Preparation method and application of phthalazine-cobalt metal organic complex

Abstract

A preparation method and application of a phthalazine-cobalt metal-organic complex, which belong to the fields of energy and catalytic technology. The preparation method uses cobalt chloride hexahydrate and phthalazine as raw materials, and obtains the phthalazine-cobalt metal-organic complex through a simple in-situ mixing method, and uses it as a catalyst for photocatalytic and electrocatalytic water oxidation. In a borate buffer solution with a pH of 8.5, a three-component photocatalytic system composed of [Ru(bpy)3]Cl2 (bpy = 2,2'-bipyridine) and sodium persulfate is used to selectively oxidize water to form oxygen. At the same time, the phthalazine-cobalt metal-organic complex can also drive water oxidation in a three-electrode system formed by a silver / silver chloride electrode and a glassy carbon electrode. The preparation method of the phthalazine-cobalt metal-organic complex in the present invention is simple, the raw materials are cheap and easily available, and it is economical and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the field of energy and catalytic technology, and in particular to a preparation method of a phthalazine-cobalt metal organic complex and application thereof in photocatalytic and electrocatalytic water oxidation. Background Art

[0002] The development and utilization of new renewable energy sources have always been a topic of widespread concern. Hydrogen, as a high-energy carrier, has a high combustion calorific value and only produces water, which is favored by people. However, the energy source for producing hydrogen is still largely dependent on the combustion of fossil fuels, with low production efficiency and accompanied by a large amount of pollution and carbon emissions. By constructing an artificial photosynthesis system to absorb solar energy to decompose water to produce oxygen and hydrogen, not only can the production energy consumption be greatly reduced, but the entire production process can also be cyclically sustainable.

[0003] From the perspective of sustainable energy utilization, using the abundant water in the environment as a substrate and introducing photochemical catalysts or electrochemical catalysts to convert it can not only alleviate environmental problems, but also obtain hydrogen with higher added value, killing two birds with one stone. However, the current water oxidation molecular catalysts for water decomposition still have the following problems:

[0004] (1) This process is a complex process involving the transfer of four electrons and four protons, involving multiple intermediates and products, and has a high chemical energy barrier;

[0005] (2) Most of the highly active homogeneous molecular water oxidation catalysts reported so far are mainly based on precious metals such as Ru and Ir. Considering the cost and stability issues that have not been resolved, their practical applications are greatly limited;

[0006] (3) Many of the photocatalytic and electrocatalytic water oxidation catalysts reported so far have complex structures and cumbersome preparation processes, which also seriously limits their practical applications.

[0007] Therefore, it is very necessary to develop a molecular catalyst that is easy to prepare and has both photocatalytic and electrocatalytic water oxidation properties. Summary of the invention

[0008] In order to solve the above technical problems, the present invention aims to provide a method for preparing a phthalazine-cobalt metal organic complex and apply it to the photocatalytic and electrocatalytic water oxidation process. The catalyst can decompose water to produce oxygen under photocatalytic or electrocatalytic conditions and has a high oxygen production rate. At the same time, the catalyst preparation method is simple, the raw materials are cheap and easy to obtain, the energy consumption is low, and it has certain practical value.

[0009] In order to achieve the above object, the present invention adopts the following specific technical solutions:

[0010] One of the purposes of the present invention is a method for preparing a phthalazine-cobalt metal organic complex, comprising the following steps:

[0011] (a) preparing a borate buffer solution using boric acid and sodium tetraborate decahydrate, wherein the pH value of the buffer solution is 8.5;

[0012] (b) adding a soluble cobalt salt and phthalazine in a molar ratio of 1:2-4 to a borate buffer solution to obtain a phthalazine-cobalt metal organic complex with a concentration of 10-100 μM.

[0013] The cobalt salt is one or more of cobalt chloride, cobalt nitrate and cobalt sulfate.

[0014] The phthalazine-cobalt metal organic complex is applied to photocatalytic and electrocatalytic water oxidation reactions.

