Preparation method of CuAg-coated NTA catalyst and application of CuAg-coated NTA catalyst in electro-catalysis of CO2RR

Abstract

The invention belongs to the technical field of nano composite materials, relates to an electrocatalytic carbon dioxide reduction electrode material, and relates to a preparation method of a CuAg-coated NTA (nitrilotriacetic acid) catalyst, which comprises the following steps: ultrasonically dispersing disodium nitrilotriacetate NTA, concentrated sulfuric acid and water uniformly, sequentially adding soluble silver salt and soluble copper salt, and uniformly stirring; taking the obtained mixed solution as an electrolyte, preparing a catalyst by adopting an electro-deposition mode, and performing vacuum drying to obtain the catalyst. The adopted constant-voltage electro-deposition preparation process has remarkable technical economy, and the three-dimensional morphology of the dendritic crystal can be accurately regulated and controlled by adjusting process parameters; the preparation conditions are mild, the synthesis time is shortened, NTA in-situ modification and structure forming are completed synchronously, and active site coverage caused by a post-modification process is avoided. The catalyst prepared according to the method provided by the invention still keeps 70% ethanol selectivity and more than 300 hours stability under the industrial current density of-250 mA cm <-2 >, and shows the outstanding advantage of industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocomposites, relates to an electrocatalytic carbon dioxide reduction electrode material, and particularly relates to a preparation method of a nitrilotriacetic acid-coated CuAg tandem (CuAg@NTA) catalyst and its application in electrocatalytic CO 2 RR. Background Art

[0002] The electrocatalytic carbon dioxide (CO 2 ), reduction reaction (CO 2 RR) to convert CO 2 into valuable chemicals and fuels is a promising approach to promote the storage and transportation of renewable energy and provides solutions to urgent energy and environmental challenges. Among them, compared with single-carbon (C 1 ) products, multi-carbon (C 2+ ) products are more attractive due to their higher energy density and economic value per unit mass. Currently, significant progress has been made in the electrocatalytic conversion of CO 2 to C 2+ products such as ethylene (C 2 H 4 ) and ethanol (C 2 H 5 OH), but the research focus still mainly concentrates on the production of C 2 H 4 . This situation occurs because the stability of the C 2 H 5 OH intermediate *CH 3 CH 2 O on the catalyst surface is relatively lower than that of the ethylene intermediate *C 2 H 4 . In addition, C 2 H 4 and C 2 H 5 OH share a key intermediate *CH 2 CHO. At this stage, there is a fierce competition between further hydrogenation to form C 2 H 5 OH and the cleavage of the C-O bond to form C 2 H 4 . Therefore, designing and constructing a catalyst that can efficiently and stably reduce CO 2 to C 2 H 5 OH at industrial current density is still a huge challenge.

[0003] In recent years, many studies have reported efforts aimed at enhancing the conversion of CO 2 to C 2 H5 Various methods and strategies for the electrochemical reduction of OH. These efforts include modulating the oxidation state of the metal, utilizing tandem strategies, adjusting the metal content on the catalyst surface, and functionalizing the catalyst surface. Unfortunately, at high current densities, the electrocatalytic reaction at the gas-liquid-solid three-phase interface of the gas diffusion / membrane electrode is accompanied by structural and phase changes in the catalyst, which significantly reduces the selectivity and stability of the conversion of CO 2 RR to C 2 H 5 OH. Therefore, the design and development of stable catalysts with high C 2 H 5 OH selectivity has always been a key goal for researchers. However, so far, there has not been an ideal catalyst that can continuously reduce CO C2H5OH to C 2 with a high Faraday efficiency (FE 2 H 5 OH) at an industrial current density for 150 h. Summary of the Invention

[0004] To solve the existing technical problems in the CO 2 RR to C 2 H 5 OH, including suppressing hydrogen evolution at industrial current densities and improving the selectivity, stability of CO 2 RR to C 2 H 5 OH, and the stability of the catalyst during long-term testing, etc., the present invention discloses a CuAg@NTA catalyst prepared by electrodeposition, which is an organic small molecule-wrapped CuAg tandem catalytic core.

[0005] Technical Solution

[0006] A method for preparing a CuAg@NTA catalyst, comprising: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid, and water uniformly, and successively adding soluble silver salt and soluble copper salt and stirring evenly; using the obtained mixed solution as an electrolyte, preparing the catalyst by electrodeposition, and obtaining the CuAg@NTA catalyst after vacuum drying.

[0007] In a preferred embodiment of the present invention, the soluble silver salt is silver nitrate.

[0008] In a preferred embodiment of the present invention, the soluble copper salt is copper nitrate.

