvements and modifications can be made to the technical solution and patent concept of this patent, and these improvements and modifications should also be considered within the scope of protection of this patent.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a nickel complex containing an S2N2-type ligand in electrocatalytic hydrogen production, characterized in that: The molecular formula of the nickel complex is [{edt(CH2Py')2}Ni(NCS)2], and its chemical structure is as follows: The acidic medium for electrocatalytic hydrogen production is acetic acid, trifluoroacetic acid, or p-toluenesulfonic acid.

2. The application of a nickel complex containing an S2N2-type ligand as described in claim 1 in electrocatalytic hydrogen production, characterized in that... The preparation route for the nickel complex is as follows: 。 3. The application of a nickel complex containing an S2N2-type ligand as described in claim 2 in electrocatalytic hydrogen production, characterized in that... The preparation method of the nickel complex includes the following steps: 1) CH3ONa was added to a methanol solution of ethylenedithiol, and the mixture was stirred at room temperature for a period of time to obtain a colorless and transparent solution; 2) Add a methanol solution containing 2-chloromethyl-3,4-dimethoxypyridine hydrochloride to the colorless and transparent solution obtained in step 1), and continue to stir the reaction at room temperature for a period of time. 3) Remove the solvent from the reaction product after step 2) using a rotary evaporator under reduced pressure. Dissolve the residue in methanol, filter, collect the filtrate, remove the solvent again using a rotary evaporator under reduced pressure, dissolve and filter in dichloromethane, and collect the filtrate. 4) Concentrate the filtrate, use a mixed solvent as the developing solvent, perform thin-layer chromatography separation, collect the corresponding product bands, and elute to obtain a white solid edt(CH2Py')2; 5) Mix edt(CH2Py')2, NiCl2·6H2O and NaSCN with an organic solvent, stir and react at room temperature for a period of time, filter and wash to obtain a light blue nickel complex [{edt(CH2Py')2}Ni(NCS)2] solid.

4. The application of a nickel complex containing an S2N2-type ligand as described in claim 3 in electrocatalytic hydrogen production, characterized in that: In step 1), the molar ratio of CH3ONa to ethylenedithiol is 4-4.3:2; the stirring reaction time at room temperature is 20-30 min.

5. The application of a nickel complex containing an S2N2-type ligand as described in claim 3 in electrocatalytic hydrogen production, characterized in that: The molar ratio of ethylenedithiol to 2-chloromethyl-3,4-dimethoxypyridine hydrochloride was 1:2-2.4; the reaction was carried out at room temperature for 3-6 h with stirring.

6. The application of a nickel complex containing an S2N2-type ligand as described in claim 3 in electrocatalytic hydrogen production, characterized in that: The developing solvent mentioned in step 4) is a mixture of petroleum ether and ethyl acetate, with a volume ratio of 1:2-3; the silica gel plate required for thin-layer chromatography separation has dimensions of 26 × 20 × 0.25 cm. 3 .

7. The application of a nickel complex containing an S2N2-type ligand as described in claim 3 in electrocatalytic hydrogen production, characterized in that: In step 5), the ratio of edt(CH2Py')2, NiCl2·6H2O, NaSCN and organic solvent is 1 mmol : 1 mmol : 2 mmol : 40-60 mL.

8. The application of a nickel complex containing an S2N2-type ligand as described in claim 3 in electrocatalytic hydrogen production, characterized in that: In step 5), the organic solvent is acetonitrile, methanol, or ethanol; the reaction time at room temperature is 2-4 h.

Images