Tetradentate complex based on a metal center cu connected to four nitrogen atoms and applications

Abstract

The present application relates to the technical field of transition metal complex catalysis, and particularly discloses a tetradentate complex based on a metal center Cu connected with four nitrogen atoms and application of the tetradentate complex in an oxygen reduction electrocatalyst; the present application forms a complex with an active site by preparing three different organic ligands under simple water bath conditions and performing coordination and combination with a Cu metal atom. The oxygen reduction activity of the complex is tested. The three complexes all exhibit good oxygen reduction activity in an alkaline environment and can effectively reduce the overpotential of ORR. By comparing the initial potential and half-wave potential of the three complexes, it can be seen that the oxygen reduction activity of the complex 3 is the highest among the three, and the complex 2 is the lowest among the three; the research results of the three complexes show the usability of the complex of the present application, and can provide another method and data support for developing transition metal catalysts under alkaline conditions.

Description

Technical Field

[0001] This invention relates to the field of transition metal complex catalysis technology, and particularly discloses a Cu-based metal-centered catalysis method.

[0002] Tetradentate complexes linked to four nitrogen atoms and their application in oxygen reduction electrocatalysts. Background Technology

[0003] Since their excellent physical and chemical properties, including high thermal conductivity, stability, high electrical conductivity, and unique electrical and optical properties, precious metals have been widely used in all aspects of social production and daily life. Precious metals include eight elements: iridium (Ir), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), platinum (Pt), gold (Au), and silver (Ag). Platinum, palladium, ruthenium, rhodium, iridium, and osmium, represented by platinum, are collectively known as the platinum group metals. Due to their scarcity and high prices, precious metals have historically served as currency, fulfilling financial functions. With the rapid development of national industry and science and technology, the industrial value of precious metals has become increasingly apparent, and the demand for them has grown accordingly, gradually occupying a significant place in industrial development.

[0004] Statistics show that approximately 25% of industrial products worldwide use precious metals. Therefore, precious metals are often referred to as "vitamins of modern industry." In the environmental field, due to their high catalyst activity, ability to catalyze at low temperatures, and high-temperature resistance, precious metal catalysts are used in automotive exhaust treatment and waste gas purification. In recent years, precious metal materials have been widely used as electrodes, heating elements, or dopants in gas sensors. In the field of catalysts, the use of precious metal materials is unparalleled. The performance of fuel electrodes depends on the electrode used; among precious metals, platinum electrodes are the most widely used, including Pt / C supported catalysts, Pt-Cr / C, Pt-V / C, and Pt / Ru multi-element catalysts. Platinum is currently the most common catalyst used for ORR in fuel cells and metal-air batteries, but its scalable use is limited due to its scarcity, high cost, and toxicity.

[0005] Given these issues, current research focuses on reducing the size of platinum nanoparticles; controlling the exposed plane (or shape) of Pt nanocrystals; or mixing platinum with other metals to form multimetallic nanocrystals with alloy, core-shell, branched, or anisotropic structures. Significant progress has been made in the research of Pt-based catalysts to date. However, none of these methods fundamentally solve the problem. Since all these measures utilize Pt to some extent, the demand for Pt will increase with the commercialization of fuel cell vehicles, while the supply of Pt will rapidly decline. Furthermore, alloying Pt with any metal will greatly increase the difficulty of platinum recovery and recycling. Therefore, these advances are still insufficient for the commercialization of fuel cell vehicles. Thus, the need to develop widely available catalysts with good oxygen reduction performance and low cost has become extremely urgent. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a tetradentate complex based on a metal center Cu and four nitrogen atoms connected together and its application in oxygen reduction electrocatalysts.

[0007] To achieve the above objectives, the present invention provides a tetradentate complex based on a metal center Cu connected to four nitrogen atoms, wherein the complex is CuN4C. 12 H 22 O2, CuN4C8H 22 .

[0008] Furthermore, the CuN4C 12 H 22 The method for preparing O2 includes the following steps:

[0009] Step (1): Slowly add 0.01 mol of diethyl oxalate to 2 mL of anhydrous ethanol, and then quickly add 0.03 mol of 2,2-dimethyl-1,3-propanediamine to 3 mL of anhydrous ethanol in an ice-water bath. After mixing them thoroughly, pour them into a three-necked beaker and stir until a transparent liquid is formed.

