Silver-doped MOF (Metal Organic Framework) derivative catalyst as well as preparation method and application thereof

Abstract

The invention discloses a synthesis method of a silver-doped MOF derivative catalyst composite material prepared on the basis of a copper-based organic metal framework material and application of the silver-doped MOF derivative catalyst composite material in preparation of acetaldehyde by electro-catalytic reduction of carbon dioxide. The silver-doped MOF derivative catalyst is synthesized mainly through a copper-based metal organic framework, and the silver-doped MOF derivative catalyst can be directly coated on a gas diffusion layer to be used as a cathode after being centrifuged by ethanol and deionized water and dried by nitrogen. The silver-doped MOF derivative catalyst is mainly applied to electrocatalytic carbon dioxide reduction, the synergistic effect between silver and copper particles in the silver-doped MOF derivative catalyst is fully utilized, and the acetaldehyde selectivity of the copper-based catalyst in electrochemical carbon dioxide reduction is improved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation and application of clean and sustainable new energy, and in particular relates to a silver-doped MOF-derived catalyst and a preparation method and application thereof. Background Art

[0002] With the progress of industrialization and the increase of human activities, the concentration of carbon dioxide (CO2) in the atmosphere has continued to rise, causing the problem of global warming. In order to meet this challenge, the international community has begun to work on reducing CO2 emissions and exploring CO2 reduction technologies in order to reduce the CO2 concentration in the environment and convert CO2 into usable renewable energy. Since the 1960s, more and more scientists have been committed to discovering catalysts for electrochemical carbon dioxide reduction and modifying them to have higher carbon dioxide conversion efficiency and better single product selectivity. Traditional electrocatalytic cathode materials such as metal copper, silver, gold and their oxides, although these materials have the potential to reduce CO2, still have certain disadvantages, such as difficulty in producing reduction products with longer carbon chains and poor product selectivity.

[0003] So far, there are many mature synthesis systems of metal organic framework compounds (MOF). However, the generally low conductivity and low stability of MOF in the electrocatalytic reaction process greatly limit the research and application of MOF in the electrocatalytic CO2 reduction reaction. Summary of the invention

[0004] The present invention provides a method for preparing a silver-doped MOF-derived catalyst, wherein the silver-doped MOF-derived catalyst composite material realizes efficient electroreduction of CO2 by reconstructing a highly active copper interface and preparing a silver-doped MOF-derived catalyst using a copper-based MOF material. This method demonstrates the potential of MOF in reconstructing a highly active copper interface and provides a new approach for the efficient conversion of CO2. In addition, the introduction of a second metal element (e.g., silver (Ag), gold (Au), and palladium (Pd)) enables the copper-based catalyst to convert CO2 into CO in a highly selective manner at a lower overpotential. The resulting CO then overflows to the nearby Cu site, where CO will be further reduced to C through a carbon-carbon (CC) coupling process. 2+ The product is the reduction product of more than two carbon atoms in the reduction of carbon dioxide. The composite material has the characteristics of simple preparation and high selectivity for acetaldehyde (CH3CHO).

[0005] The technical solution of the present invention is to provide a method for preparing a silver-doped MOF-derived catalyst, comprising the following steps:

[0006] 1) Preparing a copper-based organic metal framework compound;

[0007] 2) heating the copper-based organic metal framework compound to obtain a MOF-derived catalyst based on the copper-based organic metal framework compound;

[0008] 3) Preparation of silver-doped MOF-derived catalysts;

[0009] Further, in some embodiments of the present invention, preparing a copper-based organic metal framework compound comprises the following steps:

[0010] (1) Add anhydrous ethanol and dimethylformamide (DMF) (ratio 1:1) into a 250 mL beaker, then add 4.0 g of trimesic acid and stir until a transparent solution is obtained.

[0011] (2) Add 8.0 g of polyvinyl pyrrolidone to the transparent solution in step 1, stir at the same speed for 10 min, and then sonicate to obtain a transparent solution.

[0012] (3) Take another 250 mL beaker and add deionized water, then add copper salt to make a 0.8 M copper ion solution, and stir until a blue transparent solution is obtained.

[0013] (4) Add the transparent solution obtained in step 2 to the blue transparent solution in step 3 using a dropper and stir for 10 minutes.

