Electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of electro-catalysis, and discloses an electro-catalyst which has a mastoid nearly-spherical morphology, and the mastoid nearly-spherical morphology is composed of an aggregate which is formed by aggregating cuprous oxide particles with a primary particle size and has a secondary particle size. The electrocatalyst has the characteristic of simple preparation process, and has good multi-carbon product selectivity and stability in electrocatalytic carbon dioxide reduction.

Description

Electrocatalysts, their preparation methods and applications Technical Field

[0001] This invention relates to the field of electrocatalysis, specifically to an electrocatalyst, its preparation method, and its application. Background Technology

[0002] Since the Industrial Revolution, society's utilization of fossil fuels has increased elevenfold, and carbon dioxide emissions have continued to rise. With the increase in global energy consumption, coupled with the intensification of anthropogenic climate change, there is an urgent need to develop clean and efficient new energy sources, and at the same time, to find efficient and economical ways to achieve the recycling of carbon dioxide. In recent years, the use of renewable energy to generate electricity and convert carbon dioxide into high-value-added chemicals for reuse has attracted widespread attention from the scientific community. On the one hand, the cost of renewable electricity resources is decreasing year by year. For example, the average cost of electricity generated by solar power ($0.04-0.06 per kilowatt-hour) and wind power ($0.06-0.08 per kilowatt-hour) is gradually approaching the price level of fossil fuels, making the widespread application of renewable energy generation possible. On the other hand, research on the electroreduction of carbon dioxide into high-value-added chemicals is becoming increasingly abundant. Numerous studies have proven that carbon dioxide can be converted into C1 (methane, carbon monoxide) or C2 (ethylene, ethanol) products through electroreduction technology, making it one of the important ways to achieve the recycling of carbon dioxide.

[0003] One of the core technologies for carbon dioxide electroreduction is the preparation of high-performance catalysts. Multi-carbon products are preferred for carbon dioxide electroreduction due to their high added value, and copper-based catalysts have attracted significant attention due to their excellent selectivity for multi-carbon products. The morphology, crystal facets, and valence states of copper-based catalysts have a significant impact on their catalytic performance in carbon dioxide electroreduction. For example, Wang et al. prepared copper nanoparticles with different morphologies and found that the carbon dioxide electroreduction reaction is highly sensitive to the surface structure of copper; the (100) crystal facet is favorable for the production of ethylene, while the (110) crystal facet is favorable for the production of oxygen-containing compounds such as ethanol and acetic acid (Nano Lett., 2019, 19, 8461). Choi et al. prepared surface-roughened copper nanowires that can efficiently catalyze the carbon dioxide electroreduction to obtain ethylene products (Nat. Catal., 2020, 3, 804). Copper-based catalysts treated with oxygen plasma have certain oxidation states, which are beneficial for the production of multi-carbon products (Nat. Commun., 2016, 7, 12123). Therefore, controlling the morphology and valence state of copper-based catalysts is an important method for obtaining high-performance carbon dioxide electroreduction catalysts. The presence of oxidized copper sites in polycrystalline cuprous oxide and the abundant grain boundaries within the catalyst are crucial for improving the selectivity of multi-carbon products. Furthermore, commonly used methods for preparing cuprous oxide nanoparticles require hydrothermal conditions, are cumbersome, and produce products with uneven particle size distributions. There is an urgent need to develop simpler and more convenient catalyst synthesis methods. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of cumbersome catalyst preparation steps, low catalytic stability and selectivity in the existing electrocatalytic carbon dioxide reduction technology, and to provide an electrocatalyst, its preparation method and application. This electrocatalyst has the characteristics of simple preparation process and good selectivity and stability of multi-carbon products in electrocatalytic carbon dioxide reduction.

[0005] To achieve the above objectives, a first aspect of the present invention provides an electrocatalyst having a papillary near-spherical morphology, wherein the papillary near-spherical morphology is composed of aggregates of cuprous oxide particles having a primary particle size and having a secondary particle size.

