Copper-nickel bimetallic series catalyst as well as preparation method and application thereof

Abstract

The invention discloses a copper-nickel bimetallic series catalyst and a preparation method and application thereof, and belongs to the technical field of electrochemical catalysts.The preparation method comprises the steps that in a magnetron sputtering cavity, graphene is placed in a quartz container and transferred to a sample introduction chamber, and after the sample introduction chamber is vacuumized to background pressure, the graphene is sent into a main chamber for sputtering deposition; the sample table rotates at the rotating speed of 10 rpm, a nickel target is used for sputtering deposition, it is ensured that metal atoms make full contact with graphene, finally, a stable graphene-loaded nickel monatomic catalyst Ni SAC is formed at the room temperature, then a copper target is used for sputtering deposition, it is ensured that clusters make full contact with graphene, and finally, the stable graphene-loaded copper nanoclusters Cu SCC are formed at the room temperature. After sputtering is completed, uncombined metal particles are washed with an ammonium persulfate aqueous solution, finally, a finished product of the copper-nickel bimetallic series catalyst is obtained through vacuum freeze drying, and the efficiency of preparing a C2 + product through CO2 electrochemical reduction can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical catalysts, and particularly relates to a copper-nickel bimetallic tandem catalyst and a preparation method and application thereof. BACKGROUND

[0002] The large-scale use of fossil energy in the modernization process has directly led to a sharp increase in the emission of greenhouse gases such as CO2, and the resulting climate change has become the primary factor threatening global ecological security. The electrochemical reduction of CO2 has become one of the most promising environmental protection strategies, which can not only effectively reduce CO2 emissions, but also store renewable electrical energy in the form of chemical energy in fuels. The reaction can generate a variety of products, and at present, one-carbon products (such as CO and HCOOH) are the main products, and the faradaic efficiency has reached nearly 100%. However, multi-carbon products (such as ethanol, ethylene, n-propanol, and acetone) are more attractive due to their higher energy density and commercial value. Despite the advantages, only a few C2 products such as ethylene and ethanol can achieve significant activity. For C3 products, it is more challenging to achieve high activity and high selectivity due to the complex reaction kinetics involving C1-C1 coupling and C1-C2 coupling. For example, most of the reported faradaic efficiencies for acetone are less than 40%. 2+

[0003] It has been proven that reducing the metal active site to atomic scale can significantly improve its electrocatalytic performance. Compared with traditional metal nanoparticles / bulk materials, atomic-scale catalysts such as single-atom catalysts and single-cluster catalysts have the advantages of high atom utilization, clear coordination environment, and reliable durability, and exhibit significantly enhanced catalytic activity. Studies have shown that transition metal single-atom catalysts can be used as substitutes for noble metal catalysts to effectively catalyze the reduction of CO2 to CO. Among them, nickel single-atom catalysts exhibit excellent conversion activity of CO2 to CO in a wide voltage range, and are one of the most promising low-cost catalysts. In addition, copper nanocluster catalysts are considered to be an ideal platform for the production of C 2+ products from CO2 reduction, and by adjusting parameters such as cluster size and coordination geometry, their electronic behavior can be effectively adjusted to obtain unique CO2 reduction characteristics. Therefore, constructing a nickel single-atom catalyst and a copper nanocluster catalyst into a tandem catalyst is expected to improve the performance of CO2 reduction and achieve high selectivity synthesis of C3 products. SUMMARY

[0004] The technical problems solved by the present application are: in order to solve the technical problems in the prior art that only a few C2 products such as ethylene and ethanol can achieve significant activity, and it is more challenging to achieve high activity and high selectivity due to the complex reaction kinetics involving C1-C1 coupling and C1-C2 coupling, etc., the present application proposes a copper-nickel bimetallic tandem catalyst and a preparation method and application thereof. ​

[0005] Technical solution

[0006] A method for preparing a copper-nickel bimetallic tandem catalyst, comprising the following steps:

[0007] Step a: In the magnetron sputtering chamber, place 100 mg of graphene in a quartz container and transfer it to the sample injection chamber. After the sample injection chamber is evacuated to the base pressure, send the graphene into the main chamber for sputtering deposition.