[0010] Step (2): Fix the three-necked flask in a constant temperature water bath and bathe it at 55°C for 60 minutes under reflux conditions; after the 60-minute water bath, cool it to room temperature to obtain the ligand.

[0011] Step (3): Weigh 1.26g of anhydrous copper sulfate and 0.64g of sodium hydroxide particles into 50mL of water to prepare a copper hydroxide suspension of 0.008mol / L;

[0012] Step (4): Pour the copper hydroxide suspension prepared in step (3) into a three-necked flask and react it with the ligand prepared in step (2) to carry out a coordination reaction; after stirring thoroughly and standing for 30 minutes, a light red solid is obtained, which is the complex CuN4C. 12 H 22 O2.

[0013] Furthermore, the CuN4C8H 22 The preparation method includes the following steps:

[0014] Step (1): Weigh 6.3g of anhydrous copper sulfate and 3.2g of sodium hydroxide particles into 50mL of water to prepare a 0.04mol / L copper hydroxide suspension;

[0015] (2) According to the molar ratio of Cu to N,N-dimethyl-I,I-ethylenediamine of 1.2:1, the copper hydroxide suspension from step (1) was poured into a three-necked flask and reacted with N,N-dimethyl-I,I-ethylenediamine for coordination reaction. After stirring thoroughly, it was allowed to stand for 30 minutes to obtain a dark blue solution and a brown solid. The solid-liquid mixture obtained above was separated by a vacuum filter. The liquid was divided into 5 equal portions, sealed, and placed in a 35°C constant temperature water bath for 1 day to obtain CuN4C8H with a crystalline structure. 22 Coordination compounds.

[0016] A second objective of this invention is to provide an application of the above-mentioned tetradentate complex based on a metal center Cu and four nitrogen atoms, wherein the application is in an oxygen reduction electrocatalyst.

[0017] The beneficial effects of this invention are:

[0018] 1. Two different planar tetradentate complexes based on a metal center Cu bonded to four nitrogen atoms were prepared under simple water bath conditions, forming complexes with active sites; their oxygen reduction activity was tested. Both complexes exhibited good oxygen reduction activity under alkaline conditions and could effectively reduce the overpotential of ORR;

[0019] 2. By comparing the onset potential and half-wave potential of the two complexes, it can be seen that the complex CuN4C8H 22 The oxygen reduction activity is higher than that of the complex CuN4C 12 H 22 O2 is high. Attached Figure Description

[0020] Figure 1 The complex CuN4C of this invention 12 H 22 The steps for synthesizing O2;

[0021] Figure 2The complex CuN4C8H of this invention 22 The synthesis steps;

[0022] Figure 3 The complex CuN4C8H is shown in Comparative Example 1 of this invention. 14 The steps for synthesizing O2;

[0023] Figure 4 The complex CuN4C of this invention 12 H 22 The molecular structure of O2;

[0024] Figure 5 The complex CuN4C8H of this invention 22 The molecular structure;

[0025] Figure 6 The complex CuN4C8H is shown in Comparative Example 1 of this invention. 14 The molecular structure of O2;

[0026] Figure 7 The complex CuN4C8H is shown in Comparative Example 1 of this invention. 14 High-resolution mass spectrometry characterization of O2 in water;

[0027] Figure 8 The complex CuN4C of this invention 12 H 22 High-resolution mass spectrometry characterization of O2 in water;

[0028] Figure 9 The complex CuN4C8H is shown in Comparative Example 1 of this invention. 14 Experimental (black) and simulated (red) XRD patterns of O2;

[0029] Figure 10 The complex CuN4C of this invention 12 H 22 Experimental (black) and simulated (red) XRD patterns of O2;

[0030] Figure 11 The complex CuN4C8H of this invention 22 Experimental (black) and simulated (red) XRD patterns;

[0031] Figure 12 The complex CuN4C8H of Comparative Example 1 of the present invention 14 XPS full spectrum of O2 (a), XPS fine spectrum of Cu (b);

[0032] Figure 13 The complex CuN4C of this invention 12 H 22XPS full spectrum of O2 (a), XPS fine spectrum of Cu (b);

[0033] Figure 14 The complex CuN4C8H of Comparative Example 1 of the present invention 14 Cyclic voltammogram (a) of O2 (0.005 g) in phosphate buffer solution (0.1 M phosphate buffer, pH = 7.5) at a scan rate of 0.05 V / s; complex CuN4C 12 H 22 O2 (0.0028 g) at a scan rate of 0.05 V / s, phosphate buffer solution (0.1 M)