[0014] (5) The blue solution obtained in step 4 was transferred to a reactor and hydroheated at 100°C for 6 h.

[0015] (6) Centrifuge the blue suspension obtained in step 5, remove the supernatant, and keep the blue precipitate. Wash and centrifuge three times with DMF, anhydrous ethanol, and deionized water respectively.

[0016] (7) The blue precipitate obtained by centrifugal washing was placed in a vacuum drying oven at 60° C. to obtain a copper-based organic metal framework compound (HKUST-1).

[0017] Furthermore, in some embodiments of the present invention, the specific operation of heating the copper-based organic metal framework compound (HKUST-1) is as follows: 8 g of HKUST-1 is placed in a clean porcelain boat, and then placed in a tubular furnace and introduced with a hydrogen-argon mixture for 1 hour, and then heated to 300° C. at a heating rate of 5° C. / min, and kept warm for 1 hour to obtain a MOF-derived catalyst based on HKUST-1.

[0018] Further, in some embodiments of the present invention, the specific operation method for preparing the silver-doped MOF-derived catalyst is as follows: take a 60 mL beaker, add deionized water and the MOF-derived catalyst, stir for 30 minutes in a CO atmosphere after ultrasonication, then add silver salt, and continue stirring for 30 minutes. The silver-doped MOF-derived catalyst is centrifuged, and after repeating the centrifugation operation three times, it is placed in a vacuum drying oven at 60°C to dry to obtain the silver-doped MOF-derived catalyst.

[0019] Beneficial effects of the present invention: a silver-doped MOF-derived catalyst is synthesized and used as a cathode for electrochemical catalytic carbon dioxide reduction. In terms of catalytic activity, due to the synergistic effect between copper and silver, the introduction of silver elements is conducive to increasing the CO concentration on the catalyst surface, and when these CO are transferred to nearby copper sites, the strong adsorption of copper on CO increases the possibility of CC coupling, thereby increasing the C 2+ Products, that is, the yield of reduction products with more than two carbon atoms in the reduction of carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a scanning electron microscope image (SEM) of Example 1.

[0021] Figure 2 This is the EDS image of Example 1.

[0022] Figure 3 This is the X-ray electron diffraction pattern (XRD) of Example 1.

[0023] Figure 4 It is the Faradaic Efficiency of the reduction product of electrochemical carbon dioxide reduction in 0.1 M potassium bicarbonate solution of Example 1.

[0024] Figure 5 It is the X-ray photoelectron spectroscopy (XPS) of various elements in Example 1. DETAILED DESCRIPTION

[0025] The following examples are used to further illustrate the present invention, and their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all parts by weight and weight percentages are used below.

[0026] The raw materials used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0027] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0029] Example 1

[0030] This embodiment prepares a silver-doped MOF-derived catalyst, specifically comprising the following steps:

[0031] (1) Add anhydrous ethanol and dimethylformamide (DMF) (ratio 1:1) into a 250 mL beaker, then add 4.0 g of trimesic acid and stir until a transparent solution is obtained.

[0032] (2) Add 8.0 g of polyvinyl pyrrolidone into the transparent solution in step 1, stir at the same speed for 10 min, and then sonicate to obtain a transparent solution.

[0033] (3) Take another 250 mL beaker and add deionized water, then add copper salt to make a 0.8 M copper ion solution, and stir until a blue transparent solution is obtained.

[0034] (4) Add the transparent solution obtained in step 2 to the blue transparent solution in step 3 using a dropper and stir for 10 minutes.

[0035] (5) The blue solution obtained in step 4 was transferred to a reactor and hydroheated at 100°C for 6 h.

[0036] (6) Centrifuge the blue suspension obtained in step 5, remove the supernatant, and leave the blue precipitate. Wash and centrifuge three times with DMF, anhydrous ethanol, and deionized water respectively.

[0037] (7) The blue precipitate obtained by centrifugal washing was placed in a vacuum drying oven at 60° C. to obtain a copper-based organic metal framework compound (HKUST-1).

[0038] (8) 8 g of HKUST-1 was placed in a clean porcelain boat, which was then placed in a tubular furnace and introduced with a hydrogen-argon mixture for 1 h. The furnace was then heated to 300 °C at a heating rate of 5 °C / min and kept at this temperature for 1 h to obtain a MOF-derived catalyst based on HKUST-1.

