Nickel complexes based on 1,4,7,10-tetraazacyclododecane and uses thereof

Abstract

The present application relates to tetraazacyclo nickel complex catalysis technical field, especially disclose a kind of nickel complex based on 1,4,7,10-tetraazacyclo dodecane and its application in catalytic hydrogen production;The present application synthesizes mononuclear nickel complex [Ni (cyen) Cl]Cl, binuclear nickel complex [Ni (cyen) Cl2Ni (cyen]Cl, and tetranuclear nickel complex [Ni (cyen) (SCN) 3Ni2 (SCN) 3Ni (cyen)];Under the condition that overpotential (OP) is 837.6mV, NiL1, Ni2L2 and Ni4L3 respectively with 956.44, 1989.45 and 2675.25mol of turnover frequency (TOF) per hour per mole of catalyst (mol H2 / mol catalyst / h) electrocatalytic neutral water hydrogen evolution.The results show that Ni4L3 has higher H2 generation activity than Ni2L2 and NiL1.The catalyst is electrochemically tested and analyzed, and the mechanism of catalyst catalytic hydrogen production is studied.

Description

Technical Field

[0001] This invention relates to the field of tetraazacyclonickel complex catalysis technology, and in particular discloses a nickel complex based on 1,4,7,10-tetraazacyclododecane and its application in catalytic hydrogen production. Background Technology

[0002] To reduce our dependence on fossil fuels, hydrogen is a promising energy source and a potential alternative; electrochemically driven water splitting offers an ideal pathway for producing high-purity and large quantities of hydrogen or oxygen. Specifically, electrocatalytic water splitting is an attractive prospect for solar energy harvesting elements and sustainable energy production. To improve hydrogen production efficiency and reduce energy consumption, catalysts must be added. Recent studies have shown that hydrogenases combined with transition metal complexes can efficiently catalyze hydrogen production.

[0003] Several groups, including ours, have focused on studying abundant metal-based catalysts and have designed several molecular catalysts based on cobalt, iron, and nickel complexes for hydrogen production. To develop highly efficient metal complex-based hydrogen production catalysts, the influence of the metal center in the complex on catalytic activity has been extensively investigated.

[0004] Macrocyclic complexes exhibit greater activity compared to their non-macrocyclic counterparts, which are among the most rigid catalysts. The catalytic performance of macrocyclic complexes has been extensively studied in oxygen evolution, hydrogen evolution, and carbon dioxide reduction, with macrocyclic nickel complexes showing excellent catalytic applications in electrocatalytic hydrogen production. However, reports on the catalytic efficiency of molecular catalysts based on polynuclear nickel macrocyclic complexes for the hydrogen evolution reaction are scarce. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a nickel complex based on 1,4,7,10-tetraazacyclododecane and its application in catalytic hydrogen production. Using macrocyclic 1,4,7,10-tetraazacyclododecane (cyclen) as a ligand, mono-nickel complexes, binuclear nickel complexes, and tetra-nickel complexes were designed and synthesized, and their applications in catalytic hydrogen production were studied.

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

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

[0008] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0009] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0010] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0011] Step 4: Add 3.0 mmol KSCN to the mixed solution in Step 3, place it in a nitrogen atmosphere at room temperature, and filter and collect the solid after a few days to obtain [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; yield (0.912 g, 68.13%).

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

[0013] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0014] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0015] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0016] Step 4: Add 4 mL of DMF (dimethylformamide) to the mixed solution in Step 3, place it in a nitrogen atmosphere at 0 °C, and collect the solid after a few days by filtration to obtain [Ni(cyclen)Cl2Ni(cyclen)]Cl2; yield (0.612 g, 82.28%).

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

[0018] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0019] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0020] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0021] Step 4: Add 4 mL of DMF (dimethylformamide) to the mixed solution in Step 3, place it in an air atmosphere at room temperature, and filter and collect the solid after a few days to obtain [Ni(cyclen)Cl]Cl; yield (0.3596, 87.77%).

