Nickel phthalocyanine molecular catalyst constructed on surface of oxygen-doped carbon material as well as preparation method and application of nickel phthalocyanine molecular catalyst

Abstract

The invention discloses a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material and a preparation method and application of the nickel phthalocyanine molecular catalyst, and belongs to the technical field of molecular catalysts, the nickel phthalocyanine molecular catalyst comprises a carbon material with the surface rich in oxygen-containing functional groups and NiPc molecules loaded on the surface of the carbon material, and the specific process comprises the steps that the carbon material is subjected to oxidation treatment to obtain the oxygen-doped carbon material; after washing and drying, adding into DMF together with NiPc molecules, and after fully stirring, washing and drying to obtain the NiPc / NiPc composite material. Based on an axial Ni-O coordination induced electron localization strategy, NiPc molecules are loaded on the surface of a carbon material rich in oxygen-containing functional groups, asymmetric coordination of NiN4 sites in the NiPc molecules is achieved, the adsorption and activation capacity of the NiPc molecules to O2 is improved, and then the activity and selectivity of a two-electron oxygen reduction reaction in the hydrogen peroxide synthesis process are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular catalysts, and particularly relates to a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] As an environmentally friendly and highly efficient oxidant, hydrogen peroxide (H2O2) is widely used in fields such as water purification, medical disinfection, bleaching, food processing, and chemical synthesis. Currently, the industrial production of hydrogen peroxide mainly uses the traditional energy-intensive anthraquinone method, with alkyl anthraquinone as a circulating carrier to indirectly synthesize hydrogen peroxide. However, there will be residual organic substances and alkyl anthraquinone in the process of producing hydrogen peroxide by the anthraquinone method, which limits the production of high-concentration hydrogen peroxide, and the implementation of the anthraquinone method requires large-scale and complex infrastructure.

[0003] In addition, synthesizing hydrogen peroxide through the two-electron oxygen reduction reaction (2e - -ORR) is one of the technologies that has the potential to replace the traditional anthraquinone process. However, the pathway of synthesizing hydrogen peroxide by 2e - -ORR competes with the pathway of generating water (H2O) by 4e - -ORR. Therefore, the key to promoting the electrocatalytic oxygen reduction (ORR) to synthesize H2O2 lies in preparing a catalyst with high selectivity and high activity.

[0004] Carbon materials have the advantages of rich reserves, low price, good conductivity, and controllable morphology. Currently, many studies have been carried out on the electrocatalytic oxygen reduction to synthesize H2O2 by using carbon materials such as graphite, carbon black, carbon felt, and carbon cloth as catalyst carriers. In view of this, the present invention synthesizes an efficient electrocatalyst for electrocatalytic oxygen reduction to synthesize hydrogen peroxide based on carbon materials, which has high two-electron oxygen reduction reaction activity and selectivity. Summary of the Invention

[0005] Aiming at the problems existing in the process of producing hydrogen peroxide by the traditional anthraquinone method, the present invention provides a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, a preparation method thereof, and an application thereof, realizing high selectivity for electrocatalytic two-electron oxygen reduction reaction to synthesize hydrogen peroxide at room temperature, while reducing the reaction overpotential. The preparation method is simple and controllable, and is suitable for industrial applications.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, comprising a carbon material and nickel phthalocyanine (NiPc) molecules loaded on the surface of the carbon material; wherein, the surface of the carbon material is rich in oxygen-containing functional groups.

[0008] Further, the carbon material is graphite, carbon black, porous carbon, carbon nanotubes, etc.

[0009] The preparation method of nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon material comprises the following steps:

[0010] Step 1, oxidizing the carbon material to enrich its surface with oxygen-containing functional groups to obtain an oxygen-doped carbon material;

[0011] Step 2, centrifugally washing the oxygen-doped carbon material to neutrality, and drying to obtain a carbon carrier;

[0012] Step 3, adding NiPc molecules and carbon carriers to nitrogen-dimethylformamide (DMF), and stirring thoroughly to obtain a suspension; wherein the mass volume ratio of NiPc molecules to DMF is 1-2:6-12 g / L; the mass volume ratio of carbon carriers to DMF is 3-5:3-6 g / L;

[0013] Step 4: washing the suspension and drying to obtain the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material.

