Alkaline-earth metal modified copper-loaded carbon catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to an alkaline earth metal modified copper-loaded carbon catalyst and a preparation method and application thereof.The alkaline earth metal modified copper-loaded carbon catalyst is prepared by adding an alkaline earth metal salt solution into PVP dispersion liquid containing CuCl2. 2H2O, drying the alkaline earth metal salt solution to obtain a solid precursor and then conducting pre-oxidation and calcination treatment on the solid precursor; and washing and finally drying to obtain the alkaline earth metal modified copper-loaded carbon catalyst. When the catalyst provided by the invention is used for electrically reducing CO2 into CH4, compared with a copper-loaded carbon catalyst which is not modified by an alkaline earth metal element, the catalyst provided by the invention can effectively relieve local pH change on the surface of an electrode in a CO2 reduction process, so that a C-C coupling reaction is inhibited, and efficient CO2 is electrically reduced into CH4.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to an alkaline earth metal modified copper-supported carbon catalyst and a preparation method and application thereof. Background Art

[0002] Electrocatalytic CO 2 Reduction (ECO 2 RR) is a method that can achieve CO 2 Conversion technologies that can convert renewable electricity and CO 2 The conversion of molecules into chemicals and energy for storage has become an important way to close the carbon cycle. 2 The core of RR technology lies in the preparation of efficient electrocatalysts. Based on the application of some advanced catalysts, ECO 2 RR technology has made significant progress in the selectivity, current density, overpotential, etc. of some specific products. 2 RR to CH 4 This is a research field with important application prospects. 2 It is of great significance to resource utilization, climate change mitigation and sustainable development.

[0003] Cu-based catalysts can be used as a class of catalysts to achieve CO 2 Deeply reduced electrode materials. In order to improve the catalytic performance of copper-based catalysts, researchers have conducted a lot of research and optimization work. 2 O catalyst, and successfully constructed a chemically bonded Ag-Cu 2 O boundary. Due to the interface confinement effect, it is beneficial to maintain the Ag-Cu 2 The Cu+ sites at the O boundary increase the active sites on the catalyst surface and improve its CO 2 The adsorption capacity of CO 2 During the reduction process, CH 4 Recently, Mg as an inert component has been used in ECO 2 Research in the field of RR found that its multivalent characteristics and small cation radius are related to *CO 2- The intermediates have stronger short-range interactions and are more likely to promote water dissociation. 2 The application in the field of RR has attracted widespread attention from researchers.

[0004] However, for CO 2 When reduced to multi-electron products, its technical indicators are still difficult to meet the requirements of large-scale use. Summary of the invention

[0005] The purpose of the present invention is to provide an alkaline earth metal modified copper-supported carbon catalyst and its preparation method and application. When the catalyst is used for electrocatalytic carbon dioxide reduction to produce methane, it is more conducive to the formation of the key intermediate *COOH than the copper-supported carbon catalyst, and it also effectively reduces the local pH of the catalyst surface during the reaction, inhibits the CC coupling reaction, and thus achieves CH 4 Highly selective generation.

[0006] To achieve the above object, the present invention provides a method for preparing an alkaline earth metal modified copper-supported carbon catalyst, comprising the following steps:

[0007] Polyvinyl pyrrolidone was added to N, N-dimethylformamide solution and stirred for a period of time to obtain dispersion A. CuCl 2 ·2H 2 O is dissolved in N, N-dimethylformamide solution to form dispersion B, and dispersion B is slowly added into dispersion A to form solution C;

[0008] dissolving an alkaline earth metal salt in deionized water to form a solution D;

[0009] Solution D was slowly added to solution C to form dispersion E;

[0010] The dispersion E was dried at 80°C to obtain a yellow-green solid powder;

[0011] The yellow-green solid powder is subjected to a pre-oxidation treatment, and then the obtained powder is calcined at a high temperature. After the powder is cooled, it is washed with deionized water and dried to finally obtain an alkaline earth metal-modified copper-supported carbon catalyst.

[0012] Among them, in “adding polyvinyl pyrrolidone to N, N-dimethylformamide solution and stirring for a period of time to obtain dispersion A, dissolving CuCl2·2H2O in N, N-dimethylformamide solution to form dispersion B, and slowly adding dispersion B to dispersion A to form solution C”;

[0013] 0.5 g of polyvinyl pyrrolidone was weighed and added to 1.8 mL of N, N-dimethylformamide solution, and stirred for 6 h to form dispersion A. 0.24 mmol CuCl2·2H2O was dissolved in 0.7 mL of N, N-dimethylformamide solution to form dispersion B. Dispersion B was slowly added to dispersion A to form solution C.

[0014] Wherein, in “dissolving an alkaline earth metal salt in deionized water to form a solution D”;

[0015] The amount of the alkaline earth metal salt used is 0.16 mmol.

