Nickel complex based on 1, 4, 7, 10-tetraazacyclododecane and application

Abstract

The invention relates to the technical field of catalysis of tetraazacyclo nickel complexes, and particularly discloses a nickel complex based on 1, 4, 7, 10-tetraazacyclo dodecane and application of the nickel complex in catalytic hydrogen production. According to the invention, a mononuclear nickel complex [Ni (cyen) Cl] Cl, a binuclear nickel complex [Ni (cyen) Cl2Ni (cyen) Cl and a tetranuclear nickel complex [Ni (cyen) (SCN) 3Ni2 (SCN) 3Ni (cyen)] are synthesized; under the condition that the overpotential (OP) is 837.6 mV, NiL1, Ni2L2 and Ni4L3 electro-catalyze hydrogen evolution of neutral water at the turnover frequencies (TOF) of 956.44, 1989.45 and 2675.25 mol per mole of catalyst per hour (mol H2 / mol catalyst / h) respectively. The result shows that Ni4L3 has higher H2 generation activity than Ni2L2 and NiL1. Electrochemical testing and analysis are carried out on the catalyst, and the hydrogen production catalysis mechanism of the catalyst is researched.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tetraazamacrocyclic nickel complex catalysis, and particularly discloses a nickel complex based on 1,4,7,10-tetraazacyclododecane and application thereof in catalytic hydrogen production. BACKGROUND

[0002] In order to reduce our dependence on fossil fuels, hydrogen is a promising energy source and potential alternative; electrochemically driven water splitting provides an ideal way to produce high-purity and large amounts of hydrogen or oxygen. Specifically, electrocatalytic water splitting is an attractive prospect for solar energy collection elements and sustainable energy production. In order to improve hydrogen production efficiency and reduce energy consumption, catalysts must be added. Recent studies have shown that hydrogenase combined with transition metal complexes can effectively catalyze hydrogen production.

[0003] Several groups, including ours, have focused on studying rich metal-based catalysts and have designed several molecular catalysts based on cobalt, iron, and nickel complexes for hydrogen production. In order to develop efficient metal complex-based hydrogen production catalysts, the influence of the metal center in the complex on catalytic activity has been widely studied.

[0004] Macrocyclic complexes have greater activity than their non-macrocyclic counterparts and the most rigid catalysts. The catalytic performance of macrocyclic complexes has been widely studied in terms of oxygen evolution, hydrogen evolution, and carbon dioxide reduction, and macrocyclic nickel complexes have excellent catalytic applications in electrocatalytic hydrogen production. However, there are few reports on the catalytic efficiency of molecular catalysts based on polynuclear nickel macrocyclic complexes for hydrogen evolution reactions. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present application is to provide a nickel complex based on 1,4,7,10-tetraazacyclododecane and application thereof in catalytic hydrogen production, in which a macrocyclic 1,4,7,10-tetraazacyclododecane (cyclen) is used as a ligand, a single nickel complex, a binuclear nickel complex, and a tetranuclear nickel complex are designed and synthesized, and the application of the single nickel complex, the binuclear nickel complex, and the tetranuclear nickel complex in catalytic hydrogen production is studied.

[0006] To achieve the above object, the present application provides a nickel complex based on 1,4,7,10-tetraazacyclododecane, the nickel complex is ([Ni(cyclen)Cl]Cl, [Ni(cyclen)Cl2Ni(cyclen)]Cl2, [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; wherein, ([Ni(cyclen)Cl]Cl is a single nickel complex, namely NiL1, L1 = [(cyclen)Cl]Cl; [Ni(cyclen)Cl2Ni(cyclen)]Cl2 is a binuclear nickel complex, namely Ni2L2, L2 = [(cyclen)Cl2(cyclen)]Cl2; [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 is a tetranuclear nickel complex, namely Ni4L3, L3 = [(cyclen)(SCN)3(SCN)3(cyclen)]Cl2.

[0007] Further, the preparation method of the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 comprises the following steps:

[0008] Step 1, 1.0 mmol of NiCl2·6H2O is added to 1 ml of methanol, and fully stirred to dissolve, to obtain a NiCl·6H2O solution.