[0014] Furthermore, in step 1, the carbon material is oxidized using a strong acid solution having oxidizing properties.

[0015] Furthermore, the strong acid solution with oxidizing properties is 10-15 mol / L sulfuric acid or nitric acid.

[0016] Furthermore, in step 1, the temperature of the oxidation treatment is 80-95° C., and the duration is 3-4 hours.

[0017] Furthermore, in step 2, the rotation speed of the centrifugal washing is 8000-12000 rpm, and the drying temperature is 80-100°C.

[0018] Furthermore, in step 3, the stirring time is 12 to 24 hours.

[0019] Furthermore, in step 4, anhydrous ethanol or DMF is used for washing, and the drying temperature is 80-100°C.

[0020] The present invention also provides an application of a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material as described in any of the above technical solutions or a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material obtained by the preparation method of any of the above technical solutions in the two-electron oxygen reduction reaction to prepare hydrogen peroxide.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials proposed by the present invention, its preparation method and application, based on the axial Ni-O coordination-induced electron localization strategy, load NiPc molecules on the surface of carbon materials rich in oxygen-containing functional groups, realize the asymmetric coordination of the NiN4 site in the NiPc molecule, improve the adsorption and activation ability of the NiPc molecule to O2, enable O2 to adsorb in an end-on mode, reduce the bond-breaking energy barrier of the O-O bond, and thus improve the activity and selectivity of the two-electron oxygen reduction reaction in the process of synthesizing hydrogen peroxide;

[0023] 2. Preferably, the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials prepared by the present invention can be in a flow-type reaction cell at a current density of -700 mA / cm 2 The Faraday efficiency (FE) of H2O2 exceeds 90%, and the partial current density of the corresponding H2O2 is -665 mA / cm 2 , and the reaction potential is only 0.152 V (vs. RHE) compared to the reversible hydrogen electrode scale, with excellent overall catalytic performance;

[0024] 3. The preparation method of the present invention is novel, simple and controllable, easy to implement, and suitable for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a high-resolution transmission electron microscope photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials obtained in Example 1 of the present invention;

[0027] Figure 2 It is a spherical aberration-corrected transmission electron microscope photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials obtained in Example 1 of the present invention;

[0028] Figure 3 It is an energy-dispersive X-ray spectrometer photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials obtained in Example 1 of the present invention;

[0029] Figure 4 It is a histogram of the selectivity of H2O2 of the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon materials obtained in Example 1 of the present invention under alkaline conditions in a flow-type reaction cell;

[0030] Figure 5The polarization curves of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in Example 1 of the present invention, the oxygen-doped carbon material catalyst without nickel phthalocyanine obtained in Comparative Example 1, and the nickel phthalocyanine molecular catalyst constructed on the surface of the pure carbon material obtained in Comparative Example 2 under alkaline conditions in a flow-type reaction cell. Detailed implementation manners

[0031] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0032] There are no particular restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared according to conventional methods well-known to those skilled in the art.

[0033] There are no particular restrictions on the purity of all raw materials of the present invention. The present invention preferably uses analytical pure or the conventional purity requirements in the field of atomic layer deposition.

[0034] For all raw materials and process procedures of the present invention, their trade names or abbreviations are all conventional trade names or abbreviations in the art, and each trade name or abbreviation is clear and definite in the field of its relevant uses. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the trade names, abbreviations and corresponding uses, or implement them using the corresponding equipment.