[0022] Furthermore, in the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2, the nickel atoms are bonded to the four nitrogen atoms of 1,4,7,10-tetraazacyclododecane and the nitrogen atom of the SCN atom, respectively; the sulfur atom of the SCN atom is bonded to the nickel center of Ni(SCN)4, ultimately synthesizing a macrocyclic complex with four nickel atoms linked by thiocyanate; the bond length between the nitrogen atom and the nickel center is... Between, the Ni(1)-NCS bond distance is

[0023] Furthermore, in the [Ni(cyclen)Cl2Ni(cyclen)]Cl2, the nickel atom is bonded to four nitrogen atoms and two chlorine atoms of 1,4,7,10-tetraazacyclododecane, wherein the bond length between the nitrogen atom and the nickel center is [missing information]. The bond distance of Ni(1)-Cl is

[0024] Furthermore, in the [Ni(cyclen)Cl]Cl, the nickel atom is bonded to four nitrogen atoms and one chlorine atom; the bond length between the nitrogen atom and the nickel center is... Between; Ni(1)-Cl bond distance is

[0025] A second objective of this invention 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 this invention are:

[0027] This invention 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), all of which can serve as catalysts for electrochemically driven hydrogen evolution. At an overpotential (OP) of 837.6 mV, NiL1, Ni2L2, and Ni4L3 exhibited electrocatalytic hydrogen evolution from neutral water at turnover rates (TOF) of 956.44, 1989.45, and 2675.25 mol H2 / mol catalyst / h, respectively. The results show that the tetranuclear nickel complex Ni4L3 exhibits higher H2 generation activity than the mononuclear and binuclear nickel complexes Ni2L2 and NiL1. Attached Figure Description

[0028] Figure 1 The steps for synthesizing the complex NiL1 of this invention are as follows;

[0029] Figure 2 These are the steps for synthesizing the complex Ni2L2 of this invention;

[0030] Figure 3 The steps for synthesizing the complex Ni4L3 of this invention are as follows;

[0031] Figure 4 The present invention relates to the NiL1 molecular structure;

[0032] Figure 5 This is the Ni2L2 molecular structure of the present invention;

[0033] Figure 6 The present invention relates to the Ni4L3 molecular structure;

[0034] Figure 7 The CV plots of 0.1 mM NiL1, 0.1 mM Ni2L2, and 0.1 mM Ni4L3 of the present invention are obtained on a GC electrode in 0.1 mM TBAPF6 DMF solution, in the range of -2.0 to 1.0 V (relative to Ag / AgNO3), at a scan rate of 50 mV / s.

[0035] Figure 8 The CV plots of 0.1 mM Ni2L2 (a) and 0.1 mM Ni4L3 (b) of the present invention in N2-saturated 0.1 M TBAPF6 DMF solution, at different concentrations of acetic acid, on a GC electrode at a scan rate of 50 mV / s in the range of -1.1 to 1.0 V (relative to Ag / AgNO3);

[0036] Figure 9 This is a diagram illustrating a possible electrocatalytic mechanism for hydrogen evolution in this invention;

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

[0038] Figure 11 The charge-time graph shows the electrolysis of 0.1 mM NiL1, 0.1 mM Ni2L2, and 0.1 mM Ni4L3 in a neutral aqueous phosphate buffer solution for 2 minutes at -1.45 V (relative to Ag / AgCl).

[0039] Figure 12The graph shows the time-of-flight (TOF) values ​​of 0.1 mM NiL1, 0.1 mM Ni2L2, and 0.1 mM Ni4L3 in neutral water phosphate buffer solution at different overpotentials at -1.45 V (relative to Ag / AgCl).

[0040] Figure 13 The charge diagrams of NiL1, Ni2L2, and Ni4L3 of the present invention, when electrolyzed for 2 minutes in a neutral buffer solution (pH=7.0) without the presence of a complex, at an applied potential of -1.45V (relative to Ag / AgCl).

[0041] Figure 14 The catalytic performance of NiL1, Ni2L2, and Ni4L3 of the present invention after electrolysis in a buffer solution at -1.45V for 1 hour;

[0042] Figure 15 The figure shows the hydrogen production performance of the complexes of NiL1, Ni2L2, and Ni4L3 in the present invention when electrolyzed in a buffer solution at -1.45V for 1 hour.

[0043] Figure 16 The figure shows the hydrogen production of NiL1, Ni2L2 and Ni4L3 in buffer solution after 1 hour of electrolysis.

