Bismuth-copper bimetallic composite catalyst for electroreduction of carbon dioxide, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of the preparation of electrocatalysts, and in particular relates to a bismuth-copper bimetallic composite catalyst, and a preparation method therefor and the use thereof. The catalyst comprises ultra-small copper nanoclusters and bismuth nanosheets, wherein the bismuth nanosheets are of a polycrystalline structure, and the copper nanoclusters are highly dispersed on the bismuth nanosheets; and the number of copper atoms in each copper nanocluster is less than 10. In the present invention, highly-dispersed ultra-small copper nanoclusters are loaded on bismuth nanosheets by means of the thermal decomposition of a metal complex and a subsequent in-situ electroreduction method, the electronic state of bismuth atoms is adjusted, and therefore the carbon dioxide activating capacity of the bismuth-copper bimetallic compound is improved, thereby achieving high-selectivity and high-activity preparation of a formate by means of the electrocatalytic reduction of carbon dioxide, and providing a new path for the efficient conversion of carbon dioxide. The bismuth-copper bimetallic composite catalyst provided by the present invention achieves both a formate selectivity of more than 90% and an ultrahigh activity under conditions of 1.2 A cm-2.

Description

Bismuth-copper bimetallic composite catalyst for carbon dioxide electroreduction and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of electrocatalyst preparation, and in particular to a bismuth-copper bimetallic composite catalyst and a preparation method and application thereof. Background Art

[0002] The massive emission of the greenhouse gas carbon dioxide (CO2) has triggered a series of energy shortages and climate change issues. The electrocatalytic CO2 reduction process, which uses clean electricity generated by renewable energy sources such as solar and wind power to convert CO2 into fuels and chemicals, is considered one of the most promising methods for achieving carbon neutrality.

[0003] Among the various electrocatalytic reduction products, formic acid / formates have the highest performance due to their unique properties, including high mass / volume hydrogen capacity (53 g H2 L -1 ), low toxicity, flammability, and ease of transport make it an ideal hydrogen carrier for fuel cells. It is also an important chemical raw material or intermediate in many industrial processes and is widely used in the agricultural, food, textile, and pharmaceutical industries. However, due to competition with the hydrogen evolution reaction, high formate selectivity is usually achieved at the expense of low current density and deteriorates rapidly with increasing cathode potential. Therefore, the design and synthesis of catalysts with both high selectivity and ultrahigh activity for formic acid / formate is one of the current research hotspots.

[0004] Bismuth-based catalysts are inert to the hydrogen evolution reaction and are therefore widely used in the study of the electrochemical reduction of carbon dioxide to formic acid. By designing and synthesizing bismuth nanosheets, not only can the active surface area of ​​the catalyst be increased, the number of exposed active sites can be increased, but also the charge conduction capacity of the catalyst can be enhanced. Although some progress has been made in the study of bismuth-based catalysts, the current density of most bismuth-based materials for the electrochemical reduction of carbon dioxide to formic acid or formate is no more than 1A / cm 2 , and it is difficult to achieve both high selectivity and high activity at the same time. Developing new materials to achieve both high selectivity and high activity remains the current research goal.

[0005] Bimetallic composite catalysts have been extensively explored due to their potential for synergistic effects, electron modulation, and strong metal-support interactions. These effects often contribute to superior catalytic performance. Consequently, leveraging the unique effects of bimetallic materials to develop novel CO2 reduction catalysts is attracting increasing attention.

[0006] Based on the above research status, it can be seen that seeking a relatively simple method to prepare bimetallic composite catalysts and using them to produce formate with high selectivity and high activity in electrocatalytic carbon dioxide reduction has important theoretical significance and industrial application value.

[0007] Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a bismuth-copper bimetallic composite catalyst, a preparation method and application thereof, which is used in the electrocatalytic carbon dioxide reduction reaction, and can simultaneously achieve highly selective and ultra-high activity electrochemical carbon dioxide reduction to formate.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] On one hand, the present invention provides a bismuth-copper bimetallic composite catalyst, which includes ultrasmall copper nanoclusters and bismuth nanosheets; the bismuth nanosheets are polycrystalline, and the copper nanoclusters are dispersed on the bismuth nanosheets in a highly dispersed form; the number of copper atoms in the copper nanoclusters is less than 10.