[0006] Preferably, the primary particle size distribution is 5-30 nm.

[0007] Preferably, the secondary particle size distribution is 50-200 nm.

[0008] Preferably, the catalyst further includes a non-metallic element selected from at least one of nitrogen, phosphorus, sulfur, and halogen.

[0009] A second aspect of the present invention provides a method for preparing an electrocatalyst, wherein the method includes the following steps:

[0010] (1) In the presence of a solvent, a copper source and optionally a non-metallic element source are mixed to obtain a dispersion;

[0011] (2) Add a portion of the alkaline substance to the dispersion for the first mixing, and then add the remaining portion of the alkaline substance for the second mixing to obtain a mixed substance;

[0012] (3) The mixture is reacted with a reducing agent and then dried.

[0013] The third aspect of the present invention provides an electrocatalyst prepared by the preparation method described in the second aspect above.

[0014] The fourth aspect of the present invention provides the application of the electrocatalyst described in the first aspect or the electrocatalyst described in the third aspect in the electroreduction of carbon dioxide.

[0015] Through the above technical solution, this invention provides a papillary near-spherical electrocatalyst, its preparation method, and its application, mainly for the electrocatalytic reduction of carbon dioxide. This catalyst has uniform particle size, a simple preparation method, and exhibits high stability and selectivity, particularly demonstrating excellent performance in the formation of multi-carbon products. By employing a method of adding alkaline substances in multiple stages, catalyst nucleation and growth are further promoted, enhancing the catalyst's selectivity and stability, and improving the selectivity for ethylene. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0017] Figure 1 is a SEM image of the electrocatalyst prepared in Example 1 of the present invention;

[0018] Figure 2 is the XRD pattern of the electrocatalyst prepared in Example 1 of the present invention;

[0019] Figure 3 is a selected area electron diffraction (SAED) image of the electrocatalyst prepared in Example 1 of the present invention;

[0020] Figure 4 is a SEM image of the electrocatalyst prepared in Example 2 of the present invention;

[0021] Figure 5 is a SEM image of the electrocatalyst prepared in Comparative Example 1 of the present invention.

[0022] Figure 6 is a SEM image of the electrocatalyst prepared in Comparative Example 2 of the present invention.

[0023] Figure 7 shows the selectivity of carbon dioxide electrocatalytic reduction of the electrocatalysts prepared in Test Examples 1-4 of the present invention;

[0024] Figure 8 shows the stability of the electrocatalysts for carbon dioxide electrocatalytic reduction prepared in Test Examples 1-4 of this invention. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] Unless otherwise specified, all percentages, ratios, etc. mentioned in this invention are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0027] To achieve the above objectives, a first aspect of the present invention provides an electrocatalyst having a papillary near-spherical morphology, wherein the papillary near-spherical morphology is composed of aggregates of cuprous oxide particles having a primary particle size and having a secondary particle size.

[0028] In this invention, the morphology of the catalyst is obtained by SEM imaging.

[0029] In this invention, the electrocatalyst comprises cuprous oxide. The presence of cuprous oxide can be determined by XRD. Those skilled in the art can confirm this by comparing the XRD pattern with standard spectra.

[0030] The present invention does not particularly limit the way of describing the morphological characteristics of the catalyst. Preferably, the papillary near-spherical morphology refers to the appearance and / or structural characteristics of the catalyst material. Here, the "papillary near-spherical" morphology means that the appearance of the catalyst particles looks like an approximate sphere with many small protrusions (similar to papillae) clustered together.

[0031] In this invention, cuprous oxide particles with a primary particle size refer to the basic structural unit of the catalyst.

[0032] The present invention does not particularly limit the formation mode of agglomerates with secondary particle size. Preferably, agglomerates with secondary particle size refer to larger structures formed by the aggregation of cuprous oxide particles with primary particle size, i.e., agglomerates with secondary particle size.