[0008] Step b: The sample stage rotates at 10 rpm. First, a nickel target is used for sputtering deposition to ensure that the metal atoms are in full contact with the graphene, and a stable graphene-supported nickel single-atom catalyst Ni SAC is formed at room temperature. Then, a copper target is used for sputtering deposition to ensure that the clusters are in full contact with the graphene, and a stable graphene-supported copper nanoclusters Cu SCC are formed at room temperature. Finally, a graphene-supported nickel single-atom and copper nanocluster tandem catalyst Ni SAC@Cu SCC is obtained.

[0009] Step c: After sputtering, the unbound metal particles are washed with a 7wt.% ammonium persulfate aqueous solution, and finally the copper-nickel bimetallic tandem catalyst is obtained by vacuum freeze drying.

[0010] As a preferred technical solution of this application: the background pressure in step a is 10. -1 Pa.

[0011] As a preferred technical solution of this application: the sputtering parameters in step a are: substrate temperature 25℃, deposition time 5-10 seconds, and chamber pressure 5Pa.

[0012] As a preferred technical solution of this application: in step b, the sample stage rotates at a speed of 10 rpm to ensure that the metal atoms / clusters are in full contact with the graphene, and finally form a stable graphene-supported nickel single-atom catalyst NiSAC or copper nanoclusters CuSCC at room temperature.

[0013] As a preferred technical solution of this application: in step b, the deposition rate is precisely controlled to... High-energy metallic plasmas are generated, thereby obtaining highly active metal single atoms or nanoclusters.

[0014] As a preferred technical solution of this application: the temperature of vacuum freeze drying in step c is -20℃ and the time is 48h.

[0015] A copper-nickel bimetallic tandem catalyst prepared by any of the above preparation methods.

[0016] This application also discloses the application of a copper-nickel bimetallic tandem catalyst in the electrochemical reduction of CO2 to acetone.

[0017] Explanation of the principle of this application: Due to its unique electronic properties, copper is currently the only material capable of efficiently converting CO2 into C. 2+ The product is metallic, but the slow C-C coupling kinetics on the pure copper surface severely restrict the C-C coupling. 2+ The product formation efficiency can be effectively improved by changing the adsorption energy of *CO on the catalyst surface and the surface coverage of *CO. 2+ Product selectivity (* indicates adsorbed state); among which, tandem catalysis is considered to enhance C 2+ An effective way to improve product yield is through a tandem catalytic process from CO2 to C2 products, which can be broken down into CO2→CO and CO→C. 2+ This invention proposes a copper-nickel tandem catalyst that connects two independent reaction stages via a CO intermediate. Currently, copper-based cascade catalysts such as Ag@Cu2O, AgI-CuO, Au-bipy-Cu, and Au / CuNRs have been developed, but these systems all rely on noble metals (Au / Ag) for CO2→CO conversion. Furthermore, existing catalysts primarily produce C2 products such as ethanol and ethylene with high selectivity, while highly selective cascade catalytic systems targeting C3 products still face significant challenges. This invention proposes a copper-nickel cascade catalyst where CO2 is first efficiently converted to CO at nickel single-atom sites, and the abundant CO is further adsorbed by copper nanoclusters, thus achieving C / C coupling to obtain C3. 2+ product. Attached image description:

[0018] Figure 1 The images shown are electron microscope (TEM) images of Ni SAC@Cu SCC prepared in Example 3 of this application, where (a) is a TEM image and (b) is a TEM image.

[0019] HAADF-STEM plot, (c) is the element distribution plot corresponding to plot (b);

[0020] Figure 2 The XRD patterns of the catalysts prepared in Examples 1, 2 and 3 of this application;

[0021] Figure 3 The X-ray absorption near-edge structure pattern of Ni element in Ni SAC@Cu SCC prepared in Example 3 of this application is shown.