[0009] Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) is added to 1 ml of methanol, and fully stirred to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0010] Step 3, then the NiCl·6H2O solution in step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane (cyclen) solution in step 2, to obtain a mixed solution;

[0011] Step 4, 3.0 mmol of KSCN is added to the mixed solution in step 3, and placed in a nitrogen atmosphere at room temperature, and after several days, the solid is collected by filtration, to obtain [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; yield (0.912 g, 68.13%).

[0012] Further, the preparation method of the [Ni(cyclen)Cl2Ni(cyclen)]Cl2 comprises the following steps:

[0013] Step 1, 1.0 mmol of NiCl2.6H2O was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of NiCl.6H2O.

[0014] Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of 1,4,7,10-tetraazacyclododecane (cyclen).

[0015] Step 3, then the solution of NiCl.6H2O in step 1 was quickly added into the solution of 1,4,7,10-tetraazacyclododecane (cyclen) in step 2, to obtain a mixed solution;

[0016] Step 4, 4 ml of DMF (dimethylformamide) was added into the mixed solution in step 3, and placed in a nitrogen atmosphere at 0°C, and after several days, the solid was collected by filtration, to obtain [Ni(cyclen)Cl2Ni(cyclen)]Cl2; yield (0.612 g, 82.28%).

[0017] Further, the preparation method of the [Ni(cyclen)Cl]Cl includes the following steps:

[0018] Step 1, 1.0 mmol of NiCl2.6H2O was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of NiCl.6H2O.

[0019] Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of 1,4,7,10-tetraazacyclododecane (cyclen).

[0020] Step 3, then the solution of NiCl.6H2O in step 1 was quickly added into the solution of 1,4,7,10-tetraazacyclododecane (cyclen) in step 2, to obtain a mixed solution;

[0021] Step 4, 4 ml of DMF (dimethylformamide) was added into the mixed solution in step 3, and placed in an air atmosphere at room temperature, and after several days, the solid was collected by filtration, to obtain [Ni(cyclen)Cl]Cl; yield (0.3596, 87.77%).

[0022] Further, in the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2, the nickel atoms are combined with the four nitrogen atoms of 1,4,7,10-tetraazacyclododecane and the nitrogen atoms in SCN- respectively; the sulfur atoms of SCN are bonded to the nickel center of Ni(SCN)4, and finally a macrocyclic complex is synthesized with four nickel atoms as the center connected by thiocyanate; the bond length between the nitrogen atom and the nickel center is between The Ni(1)-NCS bond distance is

[0023] Further, in the [Ni(cyclen)Cl2Ni(cyclen)]Cl2, the nickel atoms are combined with the four nitrogen atoms of 1,4,7,10-tetraazacyclododecane and two chlorine atoms, wherein the bond length between the nitrogen atom and the nickel center is The Ni(1)-Cl bond distance is

[0024] Further, in the [Ni(cyclen)Cl2Ni(cyclen)]Cl2, the nickel atoms are combined with the four nitrogen atoms of 1,4,7,10-tetraazacyclododecane and two chlorine atoms, wherein the bond length between the nitrogen atom and the nickel center is The Ni(1)-Cl bond distance is

[0025] The second object of the present application is to provide an application of the above-mentioned nickel complex based on 1,4,7,10-tetraazacyclododecane in electrocatalysis.

[0026] The beneficial effects of the present application are:

[0027] The present application designs, synthesizes and characterizes mononuclear, binuclear and tetranuclear nickel complexes [Ni(cyen)Cl]Cl, (NiL1), [Ni(cyen)Cl2Ni(cyen)]Cl2, (Ni2L2) and [Ni(cyen)(SCN)3Ni2(SCN)3Ni(cyen)]Cl2, (Ni4L3), which can all be used as catalysts for electrochemically driven hydrogen evolution. At an overpotential (OP) of 837.6 mV, NiL1, Ni2L2 and Ni4L3 electrocatalyze the evolution of hydrogen from neutral water with a turnover frequency (TOF) of 956.44, 1989.45 and 2675.25 mol (mol H2 / mol catalyst / h) respectively. The results show that the tetranuclear nickel complex Ni4L3 has higher H2 generation activity than the mononuclear and binuclear nickel complexes Ni2L2 and NiL1. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The synthesis steps of the complex NiL1 of the present application are as follows:

[0029] Figure 2 Synthesis procedure for the complex Ni2L2 of the present invention;

[0030] Figure 3 Synthesis procedure for the complex Ni4L3 of the present invention;

[0031] Figure 4 Molecular structure of NiL1 of the present invention;

[0032] Figure 5 Molecular structure of Ni2L2 of the present invention;

[0033] Figure 6 Molecular structure of Ni4L3 of the present invention;

[0034] Figure 7 CV plots of 0.1 mM NiL1, 0.1 mM Ni2L2, 0.1 mM Ni4L3 of the present invention in 0.1 M TBAPF6DMF solution, in the range of -2.0 to 1.0 V (vs. Ag / AgNO3) at a scan rate of 50 mV / s on GC electrode, respectively;

[0035] Figure 8 CV plots of 0.1 mM Ni2L2 (a), 0.1 mM Ni4L3 (b) of the present invention in 0.1 M TBAPF6DMF solution saturated with N2, in the presence of acetic acid at different concentrations, in the range of -1.1 to 1.0 V (vs. Ag / AgNO3) at a scan rate of 50 mV / s on GC electrode;

[0036] Figure 9 Possible electrocatalytic mechanism for hydrogen evolution of the present invention;

[0037] Figure 10 CV plots of 0.1 mM NiL1, Ni2L2, Ni4L3 of the present invention in neutral aqueous phosphate buffer solution, in the range of -2.0 to 2.0 V (vs. Ag / AgCl) at a scan rate of 50 mV / s on GC electrode;

[0038] Figure 11 Charge time plots of 0.1 mM NiL1, 0.1 mM Ni2L2, 0.1 mM Ni4L3 of the present invention in neutral aqueous phosphate buffer solution, respectively, at -1.45 V (vs. Ag / AgCl) for 2 minutes electrolysis;

[0039] Figure 12 Turnover frequency (TOF) plots of 0.1 mM NiL1, 0.1 mM Ni2L2, 0.1 mM Ni4L3 of the present invention in neutral aqueous phosphate buffer solution, respectively, for catalytic hydrogen evolution at -1.45 V (vs. Ag / AgCl) at different overpotentials;

[0040] Figure 13 Charge profile of NiL1, Ni2L2, Ni4L3 of the present application in the absence of complex in neutral buffer (pH = 7.0) for 2 minutes of electrolysis at -1.45 V (vs. Ag / AgCl) applied potential;

[0041] Figure 14 Catalytic performance of NiL1, Ni2L2, Ni4L3 of the present application in buffer solution for 1 hour of electrolysis at -1.45 V;

[0042] Figure 15 Hydrogen production performance profile of NiL1, Ni2L2, Ni4L3 of the present application in buffer solution for 1 hour of electrolysis at -1.45 V of the complex;

[0043] Figure 16 Hydrogen production profile of NiL1, Ni2L2 and Ni4L3 of the present application in buffer solution for 1 hour of electrolysis;

[0044] Figure 17 Faradaic efficiency profile of NiL1, Ni2L2 and Ni4L3 of the present application for H2;

[0045] Figure 18 Stability profile of Ni4L3 of the present application for long time electrolysis of 72 hours at -1.45 V;

[0046] Figure 19 UV-Visible spectrum profile of Ni4L3 of the present application at different electrolysis times. DETAILED DESCRIPTION

[0047] For the convenience of the person skilled in the art, the following examples and the attached figures are provided to illustrate the present application. Figures 1-19 The present application is further illustrated by the content mentioned in the embodiments, which is not a limitation of the present application.

[0048] Example 1

[0049] Please refer to Figures 4-6 As shown in the figure, a nickel complex based on 1,4,7,10-tetraazacyclododecane, the nickel complex is ([Ni(cyclen)Cl]Cl, [Ni(cyclen)Cl2Ni(cyclen)]Cl2,

[0050] [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; wherein, ([Ni(cyclen)Cl]Cl is a single nickel complex, that is

[0051] NiL1, L1= [(cyclen)Cl]Cl; [Ni(cyclen)Cl2Ni(cyclen)]Cl2is a binuclear nickel complex, i.e. Ni2L2,

[0052] L2= [(cyclen)Cl2(cyclen)]Cl2; [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2is a tetranuclear nickel complex; i.e. Ni4L3, L3= [(cyclen)(SCN)3(SCN)3(cyclen)]Cl2.