[0033] The present invention provides a catalyst with a specific morphology, wherein the primary cuprous oxide particles have a uniform size, and these uniform particles further aggregate to form secondary particle size agglomerates with a uniform size distribution. This structural design helps to improve the selectivity and stability of the catalyst, especially exhibiting excellent performance in the formation of multi-carbon products.

[0034] The primary particle size described in this invention has the conventional interpretation in the art, preferably referring to the size of the initially formed cuprous oxide particles, preferably with a primary particle size distribution of 5-30 nm, and more preferably 10-20 nm.

[0035] The secondary particle size described in this invention has the conventional interpretation in the art. Secondary particle size refers to the size of a larger particle formed by the aggregation of many primary particle size particles. Preferably, the secondary particle size distribution is 50-200 nm, and more preferably 80-150 nm.

[0036] In this invention, the primary particle size is obtained by XRD testing and by fitting the XRD data using the Williamson-Hall analysis method.

[0037] In this invention, the size of the secondary particle size can be obtained by SEM observation.

[0038] By optimizing the primary and secondary particle size distribution of the catalyst, the contact between reactants and the catalyst surface can be promoted. A uniform aggregate structure provides consistent reaction conditions, reduces side reactions, and improves the selectivity of the target product. Furthermore, by adjusting the primary and secondary particle size distribution, the grain boundary density in the polycrystalline catalyst can be controlled. Appropriate grain boundary density and primary particle size are beneficial for improving catalyst stability. Using the above-mentioned preferred range, the present invention further improves the selectivity and stability of the catalyst and the formation of multi-carbon products.

[0039] According to the present invention, preferably, the catalyst has a polycrystalline structure.

[0040] The polycrystalline structure of the catalyst in this invention was obtained by SAED testing.

[0041] The polycrystalline structure described in this invention has the conventional interpretation in the art. Preferably, a polycrystalline structure refers to a catalyst composed of multiple grains or crystal regions, each grain or crystal region having its own lattice orientation.

[0042] Polycrystalline structures indicate the presence of numerous grain boundaries and grains on the catalyst surface. The interfaces between these grain boundaries and grains are concentrated regions of active sites. Compared to single-crystal structures, polycrystalline structures can provide more active sites, enhancing the selectivity and stability of the catalyst.

[0043] In this invention, preferably, based on the total amount of catalyst, the cuprous oxide content is 5-100% by weight, more preferably 50-100% by weight, and even more preferably 80-100% by weight. The cuprous oxide content can be obtained by XRD testing.

[0044] Cuprous oxide can improve the selectivity of catalysts. Using cuprous oxide within the above-mentioned preferred content range is more conducive to improving the selectivity and stability of catalysts, as well as the conversion efficiency of carbon dioxide and the selectivity of ethylene.

[0045] According to the present invention, preferably, the catalyst also includes non-metallic elements.

[0046] The present invention does not particularly limit the types of non-metallic elements. Preferably, the non-metallic element is selected from at least one of nitrogen, phosphorus, sulfur and halogens, and more preferably nitrogen and / or halogens.

[0047] The present invention does not particularly limit the content of non-metallic elements in the catalyst, as long as it meets the requirements of the present invention. Preferably, based on the total amount of catalyst, the content of non-metallic elements is 0-5% by weight, more preferably 0-2% by weight, and even more preferably 0-1% by weight.

[0048] In this invention, the content of non-metallic elements can be obtained through elemental analysis.

[0049] A second aspect of the present invention provides a method for preparing an electrocatalyst, wherein the method includes the following steps:

[0050] (1) In the presence of a solvent, a copper source and optionally a non-metallic element source are mixed to obtain a dispersion;

[0051] (2) Add a portion of the alkaline substance to the dispersion for the first mixing, and then add the remaining portion of the alkaline substance for the second mixing to obtain a mixed substance;

[0052] (3) The mixture is reacted with a reducing agent and then dried.