[0009] In a preferred disclosed example of the present invention, the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, soluble silver salt and copper salt participating in the reaction is 0.5 - 5 mmol: 1 - 2 mL: 40 mL: 0.1 - 1 mmol: 0.05 - 0.5 mmol, preferably 2 mmol: 1 mL: 40 mL: 0.5 mmol: 0.5 mmol.

[0010] In a preferred disclosed example of the present invention, the concentration of concentrated sulfuric acid is 98%.

[0011] In a preferred disclosed example of the present invention, the electro-deposition process parameters are voltage -0.5 to -3 V RHE, time 10 - 60 s, preferably voltage -1 V RHE, time 50 s.

[0012] In a preferred disclosed example of the present invention, the temperature of vacuum drying is 60 - 70 °C, the drying time is 10 - 30 min, preferably 60 °C, drying time 30 min.

[0013] The CuAg@NTA catalyst prepared by the method according to the present invention has a morphology of CuAg in series wrapped by nitrilotriacetic acid, presenting a dendritic morphology, having a pore structure similar to that of disodium nitrilotriacetate, and the pore diameter is 1 - 5 nm.

[0014] An X-ray diffractometer (XRD), a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and an electrochemical workstation are used to characterize its material and its CO 2 RR performance.

[0015] The second object of the present invention is to apply it to electrocatalytic CO 2 RR.

[0016] Experimental data show that the maximum ethanol Faraday efficiency (FE -2 ) of the CuAg@NTA catalyst at -250 mA cm C2H5OH is 87.21%, and the ethanol yield (Y C2H5OH ) is 1.80 mmol s -1 cm -2 .

[0017] In addition, after 300 h of stability test, FE C2H5OH remains above 70%.

[0018] The dendritic CuAg@NTA catalyst prepared by the electro - deposition method in the present invention forms a core - shell protection structure through the surface coating and modification of the CuAg bimetallic core by NTA. Compared with the physical mixing system of traditional tandem catalysts, this structural design realizes the regulation of the electronic structure of active centers through the coordination effect of NTA, and at the same time, its three - dimensional coating characteristics effectively isolate the direct erosion of the electrolyte on the active components, significantly improving the long - term operation stability of the catalyst in CO 2 RR. Tests show that the selectivity decay of ethanol is less than 20% after the catalyst operates at a current density of - 250 mA cm -2 for 300 hours, effectively solving the problem of insufficient stability of tandem catalysts or metal catalysts in the CO 2 RR process.

[0019] Micro - environment co - regulation mechanism: Breaking through the limitations of single - regulation by traditional surface modifiers, the carboxylic acid group (-COOH) and amino group (-NH-) in the NTA molecule form a synergistic effect of bifunctional sites. Among them, the negatively charged carboxylic acid group enriches CO 2 molecules through electrostatic interaction, increasing the local CO 2 concentration on the catalyst surface to 2 - 3 times that of the bulk solution; the amino group adjusts the adsorption strength of the *CO intermediate through hydrogen - bonding interaction, reduces the CO dimerization energy barrier, and promotes the C - C coupling path. The synergistic effect of the two enables the Faraday efficiency of ethanol to reach 87.21% at a current density of - 250 mA cm -2 , realizing the improvement of the selectivity of CO 2 RR to ethanol.

[0020] Beneficial effects

[0021] The constant - voltage electro - deposition preparation process adopted in the present invention has significant technical economy. By adjusting the process parameters, the three - dimensional morphology of dendrites can be precisely controlled; the preparation conditions are mild, and the synthesis time is shortened. The in - situ modification of NTA and the formation of the structure are completed simultaneously, avoiding the coverage of active sites caused by the post - modification process. The prepared catalyst still maintains 70% ethanol selectivity and a stability of more than 300 hours at an industrial current density of - 250 mA cm -2 , showing outstanding advantages for industrial applications. Description of the drawings

[0022] Figure 1 . XRD diffraction pattern of the CuAg@NTA catalyst prepared in Example 1;

[0023] Figure 2 . X - ray photoelectron spectroscopy analysis of the CuAg@NTA catalyst prepared in Example 1;

[0024] Figure 3. Synchrotron radiation analysis of the CuAg@NTA catalyst prepared in Example 1;

[0025] Figure 4 . Pore size distribution analysis of the CuAg@NTA catalyst prepared in Example 2;

[0026] Figure 5 . Infrared test analysis of the CuAg@NTA catalyst prepared in Example 2;

[0027] Figure 6 . Transmission image of the CuAg@NTA catalyst prepared in Example 3;

[0028] Figure 7 . FE of the CuAg@NTA catalyst prepared in Example 4 at different current densities C2+ ;

[0029] Figure 8 . FE of the CuAg@NTA catalyst prepared in Example 5 at different current densities C2H5OH ;

[0030] Figure 9 . 300-hour stability test of the CuAg@NTA catalyst prepared in Example 5 at a current density of -250 mA cm -2 ; Detailed implementation mode

[0031] The present invention will be described in detail below in conjunction with examples, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following examples.