[0016] Among them, in "pre-oxidation treatment of the obtained yellow-green solid powder, and then high-temperature calcination of the obtained powder, washing with deionized water and drying the powder after cooling, finally obtaining an alkaline earth metal modified copper-supported carbon catalyst";

[0017] During the pre-oxidation treatment, the air atmosphere was heated to 220°C at a rate of 1°C / min and kept at this temperature for 3 h. Then, N 2 The calcination temperature was increased to 550°C at a heating rate of 2°C / min and maintained for 5 h.

[0018] Among them, in "pre-oxidation treatment of the obtained yellow-green solid powder, and then high-temperature calcination of the obtained powder, washing with deionized water and drying the powder after cooling, finally obtaining an alkaline earth metal modified copper-supported carbon catalyst";

[0019] After the powder is cooled to room temperature, it is washed with deionized water to remove the metal salt that has not participated in the reaction, and dried overnight to obtain a solid powder.

[0020] Wherein, in “dissolving an alkaline earth metal salt in deionized water to form a solution D”;

[0021] The alkaline earth metal salt is at least one of alkaline earth metal nitrate, chloride and sulfate solutions.

[0022] Wherein, in “Solution D is slowly added to Solution C to form dispersion E”;

[0023] Solution D was added to solution C, stirred overnight, and allowed to stand for 2 h.

[0024] The present invention also comprises an alkaline earth metal modified copper-supported carbon catalyst, which is prepared by adopting the preparation method of the alkaline earth metal modified copper-supported carbon catalyst.

[0025] The present invention also includes an application of an alkaline earth metal modified copper-loaded carbon catalyst, which is used to electrocatalyze carbon dioxide reduction to produce methane.

[0026] The alkaline earth metal modified copper-supported carbon catalyst and its preparation method and application of the present invention have at least the following beneficial effects or advantages compared with the prior art:

[0027] The introduction of Mg component in Cu-based catalyst not only facilitates the formation of *COOH key intermediate, but also effectively reduces the local pH on the catalyst surface during the reaction, inhibiting the CC coupling reaction, thereby achieving CH 4 Among them, the alkaline earth metal modified copper supported carbon catalyst (Mg-Cu@C) can achieve 66.7% FE at -1.38V vs.RHE.CH4 and -238.3 mA cm -2 J CH4 In addition, the modification strategy of alkaline earth metals is also universal. The Cu-based catalysts modified by the second main group elements Ca and Ba are very effective for CH 4 This work reveals that the introduction of alkaline earth metals can effectively improve the interfacial pH of Cu-based catalysts and has a significant impact on the efficient CO 2 Electroreduction to CH 4 Plays a key role. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0029] Figure 1 It is the X-ray diffraction pattern of alkaline earth metal modified copper supported carbon catalyst and Cu@C catalyst.

[0030] Figure 2 This is a scanning electron microscope image of Cu@C and alkaline earth metal modified copper-supported carbon catalysts.

[0031] Figure 3 This is a transmission electron microscopy image of an alkaline earth metal-modified copper-supported carbon catalyst.

[0032] Figure 4 The best performance comparison of the prepared catalyst and the CH 4 Some current density comparisons.

[0033] Figure 5 The present invention is a flow chart of the preparation method of the alkaline earth metal modified copper supported carbon catalyst. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0035] Embodiment 1:

[0036] This example provides the preparation of Cu-supported C catalyst (Cu@C).

[0037] 0.5 g of polyvinyl pyrrolidone (PVP) was weighed and added to 1.8 mL of N, N-dimethylformamide (DMF) solution and stirred for 6 h to obtain dispersion A. Then, 0.24 mmol of CuCl 2 ·2H 2O was dissolved in 0.7 mL of DMF to form dispersion B; dispersion B was slowly added to dispersion A and stirred for 6 h to form a uniform solution C. Solution C was dried at 80 °C to obtain a yellow-green solid precursor. The precursor was then placed in a tube furnace for pre-oxidation treatment. The temperature was raised to 220 °C at a rate of 1 °C / min in an air atmosphere and kept for 3 h. N was then introduced into the tube furnace. 2 The calcination temperature was raised to 550°C at a heating rate of 2°C / min and kept for 5 hours. After cooling to room temperature, it was washed with deionized water to remove the metal salts that did not participate in the reaction. After drying, the Cu-loaded C catalyst was finally obtained.

[0038] Embodiment 2:

[0039] This example provides the preparation of Mg-modified Cu-supported C catalyst.