[0053] It should be noted that in step (1), "optionally" means that a non-metallic element source can be added or not. In this invention, it is preferred to add a non-metallic element source.

[0054] The present invention does not have any special requirements for the mixing method in step (1) of the preparation method. As long as it is conducive to fully mixing the substances in step (1), those skilled in the art can make the selection according to actual needs, such as stirring.

[0055] The present invention does not have any particular limitation on the drying method and conditions described in step (3), and can refer to conventional methods in the art. Preferably, the drying in step (3) is carried out under vacuum conditions.

[0056] According to the present invention, preferably, the molar ratio of the copper source and the non-metallic element source in step (1) is 1:0.5-4, more preferably 1:2-4.

[0057] According to the present invention, preferably, the nonmetallic element in the nonmetallic element source is selected from at least one of nitrogen, phosphorus, sulfur and halogen.

[0058] According to the present invention, preferably, the molar content of copper source in the dispersion in step (1) is 0.1-1000 mmol / L, more preferably 50-150 mmol / L.

[0059] By controlling the content of copper source and non-metallic element source, the composition, morphology and structure of the catalyst can be adjusted, which helps to optimize the performance of the catalyst. This optimization method is more conducive to improving the stability and selectivity of the catalyst.

[0060] The present invention does not particularly limit the type of copper source. Preferably, the copper source is selected from at least one of copper sulfate, copper nitrate, copper perchlorate, copper chloride, copper bromide and copper iodide, and more preferably copper sulfate.

[0061] The present invention does not particularly limit the type of non-metallic element source. Preferably, the non-metallic element source is selected from at least one of ammonia, alkali metal phosphides, alkali metal sulfides and alkali metal halides, and more preferably ammonia and / or alkali metal halides.

[0062] In this invention, the alkali metal is preferably sodium and / or potassium.

[0063] Preferably, the alkali metal phosphide is selected from Na3P and / or K3P.

[0064] Preferably, the alkali metal sulfide is selected from Na2S and / or K2S.

[0065] Preferably, the alkali metal halide is selected from at least one of NaCl, NaBr, KCl and KBr, and more preferably NaBr and / or KCl.

[0066] This invention confirms through XPS that the catalyst contains no residual alkali metal elements.

[0067] The present invention does not particularly limit the type and amount of solvent used in step (1), as long as it can provide the mixing environment. It can be added alone or mixed with other raw materials before being added. Preferably, the solvent is selected from at least one of water, C1-C3 monohydric alcohols, C2-C3 dihydric alcohols and glycerol, and more preferably water.

[0068] In this invention, the C1-C3 monohydric alcohols have the conventional meaning in the art. Preferably, the C1-C3 monohydric alcohols in this invention refer to monohydric alcohols with a single hydroxyl (-OH) functional group having a carbon chain length of 1 to 3 carbon atoms, including but not limited to methanol, ethanol and propanol.

[0069] In this invention, the C2-C3 diols have the conventional meaning in the art. Preferably, the C2-C3 diols in this invention refer to alcohols containing 2 to 3 carbon atoms and having two hydroxyl (-OH) functional groups, including but not limited to ethylene glycol and / or propylene glycol.

[0070] According to the present invention, preferably, the molar ratio of the copper source to the alkaline substance is 1:1-4, more preferably 1:2-4.

[0071] This invention does not particularly limit the type of alkaline substance, as long as it meets the requirements of this invention. Preferably, the alkaline substance is selected from at least one of alkali metal hydroxides and alkali metal carbonates, more preferably alkali metal hydroxides.

[0072] In this invention, the alkali metal is preferably sodium and / or potassium.

[0073] Preferably, the alkali metal hydroxide is selected from at least one of NaOH, KOH and CsOH, and more preferably NaOH and / or KOH.

[0074] Preferably, the alkali metal carbonate is selected from at least one of Na₂CO₃, K₂CO₃, and C₂CO₃, and more preferably Na₂CO₃ and / or K₂CO₃.