[0032] Example 1

[0033] A preparation method of a CuAg@NTA catalyst includes: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid and water uniformly, and successively adding silver nitrate and copper nitrate and stirring evenly; using the obtained mixed solution as an electrolyte, -0.5 VRHE, the reaction time is 60 s each time, and the catalyst is prepared by electrodeposition. After vacuum drying at 60 °C for 30 min, the CuAg@NTA catalyst is obtained. Among them, the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, silver nitrate and copper nitrate participating in the reaction is 1 mmol: 1 mL: 40 mL: 0.1 mmol: 0.05 mmol.

[0034] As Figure 1 shown, for the sample CuAg@NTA obtained in this example, due to the encapsulation of NTA, the crystal structure of the tandem catalytic core cannot be accurately obtained;

[0035] As Figure 2As shown, the X-ray photoelectron spectroscopy of Cu in the sample CuAg@NTA obtained in this example shows the presence of Cu 1+ / 0 and Cu 2+ species, indicating that some Cu could not be reduced to the metallic state.

[0036] As Figure 3 shown, the extended X-ray absorption fine structure fitting results of the sample CuAg@NTA prepared in the present invention elucidate the presence of Cu-N and Cu-O bonds in the catalyst, which is beneficial to the stability of the catalytic core Cu.

[0037] Example 2

[0038] A preparation method of a CuAg@NTA catalyst includes: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid and water uniformly, and successively adding silver nitrate and copper nitrate and stirring evenly; using the obtained mixed solution as an electrolyte, -1 VRHE, the reaction time is 50 s each time, and the catalyst is prepared by electrodeposition. After vacuum drying at 60 °C for 30 min, the CuAg@NTA catalyst is obtained. Among them, the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, silver nitrate and copper nitrate participating in the reaction is 2 mmol: 1 mL: 40 mL: 0.5 mmol: 0.5 mmol.

[0039] As Figure 4 shown, Brunauer–Emmett–Teller (BET) analysis of the CuAg@NTA sample and NTA prepared in the present invention found that the pore structure of CuAg@NTA (3.83 nm) is very similar to that of NTA (3.46 nm). This indicates that after NTA modifies the CuAg tandem catalytic core, it is very likely to retain its own physical properties. The retention of this physical property provides favorable conditions for the adsorption of CO 2 and the transmission of CO 2 across NTA to the active center surface, and the retained pore structure provides a favorable pathway for the diffusion of the generated products.

[0040] As Figure 5 shown, Fourier transform infrared spectroscopy (FT-IR) analysis of the CuAg@NTA sample and NTA prepared in the present invention found that the CuAg@NTA catalyst contains -OH, -CH 2 , -CON-, C-H functional groups similar to those of NTA. This finding fully demonstrates the presence of NTA in the CuAg@NTA catalyst.

[0041] Example 3

[0042] A preparation method of a CuAg@NTA catalyst includes: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid and water uniformly, and successively adding silver nitrate and copper nitrate and stirring evenly; using the obtained mixed solution as an electrolyte, at -1.5 VRHE, with a reaction time of 30 s each time, preparing the catalyst by electrodeposition, and obtaining the CuAg@NTA catalyst after vacuum drying at 60°C for 30 min. Among them, the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, silver nitrate and copper nitrate participating in the reaction is 3 mmol: 2 mL: 40 mL: 1 mmol: 0.2 mmol.

[0043] As Figure 6 shown, the transmission image of the CuAg@NTA catalyst shows that the catalyst presents a dendritic structure, and the dendritic structures are interconnected. Such a structure can effectively increase the surface area of the catalyst to have sufficient contact area with CO 2 and the electrolyte to enhance the reaction activity of the catalyst. At the same time, it shows that the constant voltage electrodeposition method used in the present invention can effectively and stably prepare a uniform and consistent dendritic morphology.

[0044] Example 4

[0045] A preparation method of a CuAg@NTA catalyst includes: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid and water uniformly, and successively adding silver nitrate and copper nitrate and stirring evenly; using the obtained mixed solution as an electrolyte, at -2.0 VRHE, with a reaction time of 20 s each time, preparing the catalyst by electrodeposition, and obtaining the CuAg@NTA catalyst after vacuum drying at 60°C for 30 min. Among them, the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, silver nitrate and copper nitrate participating in the reaction is 4 mmol: 2 mL: 40 mL: 1 mmol: 0.5 mmol.

