Preparation of nickel complex containing S2N2 type ligand and application of nickel complex in catalytic hydrogen production

Abstract

The invention belongs to the technical field of chemical synthesis technology and hydrogen energy science, and particularly relates to preparation of a nickel complex containing an S2N2 type ligand and application of the nickel complex in catalytic hydrogen production. The nickel complex is bis (isothiocyanate). 1, 2-bis (2-(3, 4-difluorophenyl)-1, 2, 3, 3, 3, 3, 3, 3, 3, the nickel complex has the chemical structure of [{edt (CH2Py ') 2} Ni (NCS) 2]: # imgabs0 #, has the advantages of simple preparation method, mild reaction conditions, short preparation period, high yield and the like, and can be applied to preparation of nickel complexes of S2N2 type ligands modified by other nitrogen heterocyclic rings on dithiol. The nickel complex shows efficient electro-catalytic hydrogen production activity and photocatalytic hydrogen production activity, and has potential application value in the field of hydrogen energy.

Description

Technical Field

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

[0002] As human society's demand for energy grows, traditional energy resources are becoming increasingly depleted, and environmental problems are becoming more serious; in order to meet this challenge, researchers around the world are actively exploring and developing various renewable energy sources. Hydrogen energy, as an efficient, clean, and renewable energy form, is regarded as an important development direction for future energy. The high efficiency of hydrogen energy lies in its extremely high energy density, which is 3 times that of oil and 2.5 times that of natural gas. In addition, the heat generated by hydrogen combustion is two to three times that of fossil fuels of the same mass. 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 the metal hydrogenases that efficiently catalyze proton reduction to produce hydrogen, a large number of nickel complexes containing bidentate or tetradentate ligands have been synthesized to continuously explore the ability of catalysts with non-precious metal complexes to catalyze proton reduction to produce hydrogen. Hydrogen is a clean energy source and one of the most ideal substitutes for fossil fuels in the future. It is one of the important measures to reduce human over-dependence on fossil fuels. Electrolysis or photolysis of water is an ideal way to produce hydrogen. In particular, light-driven hydrogen production is one of the most attractive solutions for utilizing solar energy and sustainable energy production. In order to reduce energy consumption and improve hydrogen production efficiency, electrocatalysts and photocatalysts need to be introduced. Obviously, hydrogenases containing nickel or iron complexes can effectively catalyze the production of hydrogen. Inspired by this biological simulation, many researchers have focused on designing and synthesizing novel transition metal complexes of non-precious metals (such as nickel, cobalt, iron, etc.) as electrocatalysts and photocatalysts for hydrogen production. Compared with metal hydrogenases, these transition metal complexes have technical advantages such as mild synthesis conditions, low preparation cost, and strong stability under electrocatalytic and photocatalytic conditions. However, the catalytic hydrogen production activity of transition metal complexes varies greatly, which mainly depends on the properties of the metal center and ligands as well as the molecular structure of the complex.

[0004] Therefore, the development of transition metal complexes with catalytic hydrogen production performance, simple preparation methods and mild reaction conditions has important practical significance for alleviating the increasingly serious energy crisis and environmental pollution control. Summary of the invention

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

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned nickel complex, which has the characteristics of simple synthesis route, mild reaction conditions, simple operation, short preparation cycle and high yield; and can also be used to prepare derivatives of this type of complex.

[0007] In order to achieve the above invention object, the specific technical solution of the present invention is:

[0008] A nickel complex containing a S2N2 type ligand, whose name is bis(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane nickel, whose molecular formula is [{edt(CH2Py')2}Ni(NCS)2], and whose molecular structure is as follows:

[0009]

[0010] Furthermore, the preparation route of the above-mentioned nickel complex is:

[0011]

[0012] Furthermore, the method for preparing the nickel complex described above comprises the following steps:

[0013] 1) Add CH3ONa to the methanol solution of ethanedithiol and stir the reaction at room temperature for a period of time to obtain a transparent colorless solution:

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

[0015] 3) using a rotary evaporator to remove the solvent in the substance after the reaction in step 2) under reduced pressure, dissolving the residue with methanol and filtering, collecting the filtrate, removing the solvent again, dissolving with dichloromethane and filtering, and collecting the filtrate;

[0016] 4) The filtrate was concentrated, and thin layer chromatography was performed using a mixed solvent as a developing solvent to collect the product band, and white solid edt(CH2Py')2 was obtained after elution;

[0017] 5) {edt(CH2Py')2}, NiCl2·6H2O and NaSCN are mixed with an organic solvent, stirred and reacted at room temperature for a period of time, and a light blue nickel complex solid is obtained after filtering and washing.