[0075] The present invention does not particularly limit the form in which the alkaline substance is provided. Preferably, the alkaline substance is provided in the form of an alkaline substance solution, wherein the concentration of the alkaline substance in the alkaline substance solution is 1-10 mol / L, more preferably 1-3 mol / L.

[0076] It should be noted that the present invention does not particularly limit the type and amount of alkaline substance solution, as long as the environment required for alkaline substances can be provided. According to a preferred embodiment of the present invention, the solvent in the alkaline substance solution is water.

[0077] According to the present invention, preferably, the volume ratio of the partial alkaline substance to the remaining alkaline substance in step (2) is 1:0.5-5, more preferably 1:1-4.

[0078] The present invention offers a wide range of options for the time and method of the first mixing in step (2). Preferably, the first mixing is carried out under stirring conditions. Preferably, the first mixing time is 1-10 minutes.

[0079] The present invention offers a wide range of options for the time and method of the second mixing in step (2). Preferably, the second mixing is carried out under stirring conditions. The preferred time for the second mixing is 5-30 minutes.

[0080] In this invention, the alkaline substance is added in multiple stages, which is beneficial to catalyst nucleation and growth. The above-mentioned preferred number of additions and proportions are more conducive to uniform catalyst particle size, improved stability and selectivity, and especially to the excellent performance in generating multi-carbon products.

[0081] According to the present invention, preferably, the molar ratio of the copper source to the reducing agent is 1:0.5-4, more preferably 1:1-2.

[0082] The present invention does not particularly limit the type of reducing agent. Preferably, the reducing agent is selected from at least one of sodium borohydride, glucose, ascorbic acid and its salts, and more preferably ascorbic acid.

[0083] This invention does not particularly limit the use of ascorbic acid and its salts, as long as the desired effect of this invention can be achieved, such as sodium salts.

[0084] The present invention does not particularly limit the form in which the reducing agent is provided. Preferably, the reducing agent is provided in the form of a reducing agent solution, wherein the concentration of the reducing agent in the reducing agent solution is 0.1-5 mol / L, more preferably 1-2 mol / L.

[0085] It should be noted that the present invention does not particularly limit the type and amount of reducing agent solution, as long as the environment required for the reducing agent can be provided. According to a preferred embodiment of the present invention, the solvent in the reducing agent solution is water.

[0086] Adding a reducing agent during catalyst preparation can improve the catalyst's selectivity and stability. Using the preferred range of reducing agents and their concentrations described above further enhances the catalyst's selectivity and stability, thereby increasing the carbon dioxide conversion efficiency and ethylene selectivity.

[0087] The present invention does not have any special requirements for the contact described in step (3), as long as it is conducive to sufficient contact and reaction of the substances described in step (3). Those skilled in the art can make the selection according to actual needs, for example, it can be stirring. Preferably, the contact reaction time is 5 minutes to 24 hours, more preferably 10 minutes to 2 hours.

[0088] The present invention also includes separating and washing the solid product obtained after the contact reaction in step (3).

[0089] The present invention does not particularly limit the separation method. Those skilled in the art can choose according to actual needs, as long as the desired solid product can be separated, such as centrifugal separation.

[0090] There are no particular limitations on the washing reagents and amounts; conventional methods in the field can be used, such as deionized water, as long as the impurities can be removed through washing.

[0091] The third aspect of the present invention provides an electrocatalyst prepared by the preparation method described in the second aspect above.

[0092] The fourth aspect of the present invention provides the application of the electrocatalyst described in the first aspect or the electrocatalyst described in the third aspect in the electroreduction of carbon dioxide.

[0093] The specific methods of applying the electrocatalyst in the electroreduction of carbon dioxide are well known to those skilled in the art and are not particularly limited. Preferably, the electrocatalyst is used as a catalyst in the working electrode. There are no particular limitations on the preparation of the working electrode; for example, the electrocatalyst can be mixed with a solvent to obtain a mixed solution, and then Nafion (perfluorosulfonic acid) solution can be added to obtain a catalyst ink. The catalyst ink can then be loaded onto carbon paper by spraying to serve as the working electrode.