[0053] Materials and physical measurements

[0054] Elemental analysis for C, H and N was performed using a PerkinElmer analyzer (model 240). Nuclear magnetic resonance analysis was performed using a Bruker AV-500 instrument. The ultraviolet-visible spectra of the samples were measured with a Hitachi U-3010 spectrometer. All electrochemical measurements and analysis were performed using a CHI-660E electrochemical analyzer. Fluorescence spectra were recorded on an F-7000 fluorescence spectrometer. Dynamic light scattering was performed on a Bruker Haverhill instrument zetapplus particle size. Transmission electron microscopy (TEM) images and energy dispersive X-ray (EDX) elemental mapping experiments were performed on a JEOL JEM-2100 microscope at an accelerating voltage of 200 kV. Electrochemical impedance spectroscopy (EIS) measurements were performed in 0.1 M KCl solution with a 0.010 M K3[Fe(CN)6] / K4[Fe(CN)6] (1 : 1) mixture as a redox probe.

[0055] X-ray crystallography was performed to determine the structure of the nickel complexes,

[0056] Measurements and analyses were performed using a Bruker Smart APEX II Duo area detector equipped with graphite monochromatic Mo-Ka radiation at 50 kV and 30 mA. Empirical absorption correction was then performed using SADABS software. The structure was solved using direct methods and refined against the corresponding non-hydrogen atoms using the XL refinement package. All calNilation was performed using the Olex2 structure software. Hydrogen atoms on carbon atoms were generated geometrically and refined with isotropic displacement parameters, while non-hydrogen atoms were refined with anisotropic displacement parameters.

[0057] Table 1 Crystal data and structure refinement parameters for the complex [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2

[0058]

[0059] Table 3 Crystal data and structure refinement parameters of complex [Ni(cyclen)Cl]Cl

[0060]

[0061]

[0062] Table 3 Crystal data and structure refinement parameters of complex [Ni(cyclen)Cl]Cl

[0063]

[0064]

[0065] Example 2

[0066] As Figure 3 shown, the preparation method of the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 includes the following steps:

[0067] Step 1, add 1.0 mmol of NiCl2·6H2O in 1 ml of methanol, fully stir to dissolve, and obtain a NiCl·6H2O solution.

[0068] Step 2, add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, fully stir to dissolve, and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0069] Step 3, then quickly add the NiCl·6H2O solution in step 1 to the 1,4,7,10-tetraazacyclododecane (cyclen) solution in step 2, to obtain a mixed solution;

[0070] Step 4, add 3.0 mmol of KSCN to the mixed solution in step 3, place it in a nitrogen atmosphere at room temperature, and after a few days, filter to collect the solid, to obtain [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; yield (0.912 g, 68.13%).

[0071] As Figure 6 shown, the nickel atoms in the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 are respectively combined with the four nitrogen atoms of the 1,4,7,10-tetraazacyclododecane and the nitrogen atom in the SCN-atom; the sulfur atom of the SCN atom is bonded to the nickel center of Ni(SCN)4, and finally a macrocyclic complex with four nickel atoms as the center connected by thiocyanate is synthesized; the bond length of the nitrogen atom and the nickel center is between Ni(l)-NCS bond distance

[0072] Example 3

[0073] As shown in the following scheme, the preparation of [Ni(cyclen)Cl2Ni(cyclen)]Cl2comprises the following steps: Figure 2

[0074] Step 1, 1.0 mmol of NiCl2-6H2O was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of NiCl-6H2O.

[0075] Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) was added into 1 ml of methanol, and stirred well to dissolve and obtain a solution of 1,4,7,10-tetraazacyclododecane (cyclen).