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

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

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

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

[0022] As 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 is 2-4 hours with stirring at room temperature.

[0023] As a preferred method in a specific embodiment of the preparation method of the nickel complex described in the present invention, the 1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane ligand in the nickel complex obtained by any of the above methods or a combination of methods is coordinated with the nickel atom in a S2N2 type chelating manner, and the nickel complex has a hexacoordinated distorted octahedral configuration.

[0024] The third invention objective of the present invention is to protect the application of the above-mentioned nickel complex in electrocatalytic hydrogen production.

[0025] Furthermore, the nickel complex can be used as an electrocatalyst for hydrogen production. The acidic medium for electrocatalytic hydrogen production is acetic acid, trifluoroacetic acid or p-toluenesulfonic acid.

[0026] The fourth invention objective of the present invention is to protect the application of the above-mentioned nickel complex in photocatalytic hydrogen production.

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

[0028] Compared with the prior art, the nickel complex of the present invention has the following positive effects:

[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 with respect to existing tetradentate ligands. Its structure is significantly different from the related nickel complexes disclosed so far 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, a three-component raw material "one-pot" preparation process is adopted in the preparation of the nickel complex, which effectively simplifies the preparation process and reaction flow, and achieves the purpose of reducing the preparation cost. The preparation method can be suitable for the preparation of other nickel complexes of S2N2 type ligands modified by nitrogen heterocyclic dithiols.

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

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

[0033] (V) The nickel complex of the present invention has great stability under electrocatalytic and photocatalytic conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the hydrogen nuclear magnetic resonance spectrum of edt(CH2Py')2 prepared in Example 1;

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

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

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

[0038] Figure 5 is 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 is the i of [{edt(CH2Py')2}Ni(NCS)2] in Example 2 cat / i pc Plotted against the square root of acetic acid concentration;

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

[0042] Fig. 9 is the i of [{edt(CH2Py')2}Ni(NCS)2] in Example 3 cat / i pc Plotted against the square root of trifluoroacetic acid concentration;

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

[0044] Fig.11 is the i of [{edt(CH2Py')2}Ni(NCS)2] in Example 4 cat / i pc Plotted against the square root of p-toluenesulfonic acid concentration.

[0045] Fig.12 This is the coulomb accumulation diagram of [{edt(CH2Py')2}Ni(NCS)2] in Example 5 electrolyzed in a tetrabutylammonium hexafluorophosphate acetonitrile solution containing trifluoroacetic acid under constant potential conditions for 4 h.

[0046] Fig.13 This is the gas chromatogram in the electrolytic cell of [{edt(CH2Py')2}Ni(NCS)2] in Example 5.

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

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

[0049] Fig.16 This is a graph showing the cumulative amount of hydrogen produced by photocatalysis of [{edt(CH2Py')2}Ni(NCS)2] in an aqueous solution of CdS NRs and lactic acid in Example 8. DETAILED DESCRIPTION

[0050] In order to make the technical solutions, purposes and advantages of the present invention clearer, the following will be described in detail in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and do not limit its scope. In addition, after understanding the content of the present invention, the technical staff can make various changes or modifications to it, and these equivalent forms also belong to the scope defined by the claims attached to this application.