[0022] Figure 4 This is a fine X-ray absorption structure diagram of Ni element at the k-side of Ni SAC@Cu SCC prepared in Example 3 of this application;

[0023] Figure 5 High-resolution XPS spectra of Cu element in Ni SAC@Cu SCC prepared in Example 3 of this application;

[0024] Figure 6Linear scan voltammetry plots of the catalysts prepared in Examples 1, 2 and 3 of this application, after passing CO2 gas through a flow electrolyzer with 1 MKOH as electrolyte;

[0025] Figure 7 This is a product distribution diagram of the electrochemical reduction of CO2 by Ni SAC prepared in Example 1 of this application;

[0026] Figure 8 This is a product distribution diagram of Cu SCC electrochemical reduction of CO2 prepared in Example 2 of this application;

[0027] Figure 9 This is a product distribution diagram of the electrochemical reduction of CO2 by Ni SAC@Cu SCC prepared in Example 3 of this application;

[0028] Figure 10 Catalysts for the electrochemical reduction of C in CO2 were prepared in Examples 2 and 3 of this application. 2+ Faraday efficiency plot of the product;

[0029] Figure 11 The partial current density diagrams for the electrochemical reduction of acetone products in CO2 by the catalysts prepared in Examples 2 and 3 of this application are shown.

[0030] Figure 12 This is a stability test graph of the catalyst prepared in Example 3 of this application for the electrochemical reduction of CO2;

[0031] Figure 13 This is a process flow diagram for this application.

[0032] Beneficial effects:

[0033] 1. The copper-nickel bimetallic tandem catalyst provided by this invention, compared with single-active-site catalysts, has dual active sites, which can significantly regulate the interaction between reaction intermediates and active sites, thereby improving C 2+ Product selectivity offers new opportunities;

[0034] 2. This invention employs a novel, controllable vapor deposition method to prepare a tandem catalyst composed of nickel single atoms and copper nanoclusters using graphene as a support. This significantly enhances the electrochemical reduction of CO2 to produce C. 2+ Product efficiency;

[0035] 3. The copper-nickel bimetallic tandem catalyst provided by this invention, when applied in the electrochemical reduction of CO2, can efficiently reduce CO2 to C. 2+ The products exhibited a Faraday efficiency of up to 84.1%, with the C3 product acetone achieving a Faraday efficiency of 48.8%.

[0036] 4. In the copper-nickel tandem catalyst obtained in this application, copper and nickel elements are highly uniformly dispersed on the graphene support, wherein copper has a nanocluster structure and nickel has a single-atom structure.

[0037] 5. In the copper-nickel tandem catalyst obtained in this application, the valence state of nickel is between 0 and +2, and nickel forms a coordination structure with the surrounding carbon atoms, and there are no nickel nanoparticles.

[0038] 6. In the copper-nickel tandem catalyst obtained in this application, the valence state of copper is 0, and copper exists in the form of nanoclusters;

[0039] 7. The current densities obtained in this application under CO2 atmosphere are all greater than those under Ar atmosphere, indicating that the catalysts all have CO2 reduction performance. In addition, under CO2 atmosphere, the current density of the copper-nickel series catalyst is greater than that of the pure copper and pure nickel catalysts, indicating that the copper-nickel series catalyst has better CO2 reduction performance.

[0040] 8. The pure nickel catalyst of this application can efficiently reduce CO2 to CO, and the Faraday efficiency of CO is maintained above 90% in a wide voltage range of -0.5 to -1.1V;

[0041] 9. The pure copper catalyst of this application produces abundant CO2 reduction products. In addition to CO and methanol, the two C1 products, C2 can also be obtained. 2+ Products, such as ethanol, acetone, ethylene glycol, C 2+ The Faraday efficiency of the products reaches a maximum of 63.2% at -0.6V, with the Faraday efficiency of acetone, the C3 product, being 22%.

[0042] 10. Compared to pure copper catalysts, copper-nickel tandem catalysts can effectively increase C. 2+ The Faraday efficiency of the product, at -0.6V, C 2+ The product's Faradaic efficiency reached a maximum of 84.1%, with the C3 product acetone achieving a Faradaic efficiency of 48.8%.

[0043] 11. Within a wide voltage range of -0.4 to -1.1 V, copper-nickel tandem catalysts can effectively improve C. 2+ The Faraday efficiency of the product; due to the high current density and the Faraday efficiency of acetone, the copper-nickel tandem catalyst can achieve a higher acetone fractional current density; the copper-nickel tandem catalyst can operate continuously and stably for 20 hours. Detailed Implementation

[0044] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiment.