[0046] As Figure 7 shown, the CO -2 RR tests of the CuAg@NTA catalyst at current densities of -210, -230, -250, -270, -290 and -310 mA cm 2 show that its FE C2+ is 84.70%, 83.76%, 89.68%, 78.97%, 62.22% and 53.15% respectively. Among them, the maximum FE -2 is 89.68% at a current density of -250 mA cm C2+ , and as the current density increases, the FE C2+ gradually decreases, which is related to the increase in hydrogen evolution caused by the increase in current density.

[0047] AsFigure 8 As shown, the CuAg@NTA catalyst has a CO -2 at current densities of -210, -230, -250, -270, -290, and -310 mA cm 2 RR test shows that its FE C2H5OH is 82.61%, 80.90%, 87.21%, 77.57%, 47.82%, and 39.50% respectively. Among them, at a current density of -250 mA cm -2 shows the maximum FE C2H5OH of 87.21%, which is also the maximum FE at the current industrial density C2H5OH , and the ethanol yield (Y C2H5OH ) is 1.80 mmol s -1 cm -2 . And as the current density increases, the FE C2H5OH gradually decreases, which is related to the change in the Faraday efficiency of other products caused by the increase in the current density.

[0048] Example 5

[0049] A preparation method of a CuAg@NTA catalyst, comprising: ultrasonically dispersing disodium nitrilotriacetate (NTA), concentrated sulfuric acid, and water uniformly, and successively adding silver nitrate and copper nitrate and stirring evenly; using the obtained mixed solution as an electrolyte, -3.0 VRHE, the reaction time is 10 s each time, and the catalyst is prepared by electrodeposition. After vacuum drying at 60°C for 30 min, the CuAg@NTA catalyst is obtained, wherein the material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, silver nitrate, and copper nitrate participating in the reaction is 5 mmol: 2 mL: 40 mL: 1 mmol: 0.5 mmol.

[0050] As Figure 9 shown, the stability test of the CuAg@NTA catalyst at a current density of -250 mA cm -2 for 300 hours. During the stability test process, the FE C2H5OH always remains above 70%, and the minimum value is 71.21%. The FE C2+ always remains above 80%, and the maximum value is 90.99%. The excellent stability and selectivity of this catalyst at industrial current densities are mainly attributed to the encapsulation of NTA on the tandem catalytic core and the regulation of the reaction path.

[0051] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a CuAg@NTA catalyst, characterized in that: include: Disodium nitrilotriacetate (NTA), concentrated sulfuric acid and water are evenly dispersed by ultrasonication, and soluble silver salt and soluble copper salt are added successively and stirred evenly; the obtained mixed solution is used as an electrolyte, and a catalyst is prepared by electrodeposition, and after vacuum drying, a CuAg@NTA catalyst is obtained, wherein the soluble silver salt is silver nitrate, and the soluble copper salt is copper nitrate.

2. The method for preparing the CuAg@NTA catalyst according to claim 1, characterized in that: The material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, soluble silver salt and copper salt involved in the reaction is 0.5-5mmol:1-2mL:40mL: 0.1-1mmol: 0.05-0.5mmol.

3. The method for preparing the CuAg@NTA catalyst according to claim 2, characterized in that: The material ratio of disodium nitrilotriacetate, concentrated sulfuric acid, water, soluble silver salt and copper salt involved in the reaction is 2mmol:1mL:40mL:0.5mmol:0.5mmol.

4. The method for preparing the CuAg@NTA catalyst according to claim 1, characterized in that: The concentration of concentrated sulfuric acid is 98%.

5. The method for preparing the CuAg@NTA catalyst according to claim 1, characterized in that: The electrodeposition process parameters are voltage -0.5 to -3 V RHE and time 10 to 60 s.

6. The method for preparing the CuAg@NTA catalyst according to claim 5, characterized in that: The electrodeposition process parameters are voltage of -1 V RHE and time of 50 s.

7. The method for preparing the CuAg@NTA catalyst according to claim 1, characterized in that: The vacuum drying temperature is 60-70°C, and the drying time is 10-30 min, preferably 60°C, and the drying time is 30 min.

8. The CuAg@NTA catalyst prepared according to any one of claims 1 to 7.

9. The CuAg@NTA catalyst according to claim 8, characterized in that: The morphology is that CuAg wrapped in nitrilotriacetic acid is connected in series, showing a dendrite form, and has a similar pore structure to disodium nitrilotriacetate, with a pore diameter of 1 to 5 nm.

10. A use of the CuAg@NTA catalyst as claimed in claim 8 or 9, characterized in that: It is applied to electrocatalytic CO2RR.

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