[0035] The present invention will be further described in detail below in conjunction with embodiments:

[0036] Example 1

[0037] In this example, a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material was prepared, which specifically included the following steps:

[0038] Step 1: Use 10 mol / L nitric acid to carry out reflux oxidation treatment on the porous carbon in a condenser at 85 °C for 3 h to make its surface rich in oxygen-containing functional groups, and obtain an oxygen-doped carbon material;

[0039] Step 2: Centrifuge and wash the oxygen-doped carbon material at a speed of 8000 rpm until it is neutral, and dry it in an oven at 80 °C to obtain a carbon carrier;

[0040] Step 3: Add 10 mg of NiPc molecules and 50 mg of the carbon carrier to 60 mL of DMF, and stir well for 24 h to obtain a suspension;

[0041] Step 4: Wash the suspension with absolute ethanol and dry it at 80 °C to obtain a nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material (abbreviated as NiPc-OC).

[0042] Figure 1This is a high-resolution transmission electron microscope photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example. It can be seen that there are no obvious clusters and particles on the material surface, indicating that the NiPc molecules may exist in the form of single molecules.

[0043] Figure 2 This is a spherical aberration corrected transmission electron microscope photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example. The metal single atom Ni in the prepared catalyst is uniformly distributed and has good dispersibility.

[0044] Figure 3 This is an energy dispersive X-ray spectrometer photograph of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example. It can be seen that the Ni element, C element, O element and N element are uniformly distributed in the catalyst, indicating that the oxygen-containing functional groups and NiPc molecules are uniformly distributed on the surface of the porous carbon.

[0045] Using a flow-type reaction cell, the performance of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example was tested under alkaline conditions.

[0046] Specifically, the flow-type reaction cell uses the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example as the cathode, nickel foam as the anode, mercury / mercuric oxide electrode as the reference electrode, the diaphragm used is a Nafion membrane, the cathode electrolyte and the anode electrolyte are both 1 mol / L potassium hydroxide solution, the flow rate of the electrolyte is 2 mL / min, and the flow rate of oxygen is 50 sccm. The test is carried out by the constant current method, and the applied current density range is -10~-700 mA / cm 2 。The obtained product is colored with titanium sulfate and detected by ultraviolet absorption spectroscopy to calculate the product concentration. Combining with the data of the electrochemical workstation, the Faraday efficiency of the product is obtained.

[0047] Figure 4 This is a histogram of the H2O2 selectivity of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in this example under alkaline conditions in a flow-type reaction cell. Specifically, the H2O2 Faraday efficiencies at 7 current densities of -100, -200, -300, -400, -500, -600, -700 mA / cm 2 were tested. It can be seen that the H2O2 selectivity higher than 80% was achieved at different current densities, and the catalytic performance is excellent.

[0048] Comparative Example 1

[0049] In this comparative example, an oxygen-doped carbon material catalyst without nickel phthalocyanine was prepared. The preparation process is as follows:

[0050] Step 1: Use 10 mol / L nitric acid to reflux and oxidize the porous carbon in a condenser at 85 °C for 3 h to make its surface rich in oxygen-containing functional groups, obtaining an oxygen-doped carbon material;

[0051] Step 2: Centrifuge and wash the oxygen-doped carbon material at a speed of 8000 rpm until it is neutral, and dry it in an oven at 80 °C to obtain an oxygen-doped carbon material catalyst without nickel phthalocyanine (abbreviated as OC).

[0052] Referring to the method of Example 1, use a flow-type reaction cell to test the performance of the obtained oxygen-doped carbon material catalyst without nickel phthalocyanine under alkaline conditions.

[0053] Comparative Example 2

[0054] This comparative example prepared a nickel phthalocyanine molecular catalyst (abbreviated as NiPc-Pure-C) constructed on the surface of a pure carbon material. The preparation process is as follows:

[0055] Step 1: Add 10 mg of NiPc molecules and 50 mg of porous carbon to 60 mL of DMF, and stir well for 24 h to obtain a suspension;

[0056] Step 2: Wash the suspension with absolute ethanol and dry it at 80 °C to obtain a nickel phthalocyanine molecular catalyst (abbreviated as NiPc-Pure-C) constructed on the surface of a pure carbon material.