[0040] 0.5 g of polyvinyl pyrrolidone (PVP) was weighed and added to 1.8 mL of N, N-dimethylformamide (DMF) solution and stirred for 6 h to obtain dispersion A. Then, 0.24 mmol of CuCl 2 ·2H 2 O was dissolved in 0.7 mL of N,N-dimethylformamide (DMF) solution to form dispersion B. Dispersion B was slowly added to dispersion A and stirred for 6 h to form a uniform solution C. Finally, 0.16 mmol of MgSO 4 Add to 0.5 mL of deionized water to form solution D, and add solution D to solution C, stir overnight, and stand for 2 hours to form dispersion E. The prepared dispersion E was dried at 80 °C to obtain a yellow-green solid precursor. The precursor was then placed in a tube furnace for pre-oxidation treatment. The temperature was raised to 220 °C at a rate of 1 °C / min in an air atmosphere and kept for 3 hours. Then, N was introduced into the tube furnace. 2 The calcination temperature was raised to 550°C at a heating rate of 2°C / min and kept for 5 hours. After cooling to room temperature, it was washed with deionized water to remove the metal salts that did not participate in the reaction. After drying, the Mg-modified Cu-loaded C catalyst was finally obtained.

[0041] Embodiment 3:

[0042] This embodiment is the same as embodiment 2, except that the precursor is annealed at a calcination temperature of 450° C. to prepare a Mg-Cu@C composite catalyst (Mg-Cu@C-450).

[0043] Embodiment 4:

[0044] This embodiment is the same as the embodiment 3, except that the precursor is annealed at a calcination temperature of 650° C. to prepare a Mg-Cu@C composite catalyst (Mg-Cu@C-650).

[0045] Embodiment 5:

[0046] This example is the same as Example 2, except that the amount of the carbon carrier is changed. By changing the amount of PVP added (0.4 g), Mg-Cu@C composite catalysts (Mg-Cu@C-0.4) with different loading amounts are obtained.

[0047] Embodiment 6:

[0048] This example is the same as Example 5, except that the amount of the carbon carrier is changed. By changing the amount of PVP (0.6 g), Mg-Cu@C composite catalysts with different loading amounts (Mg-Cu@C-0.6) are obtained.

[0049] Embodiment 7:

[0050] This example provides the preparation of Ca-modified Cu-supported C catalyst.

[0051] 0.5 g of polyvinyl pyrrolidone (PVP) was weighed and added to 1.8 mL of N, N-dimethylformamide (DMF) solution and stirred for 6 h to obtain dispersion A. Then, 0.24 mmol of CuCl 2 ·2H 2 O was dissolved in 0.7 mL of N,N-dimethylformamide (DMF) solution to form dispersion B; dispersion B was slowly added to dispersion A and stirred for 6 h to form a uniform solution C; finally, 0.16 mmol of Ca source was added to 0.5 mL of deionized water to form solution D, and solution D was added to solution C, stirred overnight, and allowed to stand for 2 h to form dispersion E. The prepared dispersion E was dried at 80 °C to obtain a yellow-green solid precursor. The precursor was then placed in a tube furnace for pre-oxidation treatment, and the temperature was raised to 220 °C in an air atmosphere at a rate of 1 °C / min and kept for 3 h, and then N was introduced into the tube furnace. 2 The calcination temperature was raised to 550°C at a heating rate of 2°C / min and kept for 5 h. After cooling to room temperature, it was washed with deionized water to remove the metal salts that did not participate in the reaction. After drying, the Ca-modified Cu-loaded C catalyst was finally obtained.

[0052] Embodiment 8:

[0053] This example provides the preparation of Ba-modified Cu-supported C catalyst.

[0054] 0.5 g of polyvinyl pyrrolidone (PVP) was weighed and added to 1.8 mL of N, N-dimethylformamide (DMF) solution and stirred for 6 h to obtain dispersion A. Then, 0.24 mmol of CuCl 2 ·2H 2 O was dissolved in 0.7 mL of N,N-dimethylformamide (DMF) solution to form dispersion B; dispersion B was slowly added to dispersion A and stirred for 6 h to form a uniform solution C; finally, 0.16 mmol of Ba source was added to 0.5 mL of deionized water to form solution D, which was continued to be added to solution C, stirred overnight, and allowed to stand for 2 h to form dispersion E. The prepared dispersion E was dried at 80 °C to obtain a yellow-green solid precursor. The precursor was then placed in a tube furnace for pre-oxidation treatment, and the temperature was raised to 220 °C in an air atmosphere at a heating rate of 1 °C / min and kept for 3 h, and then N was introduced into the tube furnace. 2 The calcination temperature was raised to 550°C at a heating rate of 2°C / min and kept for 5 hours. After cooling to room temperature, it was washed with deionized water to remove the metal salts that did not participate in the reaction. After drying, the Ba-modified Cu-loaded C catalyst was finally obtained.

[0055] Figure 1 It is an X-ray diffraction diagram of an alkaline earth metal modified copper-supported carbon catalyst and a Cu@C catalyst; from the diagram, it can be seen that zero-valent and divalent copper exist simultaneously in the alkaline earth metal modified copper-supported carbon catalyst of the present invention.