[0044] Figure 17 The Faraday efficiency diagrams of NiL1, Ni2L2, and Ni4L3 with respect to H2 are shown in the present invention.

[0045] Figure 18 The stability diagram of Ni4L3 of the present invention after long-term electrolysis for 72 hours at a voltage of -1.45V is shown.

[0046] Figure 19 The images show the UV-Vis spectra of Ni4L3 at different electrolysis times according to the present invention. Detailed Implementation

[0047] To facilitate understanding by those skilled in the art, the following description is provided in conjunction with embodiments and appendices. Figure 1-19 The invention will be further described below, and the content mentioned in the embodiments is not intended to limit the invention.

[0048] Example 1

[0049] Please see Figure 4-6As shown, a nickel complex based on 1,4,7,10-tetraazacyclododecane is disclosed, wherein the nickel complex is ([Ni(cyclen)Cl]Cl, [Ni(cyclen)Cl2Ni(cyclen)]Cl2, or [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; wherein ([Ni(cyclen)Cl]Cl is a mononuclear nickel complex, i.e., NiL1, L1 = [(cyclen)Cl]Cl; [Ni(cyclen)Cl2Ni(cyclen)]Cl2 is a binuclear nickel complex, i.e., Ni2L2, L2 = [(cyclen)Cl2(cyclen)]Cl2; and [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 is a tetranuclear nickel complex, i.e., Ni4L3, L3 = [(cyclen)(SCN)3(SCN)3(cyclen)]Cl2.

[0050] Materials and physical measurement

[0051] Elemental analysis of C, H, and N was performed using a PerkinElmer analyzer (model 240). Nuclear magnetic resonance analysis was performed using a Bruker AV-500 instrument. UV-Vis spectra of the samples were measured using a Hitachi U-3010 spectrometer. All electrochemical measurements and analyses 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 Brookhaven Zetapplus particle-scale instrument. Transmission electron microscopy (TEM) images and energy-dispersive X-ray (EDX) element imaging experiments were performed on a JEOL JEM-2100 microscope at an accelerating voltage of 200 kV. Electrochemical impedance spectroscopy (EIS) measurements were performed using a 0.010 M K3[Fe(CN)6] / K4[Fe(CN)6] (1:1) mixture as a redox probe in 0.1 M KCl solution.

[0052] X-ray crystallography was used to determine the structure of nickel complexes.

[0053] The equipment used contains monochromatic Mo-Kα radiation from graphite (= Measurements and analysis were performed using a Bruker Smart APEX II Duo area detector. Empirical absorption corrections were then performed using SADABS software. The structure was decomposed using a direct method, and the corresponding non-hydrogen atoms were refined using the XL refinement package. All calNilations were performed using Olex2 structure software. Hydrogen atoms on carbon atoms were geometrically generated and refined isotropically, while non-hydrogen atoms were refined anisotropically.

[0054] Table 1. Crystal data and structural refinement parameters of the complex [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2

[0055]

[0056] Table 2. Crystal data and structural refinement parameters of the complex [Ni(cyen)Cl2Ni(cyen)]Cl2

[0057]

[0058]

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

[0060]

[0061]

[0062] Example 2

[0063] like Figure 3 As shown, the preparation method of [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2 includes the following steps:

[0064] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0065] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0066] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0067] Step 4: Add 3.0 mmol KSCN to the mixed solution in Step 3, place it in a nitrogen atmosphere at room temperature, and filter and collect the solid after a few days to obtain [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; yield (0.912 g, 68.13%).

[0068] like Figure 6As shown, in the [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2, the nickel atoms are bonded to the four nitrogen atoms of 1,4,7,10-tetraazacyclododecane and the nitrogen atom of the SCN atom, respectively; the sulfur atom of the SCN atom is bonded to the nickel center of Ni(SCN)4, ultimately synthesizing a macrocyclic complex with four nickel atoms linked by thiocyanate; the bond length between the nitrogen atom and the nickel center is... Between, the Ni(1)-NCS bond distance is

[0069] Example 3

[0070] like Figure 2 As shown, the preparation method of [Ni(cyclen)Cl2Ni(cyclen)]Cl2 includes the following steps:

[0071] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0072] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0073] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0074] Step 4: Add 4 mL of DMF (dimethylformamide) to the mixed solution in Step 3, place it in a nitrogen atmosphere at 0 °C, and collect the solid after a few days by filtration to obtain [Ni(cyclen)Cl2Ni(cyclen)]Cl2; yield (0.612 g, 82.28%).