[0011] In the above technical solution, further, the copper nanoclusters in the catalyst account for 20 to 33% of the total atomic weight of the bimetallic complex.

[0012] In the above technical solution, further, the thickness of the bismuth nanosheet is 5 to 20 nm.

[0013] Another aspect of the present invention provides a method for preparing the bismuth-copper bimetallic composite catalyst, the method comprising the following steps:

[0014] (1) A soluble copper salt is mixed with water to obtain a mixed solution I, thiourea is added to the mixed solution I to react, and the obtained product I is washed with water, centrifuged, and dried to obtain a precursor A;

[0015] (2) mixing a soluble bismuth salt with water to obtain a mixed solution II, adding sodium diethyldithiocarbamate to the mixed solution II for reaction, and washing the obtained product II with water, centrifuging, and drying to obtain a precursor B;

[0016] (3) ultrasonically dispersing precursor A and precursor B in an alcohol solvent to obtain a mixed solution III;

[0017] (4) heating the mixed solution III obtained in step (3) to reflux, and washing, centrifuging, and drying the reaction product III to obtain a copper sulfide and bismuth sulfide complex precursor C;

[0018] (5) The copper sulfide and bismuth sulfide complex precursor C obtained in step (4) is coated on a carbon material as an electrode, and after electrochemical reduction, a bismuth-copper bimetallic complex catalyst is obtained.

[0019] In the above technical solution, further, the soluble copper salt includes any one of copper dichloride and copper dichloride hydrate.

[0020] The molar ratio of the soluble copper salt to thiourea is 1:(0.5-2), preferably 1:1, and the reaction time is not less than 10s.

[0021] In the above technical solution, further, the soluble bismuth salt is bismuth nitrate.

[0022] The molar ratio of the soluble bismuth salt to sodium diethyldithiocarbamate is 1:(1-4), preferably 1:3, and the reaction time is not less than 1 minute.

[0023] In the above technical solution, further, the mass ratio of the precursor A to the precursor B is (3.5-7):50.

[0024] The alcohol solvent includes ethylene glycol; the mass ratio of the alcohol solvent to the precursor B is (33-55):50.

[0025] In the above technical solution, further, the heating reflux temperature is 130-140° C., and the time is 1-4 hours.

[0026] In the above technical solution, further, the copper sulfide and bismuth sulfide composite precursor is applied to the carbon material by drip coating or spray coating.

[0027] The carbon material includes any one of glassy carbon electrode, carbon paper and carbon cloth.

[0028] The carbon material electrode is a working electrode or a cathode.

[0029] The electrochemical reduction electrolyte is potassium bicarbonate or potassium hydroxide, the electrolyte concentration is 0.1 to 1 M, the electroreduction potential range is -0.8 to -1.1 V vs. RHE, and the electroreduction reaction time is 10 to 30 minutes.

[0030] Another aspect of the present invention provides an application of the above-mentioned bismuth-copper bimetallic composite catalyst in an electrochemical carbon dioxide reduction reaction; or an application of the bismuth-copper bimetallic composite catalyst prepared by the above-mentioned preparation method in an electrochemical carbon dioxide reduction reaction.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention provides a bismuth-copper bimetallic composite catalyst. Compared with the prior art, it has a specific structure. Ultrasmall copper nanoclusters are distributed in a highly dispersed form on the surface of bismuth nanosheets. The copper nanoclusters regulate the electronic state of bismuth on the bismuth nanosheets, thereby improving the ability of the above-mentioned bismuth-copper bimetallic composite to activate carbon dioxide, thereby obtaining high selectivity and activity for the electrocatalytic reduction of carbon dioxide to formate, providing a new path for the efficient conversion of carbon dioxide.

[0033] 2. The preparation method of the present invention obtains a specific catalyst structure by electrochemically reducing copper and bismuth precursors, which has the advantage of simple operation. The content of copper clusters can be adjusted by changing the reaction conditions, thereby achieving the adjustment of catalytic performance.