[0015] When applied to photocatalytic water oxidation reaction, phthalazine-cobalt metal organic complex is used as catalyst, [Ru(bpy) 3 ]Cl 2 As a photosensitizer, sodium persulfate acts as a sacrificial electron acceptor to form a photocatalytic oxygen production system.

[0016] The concentration of the phthalazine-cobalt metal organic complex in the photocatalytic oxygen production system is 10 to 100 μM; [Ru(bpy) 3 ]Cl 2 is 1-2mM, and sodium persulfate is 10-20mM.

[0017] When applied to photocatalytic water oxidation reaction, the light used is a monochromatic light source emitted by a 300W xenon lamp corrected by a 400nm filter.

[0018] When the phthalazine-cobalt metal organic complex is used as a catalyst in the electrocatalytic water oxidation reaction, a three-electrode system is adopted, with a glassy carbon electrode as a working electrode, a silver / silver chloride electrode as a reference electrode, and a platinum wire electrode as a counter electrode. The electrocatalytic water oxidation reaction is carried out in an electrolytic cell, and the target product is oxygen.

[0019] The second object of the present invention is a method for photocatalytic water oxidation, which comprises the following steps: 3 ]Cl 2 As a photosensitizer, sodium persulfate was mixed in situ as a sacrificial electron acceptor to form a reaction solution, and the oxygen production of photocatalytic water oxidation was measured at room temperature.

[0020] Preferably, the catalyst amount is 10 to 100 μM; [Ru(bpy) 3 ]Cl 2 1mM,Na 2 S 2 O 8The light refers to the monochromatic light source emitted by a 300W xenon lamp and corrected by a 400nm filter, and the reaction time is 30 to 60 minutes.

[0021] The third object of the present invention is a method for electrocatalytic water oxidation, which specifically comprises the following steps: using the above-prepared phthalazine-cobalt organic complex as an electrocatalyst, glassy carbon as a working electrode, a silver / silver chloride electrode as a reference electrode, a platinum wire electrode as a counter electrode, using an electrochemical workstation, carrying out an electrocatalytic water oxidation process in an electrolytic cell, and using kinetic equations for quantitative calculation.

[0022] Preferably, the reaction potential is -0.4 to 1.5 V vs. NHE, and the reaction temperature is 25 to 30° C. It should be noted that the potentials mentioned in the present invention are all relative to the standard electrode.

[0023] The fourth object of the present invention is the application of the phthalazine-cobalt metal organic complex: the phthalazine-cobalt metal organic complex is applied in the photocatalytic and electrocatalytic water oxidation process.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The method for preparing the phthalazine-cobalt metal organic complex disclosed in the present invention uses cobalt chloride hexahydrate and phthalazine as raw materials, prepares the phthalazine-cobalt metal organic complex by a simple one-step in-situ mixing method, uses a boric acid buffer solution as a buffer solution, and can be used in [Ru(bpy) 3 ]Cl 2 As a photosensitizer, Na 2 S 2 O 8 It can perform photocatalytic water oxidation in a three-component system with a glassy carbon electrode as an anode, silver / silver chloride as a reference electrode, and platinum wire as a counter electrode. The raw materials are cheap and easy to obtain, the preparation method is simple, the energy consumption is low, and it is easy to operate.

[0026] (2) The present invention is the first to use the prepared phthalazine-cobalt metal organic complex for photocatalytic water oxidation to produce oxygen, and the oxygen production conversion number obtained is 150, and the oxygen production conversion frequency of electrocatalytic water oxidation is 0.21s -1 , showing good photocatalytic and electrocatalytic activity; realizing resource utilization of water oxidation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the UV-visible absorption spectrum of the phthalazine-cobalt metal organic complex prepared in Example 1 of the present invention.

[0028] Figure 2This is the infrared spectrum of the phthalazine-cobalt metal organic complex prepared in Example 1 of the present invention.

[0029] Figure 3 This is the mass spectrum of the phthalazine-cobalt metal organic complex prepared in Example 1 of the present invention.

[0030] Figure 4 The figure is a presumed structural diagram of the phthalazine-cobalt metal organic complex prepared in Example 1 of the present invention.