[0076] Step 3, then the solution of NiCl-6H2O in step 1 was quickly added into the solution of 1,4,7,10-tetraazacyclododecane (cyclen) in step 2, to obtain a mixed solution;

[0077] Step 4, 4 ml of DMF (dimethylformamide) was added into the mixed solution in step 3, and placed in a nitrogen atmosphere at 0°C, and after several days, the solid was collected by filtration, to obtain [Ni(cyclen)Cl2Ni(cyclen)]Cl2; yield (0.612 g, 82.28%).

[0078] As shown in the following scheme, the preparation of [Ni(cyclen)Cl2Ni(cyclen)]Cl2comprises the following steps: Figure 5 the bond length between the nitrogen atom and the nickel center is

[0079] Example 4

[0080] As shown in the following scheme, the preparation of [Ni(cyclen)Cl]Clcomprises the following steps: Figure 1

[0081] Step 1, 1.0 mmol of NiCl2-6H2O was added into 1 ml of methanol, and stirred well to dissolve, to obtain a solution of NiCl-6H2O.

[0082] ​​​Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) was added to 1 ml of methanol, and stirred well to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0083] Step 3, then the NiCl-6H2O solution in step 1 was quickly added to the 1,4,7,10-tetraazacyclododecane (cyclen) solution in step 2 to obtain a mixed solution;

[0084] Step 4, 4 ml of DMF (dimethylformamide) was added to the mixed solution in step 3, and placed in an air atmosphere at room temperature, and after a few days, the solid was collected by filtration to obtain [Ni(cyclen)Cl]Cl; yield (0.3596, 87.77%).

[0085] As shown in Figure 4 , the nickel atom in the [Ni(cyclen)Cl]Cl is combined with four nitrogen atoms and one chlorine atom; the bond length of the nitrogen atom to the nickel center is between ; the Ni(1)-Cl bond distance is

[0086] Example 5

[0087] Application of the above-mentioned 1,4,7,10-tetraazacyclododecane-based nickel complex in electrocatalysis;

[0088] As shown in Figure 7 , first, cyclic voltammetry (CV) of NiL1, Ni2L2 and Ni4L3 was carried out on a glassy carbon (GC) electrode in a tetrabutylammonium hexafluorophosphate (TBAPF6) DMF solution saturated with N2.

[0089] As shown in Figure 7 , quasi-reversible redox peaks were observed at -1.748 V (vs. Ag / AgNO3) corresponding to the Ni II / I of NiL1, and the redox peak at 0.498 V was due to the Ni III / Ni II of NiL1.

[0090] Two quasi-reversible redox peaks were observed at -1.61 V, -1.85 V (vs. Ag / AgNO3) corresponding to the Ni II / I of Ni2L2, and the redox peaks at 0.46 V and 0.57 V were attributed to the Ni III / Ni II of Ni2L2.

[0091] Two quasi-reversible redox peaks were observed at -1.01 V, -1.83 V (vs. Ag / AgNO3) corresponding to Ni of Ni4L3 II / I ; 0.36 V redox peak can be attributed to Ni of Ni4L III / Ni II .

[0092] It can be observed that the presence of the bimetallic and multimetallic complexes results in multiple reduction peaks and a reduction shift, which indicates a decrease in the excess potential for hydrogen production.

[0093] Next, the catalytic performance of NiL1, Ni2L2 and Ni4L3 was tested with acetic acid as the proton source, and the results are shown in Figure 8 (a). For Ni2L1, as acetic acid was added from 0.0 to 3.33 mM (proton source), the reduction peak showed a systematic increase, indicating H + combined with the Ni I metal center to form [Ni I -H] + peroxide, which is consistent with the coupling of "Ni II -H" that can be formed in situ by protonation of the original complex.

[0094] As shown in Figure 8 (b), the addition of acetic acid in Ni4L3 resulted in an increase in peak current, which is consistent with the catalytic process, and it showed similar catalytic behavior as Ni2L2. These results indicate that the reduction of Ni (II) to Ni (I) and protonation are the reasons for hydrogen production.

[0095] In combination with these observations and analysis with known work, a possible catalytic cycle through a mechanism of proton reduction of hydrogen is shown in Figure 9 .