[0034] 3. The bismuth-copper bimetallic composite catalyst provided by the present invention can be used for electrocatalytic reduction of carbon dioxide to produce formate. Specifically, the bismuth-copper bimetallic composite catalyst provided by the present invention simultaneously achieves high formate selectivity (>90%) and ultra-high activity (1.2 A cm -2 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] FIG1 is a transmission electron microscope image of the bismuth-copper bimetallic composite catalyst prepared in Example 2 of the present invention;

[0037] FIG2 is an atomic force microscope image of the bismuth-copper bimetallic composite catalyst prepared in Example 2 of the present invention;

[0038] FIG3 is an X-ray diffraction pattern of the bismuth-copper bimetallic composite catalyst prepared in Example 2 of the present invention;

[0039] FIG4 is a Fourier transform Cu K-edge X-ray absorption fine structure spectrum of the bismuth-copper bimetallic composite prepared in Example 2 of the present invention;

[0040] FIG5 is a high-resolution transmission electron microscopy image of the bismuth-copper bimetallic composite prepared in Example 2 of the present invention and the corresponding energy dispersive X-ray (EDX) elemental mapping image;

[0041] FIG6 is a Faradaic efficiency-current density curve of the bismuth-copper bimetallic composite catalyst prepared in Example 2 of the present invention catalyzing the electroreduction reaction of carbon dioxide to produce formate in a flow cell electrolytic cell;

[0042] Figure 7 shows the Faradaic efficiency-potential curves of the bismuth-copper bimetallic composite catalysts prepared in Examples 1-3 of the present invention and the bimetallic composite with a higher copper content (50 at %) prepared in Comparative Example 1, catalyzing the electroreduction reaction of carbon dioxide to produce formate in an H-type electrolytic cell. DETAILED DESCRIPTION

[0043] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0044] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0045] There is no particular limitation on the purity of all raw materials in the present invention, but analytically pure materials are preferably used in the present invention.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value within any stated value or stated range and any other stated value or intermediate value within the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art of the present invention. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. In addition, it should also be understood that the terms "comprising," "including," "having," "containing," etc. used herein are all open-ended terms, i.e., meaning including but not limited to.

[0048] Example 1

[0049] Preparation of bismuth-copper bimetallic complex catalyst;

[0050] (1) Copper chloride and thiourea were dissolved in 50 mL of water to obtain 0.1 M thiourea aqueous solution and copper chloride aqueous solution, respectively. The thiourea aqueous solution was added to the copper chloride aqueous solution, reacted for one minute, and then centrifuged, washed with water, and dried to obtain precursor A.

[0051] (2) Dissolving bismuth nitrate and sodium diethyldithiocarbamate in 50 mL of water to obtain a bismuth nitrate solution and a sodium diethyldithiocarbamate solution each having a concentration of 0.1 M, adding the bismuth nitrate solution to the sodium diethyldithiocarbamate solution, reacting for one hour, centrifuging, washing with water, and drying to obtain precursor B;

[0052] (3) 3.5 mg of precursor A and 50 mg of precursor B were weighed and ultrasonically dispersed in 40 mL of ethylene glycol. The dispersion was then placed in an oil bath and refluxed at 130°C for 3 hours. The mixture was naturally cooled to room temperature, centrifuged, washed with ethanol and water several times, and then centrifuged and dried to obtain a copper sulfide and bismuth sulfide complex precursor.

[0053] (4) Weigh 2 mg of the above copper sulfide and bismuth sulfide complex precursor and ultrasonically disperse it in 0.5 mL of ethanol, add 5 μL of perfluorosulfonic acid resin alcohol solution, mix well, and drop 5 μL of the mixed solution on the surface of a glassy carbon electrode as a working electrode, a platinum electrode as an anode, and a silver / silver chloride electrode as a reference electrode. In situ electroreduction is carried out in a 0.1 M potassium bicarbonate solution for 10 min, and the applied potential is -0.9 V (relative to RHE) to obtain a bismuth-copper bimetallic complex catalyst;

[0054] (5) After testing, the atomic percentage of copper atoms in the bismuth-copper bimetallic composite catalyst obtained in this example was 20%.