[0031] Figure 5 This is a particle size distribution diagram of the phthalazine-cobalt metal organic complex prepared in Example 1 of the present invention in a photocatalytic system.

[0032] Figure 6 This is a graph of oxygen production conversion numbers of the phthalazine-cobalt metal organic complex under photocatalysis obtained from the tests in Example 1 and Examples 3-6 of the present invention.

[0033] Figure 7 This is a graph of oxygen production conversion numbers of the phthalazine-cobalt metal organic complex under photocatalysis obtained from the tests of Example 1 and Examples 7-9 in the present invention.

[0034] Figure 8 This is a cyclic voltammetry (CV) diagram obtained by testing in Example 10 of the present invention.

[0035] Fig. 9 This is a graph of the oxygen production conversion number obtained by testing in Example 10 of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0037] In the following examples, unless otherwise specified, the specific operating methods and testing methods designed are all conventional techniques, and the reagents, drugs, materials and instruments used can be obtained through commercial means.

[0038] Example 1

[0039] The preparation of phthalazine-cobalt metal organic complex comprises the following specific steps:

[0040] 5.456 g of boric acid and 3.672 g of sodium tetraborate decahydrate were weighed and dissolved in 1000 mL of deionized water, and the pH of the mixed solution was tested with a pH meter and accurately adjusted to 8.5. Subsequently, 0.00237 g of cobalt chloride hexahydrate (1 eq) and 0.0039 g of phthalazine (3 eq) were weighed and added to the solution to form a phthalazine-cobalt metal organic complex.

[0041] Example 2

[0042] Photocatalytic water oxidation, the target product is oxygen.

[0043] The present invention uses a gas chromatograph (Techcomp GC 7890T, argon carrier gas) to test the catalytic water oxidation performance of the phthalazine-cobalt metal organic complex. The phthalazine-cobalt metal organic complex in Example 1 is used as a photocatalyst and 1 mM [Ru(bpy) 3 ]Cl 2 As photosensitizer, 10mM Na 2 S 2 O 8 As the electron sacrificial acceptor, the photocatalytic water oxidation test was carried out using a CEL-HXF300 xenon lamp light source, and the reaction temperature was 25°C.

[0044] Embodiment 3-6

[0045] Photocatalytic experiments were conducted using metal organic complexes of different ratios of phthalazine-cobalt in-situ mixtures, with the molar ratios of phthalazine to cobalt chloride being 1:1 (Example 3), 2:1 (Example 4), 4:1 (Example 5), and 6:1 (Example 6). The remaining preparation methods were the same as in Example 1, and the test steps were the same as in Example 2.

[0046] Embodiment 7-9

[0047] The preparation method of Example 1 was adopted, except that the pH value of the borate buffer solution was 7.5 (Example 7), 8.0 (Example 8) and 9.0 (Example 9).

[0048] Example 10

[0049] The present invention uses an electrochemical workstation (Shanghai Chenhua CHI 630) to test the catalytic water oxidation performance of phthalazine-cobalt metal organic complex, using the phthalazine cobalt metal organic complex in Example 1 as an electrocatalyst. A glassy carbon electrode is used as an anode, silver / silver chloride is used as a reference electrode, and a platinum wire is used as a counter electrode. A CV scanning test is performed under homogeneous conditions, and the reaction temperature is 25°C.

[0050] The structure and application of the catalyst synthesized in the examples are analyzed:

[0051] Figure 1 This is the UV-visible spectrum of the phthalazine-cobalt metal organic complex prepared in Example 1. Compared with pure phthalazine, an obvious absorption peak appears at 500 nm, which is formed by the charge transfer between the metal and the ligand, indicating that the in-situ formed phthalazine-cobalt exists in the form of a metal organic complex. Figure 2 , Figure 3The infrared spectrum and mass spectrum of the phthalazine-cobalt metal organic complex prepared in Example 1 further verify the properties of the phthalazine-cobalt metal organic complex. Figure 4 This is a possible structural diagram of phthalazine-cobalt prepared in Example 1.