[0051] The electrocatalytic hydrogen production performance tests of the nickel complex in this application were all carried out on a CHI660E electrochemical workstation. The test adopted a three-electrode system, which included a platinum wire electrode as a counter electrode, a non-mercury ion electrode as a reference electrode, and a 3mm glassy carbon electrode as a working electrode. Before each test, each electrode needs to be pretreated: the glassy carbon electrode is polished with 0.3μm aluminum oxide powder on a polishing cloth, then cleaned with deionized water, ultrasonically cleaned, and washed with acetone, and finally dried with cold air; the platinum wire electrode and the non-mercury ion electrode are also ultrasonically cleaned in an acetone solution and blown dry. The solvent used in the test was spectrally pure acetonitrile, the supporting electrolyte was tetrabutylammonium hexafluorophosphate purified by recrystallization, the electrolyte 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 proton acid concentrations were 0, 10, 20, 30, 40 and 50 mmol / L, and the scan rate was 100 mV / s. The electrochemical test was completed in a cylindrical electrolytic cell under a nitrogen atmosphere, and ferrocene was added as an internal standard before the end of the test. The potentials obtained were all calibrated with ferrocene. Among them, i pc is the catalyst reduction current when no protonic acid is added, i cat is the catalytic current at a specific acid concentration.

[0052] The nickel complex was tested for electrocatalytic hydrogen production performance as follows: when the system containing 0.25 mmol / L nickel complex was electrochemically tested, the current value of the catalytic reduction peak continued to rise as the proton acid concentration increased. cat / i pc The value is linearly related to the increase of the square root of the proton acid concentration.

[0053] Embodiment 1:

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

[0055]

[0056] The specific preparation steps are as follows:

[0057] 0.1884g of ethanedithiol (2mmol), 30mL of methanol and 5mL of methanol solution containing 0.216g of CH3ONa (4mmol) were added to a three-necked flask equipped with a magnetic stirrer, and the reaction was stirred at room temperature for 28min. The reaction solution was colorless and transparent. 20mL of methanol solution containing 0.896g of 2-chloromethyl-3,4-dimethoxypyridine hydrochloride (4mmol) was added to the above reaction system, and the reaction was stirred at room temperature for 5.5h to obtain a light yellow solution. The solvent was removed by reduced pressure evaporation on a rotary evaporator, and the residue was dissolved with 60mL of methanol and filtered. The filtrate was again removed by a rotary evaporator, and the residue was dissolved with an appropriate amount of dichloromethane and filtered. The filtrate was collected and appropriately concentrated. Then a mixed solvent with a volume ratio of petroleum ether and ethyl acetate of 1:2.5 was used as a developing agent for preparative thin layer chromatography separation, and the product band was collected. After elution, 0.634g of white product edt(CH2Py')2 was obtained, and the yield was 80%.

[0058] FTIR (KBr pellet, 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 H NMR spectrum, C NMR spectrum and IR spectrum of edt(CH2Py')2 are shown in the attached Figure 1 , Attachment Figure 2 and Figure 3 .

[0060] Preparation of nickel complex (1#): To a round-bottom flask equipped with a magnetic stirrer was added 30 mL of acetonitrile solution containing 0.396 g of gedt(CH2Py')2 (1 mmol). Under stirring, 15 mL of acetonitrile solution containing 0.237 g of NiCl2·6H2O (1 mmol) was added. Then, 10 mL of acetonitrile solution containing 0.162 g of NaSCN (2 mmol) was added. The mixture was reacted at room temperature for 2 h. A light blue precipitate was precipitated. After filtration and washing, 0.427 g of a light blue solid [{edt(CH2Py')2}Ni(NCS)2] was obtained. The yield was 78%.

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

[0062] Preparation of nickel complex (3#): To a round-bottom flask equipped with a magnetic stirrer was added 55 mL of a methanol solution containing 0.792 g of edt(CH2Py')2 (2 mmol). Under stirring, 30 mL of a methanol solution containing 0.474 g of NiCl2·6H2O (2 mmol) was added. Then, 20 mL of a methanol solution containing 0.324 g of NaSCN (4 mmol) was added. The mixture was stirred at room temperature for 3.5 h. A green precipitate was precipitated. After filtration and washing, 0.912 g of a green solid [{edt(CH2Py')2}Ni(NCS)2] was obtained. The yield was 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 pellet, 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 and infrared spectrum of [{edt(CH2Py')2}Ni(NCS)2] are shown in the attached Figure 4 and Figure 5 , and combined with the above operating methods and data, it is shown that the operating method of the present invention can synthesize a nickel complex with a high yield.

[0065] Embodiment 2:

[0066] This example provides the use of the nickel complex prepared in Example 1 to produce hydrogen by electrocatalytic reduction of protons in an acetic acid medium.