[0045] Example 1:

[0046] A method for preparing a metal catalyst, comprising the following steps:

[0047] Step a: In the magnetron sputtering chamber, 100 mg of graphene is placed in a quartz container and transferred to the sample injection chamber. After the sample injection chamber is evacuated to the base pressure, the graphene is sent into the main chamber for sputtering deposition. The base pressure is 10. -1 Pa, sputtering parameters are: substrate temperature 25℃, deposition time 5-10 seconds, chamber pressure 5Pa;

[0048] Step b: The sample stage rotates at 10 rpm, and sputtering deposition is performed using a nickel target. The deposition rate is precisely controlled to achieve the desired result. High-energy metal plasma is generated to obtain highly active metal single atoms; ensuring full contact between metal atoms and graphene, and finally forming a stable graphene-supported nickel single-atom catalyst Ni SAC at room temperature;

[0049] Step c: After sputtering, the unbonded metal particles are washed with a 7wt.% ammonium persulfate aqueous solution, and finally the catalyst product is obtained by vacuum freeze drying.

[0050] Example 2:

[0051] A method for preparing a metal catalyst, comprising the following steps:

[0052] Step a: In the magnetron sputtering chamber, 100 mg of graphene is placed in a quartz container and transferred to the sample injection chamber. After the sample injection chamber is evacuated to the base pressure, the graphene is sent into the main chamber for sputtering deposition. The base pressure is 10. -1 Pa, sputtering parameters are: substrate temperature 25℃, deposition time 5-10 seconds, chamber pressure 5Pa;

[0053] Step b: The sample stage rotates at 10 rpm, and sputtering deposition is performed using a copper target. The deposition rate is precisely controlled to achieve the desired result. High-energy metal plasma is generated to obtain highly active metal single clusters; the metal clusters are ensured to be in full contact with graphene, and finally a stable graphene-supported copper nanocluster catalyst Cu SCC is formed at room temperature.

[0054] Step c: After sputtering, the unbonded metal particles are washed with a 7wt.% ammonium persulfate aqueous solution, and finally the catalyst product is obtained by vacuum freeze drying.

[0055] Example 3:

[0056] A method for preparing a copper-nickel bimetallic tandem catalyst, comprising the following steps:

[0057] Step a: In the magnetron sputtering chamber, place 100 mg of graphene in a quartz container and transfer it to the sample injection chamber. After the sample injection chamber is evacuated to the base pressure, send the graphene into the main chamber for sputtering deposition. The base pressure is 10. -1 Pa, sputtering parameters are: substrate temperature 25℃, deposition time 5-10 seconds, chamber pressure 5Pa;

[0058] Step b: The sample stage rotates at 10 rpm. First, a nickel target is used for sputtering deposition to ensure that the metal atoms are in full contact with the graphene, and a stable graphene-supported nickel single-atom catalyst Ni SAC is formed at room temperature. Then, a copper target is used for sputtering deposition to ensure that the clusters are in full contact with the graphene, and a stable graphene-supported copper nanoclusters Cu SCC are formed at room temperature. Finally, a graphene-supported nickel single-atom and copper nanocluster tandem catalyst Ni SAC@Cu SCC is obtained.

[0059] Step c: After sputtering, the unbonded metal particles are washed with a 7wt.% ammonium persulfate aqueous solution, and finally the copper-nickel bimetallic tandem catalyst is obtained by vacuum freeze drying at -20℃ for 48 hours.