[0039] (9) Take a 60 mL beaker, add deionized water and MOF-derived catalyst, stir for 30 min under CO atmosphere after ultrasonication, then add silver salt and continue stirring for 30 min.

[0040] (10) The silver-doped MOF-derived catalyst was centrifuged, and the centrifugation operation was repeated three times, and then placed in a vacuum drying oven at 60° C. to obtain a silver-doped MOF-derived catalyst composite material.

[0041] Figure 1 This is a scanning electron microscope image (SEM) of the silver-doped MOF-derived catalyst prepared in this embodiment. It can be seen from the figure that the product is evenly distributed in the form of hexagonal micron-sized particles. It can be seen that the product maintains the structure of MOF, and the overall size is between 1μm-4μm.

[0042] Figure 2 is the EDS of the silver-doped MOF-derived catalyst prepared in this example. Figure 3 This is the X-ray electron diffraction pattern (XRD) of this embodiment. It can be seen from the figure that there are copper and silver elements, which are evenly dispersed and assembled from amorphous carbon. Figure 1 Hexagonal micron-sized particles.

[0043] Figure 5 This is the X-ray photoelectron spectrum (XPS) of this embodiment. It can be seen that the copper element has obvious valence state changes and electron transfer. The introduction of silver element causes the binding energy of copper to shift toward the direction of high binding energy, and the valence state increases.

[0044] The silver-doped MOF-derived catalyst obtained in Example 1 was directly used as a cathode for electrochemical CO2 reduction, and the test solution was 0.1M potassium bicarbonate. The prepared electrode was a working electrode, the Ag / AgCl electrode was a reference electrode, and the Pt sheet was a counter electrode to form a three-electrode system. Before the electrochemical test, saturated CO2 was introduced to achieve saturation. The Faradaic efficiency of this example can be used to compare the selectivity of the reduction products. Figure 4 It can be seen that when the voltage is -0.8 V, the Faraday efficiency of acetaldehyde reaches a peak value (43%) and becomes the main reduction product.

[0045] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the protection scope of the present invention.

[0046] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing a silver-doped MOF-derived catalyst, characterized in that: The following steps are involved: 1) Preparing a copper-based organic metal framework compound; 2) heating the copper-based organic metal framework compound to obtain a MOF-derived catalyst based on the copper-based organic metal framework compound; 3) Preparation of silver-doped MOF-derived catalysts.

2. The preparation method according to claim 1, characterized in that: The preparation of the copper-based organic metal framework compound in step 1 comprises the following steps: 1) Add 4.0 g of trimesic acid into a mixed solution of anhydrous ethanol and dimethylformamide in a volume ratio of 1:1; 2) adding 8.0 g of polyvinyl pyrrolidone to the above solution and dissolving it to obtain solution A; 3) preparing a 0.8 M copper ion solution as solution B; 4) Add solution A dropwise into solution B and stir for 10 min to obtain solution C; 5) Solution C was reacted in a reactor at 100°C for 6 h to obtain a blue suspension; 6) Centrifuge the above blue suspension to obtain a blue precipitate; wash and centrifuge it three times with DMF, anhydrous ethanol, and deionized water respectively; 7) Drying the blue precipitate obtained by centrifugal washing to obtain a copper-based organic metal framework compound.

3. The preparation method according to claim 2, characterized in that: The drying refers to drying in a vacuum drying oven at 60°C.

4. The preparation method according to claim 1, characterized in that: The method for heating the copper-based organic metal framework compound in step 2 is to keep the temperature at 300° C. for 1 hour in a tubular furnace under a protective atmosphere.

5. The preparation method according to claim 1, characterized in that: The method for preparing the silver-doped MOF-derived catalyst described in step 3 is as follows: the MOF-derived catalyst and deionized water are sonicated, then stirred for 30 minutes under a CO atmosphere, a silver salt is added, and stirring is continued for 30 minutes.

6. A silver-doped MOF-derived catalyst prepared by the preparation method as claimed in claim 1.

7. Use of the silver-doped MOF-derived catalyst as claimed in claim 6 as a cathode for electrocatalytic carbon dioxide reduction.

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