[0067] The experiment was carried out on a CHI660E electrochemical workstation using a platinum wire electrode as a counter electrode, a non-mercury ion electrode as a reference electrode, and a 3mm glassy carbon electrode as a working electrode in a cylindrical electrolytic cell under a nitrogen atmosphere. Each electrode needs to be pretreated before the electrochemical test. The glassy carbon electrode is polished with 0.3μm aluminum oxide powder, washed with deionized water, ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode is treated in the same way as the non-mercury ion electrode, ultrasonically cleaned in acetone solution, and dried with cold air. The solvent of the test system is spectrally pure acetonitrile, the supporting electrolyte is tetrabutylammonium hexafluorophosphate, and the solution system used for the electrochemical test is 0.25mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1mol / L tetrabutylammonium hexafluorophosphate in acetonitrile; the acetic acid concentration is 0, 10, 20, 30, 40 and 50mmol / L, the scanning rate is 100mV / s, and the potential of the nickel complex obtained by the test is the potential after ferrocene correction. Among them, i pc is the magnitude of the catalyst reduction current when no acetic acid is added, i cat is the size of the catalytic current at a certain acetic acid concentration.

[0068] Attached 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] Attached Figure 7 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The relationship between the concentration of acetic acid and the square root of the concentration of acetic acid shows that when the proton acid is acetic acid, i cat / i pc It is linearly related to the square root of the acetic acid concentration. When the acetic acid concentration increases, the electrocatalytic proton reduction activity of [{edt(CH2Py')2}Ni(NCS)2] for hydrogen production increases.

[0070] Embodiment 3:

[0071] This example provides the use of the nickel complex prepared in Example 1 to produce hydrogen by electrocatalytic reduction of protons in a trifluoroacetic acid medium.

[0072] The experiment was carried out on a CHI660E electrochemical workstation using a platinum wire electrode as a counter electrode, a non-mercury ion electrode as a reference electrode, and a 3mm glassy carbon electrode as a working electrode in a cylindrical electrolytic cell under a nitrogen atmosphere. Each electrode needs to be pretreated before the electrochemical test. The glassy carbon electrode is polished with 0.3μm aluminum oxide powder, washed with deionized water, ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode is treated in the same way as the non-mercury ion electrode, ultrasonically cleaned in acetone solution, and dried with cold air. The solvent of the test system is spectrally pure acetonitrile, the supporting electrolyte is tetrabutylammonium hexafluorophosphate, and the solution system used for the electrochemical test is 0.25mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1mol / L tetrabutylammonium hexafluorophosphate in acetonitrile; the concentration of trifluoroacetic acid is 0, 10, 20, 30, 40 and 50mmol / L, the scanning rate is 100mV / s, and the potential of the nickel complex obtained by the test is the potential after ferrocene correction. Among them, i pc is the reduction current of the catalyst when no trifluoroacetic acid is added, i cat is the size of the catalytic current at a certain trifluoroacetic acid concentration.

[0073] Attached 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] Attached Fig. 9 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The relationship between the concentration of trifluoroacetic acid and the square root of the concentration of trifluoroacetic acid shows that when the proton acid is trifluoroacetic acid, i cat / i pc It is linearly related to the square root of the acid concentration. When the concentration of trifluoroacetic acid is higher, the activity of [{edt(CH2Py')2}Ni(NCS)2] for electrocatalytic proton reduction to hydrogen production is greater.

[0075] Embodiment 4:

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

[0077] The experiment was carried out on a CHI660E electrochemical workstation using a platinum wire electrode as a counter electrode, a non-mercury ion electrode as a reference electrode, and a 3mm glassy carbon electrode as a working electrode in a cylindrical electrolytic cell under a nitrogen atmosphere. Each electrode needs to be pretreated before the electrochemical test. The glassy carbon electrode is polished with 0.3μm aluminum oxide powder, washed with deionized water, ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode is treated in the same way as the non-mercury ion electrode, ultrasonically cleaned in acetone solution, and dried with cold air. The solvent of the test system is spectrally pure acetonitrile, the supporting electrolyte is tetrabutylammonium hexafluorophosphate, and the solution system used for the electrochemical test is 0.25mmol / L [{edt(CH2Py')2}Ni(NCS)2] in 0.1mol / L tetrabutylammonium hexafluorophosphate in acetonitrile; the concentration of p-toluenesulfonic acid is 0, 10, 20, 30, 40 and 50mmol / L, the scanning rate is 100mV / s, and the potential of the nickel complex obtained by the test is the potential after ferrocene correction. Among them, i pc is the reduction current of the catalyst when p-toluenesulfonic acid is not added, i cat is the size of the catalytic current at a certain p-toluenesulfonic acid concentration.

