Self-supported nanocatalysts for CO2 electroreduction to ethylene: their preparation and application

Abstract

This invention relates to a self-supported nanocatalyst for the electroreduction of CO2 to ethylene, its preparation, and its application. The catalyst uses copper foil as a substrate, and the catalytically active material is obtained through in-situ growth using a wet chemical method. The catalytically active material is cuprous chloride nanoclusters. The catalyst preparation includes: acid washing of the copper foil to remove surface impurities and oxide layers; immersing the acid-washed copper foil in an acidic copper chloride solution for in-situ growth; cleaning the in-situ grown copper foil; and then vacuum drying under an inert atmosphere. The catalyst application includes using the catalyst as the working electrode to catalyze the electroreduction of CO2 to ethylene via constant-potential electrolysis. The cuprous chloride nanoclusters grown in situ on the copper foil surface of this invention provide effective charge transfer channels, accelerate electron transfer, promote mass-electron coupling on the catalyst surface, and facilitate the specific adsorption of intermediates during electrolysis, thus efficiently catalyzing the electroreduction of CO2 to ethylene.

Description

Technical Field

[0001] This invention relates to the field of CO2 electrochemical reduction technology, and in particular to a self-supporting nanocatalyst for the electroreduction of CO2 to ethylene and its preparation and application. Background Technology

[0002] Converting CO2 into high-value-added products is crucial for reducing greenhouse gas emissions. Electrochemical reduction of CO2 is one of the most attractive methods, requiring only water and electricity and operating under normal temperature, pressure, and neutral conditions. However, linear CO2 molecules are highly stable, necessitating highly active electrocatalysts to ensure efficient electrochemical conversion and product selectivity. Existing electrocatalysts include metal catalysts, metal oxide catalysts, metal complex catalysts, and carbon-based catalysts. Among these, copper possesses a unique ability to convert CO2 into high-value, multi-carbon products such as ethylene. However, the weak surface coordination of metallic copper results in poor product selectivity for CO2 electrochemical reduction, while copper oxides, copper halides, and copper nitrides exhibit good selectivity for the electroreduction of CO2 to ethylene. Nevertheless, the preparation methods for these copper derivatives are relatively complex, requiring high-temperature or high-energy processing.

[0003] Therefore, it is of great significance to develop a simple and efficient preparation method to obtain a copper-based catalyst that can electrocatalyze the reduction of CO2 to ethylene with high activity and high selectivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a self-supporting nanocatalyst for the electroreduction of CO2 to ethylene, its preparation and application, with the aim of improving the ethylene selectivity of the catalyst.

[0005] The technical solution adopted in this invention is as follows:

[0006] In one aspect, the present invention provides a self-supporting nanocatalyst for the electroreduction of CO2 to ethylene. The catalyst is based on copper foil and the catalytically active material is obtained by in-situ growth of a wet chemical method. The catalytically active material is cuprous chloride nanoclusters.

[0007] The further technical solution is as follows:

[0008] The cuprous chloride nanoclusters on the catalyst surface are irregular, sheet-like, or cubic in shape, and the shape and size of the nanoclusters can be controlled and adjusted, with a size of 100–1000 nm.

[0009] A second aspect of this invention provides a method for preparing the self-supported nanocatalyst for the electroreduction of CO2 to ethylene, comprising:

[0010] Pickling of copper foil removes surface impurities and oxide layers;

[0011] The pickled copper foil was placed in an acidic copper chloride solution for in-situ wet chemical growth.

[0012] The copper foil grown in situ is cleaned and then vacuum dried under an inert atmosphere to obtain the catalyst.

[0013] The further technical solution is as follows:

[0014] The acidic copper chloride solution is a hydrochloric acid solution of copper chloride, wherein the molar ratio of copper chloride to hydrogen chloride is 0.4 to 2.

[0015] The in-situ growth time is 20–300 s.

[0016] The solution used for pickling copper foil is acetic acid or boric acid solution, and the pickling time is 5 to 30 minutes.

[0017] A third aspect of this invention provides an application of the self-supported nanocatalyst for the electroreduction of CO2 to ethylene, wherein the catalyst is used as the working electrode to catalyze the electroreduction of CO2 to prepare ethylene, and the specific steps include:

[0018] CO2 is introduced into the cathode electrolytic cell to pre-saturate the cathode electrolyte with CO2, and the working electrode is activated.

[0019] With CO2 continuously introduced, constant potential electrolysis is used to electroreduc the CO2 into ethylene.