[0034] Cyclic voltammogram (b) of phosphate buffer (pH = 6.6); complex CuN4C8H 22 Cyclic voltammogram (c) of phosphate buffer solution (0.1M phosphate buffer, pH=6.6) at a scan rate of 0.05V / s (0.0025g);

[0035] Figure 15 The complex CuN4C8H of Comparative Example 1 of the present invention 14 O2(a), complex CuN4C 12 H 22 O2(b), complex CuN4C8H 22 (c) Comparison of LSV of the three complexes under nitrogen / oxygen conditions: 0.1M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50mV / s, pH=8.0, platinum ring electrode potential=1.2V (vs. NHE);

[0036] Figure 16 (a) Comparison of PBS and LSV with three complexes: 0.1M phosphate solution

[0037] (NaH2PO4 and Na2HPO4), scan rate 50 mV / s, pH = 9, platinum ring electrode potential = 1.2 V (vs. NHE); rotation speed 1300 rpm. (b) is a partial enlarged view of the ring electrode part in Figure (a); (c) is a comparison of the hydrogen peroxide yield calculated by Equation 1 for PBS and the addition of three complexes; (d) is a comparison of the number of transferred electrons calculated by Equation 2 for PBS and the addition of three complexes.

[0038] Figure 17(a), (d), (g), and (j) in the figure are LSV comparison graphs of PBS with complex 1 (0.05g), complex 2 (0.0478g), and complex 3 (0.048g) in different alkaline environments: 0.1M phosphate solution (NaH2PO4 and Na2HPO4), scan rate 50mV / s, rotation speed 1300rpm, platinum ring electrode potential = 1.2V (vs. NHE); Figure 17 (b), (e), (h), and (k) in the figure are comparison graphs of hydrogen peroxide yields calculated using Equation 1 with the addition of the three complexes and PBS. Figure 17 (c), (f), (i), and (l) are comparison graphs showing the electron transfer numbers calculated using Equation 2 with the addition of the three complexes and PBS.

[0039] Figure 18 (a), (d), (g), and (j) in the figure are LSV comparison graphs of complex 1 (0.05 g), complex 2 (0.0478 g), and complex 3 (0.048 g) with PBS at different rotation speeds, respectively: 0.1 M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50 mV / s, pH=8, rotation speed set from 1000 rpm to 1700 rpm, platinum ring electrode potential = 1.2 V (vs. NHE); Figure 18 (b), (e), (h), and (k) in the figure are comparison charts of the corresponding hydrogen peroxide yields; Figure 18 (c), (f), (i), and (l) are comparison graphs showing the electron transfer numbers calculated using Equation 2 with the addition of the three complexes and PBS.

[0040] Figure 19 (a), (d), (g), and (j) in the figure are LSV comparison graphs of complex 1 (0.05 g), complex 2 (0.0478 g), and complex 3 (0.048 g) with PBS at different rotation speeds, respectively: 0.1 M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50 mV / s, pH = 9, rotation speed set from 1000 rpm to 1700 rpm, platinum ring electrode potential = 1.2 V (vs. NHE). Figure 19 (b), (e), (h), and (k) in the figure are comparison charts of the corresponding hydrogen peroxide yields; Figure 19 (c), (f), (i), and (l) are comparison graphs showing the electron transfer numbers calculated using Equation 2 with the addition of the three complexes and PBS.

[0041] Figure 20(a), (d), (g), and (j) in the figure are LSV comparison graphs of complex 1 (0.05 g), complex 2 (0.0478 g), and complex 3 (0.048 g) with PBS at different rotation speeds, respectively: 0.1 M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50 mV / s, pH = 10, rotation speed set from 1000 rpm to 1700 rpm, platinum ring electrode potential = 1.2 V (vs. NHE); Figure 20 (b), (e), (h), and (k) in the figure are comparison charts of the corresponding hydrogen peroxide yields; Figure 20 (c), (f), (i), and (l) are comparison graphs showing the electron transfer numbers calculated using Equation 2 with the addition of the three complexes and PBS.