[0078] Attached Fig.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] Attached Fig.11 i is [{edt(CH2Py')2}Ni(NCS)2] cat / i pc The relationship between the concentration of p-toluenesulfonic acid and the square root of p-toluenesulfonic acid concentration shows that when the proton acid is p-toluenesulfonic acid, i cat / i pc It is linearly related to the square root of the p-toluenesulfonic acid concentration. When the p-toluenesulfonic acid concentration is higher, the electrocatalytic proton reduction hydrogen production activity of [{edt(CH2Py')2}Ni(NCS)2] is greater.

[0080] Embodiment 5:

[0081] This example provides the application of the complex prepared in Example 1 to produce hydrogen by controlled potential electrolysis in a trifluoroacetic acid medium.

[0082] The experiment was performed on a CHI660E electrochemical workstation using 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 cylindrical electrolytic cell under a nitrogen atmosphere. Each electrode needs to be pretreated before the electrochemical test. The glassy carbon electrode is polished with 0.3μm aluminum oxide powder, washed with deionized water, ultrasonically cleaned in deionized water, and finally washed with acetone and dried with cold air. The platinum wire electrode is treated in the same way as the non-mercury ion electrode, ultrasonically cleaned in acetone solution, and dried with cold air. The solvent of the test system is spectrally pure acetonitrile, the supporting electrolyte is tetrabutylammonium hexafluorophosphate, and the solution system used for the electrochemical test is an acetonitrile solution of 0.1 mol / L tetrabutylammonium hexafluorophosphate containing 0.25 mmol / L [{edt(CH2Py')2}Ni(NCS)2]; 53.8 mmol / L trifluoroacetic acid and 50 mL of 0.1 mol / L tetrabutylammonium hexafluorophosphate in acetonitrile electrolyte were added to a 100 mL electrolytic cell and electrolyzed at a constant potential of -1.51 V for 4 hours.

[0083] Fig.12This is the coulomb accumulation diagram of [{edt(CH2Py')2}Ni(NCS)2] in Example 5 electrolyzed in an acetonitrile solution of tetrabutylammonium hexafluorophosphate containing trifluoroacetic acid under constant potential conditions for 4 hours. The red line represents the coulomb accumulation without the addition of the complex, and the black line represents the coulomb accumulation after the addition of the complex. The research results show that [{edt(CH2Py')2}Ni(NCS)2] has electrocatalytic hydrogen production performance.

[0084] Fig.13 This is the gas chromatogram in the electrolytic cell of [{edt(CH2Py')2}Ni(NCS)2] in Example 5. The results show that hydrogen is produced during the 4h electrolysis process.

[0085] Embodiment 6:

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

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

[0088] Fig.14 This is a graph showing the cumulative amount of hydrogen produced by the photocatalytic production of hydrogen from water by [{edt(CH2Py')2}Ni(NCS)2] in Example 6. The results show that hydrogen is produced during the 5h photocatalytic process.

[0089] Embodiment 7:

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

[0091] The photocatalytic hydrogen production test used the CEL-PAEM-D8Pro photolysis water system. Before the test, the photocatalytic reactor and the entire pipeline were evacuated to a vacuum state by a vacuum pump to ensure the clean environment of the reactor. During the test, condensed water was used to maintain the constant reaction temperature. The light source used a 300W Xe lamp filtered by a filter with a wavelength of 420nm, which was used as a 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 detection and analysis, and detected using a GC-7980 gas chromatograph.

[0092] Attached Fig.15 This is a graph showing the cumulative amount of hydrogen produced by photocatalytic water hydrogen production when 120 mg / L CdS NRs, 0.12 mol / L triethanolamine and 0.1 mmol / L [{edt(CH2Py')2}Ni(NCS)2] are uniformly dispersed in 100 mL of water in Example 7. The results show that hydrogen is produced during the 5 h photocatalytic process.