[0056] Figure 2 It is a scanning electron microscope image of Cu@C and alkaline earth metal modified copper-supported carbon catalyst; it can be seen from the image that the alkaline earth metal modified copper-supported carbon catalyst of the present invention is block nanoparticles.

[0057] Figure 3 It is a transmission electron microscope image of an alkaline earth metal modified copper-supported carbon catalyst; it can be seen from the figure that the copper in the alkaline earth metal modified copper-supported carbon catalyst of the present invention is supported on the carbon carrier in the form of nanoparticles.

[0058] Figure 4 It is a comparison of the optimal performance of the prepared catalysts and a comparison of the CH4 partial current density of the prepared catalysts; it can be seen from the figure that the alkaline earth metal modified copper-loaded carbon catalyst of the present invention exhibits relatively excellent performance in the electrocatalytic reduction of carbon dioxide to methane.

[0059] Figure 5 The present invention is a flow chart of the preparation method of the alkaline earth metal modified copper supported carbon catalyst.

[0060] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A method for preparing an alkaline earth metal modified copper-supported carbon catalyst, characterized in that: The following steps are involved: Add polyvinyl pyrrolidone to N, N-dimethylformamide solution and stir for a period of time to obtain dispersion A, dissolve CuCl2·2H2O in N, N-dimethylformamide solution to form dispersion B, and slowly add dispersion B to dispersion A to form solution C; dissolving an alkaline earth metal salt in deionized water to form a solution D; Solution D was slowly added to solution C to form dispersion E; The dispersion E was dried at 80°C to obtain a yellow-green solid powder; The yellow-green solid powder is subjected to a pre-oxidation treatment, and then the obtained powder is calcined at a high temperature. After the powder is cooled, it is washed with deionized water and dried to finally obtain an alkaline earth metal-modified copper-supported carbon catalyst.

2. The method for preparing the alkaline earth metal modified copper-supported carbon catalyst according to claim 1, characterized in that: In "adding polyvinyl pyrrolidone to N, N-dimethylformamide solution and stirring for a period of time to obtain dispersion A, dissolving CuCl2·2H2O in N, N-dimethylformamide solution to form dispersion B, and slowly adding dispersion B to dispersion A to form solution C"; 0.5 g of polyvinyl pyrrolidone was weighed and added to 1.8 mL of N, N-dimethylformamide solution, and stirred for 6 h to form dispersion A. 0.24 mmol CuCl2·2H2O was dissolved in 0.7 mL of N, N-dimethylformamide solution to form dispersion B. Dispersion B was slowly added to dispersion A to form solution C.

3. The method for preparing the alkaline earth metal modified copper supported carbon catalyst according to claim 1, characterized in that: In "dissolving an alkaline earth metal salt in deionized water to form solution D"; The amount of the alkaline earth metal salt used is 0.16 mmol.

4. The method for preparing the alkaline earth metal modified copper supported carbon catalyst according to claim 1, characterized in that: In "pre-oxidizing the obtained yellow-green solid powder, then calcining the obtained powder at high temperature, washing the powder with deionized water and drying it after cooling, and finally obtaining an alkaline earth metal modified copper-supported carbon catalyst"; During the pre-oxidation treatment, the air atmosphere was heated to 220°C at a heating rate of 1°C / min and kept at this temperature for 3 hours. Then, N2 was introduced into the tubular furnace and the calcination temperature was increased to 550°C at a heating rate of 2°C / min and kept at this temperature for 5 hours.

5. The method for preparing the alkaline earth metal modified copper-supported carbon catalyst according to claim 4, characterized in that: In "pre-oxidizing the obtained yellow-green solid powder, then calcining the obtained powder at high temperature, washing the powder with deionized water and drying it after cooling, and finally obtaining an alkaline earth metal modified copper-supported carbon catalyst"; After the powder is cooled to room temperature, it is washed with deionized water to remove the metal salt that has not participated in the reaction, and dried overnight to obtain a solid powder.

6. The method for preparing the alkaline earth metal modified copper-supported carbon catalyst according to claim 5, characterized in that: In "dissolving an alkaline earth metal salt in deionized water to form solution D"; The alkaline earth metal salt is at least one of alkaline earth metal nitrate, chloride and sulfate solutions.

7. An alkaline earth metal modified copper-supported carbon catalyst, characterized in that: The catalyst is prepared by the method for preparing the alkaline earth metal-modified copper-supported carbon catalyst as described in any one of claims 1 to 6.

8. An application of an alkaline earth metal modified copper supported carbon catalyst, using the alkaline earth metal modified copper supported carbon catalyst as claimed in claim 7, characterized in that: Applied to electrocatalytic carbon dioxide reduction to produce methane.

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