[0042] Figure 21 (a), (d), (g), and (j) in the figure are LSV comparison graphs of complex 1 (0.05g), complex 2 (0.0478g), and complex 3 (0.048g) with PBS at different rotation speeds, respectively: 0.1M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50mV / s, pH=11, rotation speed set from 1000rpm to 1700rpm, platinum ring electrode potential = 1.2V (vs. NHE); Figure 21 (b), (e), (h), and (k) in the figure are comparison charts of the corresponding hydrogen peroxide yields; Figure 21 (c), (f), (i), and (l) are comparison graphs showing the electron transfer numbers calculated using Equation 2 with the addition of the three complexes and PBS.

[0043] Figure 22 (a), (d), (g), and (j) in the figure are LSV comparison graphs of complex 1 (0.05g), complex 2 (0.0478g), and complex 3 (0.048g) with PBS at different scanning speeds, respectively: 0.1M phosphate solution (NaH2PO4 and Na2HPO4), scan rate of 50mV / s, pH=12, scanning speed set from 1000rpm to 1700rpm, platinum ring electrode potential = 1.2V (vs. NHE); Figure 22 (b), (e), (h), and (k) in the figure are comparison charts of the corresponding hydrogen peroxide yields; Figure 22 (c), (f), (i), and (l) in the figure are comparison graphs of electron transfer numbers calculated by Equation 2 with the addition of the three complexes and PBS. Detailed Implementation

[0044] To facilitate understanding by those skilled in the art, the following description is provided in conjunction with embodiments and appendices. Figures 1-22 The invention will be further described below, and the content mentioned in the embodiments is not intended to limit the invention.

[0045] Example 1

[0046] like Figure 4 and Figure 5 As shown, this invention provides a tetradentate complex based on a metal center Cu connected to four nitrogen atoms, wherein the complex is CuN4C. 12 H 22 O2, CuN4C8H 22 .

[0047] Example 2

[0048] like Figure 1 As shown, the CuN4C 12 H 22 The method for preparing O2 includes the following steps:

[0049] Step (1): Slowly add 0.01 mol of diethyl oxalate to 2 mL of anhydrous ethanol, and then quickly add 0.03 mol of 2,2-dimethyl-1,3-propanediamine to 3 mL of anhydrous ethanol in an ice-water bath. After mixing them thoroughly, pour them into a three-necked beaker and stir until a transparent liquid is formed.

[0050] Step (2): Fix the three-necked flask in a constant temperature water bath and bathe it at 55°C for 60 minutes under reflux conditions; after the 60-minute water bath, cool it to room temperature to obtain the ligand.

[0051] Step (3): Weigh 1.26g of anhydrous copper sulfate and 0.64g of sodium hydroxide particles into 50mL of water to prepare a copper hydroxide suspension of 0.008mol / L;

[0052] Step (4): According to the molar ratio of Cu to ligand of 1.2:1, pour the copper hydroxide suspension prepared in step (3) into a three-necked flask and carry out a coordination reaction with the ligand prepared in step (2); after stirring thoroughly and standing for 30 minutes, a light red solid is obtained, which is the complex CuN4C. 12 H 22 O2.

[0053] Example 3

[0054] like Figure 2 As shown, the CuN4C8H 22 The preparation method includes the following steps:

[0055] Step (1): Weigh 6.3g of anhydrous copper sulfate and 3.2g of sodium hydroxide particles into 50mL of water to prepare a 0.04mol / L copper hydroxide suspension;

[0056] (2) According to the molar ratio of Cu to N,N-dimethyl-I,I-ethylenediamine of 1.2:1, the copper hydroxide suspension from step (1) was poured into a three-necked flask and reacted with N,N-dimethyl-I,I-ethylenediamine for coordination reaction. After stirring thoroughly and standing for 30 minutes, a solid-liquid mixture of a dark blue solution and a brown solid was obtained. The solid-liquid mixture was separated by a vacuum filter, and the liquid was divided into 5 equal portions. The portions were sealed and placed in a 35°C constant temperature water bath for 1 day to obtain CuN4C8H with a crystalline structure. 22 Coordination compounds.

[0057] Comparative Example 1

[0058] like Figure 3 As shown, the synthesis steps of the complex in Comparative Example 1 are as follows:

[0059] Step (1): Take 0.1 mol of diethyl oxalate and slowly add it to 20 mL of anhydrous ethanol. Then take 0.3 mol of 1,3-propanediamine and quickly add it to 30 mL of anhydrous ethanol in an ice-water bath. Mix them thoroughly separately and then pour them into a three-necked beaker for stirring and mixing. The mixture will appear as a white solid.