[0093] Embodiment 8:

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

[0095] The photocatalytic hydrogen production test used the CEL-PAEM-D8Pro photolysis water system. Before the test, the photocatalytic reactor and the entire pipeline were evacuated to a vacuum state by a vacuum pump to ensure the clean environment of the reactor. During the test, condensed water was used to maintain the constant reaction temperature. The light source used a 300W Xe lamp filtered by a filter with a wavelength of 420nm, which was used as a 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 detection and analysis, and detected using a GC-7980 gas chromatograph.

[0096] Attached Fig.16 This is a graph showing the cumulative amount of hydrogen produced by photocatalytic water hydrogen production when 120 mg / L of CdS NRs, 0.12 mol / L of lactic acid and 0.1 mmol / L [{edt(CH2Py')2}Ni(NCS)2] are uniformly dispersed in 100 mL of water in Example 6. The results show that hydrogen is produced during the 5 h photocatalytic process.

[0097] The above-mentioned examples are only preferred implementations of the present invention, but the protection scope of the present invention is not limited thereto. For ordinary technicians in this technical field, without departing from the principle of the present invention, according to the technical solution and patent concept of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

[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 in the protection scope of the present invention.

Claims

1. A nickel complex containing a S2N2 type ligand, characterized in that: The nickel complex is bis(isothiocyanate)·1,2-bis(2-(3,4-dimethoxypyridyl)methylthio)ethane nickel, and its molecular formula is [{edt(CH2Py')2}Ni(NCS)2], and its chemical structure is:

2. Use of the nickel complex as claimed in claim 1 in electrocatalytic hydrogen production.

3. Use of the nickel complex as claimed in claim 1 in photocatalytic hydrogen production.

4. A method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 1, characterized in that Its preparation route is:

5. A method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 1, characterized in that The following steps are involved: 1) CH3ONa is added to a methanol solution of ethanedithiol, and stirred at room temperature for a period of time to obtain a colorless transparent solution; 2) adding a methanol solution containing 2-chloromethyl-3,4-dimethoxypyridine hydrochloride to the colorless transparent solution obtained in step 1), and continuing to stir and react at room temperature for a period of time; 3) removing the solvent in the substance after the reaction in step 2) by reducing pressure using a rotary evaporator, dissolving the residue with methanol and filtering, collecting the filtrate, removing the solvent by reducing pressure using a rotary evaporator again, dissolving with dichloromethane and filtering, and collecting the filtrate; 4) The filtrate was concentrated, and thin layer chromatography was performed using a mixed solvent as a developing solvent to collect the corresponding product band, and white solid edt(CH2Py')2 was obtained after elution; 5) edt(CH2Py')2, NiCl2·6H2O and NaSCN are mixed with an organic solvent, stirred and reacted at room temperature for a period of time, and a light blue nickel complex [{edt(CH2Py')2}Ni(NCS)2] solid is obtained after filtering and washing.

6. A method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 5, characterized in that: In the step 1), the molar ratio of CH3ONa to ethanedithiol is 4-4.3:2; and the stirring reaction time is 20-30 min at room temperature.

7. A method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 5, characterized in that: In the step 2), the molar ratio of ethanedithiol to 2-chloromethyl-3,4-dimethoxypyridine hydrochloride is 1:2-2.4; and the stirring reaction time is 3-6 hours at room temperature.

8. A method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 5, characterized in that: The developing solvent in step 4) is a mixed solvent of petroleum ether and ethyl acetate, and the volume ratio of the two is 1:2-3; the specifications of the silica gel plate required for thin layer chromatography separation are 26×20×0.25cm 3 .

9. The method for preparing a nickel complex containing a S2N2 type ligand as claimed in claim 5, characterized in that: In the step 5), the usage ratio of edt(CH2Py')2, NiCl2·6H2O, NaSCN and organic solvent is 1mmol:1mmol:2mmol:40-60mL.

10. The method for preparing a nickel complex according to claim 5, characterized in that: In the step 5), the organic solvent is acetonitrile, methanol or ethanol; the reaction time is 2-4 hours under stirring at room temperature.

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