[0075] like Figure 5 As shown, in the [Ni(cyclen)Cl2Ni(cyclen)]Cl2, the nickel atom is bonded to four nitrogen atoms and two chlorine atoms of 1,4,7,10-tetraazacyclododecane, wherein the bond length between the nitrogen atom and the nickel center is [missing information]. The bond distance of Ni(1)-Cl is

[0076] Example 4

[0077] like Figure 1 As shown, the preparation method of [Ni(cyclen)Cl]Cl includes the following steps:

[0078] Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl·6H2O solution.

[0079] Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution.

[0080] Step 3: Then, the NiCl·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 1 to obtain a mixed solution;

[0081] Step 4: Add 4 mL of DMF (dimethylformamide) to the mixed solution in Step 3, place it in an air atmosphere at room temperature, and filter and collect the solid after a few days to obtain [Ni(cyclen)Cl]Cl; yield (0.3596, 87.77%).

[0082] like Figure 4 As shown, in the [Ni(cyclen)Cl]Cl, the nickel atom is bonded to four nitrogen atoms and one chlorine atom; the bond length between the nitrogen atom and the nickel center is... Between; Ni(1)-Cl bond distance is

[0083] Example 5

[0084] The above-mentioned nickel complexes based on 1,4,7,10-tetraazacyclododecane are used in electrocatalysis;

[0085] like Figure 7 As shown, NiL1, Ni2L2 and Ni4L3 were first determined by cyclic voltammetry on a glassy carbon (GC) electrode in a N2-saturated tetrabutylammonium hexafluorophosphate (TBAPF6) DMF solution.

[0086] like Figure 7 As shown, a quasi-reversible redox peak was observed at -1.748 V (relative to Ag / AgNO3), corresponding to NiL1. II / I Yes, the redox peak is at 0.498V, because of the Ni in NiL1. III / Ni II .

[0087] Two quasi-reversible redox peaks were observed at -1.61 V and -1.85 V (relative to Ag / AgNO3), corresponding to Ni in Ni2L2. II / I The redox peaks at 0.46 V and 0.57 V can be attributed to Ni₂L₂.III / Ni II .

[0088] Two quasi-reversible redox peaks were observed at -1.01 V and -1.83 V (relative to Ag / AgNO3), corresponding to Ni4L3. II / I The redox peak at 0.36 V can be attributed to Ni₄L. III / Ni II .

[0089] It can be observed that the presence of bimetallic and polymetallic complexes leads to multiple reduction peaks and reduction shifts, indicating a decrease in the potential for excess hydrogen production.

[0090] Next, the catalytic performance of NiL1, Ni2L2, and Ni4L3 was tested using acetic acid as the proton source, and the results are as follows: Figure 8 As shown in (a). For Ni2L1, when acetic acid is added from 0.0 to 3.33 mM (proton source), the reduction peak shows a systematic increase, indicating that H2L1... + with Ni I Metal cores combine to form [Ni] I -H] + Peroxides, and "Ni II -H” coupling is consistent and can be formed in situ by protonating the original complex.

[0091] like Figure 8 (b) The addition of acetic acid to Ni4L3 resulted in an increase in peak current, consistent with the catalytic process, exhibiting catalytic behavior similar to that of Ni2L2. These results indicate that Ni (II) Reduced to Ni (I) Protonation is the reason for the production of hydrogen.

[0092] Combining these observations with known work, a possible mechanism for the catalytic cycle via proton reduction of hydrogen is proposed, such as... Figure 9 As shown.

[0093] like Figure 10 As shown, the CV plots of 0.1 mM NiL1, Ni2L2, and Ni4L3 of the present invention in neutral aqueous phosphate buffer solution at a scan rate of 50 mV / s on a GC electrode in the range of -2.0 to 2.0 V (relative to Ag / AgCl); the catalytic peak shifts to a higher potential, consistent with the catalytic process. Compared with mononuclear complexes, the reduction peak currents of binuclear and tetranuclear nickel complexes show a rightward shift, indicating that polynuclear complexes can reduce the overpotential for hydrogen production.