[0096] As shown in Figure 10 , the CV plots of 0.1 mM NiL1, Ni2L2 and Ni4L3 of the present application in neutral aqueous phosphate buffer solution on GC electrode in the range of -2.0 to 2.0 V (vs. Ag / AgCl) at a scan rate of 50 mV / s; the onset of the catalytic peak shifted to a higher potential, which is consistent with the catalytic process. Compared with the mononuclear complex, the reduction peak current of the dinuclear and tetranuclear nickel complexes showed a right shift tendency, indicating that the multinuclear complex can reduce the overpotential of hydrogen production.

[0097] In the presence of NiL1, as the pH value of the buffer decreased from 7.0 to 5, the reduction peak intensity was enhanced, and the catalytic current peak was enhanced, indicating that protons led to an improved catalytic hydrogen production process.

[0098] To further understand the electrocatalytic efficiency of NiL1, Ni2L2 and Ni4L3 for hydrogen evolution in aqueous media, bulk electrolysis experiments of NiL1, Ni2L2 and Ni4L3 buffer were carried out, and the results are shown in Table 1. Figure 13 As shown in Table 1, when the applied potential is -1.45 V (vs. Ag / AgCl), the electrolysis of the neutral buffer (pH = 7.0) in the absence of the complex only provides a charge of 0.024 C during the electrolysis of 2 min. As shown in Table 1, after the addition of NiL1, Ni2L2 or Ni4L3, the electrolysis of the buffer can provide a charge of 0.8 C, 1.5 C and 4.8 C under the same conditions, and a large amount of H2 is determined by using a gas chromatograph (GC), indicating that the three complexes are indeed effective hydrogen producers under this condition, and the multi-nuclear nickel complexes have better hydrogen production catalytic performance than the single-nuclear nickel complexes. Figure 11 As shown in Table 1, when the overpotential (OP) is 837.6 mV, the turnover frequency (TOF) of NiL1 catalytic hydrogen evolution is 956.44 mol / mol / h (mol H2 / mol catalyst / h); the TOF of Ni2L2 catalyst is 1989.45 mol H2 / mol / h; and the TOF of Ni4L3 catalyst is 2675.25 mol H2 / mol / h (mol H2 / mol catalyst / h). The results show that Ni2L2 and Ni4L3 have higher electrocatalytic activity for hydrogen production. This can be attributed to the fact that the multi-nuclear nickel complexes are more likely to form vacancies on the nickel center than the single-nuclear nickel complexes, which are easy to combine with hydrogen protons and hydrogen evolution.

[0099] Figure 12 As shown in Table 1, when the overpotential (OP) is 837.6 mV, the turnover frequency (TOF) of NiL1 catalytic hydrogen evolution is 956.44 mol / mol / h (mol H2 / mol catalyst / h); the TOF of Ni2L2 catalyst is 1989.45 mol H2 / mol / h; and the TOF of Ni4L3 catalyst is 2675.25 mol H2 / mol / h (mol H2 / mol catalyst / h). The results show that Ni2L2 and Ni4L3 have higher electrocatalytic activity for hydrogen production. This can be attributed to the fact that the multi-nuclear nickel complexes are more likely to form vacancies on the nickel center than the single-nuclear nickel complexes, which are easy to combine with hydrogen protons and hydrogen evolution.

[0100] Table 4 is the electrocatalytic data of NiL1, Ni2L2 and Ni4L3 for hydrogen production in aqueous buffer, which lists the overpotential, turnover frequency (TOF) and molar hydrogen production data. The results show that the multi-nuclear nickel complexes of the present application have significantly better catalytic performance than the single-nuclear nickel complexes.

[0101] Table 4 is the electrocatalytic data of NiL1, Ni2L2 and Ni4L3 for hydrogen production in aqueous buffer

[0102]

[0103]

[0104] To further study the hydrogen production performance of the three complexes (NiL1, Ni2L2 and Ni4L3), the NiL1, Ni2L2 and Ni4L3 complexes were subjected to electrolysis for 1 hour in a buffer solution at -1.45 V (as shown in Table 2), and the hydrogen content during the electrolysis was measured by gas chromatography (GC), according to Figure 14 Figure 15 ​​During the 1-hour electrolysis process, the buffer solutions of NiL1, Ni2L2 and Ni4L3 can provide 3.17 ml, 6.15 ml and 7.99 ml of H2, respectively.