[0057] Referring to the method of Example 1, use a flow-type reaction cell to test the performance of the obtained nickel phthalocyanine molecular catalyst constructed on the surface of a pure carbon material under alkaline conditions.

[0058] Figure 5 For the polarization curves of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in Example 1, the oxygen-doped carbon material catalyst without nickel phthalocyanine obtained in Comparative Example 1, and the nickel phthalocyanine molecular catalyst constructed on the surface of the pure carbon material obtained in Comparative Example 2 under alkaline conditions in a flow-type reaction cell, the partial current density of hydrogen peroxide at different potentials was obtained. Specifically, the following 9 current densities were tested: -100, -200, -300, -400, -500, -600, -700 mA / cm 2 These 9 current densities.

[0059] It can be seen from Figure 5 that at a current density of -700 mA / cm 2 the partial current density of the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in Example 1 for H2O2 is -665 mA / cm 2, the reaction potential is only 0.152 V (vs. RHE) compared to the reversible hydrogen electrode scale. Compared with the oxygen-doped carbon material catalyst without nickel phthalocyanine obtained in Comparative Example 1 and the nickel phthalocyanine molecular catalyst constructed on the surface of pure carbon material obtained in Comparative Example 2, the overall catalytic performance is excellent. In addition, at the same current density, the reaction overpotential of the oxygen-doped carbon material catalyst without nickel phthalocyanine obtained in Comparative Example 1 is greater, indicating that the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material obtained in Example 1 helps to reduce the reaction overpotential during the synthesis of H2O2.

[0060] Example 2

[0061] In this example, a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material was prepared. The preparation process was the same as that of Example 1, except that: the stirring duration in Step 3 was adjusted to 12 h; the other steps remained unchanged.

[0062] Example 3

[0063] In this example, a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material was prepared. The preparation process was the same as that of Example 1, except that: the molecular weight of NiPc in Step 3 was adjusted to 5 mg; the other steps remained unchanged.

[0064] The above is a detailed introduction to the nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, its preparation method and application proposed by the present invention. Specific examples are used in this article to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of this invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, characterized in that: It includes a carbon material with oxygen-containing functional groups on the surface, and NiPc molecules loaded on the surface of the carbon material.

2. A method for preparing a nickel phthalocyanine molecular catalyst constructed on the surface of an oxygen-doped carbon material, characterized in that: The following steps are involved: Step 1, oxidizing the carbon material to enrich its surface with oxygen-containing functional groups to obtain an oxygen-doped carbon material; Step 2, centrifugally washing the oxygen-doped carbon material to neutrality, and drying to obtain a carbon carrier; Step 3, adding NiPc molecules and carbon carriers to DMF, and stirring thoroughly to obtain a suspension; wherein the mass volume ratio of NiPc molecules to DMF is 1-2:6-12 g / L; the mass volume ratio of carbon carriers to DMF is 3-5:3-6 g / L; Step 4: washing the suspension and drying to obtain the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material.

3. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 2, characterized in that: In step 3, the stirring time is 12 to 24 hours.

4. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 2, characterized in that: The carbon material is graphite, carbon black, porous carbon or carbon nanotube.

5. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 2, characterized in that: In step 1, the carbon material is oxidized using a strong acid solution having oxidizing properties.

6. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 5, characterized in that: In step 1, the temperature of the oxidation treatment is 80-95° C. and the duration is 3-4 hours.

7. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 2, characterized in that: In step 2, the rotation speed of the centrifugal washing is 8000-12000 rpm, and the drying temperature is 80-100°C.

8. The method for preparing the nickel phthalocyanine molecular catalyst constructed on the surface of the oxygen-doped carbon material according to claim 2, characterized in that: In step 4, anhydrous ethanol or DMF is used for washing, and the drying temperature is 80-100°C.

9. Use of the nickel phthalocyanine molecular catalyst constructed on the surface of oxygen-doped carbon material obtained by the preparation method according to any one of claims 2 to 8 in the reaction of preparing hydrogen peroxide by two-electron oxygen reduction.

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