[0094] This invention proposes an electrocatalyst, its preparation method, and its application. By precisely controlling the morphology, structure, and composition of the catalyst, a significant improvement in catalytic performance is achieved. The catalyst of this invention adopts a papillary, near-spherical morphology with a uniform primary and secondary particle size distribution, improving the selectivity and stability of the reaction, increasing the conversion rate of carbon dioxide and the selectivity of ethylene. The preparation method is simple and easy to implement, effectively controlling the structure and performance of the catalyst, effectively promoting the recycling of carbon dioxide, and providing strong support for the development of clean energy technologies.

[0095] The present invention will be described in detail below through embodiments.

[0096] Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available and / or prepared using methods known in the art.

[0097] In the following examples and comparative examples, the testing methods and instruments for the cuprous oxide content and non-metallic element content in the electrocatalysts are as described above.

[0098] In the following examples and comparative examples, the morphology of the electrocatalysts can be obtained by SEM testing.

[0099] The polycrystalline structures of the electrocatalysts in the following examples and comparative examples were obtained by SAED testing.

[0100] In the following test examples, the carbon dioxide electrocatalytic reduction products of the electrocatalyst were obtained by gas chromatography using an Agilent 8890 instrument.

[0101] Example 1

[0102] The copper source was a 0.1 mol / L CuSO4 aqueous solution, the non-metallic element source was a 0.4 mol / L NaBr aqueous solution, the alkaline substance was a 2 mol / L NaOH aqueous solution, and the reducing agent was a 1 mol / L ascorbic acid aqueous solution. 10 mL of the copper source solution and 10 mL of the non-metallic element solution were mixed at room temperature. First, 0.2 mL of the alkaline substance solution was added and stirred for 5 minutes. Then, 0.8 mL of the alkaline substance solution was added and stirred for another 10 minutes. After that, 1 mL of the reducing agent solution was added and stirred for another 10 minutes. After centrifugation, the mixture was washed three times with deionized water and dried under vacuum to obtain the electrocatalyst C1.

[0103] The SEM image of the electrocatalyst C1 prepared in this embodiment is shown in Figure 1, which shows papillary spherical particles with a secondary particle size of approximately 150 nm. XRD characterization in Figure 2 confirms that the catalyst composition is cuprous oxide, and the fitting results show that its primary particle size is 20 nm. Selected area electron diffraction results in Figure 3 confirm that the catalyst has a polycrystalline structure. Based on the total amount of catalyst, the content of the non-metallic element Br is 0 wt%, and the content of cuprous oxide is 100 wt%.

[0104] Example 2

[0105] The copper source was a 0.15 mol / L CuSO4 aqueous solution, the non-metallic element source was a 0.3 mol / L KCl aqueous solution, the alkaline substance was a 3 mol / L NaOH aqueous solution, and the reducing agent was a 1.5 mol / L ascorbic acid aqueous solution. 20 mL of the copper source solution and 20 mL of the non-metallic element solution were mixed at room temperature. First, 1 mL of the alkaline substance solution was added, and the mixture was stirred for 2 minutes. Then, another 1 mL of the alkaline substance solution was added, and the mixture was stirred for another 5 minutes. Finally, 2 mL of the reducing agent solution was added, and the mixture was stirred for another 30 minutes. The mixture was then centrifuged, washed three times with deionized water, and dried under vacuum to obtain the electrocatalyst C2.

[0106] Figure 4 shows the SEM image of the electrocatalyst C2 prepared in this embodiment. XRD characterization confirmed that the catalyst composition is cuprous oxide. The fitting results show that its primary particle size is about 15 nm, and the secondary particle size, obtained by SEM, is approximately 100 nm, consisting of papillary spherical particles. Selected area electron diffraction results confirmed that the catalyst has a polycrystalline structure. Based on the total amount of catalyst, the content of the non-metallic element Cl is 0 wt%, and the content of cuprous oxide is 100 wt%.