[0055] Example 2

[0056] Preparation of bismuth-copper bimetallic complex catalyst;

[0057] (1) Precursors A and B were prepared according to the method of Example 1;

[0058] (2) A copper sulfide and bismuth sulfide composite precursor was prepared according to the method of Example 1, except that the amount of precursor A in step (3) was 4.7 mg;

[0059] (3) preparing a bismuth-copper bimetallic composite catalyst according to the method in Example 1;

[0060] (4) After testing, the atomic percentage of copper atoms in the bismuth-copper bimetallic composite catalyst obtained in this example was 25%.

[0061] As shown in Figure 1 , the transmission electron microscopy image confirms that the obtained sample is a nanosheet structure;

[0062] As shown in Figure 2 , the atomic force microscopy image shows that the thickness of the bismuth nanosheets is ∼9.5 ​​nm;

[0063] As shown in Figure 3 , the X-ray diffraction pattern shows that the bismuth nanosheets are polycrystalline and the copper element does not form copper nanoparticles;

[0064] As shown in Figure 4, the Fourier-transformed Cu K-edge X-ray absorption fine structure spectrum confirms that the copper cluster is composed of five copper atoms. The peak intensity of the Cu-Cu bond in the cluster is significantly lower than that in the copper foil standard sample, indicating that the coordination number of the copper atoms in the cluster is significantly smaller than that in the copper foil sample. Through fitting, it can be concluded that the coordination number of copper in the cluster is 4, indicating that the copper cluster is composed of five copper atoms.

[0065] As shown in Figure 5, copper and bismuth elements are evenly dispersed without aggregation, indicating that copper clusters are highly dispersed on the bismuth nanosheets.

[0066] Example 3

[0067] Preparation of bismuth-copper bimetallic complex catalyst;

[0068] (1) Precursors A and B were prepared according to the method of Example 1;

[0069] (2) A copper sulfide and bismuth sulfide composite precursor was prepared according to the method of Example 1, except that the amount of precursor A in step (3) was 7 mg;

[0070] (3) preparing a bismuth-copper bimetallic composite catalyst according to the method in Example 1;

[0071] (4) After testing, the atomic percentage of copper atoms in the bismuth-copper bimetallic composite catalyst obtained in this example was 33%.

[0072] Comparative Example 1

[0073] The catalyst was prepared according to the method of Example 1, except that the amount of precursor A in step (3) was 14.1 mg, and the atomic percentage of copper atoms in the prepared bismuth-copper bimetallic composite catalyst was 50%.

[0074] Example 4

[0075] Test of the carbon dioxide electrocatalytic reduction performance of bismuth-copper bimetallic complex catalyst.

[0076] The catalytic performance of the bismuth-copper bimetallic composite catalysts prepared in Examples 1-3 of the present invention and Comparative Example 1 was tested for the electrocatalytic reduction reaction of carbon dioxide.

[0077] The carbon paper loaded with the bismuth-copper bimetallic composite catalyst obtained in Example 2 of the present invention was used as the working electrode, the nickel foam electrode was used as the counter electrode, the silver / silver chloride electrode was used as the reference electrode, and a 1.0 M potassium hydroxide solution was used as the electrolyte. The carbon dioxide electroreduction performance test was carried out in a flow cell electrolytic cell. During the test, the carbon dioxide flow rate was maintained at 20 sccm, and the cathode and anode electrolyte flow rates were maintained at 2 mL min. -1The test adopts the constant current method, and the applied current density range is -100~-1200mA cm -2 The gas phase products of the reaction were detected by gas chromatography, and the liquid phase products were detected by hydrogen nuclear magnetic resonance spectroscopy.

[0078] Carbon dioxide electroreduction performance was tested in an H-type electrolytic cell using a glassy carbon electrode loaded with the bismuth-copper bimetallic complex catalysts obtained in Examples 1-3 and Comparative Example 1 as the working electrode, a platinum electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode. A 0.1 M potassium bicarbonate solution was used as the electrolyte. The carbon dioxide flow rate was maintained at 10 sccm. The tests were conducted using a constant potential method with an applied potential range of -0.95 to -1.25 V vs. RHE. The gaseous products of the reaction were detected by gas chromatography, and the liquid products by proton nuclear magnetic resonance spectroscopy.