[0060] Step (2): Fix the three-necked flask in a constant temperature water bath and bathe it at 55°C for 60 minutes under reflux conditions. After the 60-minute water bath, cool it to room temperature to obtain the ligand.

[0061] Step (3): Weigh 12.6g of anhydrous copper sulfate and 6.4g of sodium hydroxide particles into 500mL of water to prepare a 0.08mol / L copper hydroxide suspension;

[0062] Step (4): According to the molar ratio of Cu to ligand of 1.2:1, pour the copper hydroxide suspension prepared in step (3) into a three-necked flask and carry out a coordination reaction with the ligand prepared in step (2). After stirring thoroughly, let it stand for 30 minutes to obtain a solid-liquid mixture of dark purple solution and brown solid.

[0063] Step (5): Separate the solid-liquid mixture obtained in step (4) using a vacuum filter. Divide the liquid into 50 equal portions, seal them, and place them in a 35°C constant temperature water bath for 3-5 days to obtain the complex CuN4C8H with a crystalline structure. 14 O2 (such as) Figure 6 (As shown).

[0064] For ease of explanation, the complex CuN4C8H in Comparative Example 1 will now be described. 14 O2 is labeled as complex 1, and complex CuN4C in Example 2. 12 H 22O2 is labeled as complex 2, and complex CuN4C8H in Example 2. 22 It is labeled as complex 3.

[0065] like Figures 4-6 As shown, the experimental principle of single-crystal X-ray diffraction is to determine the crystal structure by utilizing the diffraction effect of a single crystal on X-rays. To determine the crystal structure of the three synthesized complexes, single-crystal XRD tests were performed on them. The complex CuN4C... 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 The ball-and-stick model diagram and crystallographic data of O2 are respectively in Figures 4-6 As shown in Table 1, the combination with CuN4C... 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 O2 is a planar tetradentate complex consisting of a metal center Cu and four nitrogen atoms.

[0066] Table 1. Partial bond length and bond angle data for coordination compounds 1, 2, and 3.

[0067]

[0068] To study the complex CuN4C 12 H 22 O2, CuN4C8H 14 Whether O2 can exist stably in solution was determined by high-resolution mass spectrometry. 0.0001 g of the complex CuN4C8H was taken separately. 14 O2 and CuN4C 12 H 22 O2 was dissolved in 1.5 mL of water, and the data were obtained by high-resolution mass spectrometry. Figure 7 As shown: Complex CuN4C8H 14 The O2 signal is strongest at a mass-to-charge ratio m / z = 264.0640, and it interacts with the complex CuN4C8H. 14 The relative molecular mass of O2 matches, indicating that the complex CuN4C8H 14 O2 can exist stably in solution; due to Figure 8 As shown: Complex CuN4C 12 H 22 The O2 signal is strongest at a mass-to-charge ratio m / z = 320.1262, and it interacts with the complex CuN4C. 12 H 22 The relative molecular mass of O2 matches, indicating that the complex CuN4C 12 H 22O2 can exist stably in solution.

[0069] Complex CuN4C 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 X-ray diffraction (XRD) test of O2

[0070] The main function of XRD is to qualitatively determine and characterize solid materials, including grain size and indexing, and to determine the phase purity of synthesized complexes, such as... Figure 9 , Figure 10 , Figure 11 As shown, the complex CuN4C8H 14 O2, CuN4C 12 H 22 The positions of the measured diffraction peaks of O2 are basically consistent with those of the corresponding simulated diffraction peaks. Some differences may be due to the influence of the interaction between crystal planes caused by the stacking of crystal particles, i.e., the complex CuN4C 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 O2 has been successfully synthesized.

[0071] Complex CuN4C8H 14 O2, CuN4C 12 H 22 X-ray photoelectron spectroscopy (XPS) test of O2

[0072] XPS analysis was performed on the elemental composition and chemical valence state of complexes 1, 2, and 3, as well as the central metal Cu, to analyze their composition. Figure 12 (a) Figure 13 As shown in (a), the complex CuN4C8H 14 O2, CuN4C 12 H 22 O2 is composed of only four elements: C, N, O, and Cu. Figure 12 In (b): the double peaks at 931.5 eV and 951.6 eV correspond to Cu 2+ The double peaks of 2p3 / 2 and 2p1 / 2 spin-orbit splitting, corresponding to Cu at 941 eV and 960.4 eV. 2+ The accompanying peak corresponds to the ligand CuN4C8H. 14 O2 and metal ions Cu 2+ Electron transfer phenomena between them. For example... Figure 13 In (b): the double peaks at 931.5 eV and 951.5 eV correspond to Cu. 2+The double peaks of 2p3 / 2 and 2p1 / 2 spin-orbit splitting, corresponding to Cu at 941.5 eV and 960.8 eV, respectively. 2+ The accompanying peak corresponds to the ligand CuN4C. 12 H 22 O2 and metal ions Cu 2+ Electron transfer phenomenon between them.