[0107] Example 3

[0108] The preparation method is the same as in Example 1, with the total amount of alkaline substance solution added remaining unchanged. The difference is that the volume ratio of the alkaline substance added the first time to the second time is 1:0.5, resulting in electrocatalyst C3.

[0109] XRD characterization confirmed that the catalyst was cuprous oxide. Fitting results showed a primary particle size of approximately 30 nm, and secondary particle size, obtained by SEM, consisted of irregular, near-spherical particles of approximately 50 nm. Selected area electron diffraction (SEM) results confirmed the catalyst's polycrystalline structure. Based on the total amount of catalyst, the non-metallic element Cl content was 0 wt%, and the cuprous oxide content was 100 wt%.

[0110] Example 4

[0111] The preparation method is the same as in Example 1, except that no non-metallic elements are added. Electrocatalyst C4 is obtained.

[0112] XRD characterization confirmed that the catalyst was cuprous oxide. Fitting results showed a primary particle size of approximately 50 nm, and secondary particle size, obtained by SEM, consisted of irregular, near-spherical particles of approximately 100 nm. Selected area electron diffraction (SED) results confirmed the catalyst had a polycrystalline structure. Based on the total amount of catalyst, the non-metallic element Cl content was 0 wt%, and the cuprous oxide content was 100 wt%.

[0113] Comparative Example 1

[0114] The preparation method was the same as in Example 1, except that 4 mol / L NaBr aqueous solution was replaced with 10 mL of deionized water, and the alkaline solution was added in a single addition of 1.0 mL, to obtain electrocatalyst control sample D1.

[0115] The SEM image of the obtained irregular cuprous oxide is shown in Figure 5.

[0116] Comparative Example 2

[0117] The preparation method was the same as in Example 2, except that 400 mL of deionized water was used instead of 0.3 mol / L KCl aqueous solution, and 2.0 mL of alkaline solution was added at a time to obtain electrocatalyst control sample D2.

[0118] The SEM image of the obtained cubic cuprous oxide is shown in Figure 6.

[0119] Test case

[0120] The electrocatalysts provided in the embodiments and comparative examples of the present invention were evaluated for their electrochemical performance using the following test method: 50 mg of the prepared electrocatalyst was weighed and dispersed in 5 mL of a mixed solution of isopropanol and water with a volume ratio of 3:1. Then, 50 μl of a 5% (w / w) Nafion (perfluorosulfonic acid) solution was added, and the mixture was sonicated for 30 minutes to obtain catalyst ink. The catalyst ink was then loaded onto carbon paper (SGL-22BB) as the working electrode using a spray coating method, with a catalyst loading of 1 mg / cm³. 2 Working electrode area 1cm 2The electrocatalytic reduction activity of carbon dioxide was tested in a flow cell using a 1M KOH electrolyte and a Hg / HgO (1mol / L KOH) electrode as the reference electrode and nickel foam as the counter electrode. The anion exchange membrane used in the electrolysis cell was a Fumasep FAA-3-PK-130. The carbon dioxide gas flow rate was 20 mL / min, and the electrolyte flow rate was 10 mL / min. The gaseous products were quantitatively analyzed online using an Agilent 8890 gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0121] The results of the carbon dioxide electroreduction selectivity and stability tests are shown in Figures 7 and 8. As can be seen from Figures 7 and 8, compared to D1, C1 exhibits higher ethylene selectivity within the tested current density range; compared to D2, C2 shows higher selectivity within the high current density range (current density > 500 mA / cm²). 2 It has higher ethylene selectivity; in addition, the performance of catalysts D1 and D2 deteriorates after 20h, while catalysts C1 and C2 have higher stability compared with control samples D1 and D2.