[0052] Figure 5 This is a particle size distribution diagram of the phthalazine-cobalt metal organic complex prepared in Example 1 in photocatalysis. It can be seen from the figure that no nanoparticles are detected in the system, indicating that the metal organic complex is not converted into cobalt oxide or cobalt hydroxide nanoparticles during the photoreaction process.

[0053] Figure 6 The CV graphs are obtained from the metal organic complexes prepared in Examples 1 and 3-6 by the method of Example 2 under the photocatalytic test conditions. It can be seen that the metal organic complexes formed by in-situ mixing of phthalazine and cobalt chloride in different molar ratios will also produce different catalytic activities. When the molar ratio of phthalazine to cobalt chloride is 2:1 and 3:1, the TON is relatively close, and the maximum TON value is 150 at 3:1.

[0054] Figure 7 The CV graphs are obtained from the metal organic complexes prepared in Examples 1 and 7-9 by the method of Example 2 under the photocatalytic test conditions. It can be seen that the metal organic complexes of phthalazine and cobalt chloride (3:1) mixed in situ will also produce different catalytic activities at different pH values. When the pH of the buffer solution is 8.5, the maximum TON value is 150.

[0055] Figure 8 : is the CV cycle curve obtained by the test of Example 10, from which it can be seen that the blank solution A without phthalazine-cobalt metal organic complex is basically undetectable in the electrolysis; while the solution B of phthalazine-cobalt (3:1) metal organic complex has an obvious water oxidation current.

[0056] Fig. 9 This is the electrocatalytic oxygen production rate diagram obtained from the test of Example 10. The water oxidation process catalyzed by the phthalazine-cobalt metal organic complex conforms to the Randles-Sevcik equation, which is a diffusion process and also a first-order kinetic reaction. The calculated oxygen production conversion frequency is 0.21s -1 .

[0057] The phthalazine-cobalt metal organic complex prepared by the invention has cheap and readily available raw materials, a simple preparation method, and has photocatalytic and electrocatalytic water oxidation activities, and has good application prospects.

Claims

1. A method for preparing a phthalazine-cobalt metal organic complex, characterized in that: The following steps are involved: (a) preparing a borate buffer solution using boric acid and sodium tetraborate decahydrate, wherein the pH value of the buffer solution is 8.5; (b) adding a soluble cobalt salt and phthalazine in a molar ratio of 1:2-4 to a borate buffer solution to obtain a phthalazine-cobalt metal organic complex with a concentration of 10-100 μM; the cobalt salt is cobalt chloride; The structure of phthalazine-cobalt metal organic complex is: 。 2. The use of the phthalazine-cobalt metal organic complex prepared by the method of claim 1, characterized in that: The phthalazine-cobalt metal organic complex is applied to photocatalytic and electrocatalytic water oxidation reactions.

3. The use of the phthalazine-cobalt metal organic complex according to claim 2, characterized in that: When applied to photocatalytic water oxidation reaction, phthalazine-cobalt metal organic complex is used as catalyst, [Ru(bpy)3]Cl2 is used as photosensitizer, and sodium persulfate is used as sacrificial electron acceptor to form a photocatalytic oxygen production system.

4. The use of the phthalazine-cobalt metal organic complex according to claim 3, characterized in that: The concentration of the phthalazine-cobalt metal organic complex in the photocatalytic oxygen production system is 10-100 μM; the concentration of [Ru(bpy)3]Cl2 is 1-2 mM, and the concentration of sodium persulfate is 10-20 mM.

5. The use of the phthalazine-cobalt metal organic complex according to claim 2, characterized in that: When applied to photocatalytic water oxidation reaction, the light used is a monochromatic light source emitted by a 300W xenon lamp corrected by a 400nm filter.

6. The use of the phthalazine-cobalt metal organic complex according to claim 2, characterized in that: When the phthalazine-cobalt metal organic complex is used as a catalyst in the electrocatalytic water oxidation reaction, a three-electrode system is adopted, with a glassy carbon electrode as a working electrode, a silver / silver chloride electrode as a reference electrode, and a platinum wire electrode as a counter electrode. The electrocatalytic water oxidation reaction is carried out in an electrolytic cell, and the target product is oxygen.

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