[0073] Example 4

[0074] The above-mentioned application of tetradentate complexes based on the metal center Cu and four nitrogen atoms is in the application of oxygen reduction electrocatalysts.

[0075] Electrochemical performance characterization of coordination compounds

[0076] Cyclic Voltammetry (CV) Test

[0077] To investigate the complex CuN4C 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 To assess the ORR performance of O2, we performed a series of electrochemical characterizations. 0.025 g of the catalyst was dissolved in a 0.1 M phosphate solution (Ph = 6.6). A polished glassy carbon electrode was used as the working electrode, a platinum column electrode as the auxiliary electrode, and an Ag / AgCl electrode as the reference electrode. The three catalysts were tested according to standard operating procedures.

[0078] To compare the ORR performance of the three complexes, such as Figure 14 (a) Figure 14 (b) Figure 14 As shown in (c), we conducted cyclic voltammetry tests on the three complexes in phosphate buffered saline (PBS) containing 0.1 M phosphate (NaH₂PO₄ and Na₂HPO₄) to investigate their redox and catalytic behavior. Under N₂ (1 atm) conditions, a pair of redox peaks can be observed between 0.25 and -0.75 voltammetry, indicating a reversible Cu redox reaction. I / Cu II The redox reactions were observed. Under O2 (1 atmosphere) conditions, a significantly decreasing reduction peak appeared, with an onset potential of 0.7 V (vs. NHE). It can be seen that all three complexes exhibit a significant response to O2.

[0079] Linear sweep voltammetry (LSV) test

[0080] The test also used a three-electrode system, with a rotating ring-disk electrode (RRDE) as the working electrode in N2 / O2, 0.1M phosphate solution (NaH2PO4 and Na2HPO4) to test the complex CuN4C. 12 H 22 O2, CuN4C8H 22 CuN4C8H 14 ORR activity of O2 and its effect on 2e - / 4e - The selectivity of hydrogen peroxide generation was tested.

[0081] The electron transfer number (n) and H2O2 yield (H2O2%) during the ORR process are calculated according to the following equation:

[0082]

[0083]

[0084] Where I d For disk current, I r Given the ring current, the current collection efficiency of the Pt ring electrode is N(0.37).

[0085] First, LSV tests were performed on PBS and PBS with 1 / 2 / 3 of the complex added under N2 / O2 conditions, at a scan rate of 0.05V / s and a potential range of -0.3 to 0.9V (vs. NHE), with the loop voltage set to 1.2V (vs. NHE).

[0086] Depend on Figure 15 As shown in (a) to (c), it can be seen that the three complexes do not have obvious redox peaks under nitrogen conditions, but one or two pairs of redox peaks appear under oxygen conditions, which once again proves that the three complexes respond to oxygen.

[0087] Depend on Figure 16 As shown in (a), the initial potential (E) of complex 1 is obtained. onset =0.702V), half-wave potential (E) 1 / 2 =0.401V vs. NHE), complex 2 has the lowest activity and the lowest onset potential (E). onset =0.548V), half-wave potential (E) 1 / 2 =0.274V vs. NHE), with the final complex 3 exhibiting the highest activity and the highest onset potential (E). onset =0.716V), half-wave potential (E) 1 / 2 =0.627V vs. NHE), while the onset potential of PBS solution is only (E onset=0.515V), wave potential (E) 1 / 2 =0.2355V vs. NHE). This comparison shows that complex 3 exhibits higher ORR activity compared to the other two complexes. Complexes 1, 2, and 3 show the same trend on the LSV curves, with a certain increase in disk current within the potential range of 0.6 to -0.2V (vs. NHE). It can be seen that all three complexes have a catalytic effect on improving ORR activity. Figure 16 (b) shows the hydrogen peroxide yields of complexes 1, 2, and 3. From... Figure 16 As can be seen from (c) in the diagram, the number of electrons transferred in the phosphate solution is approximately 2.3, which indicates that the majority of the transfer is 2e. - The reduction process. The number of electrons transferred in complex 1 is approximately 3.7, indicating that the reduction primarily involves 4e electrons. - The reduction process. The electron transfer number of complex 2 is approximately 3.1, indicating that the reduction mainly occurs with 2e⁻. - Restoration and 4e - The reduction process. The electron transfer number of complex 3 is approximately 3.8, indicating that the reduction primarily occurs with 4e electrons. - The restoration process.