[0122] Table 1

[0123]

[0124] As can be seen from the attached figures and the data in Table 1, compared with the comparative catalysts D1 and D2, catalysts C1, C2, C3, and C4 exhibit higher selectivity for multi-carbon products, a larger current density corresponding to the highest selectivity, and better stability when used for carbon dioxide electroreduction. The electrocatalysts of this invention demonstrate excellent selectivity and stability for carbon dioxide electrocatalytic reduction, and their preparation method is simple, showing promising prospects for industrial application.

[0125] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electrocatalyst, characterized in that, The catalyst has a papillary, near-spherical morphology, which is composed of aggregates of cuprous oxide particles with a primary particle size that have a secondary particle size.

2. The catalyst according to claim 1, wherein, The primary particle size distribution is 5-30 nm, preferably 10-20 nm; and / or, the secondary particle size distribution is 50-200 nm, preferably 80-150 nm.

3. The catalyst according to claim 1 or 2, wherein, The catalyst has a polycrystalline structure.

4. The catalyst according to any one of claims 1-3, wherein, Based on the total amount of catalyst, the content of cuprous oxide is 5-100% by weight, preferably 50-100% by weight.

5. The catalyst according to any one of claims 1-4, wherein, The catalyst also includes non-metallic elements selected from at least one of nitrogen, phosphorus, sulfur, and halogens, preferably nitrogen and / or halogens; preferably, the content of the non-metallic elements is 0-5% by weight, more preferably 0-2% by weight, based on the total amount of the catalyst.

6. A method for preparing an electrocatalyst, characterized in that, The method includes the following steps: (1) mixing a copper source and optionally a non-metallic element source in the presence of a solvent to obtain a dispersion; (2) adding a portion of the alkaline substance to the dispersion for a first mixing, and then adding the remaining portion of the alkaline substance for a second mixing to obtain a mixed substance; (3) reacting the mixed substance with a reducing agent and then drying it.

7. The method according to claim 6, wherein, The molar ratio of the copper source to the nonmetallic element source is 1:0.5-4, preferably 1:2-4; preferably, the nonmetallic element in the nonmetallic element source is selected from at least one of nitrogen, phosphorus, sulfur and halogen; preferably, the molar content of the copper source in the dispersion is 0.1-1000 mmol / L, preferably 50-150 mmol / L.

8. The method according to claim 6 or 7, wherein, The copper source is selected from at least one of copper sulfate, copper nitrate, copper perchlorate, copper chloride, copper bromide, and copper iodide; and / or, the non-metallic element source is selected from at least one of ammonia, alkali metal phosphides, alkali metal sulfides, and alkali metal halides, preferably ammonia and / or alkali metal halides; and / or, the solvent in step (1) is selected from at least one of water, C1-C3 monohydric alcohols, C2-C3 dihydric alcohols, and glycerol.

9. The method according to any one of claims 6-8, wherein, The molar ratio of the copper source to the alkaline substance is 1:1-4, preferably 1:2-4; preferably, the alkaline substance is selected from at least one of alkali metal hydroxide and alkali metal carbonate; preferably, the alkaline substance is provided in the form of an alkaline substance solution, and the concentration of the alkaline substance in the alkaline substance solution is 1-10 mol / L; preferably, the volume ratio of the portion of alkaline substance to the remaining portion of alkaline substance in step (2) is 1:0.5-5.

10. The method according to any one of claims 6-9, wherein, The molar ratio of the copper source to the reducing agent is 1:0.5-4, preferably 1:1-2; preferably, the reducing agent is selected from at least one of sodium borohydride, glucose, ascorbic acid and its salts; preferably, the reducing agent is provided in the form of a reducing agent solution, and the concentration of the reducing agent in the reducing agent solution is 0.1-5 mol / L; preferably, the contact reaction time is 5 minutes to 24 hours.

11. An electrocatalyst prepared by any one of claims 6-10.

12. The use of the electrocatalyst according to any one of claims 1-5 and 11 in the electroreduction of carbon dioxide.

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