[0020] The constant potential is -1.1 to -0.7 V. vs (Ag / AgCl), electrolysis time is 60-240 min.

[0021] The cathode electrolyte is a KHCO3 solution or a KCl solution with a concentration of 0.1–1 mol / L.

[0022] The CO2 presaturation time for the cathode electrolyte is 10–40 min.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention uses copper foil as a substrate and constructs a self-supporting nanocatalyst in situ through a wet chemical method. It can efficiently catalyze the electroreduction of CO2 to ethylene. Compared with existing copper foil modification methods involving high temperature or high energy, the wet chemical method is simple, has low technical requirements, is easy to operate, and has low cost and great potential for large-scale production.

[0025] 2. The cuprous chloride nanoclusters grown in situ on the surface of copper foil using a wet chemical method in this invention can provide effective charge transfer channels, accelerate electron transfer, promote mass-electron coupling on the catalyst surface, and significantly improve the catalytic performance of the catalyst. Furthermore, the microstructure and size of the nanoclusters can be controlled according to the requirements of different reaction systems and application scenarios, achieving controllable preparation of the catalyst.

[0026] 3. The catalytically active substance of this invention is cuprous chloride. In the electrocatalytic reduction of CO2, Cu(I) is beneficial to the intermediate. It specifically adsorbs and subsequently undergoes CC coupling, and the Cl atom can inhibit H while stabilizing the active component Cu(I). + The adsorption of these substances inhibits the hydrogen evolution side reaction and improves the selectivity of ethylene products.

[0027] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0028] Figure 1 SEM images of catalysts A1-A3 prepared in Examples 1-3 of this invention and commercial copper foil of comparative catalysts. Detailed Implementation

[0029] The technical solution of this application will be described in detail below.

[0030] This application provides a self-supporting nanocatalyst for the electroreduction of CO2 to ethylene. The catalyst is based on copper foil and the catalytically active material is obtained by in-situ growth of a wet chemical method. The catalytically active material is a nano-cuprous chloride nanocluster.

[0031] The cuprous chloride nanoclusters on the catalyst surface are irregular, sheet-like, or cubic in shape, and the shape and size of the nanoclusters can be controlled and adjusted, with a size of 100–1000 nm.

[0032] The self-supporting nanostructure of the catalyst in this application can provide an effective charge transfer channel, accelerate electron transfer, and promote mass-electron coupling on the catalyst surface, thereby significantly improving the catalytic performance of the in-situ grown nanocatalyst.

[0033] This application also provides a method for preparing a self-supported nanocatalyst for the electroreduction of CO2 to ethylene, comprising the following steps:

[0034] Pickling of copper foil removes surface impurities and oxide layers;

[0035] The pickled copper foil was placed in an acidic copper chloride solution for in-situ wet chemical growth.

[0036] The copper foil grown in situ is cleaned and then vacuum dried under an inert atmosphere to obtain the catalyst.

[0037] The acidic copper chloride solution is a hydrochloric acid solution of copper chloride, and the molar ratio of copper chloride to hydrogen chloride is 0.4 to 2.

[0038] The in-situ growth time is 20–300 seconds.

[0039] The solution used for pickling copper foil is acetic acid or boric acid solution, and the pickling time is 5-30 minutes.

[0040] Compared with existing copper foil modification methods, the preparation method of this application uses copper foil as a substrate and constructs self-supporting nanocatalysts in situ through wet chemical methods. The process is simple, has low technical requirements, is easy to operate, and has low cost and great potential for large-scale production.

[0041] This application also provides an application of a self-supported nanocatalyst for the electroreduction of CO2 to ethylene. Using the catalyst as the working electrode, the electroreduction of CO2 to ethylene is catalyzed, and the specific steps are as follows:

[0042] CO2 is introduced into the cathode electrolytic cell to pre-saturate the cathode electrolyte with CO2, and the working electrode is then activated.

[0043] With CO2 continuously introduced, constant potential electrolysis is used to electroreduc the CO2 into ethylene.

[0044] The constant potential is -1.1 to -0.7 V. vs (Ag / AgCl), electrolysis time is 60-240 min.

[0045] The cathode electrolyte is a KHCO3 solution or a KCl solution with a concentration of 0.1–1 mol / L.

[0046] The CO2 presaturation time for the cathode electrolyte is 10–40 min.