[0094] In the presence of NiL1, the reduction peak intensity was enhanced and the catalytic current peak was enhanced when the pH of the buffer solution decreased from 7.0 to 5, indicating that protons led to an improved catalytic hydrogen production process.

[0095] To further understand the electrocatalytic efficiency of NiL1, Ni2L2, and Ni4L3 in aqueous medium for hydrogen evolution, bulk electrolysis experiments were conducted using NiL1, Ni2L2, and Ni4L3 buffer solutions. The results are as follows: Figure 13 As shown: When a potential of -1.45V (relative to Ag / AgCl) is applied, in the absence of a complex, electrolysis of a neutral buffer solution (pH = 7.0) provides only 0.024C of charge during a 2-minute electrolysis period. Figure 11 As shown, the electrolysis of the buffer solution can provide 0.8C, 1.5C and 4.8C of charge under the same conditions after the addition of NiL1, Ni2L2 or Ni4L3, and the large amount of H2 measured by gas chromatography (GC) indicates that these three complexes are indeed effective hydrogen producers under these conditions, and the polynuclear nickel complexes have better hydrogen production catalytic performance than the mononuclear nickel complexes.

[0096] like Figure 12 As shown, when the overpotential (OP) is 837.6 mV, the transition frequency (TOF) of the NiL1 catalyst for hydrogen evolution is 956.44 mol / mol / h (mol H2 / mol catalyst / h); the TOF of the Ni2L2 catalyst is 1989.45 mol H2 / mol / h; and the TOF of the Ni4L3 catalyst is 2675.25 mol H2 / mol / h (mol H2 / mol catalyst / h). The results indicate that Ni2L2 and Ni4L3 exhibit high electrocatalytic activity for hydrogen production. This can be attributed to the fact that polynuclear nickel complexes are more likely to form vacancies at the nickel center than mononuclear nickel complexes, facilitating the binding of hydrogen protons and hydrogen evolution.

[0097] Table 4 presents the electrocatalytic data for hydrogen production from NiL1, Ni2L2, and Ni4L3 in an aqueous buffer solution, listing overpotential, turnover frequency (TOF), and molar hydrogen production data. The results indicate that the polynuclear nickel complexes of this invention exhibit significantly better catalytic performance than the mononuclear nickel complexes.

[0098] Table 4 shows the electrocatalytic data for hydrogen production from NiL1, Ni2L2, and Ni4L3 in aqueous buffer solution.

[0099]

[0100]

[0101] To further investigate the hydrogen production performance of the three complexes (NiL1, Ni2L2, and Ni4L3), the NiL1, Ni2L2, and Ni4L3 complexes were electrolyzed in a buffer solution at -1.45V for 1 hour (e.g., ...). Figure 14 The hydrogen content during the electrolysis process was measured using gas chromatography (GC), based on... 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.

[0102] 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).

[0103] 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 ).

[0104] 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. A nickel complex based on 1,4,7,10-tetraazacyclododecane, characterized in that: The nickel complex is [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2, and its molecular structure is as follows: .

2. The method for preparing nickel complexes based on 1,4,7,10-tetraazacyclododecane as described in claim 1, characterized in that: Includes the following steps: Step 1: Add 1.0 mmol of NiCl2·6H2O to 1 ml of methanol, stir thoroughly to dissolve, and obtain NiCl2·6H2O solution; Step 2: Add 1.0 mmol of 1,4,7,10-tetraazacyclododecane (cyclen) to 1 ml of methanol, stir thoroughly to dissolve and obtain a 1,4,7,10-tetraazacyclododecane (cyclen) solution; Step 3: Then, the NiCl2·6H2O solution from Step 1 is quickly added to the 1,4,7,10-tetraazacyclododecane solution from Step 2 to obtain a mixed solution; Step 4: Add 3.0 mmol KSCN to the mixed solution in Step 3, place it in a nitrogen atmosphere at room temperature, and filter and collect the solid after a few days to obtain [Ni(cyclen)(SCN)3Ni2(SCN)3Ni(cyclen)]Cl2; yield 68.13%.

3. The application of the nickel complex based on 1,4,7,10-tetraazacyclododecane as described in claim 1, characterized in that: The application is in electrocatalysis.

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