[0079] As shown in FIG6 , the bismuth-copper bimetallic composite catalyst prepared in Example 2 has a high conductivity at -1200 mA cm -2 The selectivity of electrocatalytic carbon dioxide reduction to formate is still higher than 90% at ultra-high current density.

[0080] As shown in FIG7 , the bismuth-copper bimetallic composite catalysts prepared in Examples 1-3 maintain a high formate faradaic efficiency (>90%) over a wide potential range, while the material prepared in Comparative Example 1 with a higher copper atomic content (50 at %) achieves a high formate faradaic efficiency only within a narrow range.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0082] Anyone skilled in the art will be able to utilize the above-disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or to modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A bismuth-copper bimetallic composite catalyst, characterized in that: The catalyst comprises ultra-small copper nanoclusters and bismuth nanosheets; the bismuth nanosheets are polycrystalline structures, and the copper nanoclusters are dispersed on the bismuth nanosheets in a highly dispersed form; and the number of copper atoms in the copper nanoclusters is less than 10.

2. The bismuth-copper bimetallic composite catalyst according to claim 1, characterized in that: The copper nanoclusters account for 20-33% of the total atomic weight of the bimetallic complex.

3. The bismuth-copper bimetallic composite catalyst according to claim 1, characterized in that: The thickness of the bismuth nanosheet is 5-20 nm.

4. A method for preparing the bismuth-copper bimetallic composite catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) mixing a soluble copper salt with water to obtain a mixed solution I, adding thiourea to the mixed solution I for reaction, and washing the obtained product I with water, centrifuging and drying to obtain a precursor A; (2) mixing a soluble bismuth salt with water to obtain a mixed solution II, adding sodium diethyldithiocarbamate to the mixed solution II for reaction, and washing the obtained product II with water, centrifuging and drying to obtain a precursor B; (3) ultrasonically dispersing the precursor A and the precursor B in an alcohol solvent to obtain a mixed solution III; (4) heating the mixed solution III obtained in step (3) to reflux, and washing, centrifuging and drying the product III after the reaction to obtain a copper sulfide and bismuth sulfide complex precursor C; (5) The copper sulfide and bismuth sulfide complex precursor C obtained in step (4) is coated on a carbon material as an electrode, and after electrochemical reduction, a bismuth-copper bimetallic complex catalyst is obtained.

5. The preparation method according to claim 4, characterized in that: The soluble copper salt includes any one of copper dichloride and copper dichloride hydrate; The molar ratio of the soluble copper salt to thiourea is 1:(0.5-2), preferably 1:1, and the reaction time is not less than 10s.

6. The preparation method according to claim 4, characterized in that: The soluble bismuth salt is bismuth nitrate; The molar ratio of the soluble bismuth salt to sodium diethyldithiocarbamate is 1:(1-4), preferably 1:3, and the reaction time is not less than 1 minute.

7. The preparation method according to claim 4, characterized in that: The mass ratio of the precursor A to the precursor B is (3.5-7):50; The alcohol solvent includes ethylene glycol; the mass ratio of the alcohol solvent to the precursor B is (33-55):

50.

8. The preparation method according to claim 4, characterized in that: The heating reflux temperature is 130-140° C. and the time is 1-4 hours.

9. The preparation method according to claim 4, characterized in that: The copper sulfide and bismuth sulfide composite precursor is applied on the carbon material by drip coating or spray coating; The carbon material includes any one of a glassy carbon electrode, carbon paper and carbon cloth; The electrode is a working electrode or a cathode; The electrolyte for electrochemical reduction is potassium bicarbonate or potassium hydroxide, the electrolyte concentration is 0.1 to 1 M, the electroreduction potential range is -0.8 to -1.1 V vs. RHE, and the electroreduction reaction time is 10 to 30 min.

10. Use of the bismuth-copper bimetallic composite catalyst according to claims 1 to 3 or the bismuth-copper bimetallic composite catalyst prepared by the preparation method according to claims 4 to 9 in an electrochemical carbon dioxide reduction reaction.

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