[0047] In the electrocatalytic reduction of CO2, a self-supported nano-cuprous chloride catalyst obtained by in-situ growth of copper foil in an acidic copper chloride solution exhibits excellent performance. Binding ability, in which Cu(I) is favorable to intermediates Specific adsorption facilitates subsequent C-C coupling to generate the multi-carbon product ethylene, and Cl atoms can stabilize the active component Cu(I) while inhibiting H. + The adsorption of these substances inhibits the hydrogen evolution side reaction and improves the selectivity of ethylene products.

[0048] The preparation method of the nanostructured cuprous chloride catalyst for the electroreduction of CO2 to ethylene of this application is further illustrated below with specific examples 1 to 6.

[0049] Example 1

[0050] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with acetic acid for 5 min to remove surface impurities and oxide layer; the acid-washed copper foil was placed in an acidic solution with a copper chloride to hydrogen chloride molar ratio of 0.4 and grown in situ for 20 s; the copper foil after in situ growth was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with an irregular surface structure, a size of 100 nm, denoted as A1.

[0051] Example 2

[0052] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with acetic acid for 20 min to remove surface impurities and oxide layer; the acid-washed copper foil was then placed in an acidic solution with a molar ratio of copper chloride to hydrogen chloride of 1 and grown in situ for 150 s; the copper foil after in situ growth was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with a sheet-like surface structure and a size of 400 nm, denoted as A2.

[0053] Example 3

[0054] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with acetic acid for 30 min to remove surface impurities and oxide layer; the acid-washed copper foil was then placed in an acidic solution with a molar ratio of copper chloride to hydrogen chloride of 2 and grown in situ for 300 s; the copper foil after in situ growth was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with a cubic structure on the surface, with a size of 1000 nm, denoted as A3.

[0055] like Figure 1 The figures show SEM images of catalysts A1-A3 prepared in Examples 1-3 and the comparative catalyst, commercial copper foil. As can be seen from the figures, the surface of the commercial copper foil is relatively smooth, and no nanoclusters are observed. The catalysts prepared in this application all exhibit self-supporting nanostructures. Specifically, the nanoclusters on the surface of catalyst A1 have an irregular (bulk) structure, the nanoclusters on the surface of catalyst A2 have a sheet-like structure, and the nanoclusters on the surface of catalyst A3 have a cubic structure.

[0056] Example 4

[0057] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with boric acid for 5 min to remove surface impurities and oxide layer. The acid-washed copper foil was then placed in an acidic solution with a molar ratio of copper chloride to hydrogen chloride of 0.4 and grown in situ for 20 s. The copper foil after in situ growth was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with an irregular surface structure, a size of 100 nm, denoted as A4.

[0058] Example 5

[0059] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with boric acid for 20 min to remove surface impurities and oxide layer; the acid-washed copper foil was then placed in an acidic solution with a molar ratio of copper chloride to hydrogen chloride of 1 and grown in situ for 150 s; the in-situ grown copper foil was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with a sheet-like surface structure, a size of 400 nm, denoted as A5.

[0060] Example 6

[0061] Commercial copper foil (0.3 mm × 1 cm × 1 cm) was acid-washed with boric acid for 30 min to remove surface impurities and oxide layer; the acid-washed copper foil was then placed in an acidic solution with a molar ratio of copper chloride to hydrogen chloride of 2 and grown in situ for 300 s; the in-situ grown copper foil was cleaned and then vacuum dried under a nitrogen atmosphere to obtain a self-supporting nano-cuprous chloride catalyst with a cubic structure on the surface, with a size of 1000 nm, denoted as A6.

[0062] Table 1 shows the parameters and results of Examples 1 to 6.

[0063] Table 1. Parameters and results of Examples 1-6

[0064]

[0065] As shown in Table 1, by controlling the molar ratio of copper chloride to hydrogen chloride in the in-situ growth solution and the in-situ growth time, the in-situ growth of nano-cuprous chloride clusters with different micromorphologies on the surface of copper foil and the controllable adjustment of their nanoscale size can be achieved.

[0066] The following examples 7-12 illustrate the application of the catalysts prepared in Examples 1-6 in the electroreduction of CO2 to ethylene.

[0067] Example 7

[0068] Catalyst A1 was placed in an H-type electrolytic cell containing 0.1 mol / L KHCO3 pre-saturated with CO2 for 10 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -0.7 V. vsElectrocatalytic CO2 reduction was performed for 60 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 15.32% as determined by online GC analysis.