[0088] From the above Figure 17 From (a) to (l), we can obtain that as the pH value increases, the Ring current, the Disk current, and the hydrogen peroxide yield also increase; among which, from Figure 17 (a) Figure 17 (d) Figure 17 (g) in Figure 17 As shown in (j), the reaction initiation potentials of complexes 1, 2, and 3 with PBS shift positively with increasing pH. The magnitudes of the positive shifts for complexes 1, 2, and 3 are almost identical, indicating that the three complexes exhibit the same response trend to the ORR reaction under different alkaline conditions. The number of electrons transferred in the four different solutions does not change significantly with pH, ​​showing a similar overall trend.

[0089] From the above Figure 18 , Figure 19 , Figure 20 , Figure 21 , Figure 22 The LSV plots for each pH value show that, in PBS with the addition of complexes 1 and 3, the disk current increases with increasing rotation speed, while the ring current and hydrogen peroxide yield decrease. However, in the case of complex 2, the measured trend is different. With increasing rotation speed, the ring current, disk current, and hydrogen peroxide yield increase, and the number of transferred electrons in each solution increases slightly with increasing rotation speed.

[0090] This invention prepares three different organic ligands under simple water bath conditions and coordinates them with Cu metal atoms to form complexes with active sites. Their oxygen reduction (ORR) activities were then tested. All three complexes exhibited good ORR activity under alkaline conditions, effectively reducing the overpotential of ORR. Comparison of the onset potential and half-wave potential of the three complexes showed that complex 3 had the highest ORR activity, while complex 2 had the lowest.

[0091] The number of electrons transferred in each solution was calculated to determine the reaction that occurred. It can be seen that (1) in PBS solution, the reaction occurred stably regardless of changes in pH or rotation speed. - The reduction process is a two-electron reaction; (2) In the solution with added complex 1, the main reaction is 4e - The reduction process is a four-electron reaction; (3) In the solution with complex 2 added, the main reaction is 2e - Restoration and 4e - The reduction process involves both two-electron and four-electron reactions. It is significantly affected by pH; in various alkaline environments, the more alkaline the environment, the more pronounced the two-electron reaction. (4) In the solution with complex 3 added, the main reaction process involves 4e... - The reduction process is a four-electron reaction. In all four solutions, the number of electrons transferred decreases with increasing rotational speed and increasing alkalinity. The solution with complex 3 is least affected, while the solution with complex 2 is most affected. The other two solutions are not significantly affected. The results of these three complexes demonstrate the applicability of the complexes of this invention and provide another method and data support for the development of transition metal catalysts under alkaline conditions.

[0092] 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 tetradentate complex based on a metal center Cu bonded to four nitrogen atoms, characterized in that: The complex is CuN4C8H 22 Its molecular structure is: 。 2. The method for preparing a tetradentate complex based on a metal center Cu bonded to four nitrogen atoms as described in claim 1, characterized in that: Includes the following steps: Step (1): Weigh 6.3g of anhydrous copper sulfate and 3.2g of sodium hydroxide particles into 50mL of water to prepare a 0.04 mol / L copper hydroxide suspension; Step (2) According to the molar ratio of Cu to N,N-dimethyl-1,2-ethylenediamine of 1.2:1, the copper hydroxide suspension from step (1) was poured into a three-necked flask and reacted with N,N-dimethyl-1,2-ethylenediamine for coordination reaction. After stirring thoroughly, it was allowed to stand for 30 min to obtain a dark blue solution and a brown solid. Step (3) Separate the solid-liquid mixture obtained in step (2) using a vacuum filter. Divide the liquid into 5 equal portions, seal them, and place them in a 35°C constant temperature water bath for 1 day to obtain CuN4C8H with a crystalline structure. 22 Coordination compounds.

3. The application of the tetradentate complex based on the metal center Cu and four nitrogen atoms as described in claim 1, characterized in that: The application is in oxygen reduction electrocatalysts.

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