[0060] Depend on Figure 1 and Figure 2 It can be seen that in the obtained copper-nickel tandem catalyst, copper and nickel elements are highly uniformly dispersed on the graphene support; from Figure 3 and Figure 4 It can be seen that in the obtained copper-nickel tandem catalyst, the valence state of nickel is between 0 and +2, and nickel forms a coordination structure with the surrounding carbon atoms; therefore, nickel nanoparticles are not present. Figure 5 It can be seen that in the obtained copper-nickel tandem catalyst, the oxidation state of copper is 0. Figure 1 , Figure 2 It can be seen that copper exists in the form of nanoclusters; Figure 6 Linear sweep voltammetry plots were generated in a flow electrolyzer with 1.0 M KOH as the electrolyte and CO2 or Ar as the reactant gas. The results show that the current density obtained in the CO2 atmosphere is greater than that in Ar, indicating that both catalysts possess CO2 reduction performance. Furthermore, in the CO2 atmosphere, the current density of the copper-nickel tandem catalyst is greater than that of pure copper and pure nickel catalysts, indicating that the copper-nickel tandem catalyst has superior CO2 reduction performance. Figure 7 The distribution of CO2 reduction products under different voltages in a flow electrolyzer with pure nickel catalyst and 1.0 M KOH as electrolyte shows that pure nickel catalyst can efficiently reduce CO2 to CO, and the Faraday efficiency of CO remains above 90% in a wide voltage range of -0.5 to -1.1 V. Figure 8The image shows the CO2 reduction product distribution of pure copper catalyst in a flow electrolyzer with 1.0 M KOH as the electrolyte at different voltages. It can be seen that pure copper catalyst produces a relatively rich variety of CO2 reduction products, including CO and methanol (two C1 products), as well as C2. 2+ Products, such as ethanol, acetone, ethylene glycol, C 2+ The Faraday efficiency of the products reaches a maximum of 63.2% at -0.6V, with the Faraday efficiency of acetone, the C3 product, being 22%. Figure 9 The distribution of CO2 reduction products under different voltages is shown for a copper-nickel tandem catalyst in a flow electrolyzer with 1.0 M KOH as the electrolyte. Compared with pure copper catalyst, the copper-nickel tandem catalyst can effectively improve CO2 reduction. 2+ The Faraday efficiency of the product, at -0.6V, C 2+ The product's Faradaic efficiency reached a maximum of 84.1%, with the C3 product acetone achieving a Faradaic efficiency of 48.8%. Figure 10 Electrochemical reduction of CO2 to C using pure copper and copper-nickel series catalysts at different voltages. 2+ The Faraday efficiency plot of the products shows that, within a wide voltage range of -0.4 to -1.1 V, the copper-nickel tandem catalyst can effectively improve C. 2+ The Faraday efficiency of the product; Figure 11 The partial current density diagrams show the partial current density of C3 acetone products obtained by electrochemical reduction of CO2 using pure copper and copper-nickel series catalysts at different voltages. Due to the high current density and the Faraday efficiency of acetone, the copper-nickel series catalyst can obtain a higher partial current density of acetone. Figure 12 The graph shows the stability test results of the copper-nickel tandem catalyst at -0.6V, indicating that the copper-nickel tandem catalyst can operate stably for 20 hours continuously.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a copper-nickel bimetallic serial catalyst, characterized by, The specific steps are: Step a: In a magnetron sputtering chamber, 100 mg of graphene is placed in a quartz container, transferred to the sample chamber, and after the sample chamber is vacuumed to the background pressure, the graphene is sent to the main chamber for sputtering deposition; Step b: The sample table is rotated at a speed of 10 rpm, first using a nickel target for sputtering deposition to ensure that metal atoms are in full contact with graphene, and finally forming a stable graphene-supported nickel monatomic catalyst Ni SAC at room temperature, and then using a copper target for sputtering deposition to ensure that clusters are in full contact with graphene, and finally forming a stable graphene-supported copper nanocluster Cu SCC at room temperature, and finally obtaining a graphene-supported nickel monatomic and copper nanocluster tandem catalyst Ni SAC@Cu SCC; Step c: After sputtering, an aqueous solution of 7 wt.% ammonium persulfate is used to wash unbound metal particles, and finally a copper-nickel bimetallic tandem catalyst is obtained by vacuum freeze-drying.

2. The method for preparing the copper-nickel bimetallic tandem catalyst according to claim 1, characterized in that: The background pressure in step a is 10 -1 Pa.

3. The method of claim 1, wherein: The sputtering parameters in step a are: substrate temperature 25℃, deposition time 5-10 seconds, and chamber pressure 5 Pa.

4. The method of claim 1, wherein: In step b, the sample table is rotated at a speed of 10 rpm to ensure that metal atoms / clusters are in full contact with graphene, and finally a stable graphene-supported nickel monatomic catalyst Ni SAC or copper nanocluster Cu SCC is formed at room temperature.

5. The method for preparing the copper-nickel bimetallic tandem catalyst according to claim 1, characterized in that: The step b is to precisely control the deposition rate to High-energy metal plasma is generated to obtain high-activity metal monomers or nanoclusters.

6. The method of claim 1, wherein: The temperature of vacuum freeze-drying in step c is -20℃, and the time is 48 h.

7. A copper-nickel bimetallic tandem catalyst prepared by the preparation method of any one of claims 1-6.

8. The use of the copper-nickel bimetallic tandem catalyst of claim 7 in the electrochemical reduction of CO2 to acetone.

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