[0069] Example 8

[0070] Catalyst A2 was placed in an H-type electrolytic cell containing 0.5 mol / L KHCO3 pre-saturated with CO2 for 20 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -0.9 V. vs Electrocatalytic CO2 reduction was performed for 120 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 58.84% as determined by online GC analysis.

[0071] Example 9

[0072] Catalyst A3 was placed in an H-type electrolytic cell containing 1 mol / L KHCO3 pre-saturated with CO2 for 40 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -1.1 V. vs Electrocatalytic CO2 reduction was performed for 240 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 54.15% as determined by online GC analysis.

[0073] Example 10

[0074] Catalyst A4 was placed in an H-type electrolytic cell containing 0.1 mol / L KCl pre-saturated with CO2 for 10 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -0.7 V. vs Electrocatalytic CO2 reduction was performed for 60 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 16.28% as determined by online GC analysis.

[0075] Example 11

[0076] Catalyst A5 was placed in an H-type electrolytic cell containing 0.5 mol / L KCl pre-saturated with CO2 for 20 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -0.9 V. vs Electrocatalytic CO2 reduction was performed for 120 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 53.26% as determined by online GC analysis.

[0077] Example 12

[0078] Catalyst A6 was placed in an H-type electrolytic cell containing 1 mol / L KCl pre-saturated with CO2 for 40 min, serving as the working electrode. CO2 was continuously introduced, and electrolysis was performed at a constant potential at -1.1 V.vs Electrocatalytic CO2 reduction was performed for 240 min under Ag / AgCl voltage conditions. The ethylene Faradaic efficiency was 48.21% as determined by online GC analysis.

[0079] Table 2 shows the parameters and results for Examples 7-12 and their corresponding comparative examples. The only difference between the comparative examples and their corresponding examples is the use of commercial copper foil as the catalytic electrode; all other parameters and conditions are the same.

[0080] Table 2. Parameters and results of Examples 7-12 and corresponding comparative examples.

[0081]

[0082] As shown in Table 2, after commercial copper foil was grown in situ using a wet chemical method to obtain a self-supported nano-cuprous chloride catalyst, its Faraday efficiency for the electroreduction of CO2 to ethylene increased from 5.56% to 58.84%, indicating that the self-supported nano-cuprous chloride catalyst obtained by the wet chemical method in situ growth exhibited high catalytic activity and selectivity for the electroreduction of CO2 to ethylene.

[0083] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended 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 make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-supported nanocatalyst for the electroreduction of CO2 to ethylene, characterized in that, The catalyst is a copper foil substrate, and the catalytically active material is obtained by in-situ growth of a wet chemical method. The catalytically active material is cuprous chloride nanoclusters. The method for preparing the catalyst includes: Pickling of copper foil removes surface impurities and oxide layers; The pickled copper foil was placed in an acidic copper chloride solution for in-situ wet chemical growth. The copper foil grown in situ was cleaned and then vacuum dried under an inert atmosphere to obtain the catalyst. The acidic copper chloride solution is a hydrochloric acid solution of copper chloride, wherein the molar ratio of copper chloride to hydrogen chloride is 0.4 to 2. The cuprous chloride nanoclusters on the surface of the catalyst are irregular, sheet-like, or cubic in shape, and the shape and size of the nanoclusters can be controlled and adjusted, with a size of 100–1000 nm. The adjustment of the shape and size of the nanoclusters includes: changing the wet chemical reaction time and the molar ratio of copper chloride to hydrogen chloride.

2. The production method according to claim 1, characterized by, The in-situ growth time is 20–300 s.

3. The preparation method according to claim 1, characterized in that, The solution used for pickling copper foil is acetic acid or boric acid solution, and the pickling time is 5 to 30 minutes.

4. Use of a catalyst prepared according to the process of any one of claims 1 to 3, characterized in that, Using the catalyst as the working electrode, the catalytic electroreduction of CO2 to prepare ethylene includes the following specific steps: CO2 is introduced into the cathode electrolytic cell to pre-saturate the cathode electrolyte with CO2, and the working electrode is activated. With CO2 continuously introduced, constant potential electrolysis is used to electroreduc CO2 into ethylene; The cathode electrolyte is a KHCO3 solution or a KCl solution with a concentration of 0.1–1 mol / L.

5. Use according to claim 4, characterized in that, the constant potential is -1.1 to -0.7 V, vs . Ag / AgCl, electrolysis time is 60 to 240 min.

6. Use according to claim 4, characterized in that, The CO2 presaturation time for the cathode electrolyte is 10–40 min.

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