[0105] The Faraday efficiency of these three complexes for H2 was determined by dividing the pH change during the catalytic hydrogen production process by the change in the theoretical hydrogen production value. Figure 16 As shown, the Faraday efficiency NiL1 is 97.88% ( Figure 16 a) Ni2L2 is 96% ( Figure 16 b) and Ni4L3 were 98.7% ( Figure 16 c).

[0106] like Figure 17 As shown, the stability of Ni4L3 during hydrogen production was investigated, revealing the effects of constant current (relative to NHE) during long-term electrolysis for 72 hours at -1.45V. Gas chromatography analysis of the electrode and solution during electrolysis was performed. However, after 72 hours of electrolysis, no signs of decomposition were observed on the electrode surface (e.g., ...). Figure 18 Furthermore, the UV-Vis spectrum of Ni4L3 did not undergo substantial changes at different electrolysis times (e.g., Figure 19 ).

[0107] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. Nickel complex based on 1,4,7,10-tetraazacyclododecane, characterized in that: The nickel complex is [Ni(cyclen)Cl2Ni(cyclen)]Cl2, [Ni(cyclen)Cl]Cl.

2. The 1,4,7,10-tetraazacyclododecane-based nickel complex according to claim 1, characterized in that: The preparation method of the [Ni(cyclen)Cl2Ni(cyclen)]Cl2comprises the following steps: Step 1, 1.0 mmol of NiCl2·6H2O is added into 1 ml of methanol, and is fully stirred and dissolved to obtain a NiCl·6H2O solution. Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) is added into 1 ml of methanol, and is fully stirred and dissolved to obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution. Step 3, then the NiCl·6H2O solution in step 1 is quickly added into the 1,4,7,10-tetraazacyclododecane (cyclen) solution in step 2 to obtain a mixed solution; Step 4, 4 ml of DMF (dimethylformamide) is added into the mixed solution in step 3, and is placed in a nitrogen atmosphere at 0℃, and after several days, a solid is collected by filtration, and the [Ni(cyclen)Cl2Ni(cyclen)]Cl2is obtained; the yield is (0.612 g, 82.28%).

3. The 1,4,7,10-tetraazacyclododecane-based nickel complex according to claim 1, characterized in that: The preparation method of the [Ni(cyclen)Cl]Clcomprises the following steps: Step 1, 1.0 mmol of NiCl2·6H2O is added into 1 ml of methanol, and is fully stirred and dissolved to obtain a NiCl·6H2O solution. Step 2, 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) is added into 1 ml of methanol, and is fully stirred and dissolved to obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution. Step 3, then the NiCl·6H2O solution in step 1 is quickly added into the 1,4,7,10-tetraazacyclododecane (cyclen) solution in step 2 to obtain a mixed solution; Step 4, 4 ml of DMF (dimethylformamide) is added into the mixed solution in step 3, and is placed in an air atmosphere at room temperature, and after several days, a solid is collected by filtration, and the [Ni(cyclen)Cl]Clis obtained; the yield is (0.3596, 87.77%).

4. The 1,4,7,10-tetraazacyclododecane-based nickel complex of claim 1, wherein: The nickel atom in said [Ni(cyclen)Cl2Ni(cyclen)]Cl2is bound to four nitrogen atoms of the 1,4,7,10-tetraazacyclododecane and two chlorine atoms, wherein the bond length between the nitrogen atoms and the nickel center is The Ni(l)-Cl bond distance is 5. The 1,4,7,10-tetraazacyclododecane-based nickel complex of claim 1, wherein: The nickel atom in said [Ni(cyclen)Cl]Cl is bound to four nitrogen atoms and one chlorine atom; the bond lengths of the nitrogen atoms to the nickel center are between and the Ni(l)-Cl bond distance is 6. Use of a nickel complex based on 1,4,7,10-tetraazacyclododecane in electrocatalysis, characterized in that: The nickel complex based on 1,4,7,10-tetraazacyclododecane is the nickel complex according to any one of claims 1-5.

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